duckstation

avcodec.h (112853B)

---

 /*
  * copyright (c) 2001 Fabrice Bellard
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #ifndef AVCODEC_AVCODEC_H
 #define AVCODEC_AVCODEC_H
 
 /**
  * @file
  * @ingroup libavc
  * Libavcodec external API header
  */
 
 #include "libavutil/samplefmt.h"
 #include "libavutil/attributes.h"
 #include "libavutil/avutil.h"
 #include "libavutil/buffer.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/dict.h"
 #include "libavutil/frame.h"
 #include "libavutil/log.h"
 #include "libavutil/pixfmt.h"
 #include "libavutil/rational.h"
 
 #include "codec.h"
 #include "codec_id.h"
 #include "defs.h"
 #include "packet.h"
 #include "version_major.h"
 #ifndef HAVE_AV_CONFIG_H
 /* When included as part of the ffmpeg build, only include the major version
  * to avoid unnecessary rebuilds. When included externally, keep including
  * the full version information. */
 #include "version.h"
 
 #include "codec_desc.h"
 #include "codec_par.h"
 #endif
 
 struct AVCodecParameters;
 
 /**
  * @defgroup libavc libavcodec
  * Encoding/Decoding Library
  *
  * @{
  *
  * @defgroup lavc_decoding Decoding
  * @{
  * @}
  *
  * @defgroup lavc_encoding Encoding
  * @{
  * @}
  *
  * @defgroup lavc_codec Codecs
  * @{
  * @defgroup lavc_codec_native Native Codecs
  * @{
  * @}
  * @defgroup lavc_codec_wrappers External library wrappers
  * @{
  * @}
  * @defgroup lavc_codec_hwaccel Hardware Accelerators bridge
  * @{
  * @}
  * @}
  * @defgroup lavc_internal Internal
  * @{
  * @}
  * @}
  */
 
 /**
  * @ingroup libavc
  * @defgroup lavc_encdec send/receive encoding and decoding API overview
  * @{
  *
  * The avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/
  * avcodec_receive_packet() functions provide an encode/decode API, which
  * decouples input and output.
  *
  * The API is very similar for encoding/decoding and audio/video, and works as
  * follows:
  * - Set up and open the AVCodecContext as usual.
  * - Send valid input:
  *   - For decoding, call avcodec_send_packet() to give the decoder raw
  *     compressed data in an AVPacket.
  *   - For encoding, call avcodec_send_frame() to give the encoder an AVFrame
  *     containing uncompressed audio or video.
  *
  *   In both cases, it is recommended that AVPackets and AVFrames are
  *   refcounted, or libavcodec might have to copy the input data. (libavformat
  *   always returns refcounted AVPackets, and av_frame_get_buffer() allocates
  *   refcounted AVFrames.)
  * - Receive output in a loop. Periodically call one of the avcodec_receive_*()
  *   functions and process their output:
  *   - For decoding, call avcodec_receive_frame(). On success, it will return
  *     an AVFrame containing uncompressed audio or video data.
  *   - For encoding, call avcodec_receive_packet(). On success, it will return
  *     an AVPacket with a compressed frame.
  *
  *   Repeat this call until it returns AVERROR(EAGAIN) or an error. The
  *   AVERROR(EAGAIN) return value means that new input data is required to
  *   return new output. In this case, continue with sending input. For each
  *   input frame/packet, the codec will typically return 1 output frame/packet,
  *   but it can also be 0 or more than 1.
  *
  * At the beginning of decoding or encoding, the codec might accept multiple
  * input frames/packets without returning a frame, until its internal buffers
  * are filled. This situation is handled transparently if you follow the steps
  * outlined above.
  *
  * In theory, sending input can result in EAGAIN - this should happen only if
  * not all output was received. You can use this to structure alternative decode
  * or encode loops other than the one suggested above. For example, you could
  * try sending new input on each iteration, and try to receive output if that
  * returns EAGAIN.
  *
  * End of stream situations. These require "flushing" (aka draining) the codec,
  * as the codec might buffer multiple frames or packets internally for
  * performance or out of necessity (consider B-frames).
  * This is handled as follows:
  * - Instead of valid input, send NULL to the avcodec_send_packet() (decoding)
  *   or avcodec_send_frame() (encoding) functions. This will enter draining
  *   mode.
  * - Call avcodec_receive_frame() (decoding) or avcodec_receive_packet()
  *   (encoding) in a loop until AVERROR_EOF is returned. The functions will
  *   not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
  * - Before decoding can be resumed again, the codec has to be reset with
  *   avcodec_flush_buffers().
  *
  * Using the API as outlined above is highly recommended. But it is also
  * possible to call functions outside of this rigid schema. For example, you can
  * call avcodec_send_packet() repeatedly without calling
  * avcodec_receive_frame(). In this case, avcodec_send_packet() will succeed
  * until the codec's internal buffer has been filled up (which is typically of
  * size 1 per output frame, after initial input), and then reject input with
  * AVERROR(EAGAIN). Once it starts rejecting input, you have no choice but to
  * read at least some output.
  *
  * Not all codecs will follow a rigid and predictable dataflow; the only
  * guarantee is that an AVERROR(EAGAIN) return value on a send/receive call on
  * one end implies that a receive/send call on the other end will succeed, or
  * at least will not fail with AVERROR(EAGAIN). In general, no codec will
  * permit unlimited buffering of input or output.
  *
  * A codec is not allowed to return AVERROR(EAGAIN) for both sending and receiving. This
  * would be an invalid state, which could put the codec user into an endless
  * loop. The API has no concept of time either: it cannot happen that trying to
  * do avcodec_send_packet() results in AVERROR(EAGAIN), but a repeated call 1 second
  * later accepts the packet (with no other receive/flush API calls involved).
  * The API is a strict state machine, and the passage of time is not supposed
  * to influence it. Some timing-dependent behavior might still be deemed
  * acceptable in certain cases. But it must never result in both send/receive
  * returning EAGAIN at the same time at any point. It must also absolutely be
  * avoided that the current state is "unstable" and can "flip-flop" between
  * the send/receive APIs allowing progress. For example, it's not allowed that
  * the codec randomly decides that it actually wants to consume a packet now
  * instead of returning a frame, after it just returned AVERROR(EAGAIN) on an
  * avcodec_send_packet() call.
  * @}
  */
 
 /**
  * @defgroup lavc_core Core functions/structures.
  * @ingroup libavc
  *
  * Basic definitions, functions for querying libavcodec capabilities,
  * allocating core structures, etc.
  * @{
  */
 
 #if FF_API_BUFFER_MIN_SIZE
 /**
  * @ingroup lavc_encoding
  * minimum encoding buffer size
  * Used to avoid some checks during header writing.
  * @deprecated Unused: avcodec_receive_packet() does not work
  *             with preallocated packet buffers.
  */
 #define AV_INPUT_BUFFER_MIN_SIZE 16384
 #endif
 
 /**
  * @ingroup lavc_encoding
  */
 typedef struct RcOverride{
     int start_frame;
     int end_frame;
     int qscale; // If this is 0 then quality_factor will be used instead.
     float quality_factor;
 } RcOverride;
 
 /* encoding support
    These flags can be passed in AVCodecContext.flags before initialization.
    Note: Not everything is supported yet.
 */
 
 /**
  * Allow decoders to produce frames with data planes that are not aligned
  * to CPU requirements (e.g. due to cropping).
  */
 #define AV_CODEC_FLAG_UNALIGNED       (1 <<  0)
 /**
  * Use fixed qscale.
  */
 #define AV_CODEC_FLAG_QSCALE          (1 <<  1)
 /**
  * 4 MV per MB allowed / advanced prediction for H.263.
  */
 #define AV_CODEC_FLAG_4MV             (1 <<  2)
 /**
  * Output even those frames that might be corrupted.
  */
 #define AV_CODEC_FLAG_OUTPUT_CORRUPT  (1 <<  3)
 /**
  * Use qpel MC.
  */
 #define AV_CODEC_FLAG_QPEL            (1 <<  4)
 #if FF_API_DROPCHANGED
 /**
  * Don't output frames whose parameters differ from first
  * decoded frame in stream.
  *
  * @deprecated callers should implement this functionality in their own code
  */
 #define AV_CODEC_FLAG_DROPCHANGED     (1 <<  5)
 #endif
 /**
  * Request the encoder to output reconstructed frames, i.e.\ frames that would
  * be produced by decoding the encoded bistream. These frames may be retrieved
  * by calling avcodec_receive_frame() immediately after a successful call to
  * avcodec_receive_packet().
  *
  * Should only be used with encoders flagged with the
  * @ref AV_CODEC_CAP_ENCODER_RECON_FRAME capability.
  *
  * @note
  * Each reconstructed frame returned by the encoder corresponds to the last
  * encoded packet, i.e. the frames are returned in coded order rather than
  * presentation order.
  *
  * @note
  * Frame parameters (like pixel format or dimensions) do not have to match the
  * AVCodecContext values. Make sure to use the values from the returned frame.
  */
 #define AV_CODEC_FLAG_RECON_FRAME     (1 <<  6)
 /**
  * @par decoding
  * Request the decoder to propagate each packet's AVPacket.opaque and
  * AVPacket.opaque_ref to its corresponding output AVFrame.
  *
  * @par encoding:
  * Request the encoder to propagate each frame's AVFrame.opaque and
  * AVFrame.opaque_ref values to its corresponding output AVPacket.
  *
  * @par
  * May only be set on encoders that have the
  * @ref AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE capability flag.
  *
  * @note
  * While in typical cases one input frame produces exactly one output packet
  * (perhaps after a delay), in general the mapping of frames to packets is
  * M-to-N, so
  * - Any number of input frames may be associated with any given output packet.
  *   This includes zero - e.g. some encoders may output packets that carry only
  *   metadata about the whole stream.
  * - A given input frame may be associated with any number of output packets.
  *   Again this includes zero - e.g. some encoders may drop frames under certain
  *   conditions.
  * .
  * This implies that when using this flag, the caller must NOT assume that
  * - a given input frame's opaques will necessarily appear on some output packet;
  * - every output packet will have some non-NULL opaque value.
  * .
  * When an output packet contains multiple frames, the opaque values will be
  * taken from the first of those.
  *
  * @note
  * The converse holds for decoders, with frames and packets switched.
  */
 #define AV_CODEC_FLAG_COPY_OPAQUE     (1 <<  7)
 /**
  * Signal to the encoder that the values of AVFrame.duration are valid and
  * should be used (typically for transferring them to output packets).
  *
  * If this flag is not set, frame durations are ignored.
  */
 #define AV_CODEC_FLAG_FRAME_DURATION  (1 <<  8)
 /**
  * Use internal 2pass ratecontrol in first pass mode.
  */
 #define AV_CODEC_FLAG_PASS1           (1 <<  9)
 /**
  * Use internal 2pass ratecontrol in second pass mode.
  */
 #define AV_CODEC_FLAG_PASS2           (1 << 10)
 /**
  * loop filter.
  */
 #define AV_CODEC_FLAG_LOOP_FILTER     (1 << 11)
 /**
  * Only decode/encode grayscale.
  */
 #define AV_CODEC_FLAG_GRAY            (1 << 13)
 /**
  * error[?] variables will be set during encoding.
  */
 #define AV_CODEC_FLAG_PSNR            (1 << 15)
 /**
  * Use interlaced DCT.
  */
 #define AV_CODEC_FLAG_INTERLACED_DCT  (1 << 18)
 /**
  * Force low delay.
  */
 #define AV_CODEC_FLAG_LOW_DELAY       (1 << 19)
 /**
  * Place global headers in extradata instead of every keyframe.
  */
 #define AV_CODEC_FLAG_GLOBAL_HEADER   (1 << 22)
 /**
  * Use only bitexact stuff (except (I)DCT).
  */
 #define AV_CODEC_FLAG_BITEXACT        (1 << 23)
 /* Fx : Flag for H.263+ extra options */
 /**
  * H.263 advanced intra coding / MPEG-4 AC prediction
  */
 #define AV_CODEC_FLAG_AC_PRED         (1 << 24)
 /**
  * interlaced motion estimation
  */
 #define AV_CODEC_FLAG_INTERLACED_ME   (1 << 29)
 #define AV_CODEC_FLAG_CLOSED_GOP      (1U << 31)
 
 /**
  * Allow non spec compliant speedup tricks.
  */
 #define AV_CODEC_FLAG2_FAST           (1 <<  0)
 /**
  * Skip bitstream encoding.
  */
 #define AV_CODEC_FLAG2_NO_OUTPUT      (1 <<  2)
 /**
  * Place global headers at every keyframe instead of in extradata.
  */
 #define AV_CODEC_FLAG2_LOCAL_HEADER   (1 <<  3)
 
 /**
  * Input bitstream might be truncated at a packet boundaries
  * instead of only at frame boundaries.
  */
 #define AV_CODEC_FLAG2_CHUNKS         (1 << 15)
 /**
  * Discard cropping information from SPS.
  */
 #define AV_CODEC_FLAG2_IGNORE_CROP    (1 << 16)
 
