duckstation

frame.h (38049B)

---

 /*
  * 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
  */
 
 /**
  * @file
  * @ingroup lavu_frame
  * reference-counted frame API
  */
 
 #ifndef AVUTIL_FRAME_H
 #define AVUTIL_FRAME_H
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "avutil.h"
 #include "buffer.h"
 #include "channel_layout.h"
 #include "dict.h"
 #include "rational.h"
 #include "samplefmt.h"
 #include "pixfmt.h"
 #include "version.h"
 
 
 /**
  * @defgroup lavu_frame AVFrame
  * @ingroup lavu_data
  *
  * @{
  * AVFrame is an abstraction for reference-counted raw multimedia data.
  */
 
 enum AVFrameSideDataType {
     /**
      * The data is the AVPanScan struct defined in libavcodec.
      */
     AV_FRAME_DATA_PANSCAN,
     /**
      * ATSC A53 Part 4 Closed Captions.
      * A53 CC bitstream is stored as uint8_t in AVFrameSideData.data.
      * The number of bytes of CC data is AVFrameSideData.size.
      */
     AV_FRAME_DATA_A53_CC,
     /**
      * Stereoscopic 3d metadata.
      * The data is the AVStereo3D struct defined in libavutil/stereo3d.h.
      */
     AV_FRAME_DATA_STEREO3D,
     /**
      * The data is the AVMatrixEncoding enum defined in libavutil/channel_layout.h.
      */
     AV_FRAME_DATA_MATRIXENCODING,
     /**
      * Metadata relevant to a downmix procedure.
      * The data is the AVDownmixInfo struct defined in libavutil/downmix_info.h.
      */
     AV_FRAME_DATA_DOWNMIX_INFO,
     /**
      * ReplayGain information in the form of the AVReplayGain struct.
      */
     AV_FRAME_DATA_REPLAYGAIN,
     /**
      * This side data contains a 3x3 transformation matrix describing an affine
      * transformation that needs to be applied to the frame for correct
      * presentation.
      *
      * See libavutil/display.h for a detailed description of the data.
      */
     AV_FRAME_DATA_DISPLAYMATRIX,
     /**
      * Active Format Description data consisting of a single byte as specified
      * in ETSI TS 101 154 using AVActiveFormatDescription enum.
      */
     AV_FRAME_DATA_AFD,
     /**
      * Motion vectors exported by some codecs (on demand through the export_mvs
      * flag set in the libavcodec AVCodecContext flags2 option).
      * The data is the AVMotionVector struct defined in
      * libavutil/motion_vector.h.
      */
     AV_FRAME_DATA_MOTION_VECTORS,
     /**
      * Recommmends skipping the specified number of samples. This is exported
      * only if the "skip_manual" AVOption is set in libavcodec.
      * This has the same format as AV_PKT_DATA_SKIP_SAMPLES.
      * @code
      * u32le number of samples to skip from start of this packet
      * u32le number of samples to skip from end of this packet
      * u8    reason for start skip
      * u8    reason for end   skip (0=padding silence, 1=convergence)
      * @endcode
      */
     AV_FRAME_DATA_SKIP_SAMPLES,
     /**
      * This side data must be associated with an audio frame and corresponds to
      * enum AVAudioServiceType defined in avcodec.h.
      */
     AV_FRAME_DATA_AUDIO_SERVICE_TYPE,
     /**
      * Mastering display metadata associated with a video frame. The payload is
      * an AVMasteringDisplayMetadata type and contains information about the
      * mastering display color volume.
      */
     AV_FRAME_DATA_MASTERING_DISPLAY_METADATA,
     /**
      * The GOP timecode in 25 bit timecode format. Data format is 64-bit integer.
      * This is set on the first frame of a GOP that has a temporal reference of 0.
      */
     AV_FRAME_DATA_GOP_TIMECODE,
 
     /**
      * The data represents the AVSphericalMapping structure defined in
      * libavutil/spherical.h.
      */
     AV_FRAME_DATA_SPHERICAL,
 
     /**
      * Content light level (based on CTA-861.3). This payload contains data in
      * the form of the AVContentLightMetadata struct.
      */
     AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
 
     /**
      * The data contains an ICC profile as an opaque octet buffer following the
      * format described by ISO 15076-1 with an optional name defined in the
      * metadata key entry "name".
      */
     AV_FRAME_DATA_ICC_PROFILE,
 
     /**
      * Timecode which conforms to SMPTE ST 