 /**
  * Show all frames before the first keyframe
  */
 #define AV_CODEC_FLAG2_SHOW_ALL       (1 << 22)
 /**
  * Export motion vectors through frame side data
  */
 #define AV_CODEC_FLAG2_EXPORT_MVS     (1 << 28)
 /**
  * Do not skip samples and export skip information as frame side data
  */
 #define AV_CODEC_FLAG2_SKIP_MANUAL    (1 << 29)
 /**
  * Do not reset ASS ReadOrder field on flush (subtitles decoding)
  */
 #define AV_CODEC_FLAG2_RO_FLUSH_NOOP  (1 << 30)
 /**
  * Generate/parse ICC profiles on encode/decode, as appropriate for the type of
  * file. No effect on codecs which cannot contain embedded ICC profiles, or
  * when compiled without support for lcms2.
  */
 #define AV_CODEC_FLAG2_ICC_PROFILES   (1U << 31)
 
 /* Exported side data.
    These flags can be passed in AVCodecContext.export_side_data before initialization.
 */
 /**
  * Export motion vectors through frame side data
  */
 #define AV_CODEC_EXPORT_DATA_MVS         (1 << 0)
 /**
  * Export encoder Producer Reference Time through packet side data
  */
 #define AV_CODEC_EXPORT_DATA_PRFT        (1 << 1)
 /**
  * Decoding only.
  * Export the AVVideoEncParams structure through frame side data.
  */
 #define AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS (1 << 2)
 /**
  * Decoding only.
  * Do not apply film grain, export it instead.
  */
 #define AV_CODEC_EXPORT_DATA_FILM_GRAIN (1 << 3)
 
 /**
  * The decoder will keep a reference to the frame and may reuse it later.
  */
 #define AV_GET_BUFFER_FLAG_REF (1 << 0)
 
 /**
  * The encoder will keep a reference to the packet and may reuse it later.
  */
 #define AV_GET_ENCODE_BUFFER_FLAG_REF (1 << 0)
 
 /**
  * main external API structure.
  * New fields can be added to the end with minor version bumps.
  * Removal, reordering and changes to existing fields require a major
  * version bump.
  * You can use AVOptions (av_opt* / av_set/get*()) to access these fields from user
  * applications.
  * The name string for AVOptions options matches the associated command line
  * parameter name and can be found in libavcodec/options_table.h
  * The AVOption/command line parameter names differ in some cases from the C
  * structure field names for historic reasons or brevity.
  * sizeof(AVCodecContext) must not be used outside libav*.
  */
 typedef struct AVCodecContext {
     /**
      * information on struct for av_log
      * - set by avcodec_alloc_context3
      */
     const AVClass *av_class;
     int log_level_offset;
 
     enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
     const struct AVCodec  *codec;
     enum AVCodecID     codec_id; /* see AV_CODEC_ID_xxx */
 
     /**
      * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
      * This is used to work around some encoder bugs.
      * A demuxer should set this to what is stored in the field used to identify the codec.
      * If there are multiple such fields in a container then the demuxer should choose the one
      * which maximizes the information about the used codec.
      * If the codec tag field in a container is larger than 32 bits then the demuxer should
      * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
      * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
      * first.
      * - encoding: Set by user, if not then the default based on codec_id will be used.
      * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
      */
     unsigned int codec_tag;
 
     void *priv_data;
 
     /**
      * Private context used for internal data.
      *
      * Unlike priv_data, this is not codec-specific. It is used in general
      * libavcodec functions.
      */
     struct AVCodecInternal *internal;
 
     /**
      * Private data of the user, can be used to carry app specific stuff.
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     void *opaque;
 
     /**
      * the average bitrate
      * - encoding: Set by user; unused for constant quantizer encoding.
      * - decoding: Set by user, may be overwritten by libavcodec
      *             if this info is available in the stream
      */
     int64_t bit_rate;
 
     /**
      * AV_CODEC_FLAG_*.
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int flags;
 
     /**
      * AV_CODEC_FLAG2_*
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int flags2;
 
     /**
      * some codecs need / can use extradata like Huffman tables.
      * MJPEG: Huffman tables
      * rv10: additional flags
      * MPEG-4: global headers (they can be in the bitstream or here)
      * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
      * than extradata_size to avoid problems if it is read with the bitstream reader.
      * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
      * Must be allocated with the av_malloc() family of functions.
      * - encoding: Set/allocated/freed by libavcodec.
      * - decoding: Set/allocated/freed by user.
      */
     uint8_t *extradata;
     int extradata_size;
 
     /**
      * This is the fundamental unit of time (in seconds) in terms
      * of which frame timestamps are represented. For fixed-fps content,
      * timebase should be 1/framerate and timestamp increments should be
      * identically 1.
      * This often, but not always is the inverse of the frame rate or field rate
      * for video. 1/time_base is not the average frame rate if the frame rate is not
      * constant.
      *
      * Like containers, elementary streams also can store timestamps, 1/time_base
      * is the unit in which these timestamps are specified.
      * As example of such codec time base see ISO/IEC 14496-2:2001(E)
      * vop_time_increment_resolution and fixed_vop_rate
      * (fixed_vop_rate == 0 implies that it is different from the framerate)
      *
      * - encoding: MUST be set by user.
      * - decoding: unused.
      */
     AVRational time_base;
 
     /**
      * Timebase in which pkt_dts/pts and AVPacket.dts/pts are expressed.
      * - encoding: unused.
      * - decoding: set by user.
      */
     AVRational pkt_timebase;
 
     /**
      * - decoding: For codecs that store a framerate value in the compressed
      *             bitstream, the decoder may export it here. { 0, 1} when
      *             unknown.
      * - encoding: May be used to signal the framerate of CFR content to an
      *             encoder.
      */
     AVRational framerate;
 
 #if FF_API_TICKS_PER_FRAME
     /**
      * For some codecs, the time base is closer to the field rate than the frame rate.
      * Most notably, H.264 and MPEG-2 specify time_base as half of frame duration
      * if no telecine is used ...
      *
      * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it to 2.
      *
      * @deprecated
      * - decoding: Use AVCodecDescriptor.props & AV_CODEC_PROP_FIELDS
      * - encoding: Set AVCodecContext.framerate instead
      *
      */
     attribute_deprecated
     int ticks_per_frame;
 #endif
 
     /**
      * Codec delay.
      *
      * Encoding: Number of frames delay there will be from the encoder input to
      *           the decoder output. (we assume the decoder matches the spec)
      * Decoding: Number of frames delay in addition to what a standard decoder
      *           as specified in the spec would produce.
      *
      * Video:
      *   Number of frames the decoded output will be delayed relative to the
      *   encoded input.
      *
      * Audio:
      *   For encoding, this field is unused (see initial_padding).
      *
      *   For decoding, this is the number of samples the decoder needs to
      *   output before the decoder's output is valid. When seeking, you should
      *   start decoding this many samples prior to your desired seek point.
      *
      * - encoding: Set by libavcodec.
      * - decoding: Set by libavcodec.
      */
     int delay;
 
 
     /* video only */
     /**
      * picture width / height.
      *
      * @note Those fields may not match the values of the last
      * AVFrame output by avcodec_receive_frame() due frame
      * reordering.
      *
      * - encoding: MUST be set by user.
      * - decoding: May be set by the user before opening the decoder if known e.g.
      *             from the container. Some decoders will require the dimensions
      *             to be set by the caller. During decoding, the decoder may
      *             overwrite those values as required while parsing the data.
      */
     int width, height;
 
     /**
      * Bitstream width / height, may be different from width/height e.g. when
      * the decoded frame is cropped before being output or lowres is enabled.
      *
      * @note Those field may not match the value of the last
      * AVFrame output by avcodec_receive_frame() due frame
      * reordering.
      *
      * - encoding: unused
      * - decoding: May be set by the user before opening the decoder if known
      *             e.g. from the container. During decoding, the decoder may
      *             overwrite those values as required while parsing the data.
      */
     int coded_width, coded_height;
 
     /**
      * sample aspect ratio (0 if unknown)
      * That is the width of a pixel divided by the height of the pixel.
      * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
      * - encoding: Set by user.
      * - decoding: Set by libavcodec.
      */
     AVRational sample_aspect_ratio;
 
     /**
      * Pixel format, see AV_PIX_FMT_xxx.
      * May be set by the demuxer if known from headers.
      * May be overridden by the decoder if it knows better.
      *
      * @note This field may not match the value of the last
      * AVFrame output by avcodec_receive_frame() due frame
      * reordering.
      *
      * - encoding: Set by user.
      * - decoding: Set by user if known, overridden by libavcodec while
      *             parsing the data.
      */
     enum AVPixelFormat pix_fmt;
 
     /**
      * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
      * - encoding: unused.
      * - decoding: Set by libavcodec before calling get_format()
      */
     enum AVPixelFormat sw_pix_fmt;
 
     /**
      * Chromaticity coordinates of the source primaries.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVColorPrimaries color_primaries;
 
     /**
      * Color Transfer Characteristic.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVColorTransferCharacteristic color_trc;
 
     /**
      * YUV colorspace type.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVColorSpace colorspace;
 
     /**
      * MPEG vs JPEG YUV range.
      * - encoding: Set by user to override the default output color range value,
      *   If not specified, libavcodec sets the color range depending on the
      *   output format.
      * - decoding: Set by libavcodec, can be set by the user to propagate the
      *   color range to components reading from the decoder context.
      */
     enum AVColorRange color_range;
 
     /**
      * This defines the location of chroma samples.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVChromaLocation chroma_sample_location;
 
     /** Field order
      * - encoding: set by libavcodec
      * - decoding: Set by user.
      */
     enum AVFieldOrder field_order;
 
     /**
      * number of reference frames
      * - encoding: Set by user.
      * - decoding: Set by lavc.
      */
     int refs;
 
     /**
      * Size of the frame reordering buffer in the decoder.
      * For MPEG-2 it is 1 IPB or 0 low delay IP.
      * - encoding: Set by libavcodec.
      * - decoding: Set by libavcodec.
      */
     int has_b_frames;
 
     /**
      * slice flags
      * - encoding: unused
      * - decoding: Set by user.
      */
     int slice_flags;
 #define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
 #define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
 #define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)
 
     /**
      * If non NULL, 'draw_horiz_band' is called by the libavcodec
      * decoder to draw a horizontal band. It improves cache usage. Not
      * all codecs can do that. You must check the codec capabilities
      * beforehand.
      * When multithreading is used, it may be called from multiple threads
      * at the same time; threads might draw different parts of the same AVFrame,
      * or multiple AVFrames, and there is no guarantee that slices will be drawn
      * in order.
      * The function is also used by hardware acceleration APIs.
      * It is called at least once during frame decoding to pass
      * the data needed for hardware render.
      * In that mode instead of pixel data, AVFrame points to
      * a structure specific to the acceleration API. The application
      * reads the structure and can change some fields to indicate progress
      * or mark state.
      * - encoding: unused
      * - decoding: Set by user.
      * @param height the height of the slice
      * @param y the y position of the slice
      * @param type 1->top field, 2->bottom field, 3->frame
      * @param offset offset into the AVFrame.data from which the slice should be read
      */
     void (*draw_horiz_band)(struct AVCodecContext *s,
                             const AVFrame *src, int offset[AV_NUM_DATA_POINTERS],
                             int y, int type, int height);
 
     /**
      * Callback to negotiate the pixel format. Decoding only, may be set by the
      * caller before avcodec_open2().
      *
      * Called by some decoders to select the pixel format that will be used for
      * the output frames. This is mainly used to set up hardware acceleration,
      * then the provided format list contains the corresponding hwaccel pixel
      * formats alongside the "software" one. The software pixel format may also
      * be retrieved from \ref sw_pix_fmt.
      *
      * This callback will be called when the coded frame properties (such as
      * resolution, pixel format, etc.) change and more than one output format is
      * supported for those new properties. If a hardware pixel format is chosen
      * and initialization for it fails, the callback may be called again
      * immediately.
      *
      * This callback may be called from different threads if the decoder is
      * multi-threaded, but not from more than one thread simultaneously.
      *
      * @param fmt list of formats which may be used in the current
      *            configuration, terminated by AV_PIX_FMT_NONE.
      * @warning Behavior is undefined if the callback returns a value other
      *          than one of the formats in fmt or AV_PIX_FMT_NONE.
      * @return the chosen format or AV_PIX_FMT_NONE
      */
     enum AVPixelFormat (*get_format)(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
 
     /**
      * maximum number of B-frames between non-B-frames
      * Note: The output will be delayed by max_b_frames+1 relative to the input.
      * - encoding: Set by user.
      * - decoding: unused
      */
     int max_b_frames;
 
     /**
      * qscale factor between IP and B-frames
      * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
      * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
      * - encoding: Set by user.
      * - decoding: unused
      */
     float b_quant_factor;
 
     /**
      * qscale offset between IP and B-frames
      * - encoding: Set by user.
      * - decoding: unused
      */
     float b_quant_offset;
 
     /**
      * qscale factor between P- and I-frames
      * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor + offset).
      * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
      * - encoding: Set by user.
      * - decoding: unused
      */
     float i_quant_factor;
 
     /**
      * qscale offset between P and I-frames
      * - encoding: Set by user.
      * - decoding: unused
      */
     float i_quant_offset;
 
     /**
      * luminance masking (0-> disabled)
      * - encoding: Set by user.
      * - decoding: unused
      */
     float lumi_masking;
 
     /**
      * temporary complexity masking (0-> disabled)
      * - encoding: Set by user.
      * - decoding: unused
      */
     float temporal_cplx_masking;
 
     /**
      * spatial complexity masking (0-> disabled)
      * - encoding: Set by user.
      * - decoding: unused
      */
     float spatial_cplx_masking;
 
     /**
      * p block masking (0-> disabled)
      * - encoding: Set by user.
      * - decoding: unused
      */
     float p_masking;
 
     /**
      * darkness masking (0-> disabled)
      * - encoding: Set by user.
      * - decoding: unused
      */
     float dark_masking;
 
     /**
      * noise vs. sse weight for the nsse comparison function
      * - encoding: Set by user.
      * - decoding: unused
      */
      int nsse_weight;
 
     /**
      * motion estimation comparison function
      * - encoding: Set by user.
      * - decoding: unused
      */
     int me_cmp;
     /**
      * subpixel motion estimation comparison function
      * - encoding: Set by user.
      * - decoding: unused
      */
     int me_sub_cmp;
     /**
      * macroblock comparison function (not supported yet)
      * - encoding: Set by user.
      * - decoding: unused
      */
     int mb_cmp;
     /**
      * interlaced DCT comparison function
      * - encoding: Set by user.
      * - decoding: unused
      */
     int ildct_cmp;
 #define FF_CMP_SAD          0
 #define FF_CMP_SSE          1
 #define FF_CMP_SATD         2
 #define FF_CMP_DCT          3
 #define FF_CMP_PSNR         4
 #define FF_CMP_BIT          5
 #define FF_CMP_RD           6
 #define FF_CMP_ZERO         7
 #define FF_CMP_VSAD         8
 #define FF_CMP_VSSE         9
 #define FF_CMP_NSSE         10
 #define FF_CMP_W53          11
 #define FF_CMP_W97          12
 #define FF_CMP_DCTMAX       13
 #define FF_CMP_DCT264       14
 #define FF_CMP_MEDIAN_SAD   15
 #define FF_CMP_CHROMA       256
 
     /**
      * ME diamond size & shape
      * - encoding: Set by user.
      * - decoding: unused
      */
     int dia_size;
 
     /**
      * amount of previous MV predictors (2a+1 x 2a+1 square)
      * - encoding: Set by user.
      * - decoding: unused
      */
     int last_predictor_count;
 
     /**
      * motion estimation prepass comparison function
      * - encoding: Set by user.
      * - decoding: unused
      */
     int me_pre_cmp;
 
     /**
      * ME prepass diamond size & shape
      * - encoding: Set by user.
      * - decoding: unused
      */
     int pre_dia_size;
 
     /**
      * subpel ME quality
      * - encoding: Set by user.
      * - decoding: unused
      */
     int me_subpel_quality;
 
     /**
      * maximum motion estimation search range in subpel units
      * If 0 then no limit.
      *
      * - encoding: Set by user.
      * - decoding: unused
      */
     int me_range;
 
     /**
      * macroblock decision mode
      * - encoding: Set by user.
      * - decoding: unused
      */
     int mb_decision;
 #define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
 #define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
 #define FF_MB_DECISION_RD     2        ///< rate distortion
 
     /**
      * custom intra quantization matrix
      * Must be allocated with the av_malloc() family of functions, and will be freed in
      * avcodec_free_context().
      * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
      * - decoding: Set/allocated/freed by libavcodec.
      */
     uint16_t *intra_matrix;
 
     /**
      * custom inter quantization matrix
      * Must be allocated with the av_malloc() family of functions, and will be freed in
      * avcodec_free_context().
      * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
      * - decoding: Set/allocated/freed by libavcodec.
      */
     uint16_t *inter_matrix;
 
     /**
      * custom intra quantization matrix
      * - encoding: Set by user, can be NULL.
      * - decoding: unused.
      */
     uint16_t *chroma_intra_matrix;
 
     /**
      * precision of the intra DC coefficient - 8
      * - encoding: Set by user.
      * - decoding: Set by libavcodec
      */
     int intra_dc_precision;
 
     /**
      * minimum MB Lagrange multiplier
      * - encoding: Set by user.
      * - decoding: unused
      */
     int mb_lmin;
 
     /**
      * maximum MB Lagrange multiplier
      * - encoding: Set by user.
      * - decoding: unused
      */
     int mb_lmax;
 
     /**
      * - encoding: Set by user.
      * - decoding: unused
      */
     int bidir_refine;
 
     /**
      * minimum GOP size
      * - encoding: Set by user.
      * - decoding: unused
      */
     int keyint_min;
 
     /**
      * the number of pictures in a group of pictures, or 0 for intra_only
      * - encoding: Set by user.
      * - decoding: unused
      */
     int gop_size;
 
     /**
      * Note: Value depends upon the compare function used for fullpel ME.
      * - encoding: Set by user.
      * - decoding: unused
      */
     int mv0_threshold;
 
     /**
      * Number of slices.
      * Indicates number of picture subdivisions. Used for parallelized
      * decoding.
      * - encoding: Set by user
      * - decoding: unused
      */
     int slices;
 
     /* audio only */
     int sample_rate; ///< samples per second
 
     /**
      * audio sample format
      * - encoding: Set by user.
      * - decoding: Set by libavcodec.
      */
     enum AVSampleFormat sample_fmt;  ///< sample format
 
     /**
      * Audio channel layout.
      * - encoding: must be set by the caller, to one of AVCodec.ch_layouts.
      * - decoding: may be set by the caller if known e.g. from the container.
      *             The decoder can then override during decoding as needed.
      */
     AVChannelLayout ch_layout;
 
     /* The following data should not be initialized. */
     /**
      * Number of samples per channel in an audio frame.
      *
      * - encoding: set by libavcodec in avcodec_open2(). Each submitted frame
      *   except the last must contain exactly frame_size samples per channel.
      *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
      *   frame size is not restricted.
      * - decoding: may be set by some decoders to indicate constant frame size
      */
     int frame_size;
 
     /**
      * number of bytes per packet if constant and known or 0
      * Used by some WAV based audio codecs.
      */
     int block_align;
 
     /**
      * Audio cutoff bandwidth (0 means "automatic")
      * - encoding: Set by user.
      * - decoding: unused
      */
     int cutoff;
 
     /**
      * Type of service that the audio stream conveys.
      * - encoding: Set by user.
      * - decoding: Set by libavcodec.
      */
     enum AVAudioServiceType audio_service_type;
 
     /**
      * desired sample format
      * - encoding: Not used.
      * - decoding: Set by user.
      * Decoder will decode to this format if it can.
      */
     enum AVSampleFormat request_sample_fmt;
 
     /**
      * Audio only. The number of "priming" samples (padding) inserted by the
      * encoder at the beginning of the audio. I.e. this number of leading
      * decoded samples must be discarded by the caller to get the original audio
      * without leading padding.
      *
      * - decoding: unused
      * - encoding: Set by libavcodec. The timestamps on the output packets are
      *             adjusted by the encoder so that they always refer to the
      *             first sample of the data actually contained in the packet,
      *             including any added padding.  E.g. if the timebase is
      *             1/samplerate and the timestamp of the first input sample is
      *             0, the timestamp of the first output packet will be
      *             -initial_padding.
      */
     int initial_padding;
 
     /**
      * Audio only. The amount of padding (in samples) appended by the encoder to
      * the end of the audio. I.e. this number of decoded samples must be
      * discarded by the caller from the end of the stream to get the original
      * audio without any trailing padding.
      *
      * - decoding: unused
      * - encoding: unused
      */
     int trailing_padding;
 
     /**
      * Number of samples to skip after a discontinuity
      * - decoding: unused
      * - encoding: set by libavcodec
      */
     int seek_preroll;
 
     /**
      * This callback is called at the beginning of each frame to get data
      * buffer(s) for it. There may be one contiguous buffer for all the data or
      * there may be a buffer per each data plane or anything in between. What
      * this means is, you may set however many entries in buf[] you feel necessary.
      * Each buffer must be reference-counted using the AVBuffer API (see description
      * of buf[] below).
      *
      * The following fields will be set in the frame before this callback is
      * called:
      * - format
      * - width, height (video only)
      * - sample_rate, channel_layout, nb_samples (audio only)
      * Their values may differ from the corresponding values in
      * AVCodecContext. This callback must use the frame values, not the codec
      * context values, to calculate the required buffer size.
      *
      * This callback must fill the following fields in the frame:
      * - data[]
      * - linesize[]
      * - extended_data:
      *   * if the data is planar audio with more than 8 channels, then this
      *     callback must allocate and fill extended_data to contain all pointers
      *     to all data planes. data[] must hold as many pointers as it can.
      *     extended_data must be allocated with av_malloc() and will be freed in
      *     av_frame_unref().
      *   * otherwise extended_data must point to data
      * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
      *   the frame's data and extended_data pointers must be contained in these. That
      *   is, one AVBufferRef for each allocated chunk of memory, not necessarily one
      *   AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
      *   and av_buffer_ref().
      * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
      *   this callback and filled with the extra buffers if there are more
      *   buffers than buf[] can hold. extended_buf will be freed in
      *   av_frame_unref().
      *
      * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
      * avcodec_default_get_buffer2() instead of providing buffers allocated by
      * some other means.
      *
      * Each data plane must be aligned to the maximum required by the target
      * CPU.
      *
      * @see avcodec_default_get_buffer2()
      *
      * Video:
      *
      * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
      * (read and/or written to if it is writable) later by libavcodec.
      *
      * avcodec_align_dimensions2() should be used to find the required width and
      * height, as they normally need to be rounded up to the next multiple of 16.
      *
      * Some decoders do not support linesizes changing between frames.
      *
      * If frame multithreading is used, this callback may be called from a
      * different thread, but not from more than one at once. Does not need to be
      * reentrant.
      *
      * @see avcodec_align_dimensions2()
      *
      * Audio:
      *
      * Decoders request a buffer of a particular size by setting
      * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
      * however, utilize only part of the buffer by setting AVFrame.nb_samples
      * to a smaller value in the output frame.
      *
      * As a convenience, av_samples_get_buffer_size() and
      * av_samples_fill_arrays() in libavutil may be used by custom get_buffer2()
      * functions to find the required data size and to fill data pointers and
      * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
      * since all planes must be the same size.
      *
      * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
      *
      * - encoding: unused
      * - decoding: Set by libavcodec, user can override.
      */
     int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);
 
     /* - encoding parameters */
     /**
      * number of bits the bitstream is allowed to diverge from the reference.
      *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
      * - encoding: Set by user; unused for constant quantizer encoding.
      * - decoding: unused
      */
     int bit_rate_tolerance;
 
     /**
      * Global quality for codecs which cannot change it per frame.
      * This should be proportional to MPEG-1/2/4 qscale.
      * - encoding: Set by user.
      * - decoding: unused
      */
     int global_quality;
 
     /**
      * - encoding: Set by user.
      * - decoding: unused
      */
     int compression_level;
 #define FF_COMPRESSION_DEFAULT -1
 
     float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
     float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)
 
     /**
      * minimum quantizer
      * - encoding: Set by user.
      * - decoding: unused
      */
     int qmin;
 
     /**
      * maximum quantizer
      * - encoding: Set by user.
      * - decoding: unused
      */
     int qmax;
 
     /**
      * maximum quantizer difference between frames
      * - encoding: Set by user.
      * - decoding: unused
      */
     int max_qdiff;
 
     /**
      * decoder bitstream buffer size
      * - encoding: Set by user.
      * - decoding: May be set by libavcodec.
      */
     int rc_buffer_size;
 
     /**
      * ratecontrol override, see RcOverride
      * - encoding: Allocated/set/freed by user.
      * - decoding: unused
      */
     int rc_override_count;
     RcOverride *rc_override;
 
     /**
      * maximum bitrate
      * - encoding: Set by user.
      * - decoding: Set by user, may be overwritten by libavcodec.
      */
     int64_t rc_max_rate;
 
     /**
      * minimum bitrate
      * - encoding: Set by user.
      * - decoding: unused
      */
     int64_t rc_min_rate;
 
     /**
      * Ratecontrol attempt to use, at maximum, <value> of what can be used without an underflow.
      * - encoding: Set by user.
      * - decoding: unused.
      */
     float rc_max_available_vbv_use;
 
     /**
      * Ratecontrol attempt to use, at least, <value> times the amount needed to prevent a vbv overflow.
      * - encoding: Set by user.
      * - decoding: unused.
      */
     float rc_min_vbv_overflow_use;
 
     /**
      * Number of bits which should be loaded into the rc buffer before decoding starts.
      * - encoding: Set by user.
      * - decoding: unused
      */
     int rc_initial_buffer_occupancy;
 
     /**
      * trellis RD quantization
      * - encoding: Set by user.
      * - decoding: unused
      */
     int trellis;
 
     /**
      * pass1 encoding statistics output buffer
      * - encoding: Set by libavcodec.
      * - decoding: unused
      */
     char *stats_out;
 
     /**
      * pass2 encoding statistics input buffer
      * Concatenated stuff from stats_out of pass1 should be placed here.
      * - encoding: Allocated/set/freed by user.
      * - decoding: unused
      */
     char *stats_in;
 
     /**
      * Work around bugs in encoders which sometimes cannot be detected automatically.
      * - encoding: Set by user
      * - decoding: Set by user
      */
     int workaround_bugs;
 #define FF_BUG_AUTODETECT       1  ///< autodetection
 #define FF_BUG_XVID_ILACE       4
 #define FF_BUG_UMP4             8
 #define FF_BUG_NO_PADDING       16
 #define FF_BUG_AMV              32
 #define FF_BUG_QPEL_CHROMA      64
 #define FF_BUG_STD_QPEL         128
 #define FF_BUG_QPEL_CHROMA2     256
 #define FF_BUG_DIRECT_BLOCKSIZE 512
 #define FF_BUG_EDGE             1024
 #define FF_BUG_HPEL_CHROMA      2048
 #define FF_BUG_DC_CLIP          4096
 #define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
 #define FF_BUG_TRUNCATED       16384
 #define FF_BUG_IEDGE           32768
 
     /**
      * strictly follow the standard (MPEG-4, ...).
      * - encoding: Set by user.
      * - decoding: Set by user.
      * Setting this to STRICT or higher means the encoder and decoder will
      * generally do stupid things, whereas setting it to unofficial or lower
      * will mean the encoder might produce output that is not supported by all
      * spec-compliant decoders. Decoders don't differentiate between normal,
      * unofficial and experimental (that is, they always try to decode things
      * when they can) unless they are explicitly asked to behave stupidly
      * (=strictly conform to the specs)
      * This may only be set to one of the FF_COMPLIANCE_* values in defs.h.
      */
     int strict_std_compliance;
 
     /**
      * error concealment flags
      * - encoding: unused
      * - decoding: Set by user.
      */
     int error_concealment;
 #define FF_EC_GUESS_MVS   1
 #define FF_EC_DEBLOCK     2
 #define FF_EC_FAVOR_INTER 256
 
     /**
      * debug
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int debug;
 #define FF_DEBUG_PICT_INFO   1
 #define FF_DEBUG_RC          2
 #define FF_DEBUG_BITSTREAM   4
 #define FF_DEBUG_MB_TYPE     8
 #define FF_DEBUG_QP          16
 #define FF_DEBUG_DCT_COEFF   0x00000040
 #define FF_DEBUG_SKIP        0x00000080
 #define FF_DEBUG_STARTCODE   0x00000100
 #define FF_DEBUG_ER          0x00000400
 #define FF_DEBUG_MMCO        0x00000800
 #define FF_DEBUG_BUGS        0x00001000
 #define FF_DEBUG_BUFFERS     0x00008000
 #define FF_DEBUG_THREADS     0x00010000
 #define FF_DEBUG_GREEN_MD    0x00800000
 #define FF_DEBUG_NOMC        0x01000000
 
     /**
      * Error recognition; may misdetect some more or less valid parts as errors.
      * This is a bitfield of the AV_EF_* values defined in defs.h.
      *
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int err_recognition;
 
     /**
      * Hardware accelerator in use
      * - encoding: unused.
      * - decoding: Set by libavcodec
      */
     const struct AVHWAccel *hwaccel;
 
     /**
      * Legacy hardware accelerator context.
      *
      * For some hardware acceleration methods, the caller may use this field to
      * signal hwaccel-specific data to the codec. The struct pointed to by this
      * pointer is hwaccel-dependent and defined in the respective header. Please
      * refer to the FFmpeg HW accelerator documentation to know how to fill
      * this.
      *
      * In most cases this field is optional - the necessary information may also
      * be provided to libavcodec through @ref hw_frames_ctx or @ref
      * hw_device_ctx (see avcodec_get_hw_config()). However, in some cases it
      * may be the only method of signalling some (optional) information.
      *
      * The struct and its contents are owned by the caller.
      *
      * - encoding: May be set by the caller before avcodec_open2(). Must remain
      *             valid until avcodec_free_context().
      * - decoding: May be set by the caller in the get_format() callback.
      *             Must remain valid until the next get_format() call,
      *             or avcodec_free_context() (whichever comes first).
      */
     void *hwaccel_context;
 
     /**
      * A reference to the AVHWFramesContext describing the input (for encoding)
      * or output (decoding) frames. The reference is set by the caller and
      * afterwards owned (and freed) by libavcodec - it should never be read by
      * the caller after being set.
      *
      * - decoding: This field should be set by the caller from the get_format()
      *             callback. The previous reference (if any) will always be
      *             unreffed by libavcodec before the get_format() call.
      *
      *             If the default get_buffer2() is used with a hwaccel pixel
      *             format, then this AVHWFramesContext will be used for
      *             allocating the frame buffers.
      *
      * - encoding: For hardware encoders configured to use a hwaccel pixel
      *             format, this field should be set by the caller to a reference
      *             to the AVHWFramesContext describing input frames.
      *             AVHWFramesContext.format must be equal to
      *             AVCodecContext.pix_fmt.
      *
      *             This field should be set before avcodec_open2() is called.
      */
     AVBufferRef *hw_frames_ctx;
 
     /**
      * A reference to the AVHWDeviceContext describing the device which will
      * be used by a hardware encoder/decoder.  The reference is set by the
      * caller and afterwards owned (and freed) by libavcodec.
      *
      * This should be used if either the codec device does not require
      * hardware frames or any that are used are to be allocated internally by
      * libavcodec.  If the user wishes to supply any of the frames used as
      * encoder input or decoder output then hw_frames_ctx should be used
      * instead.  When hw_frames_ctx is set in get_format() for a decoder, this
      * field will be ignored while decoding the associated stream segment, but
      * may again be used on a following one after another get_format() call.
      *
      * For both encoders and decoders this field should be set before
      * avcodec_open2() is called and must not be written to thereafter.
      *
      * Note that some decoders may require this field to be set initially in
      * order to support hw_frames_ctx at all - in that case, all frames
      * contexts used must be created on the same device.
      */
     AVBufferRef *hw_device_ctx;
 
     /**
      * Bit set of AV_HWACCEL_FLAG_* flags, which affect hardware accelerated
      * decoding (if active).
      * - encoding: unused
      * - decoding: Set by user (either before avcodec_open2(), or in the
      *             AVCodecContext.get_format callback)
      */
     int hwaccel_flags;
 
     /**
      * Video decoding only.  Sets the number of extra hardware frames which
      * the decoder will allocate for use by the caller.  This must be set
      * before avcodec_open2() is called.
      *
      * Some hardware decoders require all frames that they will use for
      * output to be defined in advance before decoding starts.  For such
      * decoders, the hardware frame pool must therefore be of a fixed size.
      * The extra frames set here are on top of any number that the decoder
      * needs internally in order to operate normally (for example, frames
      * used as reference pictures).
      */
     int extra_hw_frames;
 
     /**
      * error
      * - encoding: Set by libavcodec if flags & AV_CODEC_FLAG_PSNR.
      * - decoding: unused
      */
     uint64_t error[AV_NUM_DATA_POINTERS];
 
     /**
      * DCT algorithm, see FF_DCT_* below
      * - encoding: Set by user.
      * - decoding: unused
      */
     int dct_algo;
 #define FF_DCT_AUTO    0
 #define FF_DCT_FASTINT 1
 #define FF_DCT_INT     2
 #define FF_DCT_MMX     3
 #define FF_DCT_ALTIVEC 5
 #define FF_DCT_FAAN    6
 
     /**
      * IDCT algorithm, see FF_IDCT_* below.
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int idct_algo;
 #define FF_IDCT_AUTO          0
 #define FF_IDCT_INT           1
 #define FF_IDCT_SIMPLE        2
 #define FF_IDCT_SIMPLEMMX     3
 #define FF_IDCT_ARM           7
 #define FF_IDCT_ALTIVEC       8
 #define FF_IDCT_SIMPLEARM     10
 #define FF_IDCT_XVID          14
 #define FF_IDCT_SIMPLEARMV5TE 16
 #define FF_IDCT_SIMPLEARMV6   17
 #define FF_IDCT_FAAN          20
 #define FF_IDCT_SIMPLENEON    22
 #define FF_IDCT_SIMPLEAUTO    128
 
     /**
      * bits per sample/pixel from the demuxer (needed for huffyuv).
      * - encoding: Set by libavcodec.
      * - decoding: Set by user.
      */
      int bits_per_coded_sample;
 
     /**
      * Bits per sample/pixel of internal libavcodec pixel/sample format.
      * - encoding: set by user.
      * - decoding: set by libavcodec.
      */
     int bits_per_raw_sample;
 
     /**
      * thread count
      * is used to decide how many independent tasks should be passed to execute()
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     int thread_count;
 
     /**
      * Which multithreading methods to use.
      * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
      * so clients which cannot provide future frames should not use it.
      *
      * - encoding: Set by user, otherwise the default is used.
      * - decoding: Set by user, otherwise the default is used.
      */
     int thread_type;
 #define FF_THREAD_FRAME   1 ///< Decode more than one frame at once
 #define FF_THREAD_SLICE   2 ///< Decode more than one part of a single frame at once
 
     /**
      * Which multithreading methods are in use by the codec.
      * - encoding: Set by libavcodec.
      * - decoding: Set by libavcodec.
      */
     int active_thread_type;
 
     /**
      * The codec may call this to execute several independent things.
      * It will return only after finishing all tasks.
      * The user may replace this with some multithreaded implementation,
      * the default implementation will execute the parts serially.
      * @param count the number of things to execute
      * - encoding: Set by libavcodec, user can override.
      * - decoding: Set by libavcodec, user can override.
      */
     int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void *arg2, int *ret, int count, int size);
 
     /**
      * The codec may call this to execute several independent things.
      * It will return only after finishing all tasks.
      * The user may replace this with some multithreaded implementation,
      * the default implementation will execute the parts serially.
      * @param c context passed also to func
      * @param count the number of things to execute
      * @param arg2 argument passed unchanged to func
      * @param ret return values of executed functions, must have space for "count" values. May be NULL.
      * @param func function that will be called count times, with jobnr from 0 to count-1.
      *             threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS and so that no
      *             two instances of func executing at the same time will have the same threadnr.
      * @return always 0 currently, but code should handle a future improvement where when any call to func
      *         returns < 0 no further calls to func may be done and < 0 is returned.
      * - encoding: Set by libavcodec, user can override.
      * - decoding: Set by libavcodec, user can override.
      */
     int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);
 
     /**
      * profile
      * - encoding: Set by user.
      * - decoding: Set by libavcodec.
      * See the AV_PROFILE_* defines in defs.h.
      */
      int profile;
 #if FF_API_FF_PROFILE_LEVEL
     /** @deprecated The following defines are deprecated; use AV_PROFILE_*
      * in defs.h instead. */
 #define FF_PROFILE_UNKNOWN -99
 #define FF_PROFILE_RESERVED -100
 
 #define FF_PROFILE_AAC_MAIN 0
 #define FF_PROFILE_AAC_LOW  1
 #define FF_PROFILE_AAC_SSR  2
 #define FF_PROFILE_AAC_LTP  3
 #define FF_PROFILE_AAC_HE   4
 #define FF_PROFILE_AAC_HE_V2 28
 #define FF_PROFILE_AAC_LD   22
 #define FF_PROFILE_AAC_ELD  38
 #define FF_PROFILE_MPEG2_AAC_LOW 128
 #define FF_PROFILE_MPEG2_AAC_HE  131
 
 #define FF_PROFILE_DNXHD         0
 #define FF_PROFILE_DNXHR_LB      1
 #define FF_PROFILE_DNXHR_SQ      2
 #define FF_PROFILE_DNXHR_HQ      3
 #define FF_PROFILE_DNXHR_HQX     4
 #define FF_PROFILE_DNXHR_444     5
 
 #define FF_PROFILE_DTS                20
 #define FF_PROFILE_DTS_ES             30
 #define FF_PROFILE_DTS_96_24          40
 #define FF_PROFILE_DTS_HD_HRA         50
 #define FF_PROFILE_DTS_HD_MA          60
 #define FF_PROFILE_DTS_EXPRESS        70
 #define FF_PROFILE_DTS_HD_MA_X        61
 #define FF_PROFILE_DTS_HD_MA_X_IMAX   62
 
 
 #define FF_PROFILE_EAC3_DDP_ATMOS         30
 
 #define FF_PROFILE_TRUEHD_ATMOS           30
 
 #define FF_PROFILE_MPEG2_422    0
 #define FF_PROFILE_MPEG2_HIGH   1
 #define FF_PROFILE_MPEG2_SS     2
 #define FF_PROFILE_MPEG2_SNR_SCALABLE  3
 #define FF_PROFILE_MPEG2_MAIN   4
 #define FF_PROFILE_MPEG2_SIMPLE 5
 
 #define FF_PROFILE_H264_CONSTRAINED  (1<<9)  // 8+1; constraint_set1_flag
 #define FF_PROFILE_H264_INTRA        (1<<11) // 8+3; constraint_set3_flag
 
 #define FF_PROFILE_H264_BASELINE             66
 #define FF_PROFILE_H264_CONSTRAINED_BASELINE (66|FF_PROFILE_H264_CONSTRAINED)
 #define FF_PROFILE_H264_MAIN                 77
 #define FF_PROFILE_H264_EXTENDED             88
 #define FF_PROFILE_H264_HIGH                 100
 #define FF_PROFILE_H264_HIGH_10              110
 #define FF_PROFILE_H264_HIGH_10_INTRA        (110|FF_PROFILE_H264_INTRA)
 #define FF_PROFILE_H264_MULTIVIEW_HIGH       118
 #define FF_PROFILE_H264_HIGH_422             122
 #define FF_PROFILE_H264_HIGH_422_INTRA       (122|FF_PROFILE_H264_INTRA)
 #define FF_PROFILE_H264_STEREO_HIGH          128
 #define FF_PROFILE_H264_HIGH_444             144
 #define FF_PROFILE_H264_HIGH_444_PREDICTIVE  244
 #define FF_PROFILE_H264_HIGH_444_INTRA       (244|FF_PROFILE_H264_INTRA)
 #define FF_PROFILE_H264_CAVLC_444            44
 
 #define FF_PROFILE_VC1_SIMPLE   0
 #define FF_PROFILE_VC1_MAIN     1
 #define FF_PROFILE_VC1_COMPLEX  2
 #define FF_PROFILE_VC1_ADVANCED 3
 
 #define FF_PROFILE_MPEG4_SIMPLE                     0
 #define FF_PROFILE_MPEG4_SIMPLE_SCALABLE            1
 #define FF_PROFILE_MPEG4_CORE                       2
 #define FF_PROFILE_MPEG4_MAIN                       3
 #define FF_PROFILE_MPEG4_N_BIT                      4
 #define FF_PROFILE_MPEG4_SCALABLE_TEXTURE           5
 #define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION      6
 #define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE     7
 #define FF_PROFILE_MPEG4_HYBRID                     8
 #define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME         9
 #define FF_PROFILE_MPEG4_CORE_SCALABLE             10
 #define FF_PROFILE_MPEG4_ADVANCED_CODING           11
 #define FF_PROFILE_MPEG4_ADVANCED_CORE             12
 #define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
 #define FF_PROFILE_MPEG4_SIMPLE_STUDIO             14
 #define FF_PROFILE_MPEG4_ADVANCED_SIMPLE           15
 
 #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0   1
 #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1   2
 #define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION  32768
 #define FF_PROFILE_JPEG2000_DCINEMA_2K              3
 #define FF_PROFILE_JPEG2000_DCINEMA_4K              4
 
 #define FF_PROFILE_VP9_0                            0
 #define FF_PROFILE_VP9_1                            1
 #define FF_PROFILE_VP9_2                            2
 #define FF_PROFILE_VP9_3                            3
 
 #define FF_PROFILE_HEVC_MAIN                        1
 #define FF_PROFILE_HEVC_MAIN_10                     2
 #define FF_PROFILE_HEVC_MAIN_STILL_PICTURE          3
 #define FF_PROFILE_HEVC_REXT                        4
 #define FF_PROFILE_HEVC_SCC                         9
 
 #define FF_PROFILE_VVC_MAIN_10                      1
 #define FF_PROFILE_VVC_MAIN_10_444                 33
 
 #define FF_PROFILE_AV1_MAIN                         0
 #define FF_PROFILE_AV1_HIGH                         1
 #define FF_PROFILE_AV1_PROFESSIONAL                 2
 
 #define FF_PROFILE_MJPEG_HUFFMAN_BASELINE_DCT            0xc0
 #define FF_PROFILE_MJPEG_HUFFMAN_EXTENDED_SEQUENTIAL_DCT 0xc1
 #define FF_PROFILE_MJPEG_HUFFMAN_PROGRESSIVE_DCT         0xc2
 #define FF_PROFILE_MJPEG_HUFFMAN_LOSSLESS                0xc3
 #define FF_PROFILE_MJPEG_JPEG_LS                         0xf7
 
 #define FF_PROFILE_SBC_MSBC                         1
 
 #define FF_PROFILE_PRORES_PROXY     0
 #define FF_PROFILE_PRORES_LT        1
 #define FF_PROFILE_PRORES_STANDARD  2
 #define FF_PROFILE_PRORES_HQ        3
 #define FF_PROFILE_PRORES_4444      4
 #define FF_PROFILE_PRORES_XQ        5
 
 #define FF_PROFILE_ARIB_PROFILE_A 0
 #define FF_PROFILE_ARIB_PROFILE_C 1
 
 #define FF_PROFILE_KLVA_SYNC 0
 #define FF_PROFILE_KLVA_ASYNC 1
 
 #define FF_PROFILE_EVC_BASELINE             0
 #define FF_PROFILE_EVC_MAIN                 1
 #endif
 
     /**
      * Encoding level descriptor.
      * - encoding: Set by user, corresponds to a specific level defined by the
      *   codec, usually corresponding to the profile level, if not specified it
      *   is set to FF_LEVEL_UNKNOWN.
      * - decoding: Set by libavcodec.
      * See AV_LEVEL_* in defs.h.
      */
      int level;
 #if FF_API_FF_PROFILE_LEVEL
     /** @deprecated The following define is deprecated; use AV_LEVEL_UNKOWN
      * in defs.h instead. */
 #define FF_LEVEL_UNKNOWN -99
 #endif
 
     /**
      * Properties of the stream that gets decoded
      * - encoding: unused
      * - decoding: set by libavcodec
      */
     unsigned properties;
 #define FF_CODEC_PROPERTY_LOSSLESS        0x00000001
 #define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002
 #define FF_CODEC_PROPERTY_FILM_GRAIN      0x00000004
 
     /**
      * Skip loop filtering for selected frames.
      * - encoding: unused
      * - decoding: Set by user.
      */
     enum AVDiscard skip_loop_filter;
 
     /**
      * Skip IDCT/dequantization for selected frames.
      * - encoding: unused
      * - decoding: Set by user.
      */
     enum AVDiscard skip_idct;
 
     /**
      * Skip decoding for selected frames.
      * - encoding: unused
      * - decoding: Set by user.
      */
     enum AVDiscard skip_frame;
 
     /**
      * Skip processing alpha if supported by codec.
      * Note that if the format uses pre-multiplied alpha (common with VP6,
      * and recommended due to better video quality/compression)
      * the image will look as if alpha-blended onto a black background.
      * However for formats that do not use pre-multiplied alpha
      * there might be serious artefacts (though e.g. libswscale currently
      * assumes pre-multiplied alpha anyway).
      *
      * - decoding: set by user
      * - encoding: unused
      */
     int skip_alpha;
 
     /**
      * Number of macroblock rows at the top which are skipped.
      * - encoding: unused
      * - decoding: Set by user.
      */
     int skip_top;
 
     /**
      * Number of macroblock rows at the bottom which are skipped.
      * - encoding: unused
      * - decoding: Set by user.
      */
     int skip_bottom;
 
     /**
      * low resolution decoding, 1-> 1/2 size, 2->1/4 size
      * - encoding: unused
      * - decoding: Set by user.
      */
      int lowres;
 
     /**
      * AVCodecDescriptor
      * - encoding: unused.
      * - decoding: set by libavcodec.
      */
     const struct AVCodecDescriptor *codec_descriptor;
 
     /**
      * Character encoding of the input subtitles file.
      * - decoding: set by user
      * - encoding: unused
      */
     char *sub_charenc;
 
     /**
      * Subtitles character encoding mode. Formats or codecs might be adjusting
      * this setting (if they are doing the conversion themselves for instance).
      * - decoding: set by libavcodec
      * - encoding: unused
      */
     int sub_charenc_mode;
 #define FF_SUB_CHARENC_MODE_DO_NOTHING  -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8, or the codec is bitmap for instance)
 #define FF_SUB_CHARENC_MODE_AUTOMATIC    0  ///< libavcodec will select the mode itself
 #define FF_SUB_CHARENC_MODE_PRE_DECODER  1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the decoder, requires iconv
 #define FF_SUB_CHARENC_MODE_IGNORE       2  ///< neither convert the subtitles, nor check them for valid UTF-8
 
     /**
      * Header containing style information for text subtitles.
      * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
      * [Script Info] and [V4+ Styles] section, plus the [Events] line and
      * the Format line following. It shouldn't include any Dialogue line.
      * - encoding: Set/allocated/freed by user (before avcodec_open2())
      * - decoding: Set/allocated/freed by libavcodec (by avcodec_open2())
      */
     int subtitle_header_size;
     uint8_t *subtitle_header;
 
     /**
      * dump format separator.
      * can be ", " or "\n      " or anything else
      * - encoding: Set by user.
      * - decoding: Set by user.
      */
     uint8_t *dump_separator;
 
     /**
      * ',' separated list of allowed decoders.
      * If NULL then all are allowed
      * - encoding: unused
      * - decoding: set by user
      */
     char *codec_whitelist;
 
     /**
      * Additional data associated with the entire coded stream.
      *
      * - decoding: may be set by user before calling avcodec_open2().
      * - encoding: may be set by libavcodec after avcodec_open2().
      */
     AVPacketSideData *coded_side_data;
     int            nb_coded_side_data;
 
     /**
      * Bit set of AV_CODEC_EXPORT_DATA_* flags, which affects the kind of
      * metadata exported in frame, packet, or coded stream side data by
      * decoders and encoders.
      *
      * - decoding: set by user
      * - encoding: set by user
      */
     int export_side_data;
 
     /**
      * The number of pixels per image to maximally accept.
      *
      * - decoding: set by user
      * - encoding: set by user
      */
     int64_t max_pixels;
 
     /**
      * Video decoding only. Certain video codecs support cropping, meaning that
      * only a sub-rectangle of the decoded frame is intended for display.  This
      * option controls how cropping is handled by libavcodec.
      *
      * When set to 1 (the default), libavcodec will apply cropping internally.
      * I.e. it will modify the output frame width/height fields and offset the
      * data pointers (only by as much as possible while preserving alignment, or
      * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
      * the frames output by the decoder refer only to the cropped area. The
      * crop_* fields of the output frames will be zero.
      *
      * When set to 0, the width/height fields of the output frames will be set
      * to the coded dimensions and the crop_* fields will describe the cropping
      * rectangle. Applying the cropping is left to the caller.
      *
      * @warning When hardware acceleration with opaque output frames is used,
      * libavcodec is unable to apply cropping from the top/left border.
      *
      * @note when this option is set to zero, the width/height fields of the
      * AVCodecContext and output AVFrames have different meanings. The codec
      * context fields store display dimensions (with the coded dimensions in
      * coded_width/height), while the frame fields store the coded dimensions
      * (with the display dimensions being determined by the crop_* fields).
      */
     int apply_cropping;
 
     /**
      * The percentage of damaged samples to discard a frame.
      *
      * - decoding: set by user
      * - encoding: unused
      */
     int discard_damaged_percentage;
 
     /**
      * The number of samples per frame to maximally accept.
      *
      * - decoding: set by user
      * - encoding: set by user
      */
     int64_t max_samples;
 
     /**
      * This callback is called at the beginning of each packet to get a data
      * buffer for it.
      *
      * The following field will be set in the packet before this callback is
      * called:
      * - size
      * This callback must use the above value to calculate the required buffer size,
      * which must padded by at least AV_INPUT_BUFFER_PADDING_SIZE bytes.
      *
      * In some specific cases, the encoder may not use the entire buffer allocated by this
      * callback. This will be reflected in the size value in the packet once returned by
      * avcodec_receive_packet().
      *
      * This callback must fill the following fields in the packet:
      * - data: alignment requirements for AVPacket apply, if any. Some architectures and
      *   encoders may benefit from having aligned data.
      * - buf: must contain a pointer to an AVBufferRef structure. The packet's
      *   data pointer must be contained in it. See: av_buffer_create(), av_buffer_alloc(),
      *   and av_buffer_ref().
      *
      * If AV_CODEC_CAP_DR1 is not set then get_encode_buffer() must call
      * avcodec_default_get_encode_buffer() instead of providing a buffer allocated by
      * some other means.
      *
      * The flags field may contain a combination of AV_GET_ENCODE_BUFFER_FLAG_ flags.
      * They may be used for example to hint what use the buffer may get after being
      * created.
      * Implementations of this callback may ignore flags they don't understand.
      * If AV_GET_ENCODE_BUFFER_FLAG_REF is set in flags then the packet may be reused
      * (read and/or written to if it is writable) later by libavcodec.
      *
      * This callback must be thread-safe, as when frame threading is used, it may
      * be called from multiple threads simultaneously.
      *
      * @see avcodec_default_get_encode_buffer()
      *
      * - encoding: Set by libavcodec, user can override.
      * - decoding: unused
      */
     int (*get_encode_buffer)(struct AVCodecContext *s, AVPacket *pkt, int flags);
 
     /**
      * Frame counter, set by libavcodec.
      *
      * - decoding: total number of frames returned from the decoder so far.
      * - encoding: total number of frames passed to the encoder so far.
      *
      *   @note the counter is not incremented if encoding/decoding resulted in
      *   an error.
      */
     int64_t frame_num;
 
     /**
      * Decoding only. May be set by the caller before avcodec_open2() to an
      * av_malloc()'ed array (or via AVOptions). Owned and freed by the decoder
      * afterwards.
      *
      * Side data attached to decoded frames may come from several sources:
      * 1. coded_side_data, which the decoder will for certain types translate
      *    from packet-type to frame-type and attach to frames;
      * 2. side data attached to an AVPacket sent for decoding (same
      *    considerations as above);
      * 3. extracted from the coded bytestream.
      * The first two cases are supplied by the caller and typically come from a
      * container.
      *
      * This array configures decoder behaviour in cases when side data of the
      * same type is present both in the coded bytestream and in the
      * user-supplied side data (items 1. and 2. above). In all cases, at most
      * one instance of each side data type will be attached to output frames. By
      * default it will be the bytestream side data. Adding an
      * AVPacketSideDataType value to this array will flip the preference for
      * this type, thus making the decoder prefer user-supplied side data over
      * bytestream. In case side data of the same type is present both in
      * coded_data and attacked to a packet, the packet instance always has
      * priority.
      *
      * The array may also contain a single -1, in which case the preference is
      * switched for all side data types.
      */
     int        *side_data_prefer_packet;
     /**
      * Number of entries in side_data_prefer_packet.
      */
     unsigned nb_side_data_prefer_packet;
 
     /**
      * Array containing static side data, such as HDR10 CLL / MDCV structures.
      * Side data entries should be allocated by usage of helpers defined in
      * libavutil/frame.h.
      *
      * - encoding: may be set by user before calling avcodec_open2() for
      *             encoder configuration. Afterwards owned and freed by the
      *             encoder.
      * - decoding: unused
      */
     AVFrameSideData  **decoded_side_data;
     int             nb_decoded_side_data;
 } AVCodecContext;
 
 /**
  * @defgroup lavc_hwaccel AVHWAccel
  *
  * @note  Nothing in this structure should be accessed by the user.  At some
  *        point in future it will not be externally visible at all.
  *
  * @{
  */
 typedef struct AVHWAccel {
     /**
      * Name of the hardware accelerated codec.
      * The name is globally unique among encoders and among decoders (but an
      * encoder and a decoder can share the same name).
      */
     const char *name;
 
     /**
      * Type of codec implemented by the hardware accelerator.
      *
      * See AVMEDIA_TYPE_xxx
      */
     enum AVMediaType type;
 
     /**
      * Codec implemented by the hardware accelerator.
      *
      * See AV_CODEC_ID_xxx
      */
     enum AVCodecID id;
 
     /**
      * Supported pixel format.
      *
      * Only hardware accelerated formats are supported here.
      */
     enum AVPixelFormat pix_fmt;
 
     /**
      * Hardware accelerated codec capabilities.
      * see AV_HWACCEL_CODEC_CAP_*
      */
     int capabilities;
 } AVHWAccel;
 
 /**
  * HWAccel is experimental and is thus avoided in favor of non experimental
  * codecs
  */
 #define AV_HWACCEL_CODEC_CAP_EXPERIMENTAL 0x0200
 
 /**
  * Hardware acceleration should be used for decoding even if the codec level
  * used is unknown or higher than the maximum supported level reported by the
  * hardware driver.
  *
  * It's generally a good idea to pass this flag unless you have a specific
  * reason not to, as hardware tends to under-report supported levels.
  */
 #define AV_HWACCEL_FLAG_IGNORE_LEVEL (1 << 0)
 
 /**
  * Hardware acceleration can output YUV pixel formats with a different chroma
  * sampling than 4:2:0 and/or other than 8 bits per component.
  */
 #define AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH (1 << 1)
 
 /**
  * Hardware acceleration should still be attempted for decoding when the
  * codec profile does not match the reported capabilities of the hardware.
  *
  * For example, this can be used to try to decode baseline profile H.264
  * streams in hardware - it will often succeed, because many streams marked
  * as baseline profile actually conform to constrained baseline profile.
  *
  * @warning If the stream is actually not supported then the behaviour is
  *          undefined, and may include returning entirely incorrect output
  *          while indicating success.
  */
 #define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)
 
 /**
  * Some hardware decoders (namely nvdec) can either output direct decoder
  * surfaces, or make an on-device copy and return said copy.
  * There is a hard limit on how many decoder surfaces there can be, and it
  * cannot be accurately guessed ahead of time.
  * For some processing chains, this can be okay, but others will run into the
  * limit and in turn produce very confusing errors that require fine tuning of
  * more or less obscure options by the user, or in extreme cases cannot be
  * resolved at all without inserting an avfilter that forces a copy.
  *
  * Thus, the hwaccel will by default make a copy for safety and resilience.
  * If a users really wants to minimize the amount of copies, they can set this
  * flag and ensure their processing chain does not exhaust the surface pool.
  */
 #define AV_HWACCEL_FLAG_UNSAFE_OUTPUT (1 << 3)
 
 /**
  * @}
  */
 
 enum AVSubtitleType {
     SUBTITLE_NONE,
 
     SUBTITLE_BITMAP,                ///< A bitmap, pict will be set
 
     /**
      * Plain text, the text field must be set by the decoder and is
      * authoritative. ass and pict fields may contain approximations.
      */
     SUBTITLE_TEXT,
 
     /**
      * Formatted text, the ass field must be set by the decoder and is
      * authoritative. pict and text fields may contain approximations.
      */
     SUBTITLE_ASS,
 };
 
 #define AV_SUBTITLE_FLAG_FORCED 0x00000001
 
 typedef struct AVSubtitleRect {
     int x;         ///< top left corner  of pict, undefined when pict is not set
     int y;         ///< top left corner  of pict, undefined when pict is not set
     int w;         ///< width            of pict, undefined when pict is not set
     int h;         ///< height           of pict, undefined when pict is not set
     int nb_colors; ///< number of colors in pict, undefined when pict is not set
 
     /**
      * data+linesize for the bitmap of this subtitle.
      * Can be set for text/ass as well once they are rendered.
      */
     uint8_t *data[4];
     int linesize[4];
 
     int flags;
     enum AVSubtitleType type;
 
     char *text;                     ///< 0 terminated plain UTF-8 text
 
     /**
      * 0 terminated ASS/SSA compatible event line.
      * The presentation of this is unaffected by the other values in this
      * struct.
      */
     char *ass;
 } AVSubtitleRect;
 
 typedef struct AVSubtitle {
     uint16_t format; /* 0 = graphics */
     uint32_t start_display_time; /* relative to packet pts, in ms */
     uint32_t end_display_time; /* relative to packet pts, in ms */
     unsigned num_rects;
     AVSubtitleRect **rects;
     int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
 } AVSubtitle;
 
 /**
  * Return the LIBAVCODEC_VERSION_INT constant.
  */
 unsigned avcodec_version(void);
 
 /**
  * Return the libavcodec build-time configuration.
  */
 const char *avcodec_configuration(void);
 
 /**
  * Return the libavcodec license.
  */
 const char *avcodec_license(void);
 
 /**
  * Allocate an AVCodecContext and set its fields to default values. The
  * resulting struct should be freed with avcodec_free_context().
  *
  * @param codec if non-NULL, allocate private data and initialize defaults
  *              for the given codec. It is illegal to then call avcodec_open2()
  *              with a different codec.
  *              If NULL, then the codec-specific defaults won't be initialized,
  *              which may result in suboptimal default settings (this is
  *              important mainly for encoders, e.g. libx264).
  *
  * @return An AVCodecContext filled with default values or NULL on failure.
  */
 AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);
 
 /**
  * Free the codec context and everything associated with it and write NULL to
  * the provided pointer.
  */
 void avcodec_free_context(AVCodecContext **avctx);
 
 /**
  * Get the AVClass for AVCodecContext. It can be used in combination with
  * AV_OPT_SEARCH_FAKE_OBJ for examining options.
  *
  * @see av_opt_find().
  */
 const AVClass *avcodec_get_class(void);
 
 /**
  * Get the AVClass for AVSubtitleRect. It can be used in combination with
  * AV_OPT_SEARCH_FAKE_OBJ for examining options.
  *
  * @see av_opt_find().
  */
 const AVClass *avcodec_get_subtitle_rect_class(void);
 
 /**
  * Fill the parameters struct based on the values from the supplied codec
  * context. Any allocated fields in par are freed and replaced with duplicates
  * of the corresponding fields in codec.
  *
  * @return >= 0 on success, a negative AVERROR code on failure
  */
 int avcodec_parameters_from_context(struct AVCodecParameters *par,
                                     const AVCodecContext *codec);
 
 /**
  * Fill the codec context based on the values from the supplied codec
  * parameters. Any allocated fields in codec that have a corresponding field in
  * par are freed and replaced with duplicates of the corresponding field in par.
  * Fields in codec that do not have a counterpart in par are not touched.
  *
  * @return >= 0 on success, a negative AVERROR code on failure.
  */
 int avcodec_parameters_to_context(AVCodecContext *codec,
                                   const struct AVCodecParameters *par);
 
 /**
  * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
  * function the context has to be allocated with avcodec_alloc_context3().
  *
  * The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
  * avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
  * retrieving a codec.
  *
  * Depending on the codec, you might need to set options in the codec context
  * also for decoding (e.g. width, height, or the pixel or audio sample format in
  * the case the information is not available in the bitstream, as when decoding
  * raw audio or video).
  *
  * Options in the codec context can be set either by setting them in the options
  * AVDictionary, or by setting the values in the context itself, directly or by
  * using the av_opt_set() API before calling this function.
  *
  * Example:
  * @code
  * av_dict_set(&opts, "b", "2.5M", 0);
  * codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  * if (!codec)
  *     exit(1);
  *
  * context = avcodec_alloc_context3(codec);
  *
  * if (avcodec_open2(context, codec, opts) < 0)
  *     exit(1);
  * @endcode
  *
  * In the case AVCodecParameters are available (e.g. when demuxing a stream
  * using libavformat, and accessing the AVStream contained in the demuxer), the
  * codec parameters can be copied to the codec context using
  * avcodec_parameters_to_context(), as in the following example:
  *
  * @code
  * AVStream *stream = ...;
  * context = avcodec_alloc_context3(codec);
  * if (avcodec_parameters_to_context(context, stream->codecpar) < 0)
  *     exit(1);
  * if (avcodec_open2(context, codec, NULL) < 0)
  *     exit(1);
  * @endcode
  *
  * @note Always call this function before using decoding routines (such as
  * @ref avcodec_receive_frame()).
  *
  * @param avctx The context to initialize.
  * @param codec The codec to open this context for. If a non-NULL codec has been
  *              previously passed to avcodec_alloc_context3() or
  *              for this context, then this parameter MUST be either NULL or
  *              equal to the previously passed codec.
  * @param options A dictionary filled with AVCodecContext and codec-private
  *                options, which are set on top of the options already set in
  *                avctx, can be NULL. On return this object will be filled with
  *                options that were not found in the avctx codec context.
  *
  * @return zero on success, a negative value on error
  * @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(),
  *      av_dict_set(), av_opt_set(), av_opt_find(), avcodec_parameters_to_context()
  */
 int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);
 
 #if FF_API_AVCODEC_CLOSE
 /**
  * Close a given AVCodecContext and free all the data associated with it
  * (but not the AVCodecContext itself).
  *
  * Calling this function on an AVCodecContext that hasn't been opened will free
  * the codec-specific data allocated in avcodec_alloc_context3() with a non-NULL
  * codec. Subsequent calls will do nothing.
  *
  * @deprecated Do not use this function. Use avcodec_free_context() to destroy a
  * codec context (either open or closed). Opening and closing a codec context
  * multiple times is not supported anymore -- use multiple codec contexts
  * instead.
  */
 attribute_deprecated
 int avcodec_close(AVCodecContext *avctx);
 #endif
 
 /**
  * Free all allocated data in the given subtitle struct.
  *
  * @param sub AVSubtitle to free.
  */
 void avsubtitle_free(AVSubtitle *sub);
 
 /**
  * @}
  */
 
 /**
  * @addtogroup lavc_decoding
  * @{
  */
 
 /**
  * The default callback for AVCodecContext.get_buffer2(). It is made public so
  * it can be called by custom get_buffer2() implementations for decoders without
  * AV_CODEC_CAP_DR1 set.
  */
 int avcodec_default_get_buffer2(AVCodecContext *s, AVFrame *frame, int flags);
 
 /**
  * The default callback for AVCodecContext.get_encode_buffer(). It is made public so
  * it can be called by custom get_encode_buffer() implementations for encoders without
  * AV_CODEC_CAP_DR1 set.
  */
 int avcodec_default_get_encode_buffer(AVCodecContext *s, AVPacket *pkt, int flags);
 
 /**
  * Modify width and height values so that they will result in a memory
  * buffer that is acceptable for the codec if you do not use any horizontal
  * padding.
  *
  * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
  */
 void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height);
 
 /**
  * Modify width and height values so that they will result in a memory
  * buffer that is acceptable for the codec if you also ensure that all
  * line sizes are a multiple of the respective linesize_align[i].
  *
  * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
  */
 void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
                                int linesize_align[AV_NUM_DATA_POINTERS]);
 
 /**
  * Decode a subtitle message.
  * Return a negative value on error, otherwise return the number of bytes used.
  * If no subtitle could be decompressed, got_sub_ptr is zero.
  * Otherwise, the subtitle is stored in *sub.
  * Note that AV_CODEC_CAP_DR1 is not available for subtitle codecs. This is for
  * simplicity, because the performance difference is expected to be negligible
  * and reusing a get_buffer written for video codecs would probably perform badly
  * due to a potentially very different allocation pattern.
  *
  * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
  * and output. This means that for some packets they will not immediately
  * produce decoded output and need to be flushed at the end of decoding to get
  * all the decoded data. Flushing is done by calling this function with packets
  * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
  * returning subtitles. It is safe to flush even those decoders that are not
  * marked with AV_CODEC_CAP_DELAY, then no subtitles will be returned.
  *
  * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
  * before packets may be fed to the decoder.
  *
  * @param avctx the codec context
  * @param[out] sub The preallocated AVSubtitle in which the decoded subtitle will be stored,
  *                 must be freed with avsubtitle_free if *got_sub_ptr is set.
  * @param[in,out] got_sub_ptr Zero if no subtitle could be decompressed, otherwise, it is nonzero.
  * @param[in] avpkt The input AVPacket containing the input buffer.
  */
 int avcodec_decode_subtitle2(AVCodecContext *avctx, AVSubtitle *sub,
                              int *got_sub_ptr, const AVPacket *avpkt);
 
 /**
  * Supply raw packet data as input to a decoder.
  *
  * Internally, this call will copy relevant AVCodecContext fields, which can
  * influence decoding per-packet, and apply them when the packet is actually
  * decoded. (For example AVCodecContext.skip_frame, which might direct the
  * decoder to drop the frame contained by the packet sent with this function.)
  *
  * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
  *          larger than the actual read bytes because some optimized bitstream
  *          readers read 32 or 64 bits at once and could read over the end.
  *
  * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
  *       before packets may be fed to the decoder.
  *
  * @param avctx codec context
  * @param[in] avpkt The input AVPacket. Usually, this will be a single video
  *                  frame, or several complete audio frames.
  *                  Ownership of the packet remains with the caller, and the
  *                  decoder will not write to the packet. The decoder may create
  *                  a reference to the packet data (or copy it if the packet is
  *                  not reference-counted).
  *                  Unlike with older APIs, the packet is always fully consumed,
  *                  and if it contains multiple frames (e.g. some audio codecs),
  *                  will require you to call avcodec_receive_frame() multiple
  *                  times afterwards before you can send a new packet.
  *                  It can be NULL (or an AVPacket with data set to NULL and
  *                  size set to 0); in this case, it is considered a flush
  *                  packet, which signals the end of the stream. Sending the
  *                  first flush packet will return success. Subsequent ones are
  *                  unnecessary and will return AVERROR_EOF. If the decoder
  *                  still has frames buffered, it will return them after sending
  *                  a flush packet.
  *
  * @retval 0                 success
  * @retval AVERROR(EAGAIN)   input is not accepted in the current state - user
  *                           must read output with avcodec_receive_frame() (once
  *                           all output is read, the packet should be resent,
  *                           and the call will not fail with EAGAIN).
  * @retval AVERROR_EOF       the decoder has been flushed, and no new packets can be
  *                           sent to it (also returned if more than 1 flush
  *                           packet is sent)
  * @retval AVERROR(EINVAL)   codec not opened, it is an encoder, or requires flush
  * @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
  * @retval "another negative error code" legitimate decoding errors
  */
 int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt);
 
 /**
  * Return decoded output data from a decoder or encoder (when the
  * @ref AV_CODEC_FLAG_RECON_FRAME flag is used).
  *
  * @param avctx codec context
  * @param frame This will be set to a reference-counted video or audio
  *              frame (depending on the decoder type) allocated by the
  *              codec. Note that the function will always call
  *              av_frame_unref(frame) before doing anything else.
  *
  * @retval 0                success, a frame was returned
  * @retval AVERROR(EAGAIN)  output is not available in this state - user must
  *                          try to send new input
  * @retval AVERROR_EOF      the codec has been fully flushed, and there will be
  *                          no more output frames
  * @retval AVERROR(EINVAL)  codec not opened, or it is an encoder without the
  *                          @ref AV_CODEC_FLAG_RECON_FRAME flag enabled
  * @retval "other negative error code" legitimate decoding errors
  */
 int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
 
 /**
  * Supply a raw video or audio frame to the encoder. Use avcodec_receive_packet()
  * to retrieve buffered output packets.
  *
  * @param avctx     codec context
  * @param[in] frame AVFrame containing the raw audio or video frame to be encoded.
  *                  Ownership of the frame remains with the caller, and the
  *                  encoder will not write to the frame. The encoder may create
  *                  a reference to the frame data (or copy it if the frame is
  *                  not reference-counted).
  *                  It can be NULL, in which case it is considered a flush
  *                  packet.  This signals the end of the stream. If the encoder
  *                  still has packets buffered, it will return them after this
  *                  call. Once flushing mode has been entered, additional flush
  *                  packets are ignored, and sending frames will return
  *                  AVERROR_EOF.
  *
  *                  For audio:
  *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
  *                  can have any number of samples.
  *                  If it is not set, frame->nb_samples must be equal to
  *                  avctx->frame_size for all frames except the last.
  *                  The final frame may be smaller than avctx->frame_size.
  * @retval 0                 success
  * @retval AVERROR(EAGAIN)   input is not accepted in the current state - user must
  *                           read output with avcodec_receive_packet() (once all
  *                           output is read, the packet should be resent, and the
  *                           call will not fail with EAGAIN).
  * @retval AVERROR_EOF       the encoder has been flushed, and no new frames can
  *                           be sent to it
  * @retval AVERROR(EINVAL)   codec not opened, it is a decoder, or requires flush
  * @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
  * @retval "another negative error code" legitimate encoding errors
  */
 int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);
 
 /**
  * Read encoded data from the encoder.
  *
  * @param avctx codec context
  * @param avpkt This will be set to a reference-counted packet allocated by the
  *              encoder. Note that the function will always call
  *              av_packet_unref(avpkt) before doing anything else.
  * @retval 0               success
  * @retval AVERROR(EAGAIN) output is not available in the current state - user must
  *                         try to send input
  * @retval AVERROR_EOF     the encoder has been fully flushed, and there will be no
  *                         more output packets
  * @retval AVERROR(EINVAL) codec not opened, or it is a decoder
  * @retval "another negative error code" legitimate encoding errors
  */
 int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);
 
 /**
  * Create and return a AVHWFramesContext with values adequate for hardware
  * decoding. This is meant to get called from the get_format callback, and is
  * a helper for preparing a AVHWFramesContext for AVCodecContext.hw_frames_ctx.
  * This API is for decoding with certain hardware acceleration modes/APIs only.
  *
  * The returned AVHWFramesContext is not initialized. The caller must do this
  * with av_hwframe_ctx_init().
  *
  * Calling this function is not a requirement, but makes it simpler to avoid
  * codec or hardware API specific details when manually allocating frames.
  *
  * Alternatively to this, an API user can set AVCodecContext.hw_device_ctx,
  * which sets up AVCodecContext.hw_frames_ctx fully automatically, and makes
  * it unnecessary to call this function or having to care about
  * AVHWFramesContext initialization at all.
  *
  * There are a number of requirements for calling this function:
  *
  * - It must be called from get_format with the same avctx parameter that was
  *   passed to get_format. Calling it outside of get_format is not allowed, and
  *   can trigger undefined behavior.
  * - The function is not always supported (see description of return values).
  *   Even if this function returns successfully, hwaccel initialization could
  *   fail later. (The degree to which implementations check whether the stream
  *   is actually supported varies. Some do this check only after the user's
  *   get_format callback returns.)
  * - The hw_pix_fmt must be one of the choices suggested by get_format. If the
  *   user decides to use a AVHWFramesContext prepared with this API function,
  *   the user must return the same hw_pix_fmt from get_format.
  * - The device_ref passed to this function must support the given hw_pix_fmt.
  * - After calling this API function, it is the user's responsibility to
  *   initialize the AVHWFramesContext (returned by the out_frames_ref parameter),
  *   and to set AVCodecContext.hw_frames_ctx to it. If done, this must be done
  *   before returning from get_format (this is implied by the normal
  *   AVCodecContext.hw_frames_ctx API rules).
  * - The AVHWFramesContext parameters may change every time time get_format is
  *   called. Also, AVCodecContext.hw_frames_ctx is reset before get_format. So
  *   you are inherently required to go through this process again on every
  *   get_format call.
  * - It is perfectly possible to call this function without actually using
  *   the resulting AVHWFramesContext. One use-case might be trying to reuse a
  *   previously initialized AVHWFramesContext, and calling this API function
  *   only to test whether the required frame parameters have changed.
  * - Fields that use dynamically allocated values of any kind must not be set
  *   by the user unless setting them is explicitly allowed by the documentation.
  *   If the user sets AVHWFramesContext.free and AVHWFramesContext.user_opaque,
  *   the new free callback must call the potentially set previous free callback.
  *   This API call may set any dynamically allocated fields, including the free
  *   callback.
  *
  * The function will set at least the following fields on AVHWFramesContext
  * (potentially more, depending on hwaccel API):
  *
  * - All fields set by av_hwframe_ctx_alloc().
  * - Set the format field to hw_pix_fmt.
  * - Set the sw_format field to the most suited and most versatile format. (An
  *   implication is that this will prefer generic formats over opaque formats
  *   with arbitrary restrictions, if possible.)
  * - Set the width/height fields to the coded frame size, rounded up to the
  *   API-specific minimum alignment.
  * - Only _if_ the hwaccel requires a pre-allocated pool: set the initial_pool_size
  *   field to the number of maximum reference surfaces possible with the codec,
  *   plus 1 surface for the user to work (meaning the user can safely reference
  *   at most 1 decoded surface at a time), plus additional buffering introduced
  *   by frame threading. If the hwaccel does not require pre-allocation, the
  *   field is left to 0, and the decoder will allocate new surfaces on demand
  *   during decoding.
  * - Possibly AVHWFramesContext.hwctx fields, depending on the underlying
  *   hardware API.
  *
  * Essentially, out_frames_ref returns the same as av_hwframe_ctx_alloc(), but
  * with basic frame parameters set.
  *
  * The function is stateless, and does not change the AVCodecContext or the
  * device_ref AVHWDeviceContext.
  *
  * @param avctx The context which is currently calling get_format, and which
  *              implicitly contains all state needed for filling the returned
  *              AVHWFramesContext properly.
  * @param device_ref A reference to the AVHWDeviceContext describing the device
  *                   which will be used by the hardware decoder.
  * @param hw_pix_fmt The hwaccel format you are going to return from get_format.
  * @param out_frames_ref On success, set to a reference to an _uninitialized_
  *                       AVHWFramesContext, created from the given device_ref.
  *                       Fields will be set to values required for decoding.
  *                       Not changed if an error is returned.
  * @return zero on success, a negative value on error. The following error codes
  *         have special semantics:
  *      AVERROR(ENOENT): the decoder does not support this functionality. Setup
  *                       is always manual, or it is a decoder which does not
  *                       support setting AVCodecContext.hw_frames_ctx at all,
  *                       or it is a software format.
  *      AVERROR(EINVAL): it is known that hardware decoding is not supported for
  *                       this configuration, or the device_ref is not supported
  *                       for the hwaccel referenced by hw_pix_fmt.
  */
 int avcodec_get_hw_frames_parameters(AVCodecContext *avctx,
                                      AVBufferRef *device_ref,
                                      enum AVPixelFormat hw_pix_fmt,
                                      AVBufferRef **out_frames_ref);
 
 
 
 /**
  * @defgroup lavc_parsing Frame parsing
  * @{
  */
 
 enum AVPictureStructure {
     AV_PICTURE_STRUCTURE_UNKNOWN,      ///< unknown
     AV_PICTURE_STRUCTURE_TOP_FIELD,    ///< coded as top field
     AV_PICTURE_STRUCTURE_BOTTOM_FIELD, ///< coded as bottom field
     AV_PICTURE_STRUCTURE_FRAME,        ///< coded as frame
 };
 
 typedef struct AVCodecParserContext {
     void *priv_data;
     const struct AVCodecParser *parser;
     int64_t frame_offset; /* offset of the current frame */
     int64_t cur_offset; /* current offset
                            (incremented by each av_parser_parse()) */
     int64_t next_frame_offset; /* offset of the next frame */
     /* video info */
     int pict_type; /* XXX: Put it back in AVCodecContext. */
     /**
      * This field is used for proper frame duration computation in lavf.
      * It signals, how much longer the frame duration of the current frame
      * is compared to normal frame duration.
      *
      * frame_duration = (1 + repeat_pict) * time_base
      *
      * It is used by codecs like H.264 to display telecined material.
      */
     int repeat_pict; /* XXX: Put it back in AVCodecContext. */
     int64_t pts;     /* pts of the current frame */
     int64_t dts;     /* dts of the current frame */
 
     /* private data */
     int64_t last_pts;
     int64_t last_dts;
     int fetch_timestamp;
 
 #define AV_PARSER_PTS_NB 4
     int cur_frame_start_index;
     int64_t cur_frame_offset[AV_PARSER_PTS_NB];
     int64_t cur_frame_pts[AV_PARSER_PTS_NB];
     int64_t cur_frame_dts[AV_PARSER_PTS_NB];
 
     int flags;
 #define PARSER_FLAG_COMPLETE_FRAMES           0x0001
 #define PARSER_FLAG_ONCE                      0x0002
 /// Set if the parser has a valid file offset
 #define PARSER_FLAG_FETCHED_OFFSET            0x0004
 #define PARSER_FLAG_USE_CODEC_TS              0x1000
 
     int64_t offset;      ///< byte offset from starting packet start
     int64_t cur_frame_end[AV_PARSER_PTS_NB];
 
     /**
      * Set by parser to 1 for key frames and 0 for non-key frames.
      * It is initialized to -1, so if the parser doesn't set this flag,
      * old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
      * will be used.
      */
     int key_frame;
 
     // Timestamp generation support:
     /**
      * Synchronization point for start of timestamp generation.
      *
      * Set to >0 for sync point, 0 for no sync point and <0 for undefined
      * (default).
      *
      * For example, this corresponds to presence of H.264 buffering period
      * SEI message.
      */
     int dts_sync_point;
 
     /**
      * Offset of the current timestamp against last timestamp sync point in
      * units of AVCodecContext.time_base.
      *
      * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
      * contain a valid timestamp offset.
      *
      * Note that the timestamp of sync point has usually a nonzero
      * dts_ref_dts_delta, which refers to the previous sync point. Offset of
      * the next frame after timestamp sync point will be usually 1.
      *
      * For example, this corresponds to H.264 cpb_removal_delay.
      */
     int dts_ref_dts_delta;
 
     /**
      * Presentation delay of current frame in units of AVCodecContext.time_base.
      *
      * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
      * contain valid non-negative timestamp delta (presentation time of a frame
      * must not lie in the past).
      *
      * This delay represents the difference between decoding and presentation
      * time of the frame.
      *
      * For example, this corresponds to H.264 dpb_output_delay.
      */
     int pts_dts_delta;
 
     /**
      * Position of the packet in file.
      *
      * Analogous to cur_frame_pts/dts
      */
     int64_t cur_frame_pos[AV_PARSER_PTS_NB];
 
     /**
      * Byte position of currently parsed frame in stream.
      */
     int64_t pos;
 
     /**
      * Previous frame byte position.
      */
     int64_t last_pos;
 
     /**
      * Duration of the current frame.
      * For audio, this is in units of 1 / AVCodecContext.sample_rate.
      * For all other types, this is in units of AVCodecContext.time_base.
      */
     int duration;
 
     enum AVFieldOrder field_order;
 
     /**
      * Indicate whether a picture is coded as a frame, top field or bottom field.
      *
      * For example, H.264 field_pic_flag equal to 0 corresponds to
      * AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
      * equal to 1 and bottom_field_flag equal to 0 corresponds to
      * AV_PICTURE_STRUCTURE_TOP_FIELD.
      */
     enum AVPictureStructure picture_structure;
 
     /**
      * Picture number incremented in presentation or output order.
      * This field may be reinitialized at the first picture of a new sequence.
      *
      * For example, this corresponds to H.264 PicOrderCnt.
      */
     int output_picture_number;
 
     /**
      * Dimensions of the decoded video intended for presentation.
      */
     int width;
     int height;
 
     /**
      * Dimensions of the coded video.
      */
     int coded_width;
     int coded_height;
 
     /**
      * The format of the coded data, corresponds to enum AVPixelFormat for video
      * and for enum AVSampleFormat for audio.
      *
      * Note that a decoder can have considerable freedom in how exactly it
      * decodes the data, so the format reported here might be different from the
      * one returned by a decoder.
      */
     int format;
 } AVCodecParserContext;
 
 typedef struct AVCodecParser {
     int codec_ids[7]; /* several codec IDs are permitted */
     int priv_data_size;
     int (*parser_init)(AVCodecParserContext *s);
     /* This callback never returns an error, a negative value means that
      * the frame start was in a previous packet. */
     int (*parser_parse)(AVCodecParserContext *s,
                         AVCodecContext *avctx,
                         const uint8_t **poutbuf, int *poutbuf_size,
                         const uint8_t *buf, int buf_size);
     void (*parser_close)(AVCodecParserContext *s);
     int (*split)(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
 } AVCodecParser;
 
 /**
  * Iterate over all registered codec parsers.
  *
  * @param opaque a pointer where libavcodec will store the iteration state. Must
  *               point to NULL to start the iteration.
  *
  * @return the next registered codec parser or NULL when the iteration is
  *         finished
  */
 const AVCodecParser *av_parser_iterate(void **opaque);
 
 AVCodecParserContext *av_parser_init(int codec_id);
 
 /**
  * Parse a packet.
  *
  * @param s             parser context.
  * @param avctx         codec context.
  * @param poutbuf       set to pointer to parsed buffer or NULL if not yet finished.
  * @param poutbuf_size  set to size of parsed buffer or zero if not yet finished.
  * @param buf           input buffer.
  * @param buf_size      buffer size in bytes without the padding. I.e. the full buffer
                         size is assumed to be buf_size + AV_INPUT_BUFFER_PADDING_SIZE.
                         To signal EOF, this should be 0 (so that the last frame
                         can be output).
  * @param pts           input presentation timestamp.
  * @param dts           input decoding timestamp.
  * @param pos           input byte position in stream.
  * @return the number of bytes of the input bitstream used.
  *
  * Example:
  * @code
  *   while(in_len){
  *       len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
  *                                        in_data, in_len,
  *                                        pts, dts, pos);
  *       in_data += len;
  *       in_len  -= len;
  *
  *       if(size)
  *          decode_frame(data, size);
  *   }
  * @endcode
  */
 int av_parser_parse2(AVCodecParserContext *s,
                      AVCodecContext *avctx,
                      uint8_t **poutbuf, int *poutbuf_size,
                      const uint8_t *buf, int buf_size,
                      int64_t pts, int64_t dts,
                      int64_t pos);
 
 void av_parser_close(AVCodecParserContext *s);
 
 /**
  * @}
  * @}
  */
 
 /**
  * @addtogroup lavc_encoding
  * @{
  */
 
 int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                             const AVSubtitle *sub);
 
 
 /**
  * @}
  */
 
 /**
  * @defgroup lavc_misc Utility functions
  * @ingroup libavc
  *
  * Miscellaneous utility functions related to both encoding and decoding
  * (or neither).
  * @{
  */
 
 /**
  * @defgroup lavc_misc_pixfmt Pixel formats
  *
  * Functions for working with pixel formats.
  * @{
  */
 
 /**
  * Return a value representing the fourCC code associated to the
  * pixel format pix_fmt, or 0 if no associated fourCC code can be
  * found.
  */
 unsigned int avcodec_pix_fmt_to_codec_tag(enum AVPixelFormat pix_fmt);
 
 /**
  * Find the best pixel format to convert to given a certain source pixel
  * format.  When converting from one pixel format to another, information loss
  * may occur.  For example, when converting from RGB24 to GRAY, the color
  * information will be lost. Similarly, other losses occur when converting from
  * some formats to other formats. avcodec_find_best_pix_fmt_of_2() searches which of
  * the given pixel formats should be used to suffer the least amount of loss.
  * The pixel formats from which it chooses one, are determined by the
  * pix_fmt_list parameter.
  *
  *
  * @param[in] pix_fmt_list AV_PIX_FMT_NONE terminated array of pixel formats to choose from
  * @param[in] src_pix_fmt source pixel format
  * @param[in] has_alpha Whether the source pixel format alpha channel is used.
  * @param[out] loss_ptr Combination of flags informing you what kind of losses will occur.
  * @return The best pixel format to convert to or -1 if none was found.
  */
 enum AVPixelFormat avcodec_find_best_pix_fmt_of_list(const enum AVPixelFormat *pix_fmt_list,
                                             enum AVPixelFormat src_pix_fmt,
                                             int has_alpha, int *loss_ptr);
 
 enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
 
 /**
  * @}
  */
 
 void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode);
 
 int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2),void *arg, int *ret, int count, int size);
 int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2, int, int),void *arg, int *ret, int count);
 //FIXME func typedef
 
 /**
  * Fill AVFrame audio data and linesize pointers.
  *
  * The buffer buf must be a preallocated buffer with a size big enough
  * to contain the specified samples amount. The filled AVFrame data
  * pointers will point to this buffer.
  *
  * AVFrame extended_data channel pointers are allocated if necessary for
  * planar audio.
  *
  * @param frame       the AVFrame
  *                    frame->nb_samples must be set prior to calling the
  *                    function. This function fills in frame->data,
  *                    frame->extended_data, frame->linesize[0].
  * @param nb_channels channel count
  * @param sample_fmt  sample format
  * @param buf         buffer to use for frame data
  * @param buf_size    size of buffer
  * @param align       plane size sample alignment (0 = default)
  * @return            >=0 on success, negative error code on failure
  * @todo return the size in bytes required to store the samples in
  * case of success, at the next libavutil bump
  */
 int avcodec_fill_audio_frame(AVFrame *frame, int nb_channels,
                              enum AVSampleFormat sample_fmt, const uint8_t *buf,
                              int buf_size, int align);
 
 /**
  * Reset the internal codec state / flush internal buffers. Should be called
  * e.g. when seeking or when switching to a different stream.
  *
  * @note for decoders, this function just releases any references the decoder
  * might keep internally, but the caller's references remain valid.
  *
  * @note for encoders, this function will only do something if the encoder
  * declares support for AV_CODEC_CAP_ENCODER_FLUSH. When called, the encoder
  * will drain any remaining packets, and can then be re-used for a different
  * stream (as opposed to sending a null frame which will leave the encoder
  * in a permanent EOF state after draining). This can be desirable if the
  * cost of tearing down and replacing the encoder instance is high.
  */
 void avcodec_flush_buffers(AVCodecContext *avctx);
 
 /**
  * Return audio frame duration.
  *
  * @param avctx        codec context
  * @param frame_bytes  size of the frame, or 0 if unknown
  * @return             frame duration, in samples, if known. 0 if not able to
  *                     determine.
  */
 int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes);
 
 /* memory */
 
 /**
  * Same behaviour av_fast_malloc but the buffer has additional
  * AV_INPUT_BUFFER_PADDING_SIZE at the end which will always be 0.
  *
  * In addition the whole buffer will initially and after resizes
  * be 0-initialized so that no uninitialized data will ever appear.
  */
 void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size);
 
 /**
  * Same behaviour av_fast_padded_malloc except that buffer will always
  * be 0-initialized after call.
  */
 void av_fast_padded_mallocz(void *ptr, unsigned int *size, size_t min_size);
 
 /**
  * @return a positive value if s is open (i.e. avcodec_open2() was called on it
  * with no corresponding avcodec_close()), 0 otherwise.
  */
 int avcodec_is_open(AVCodecContext *s);
 
 /**
  * @}
  */
 
 #endif /* AVCODEC_AVCODEC_H */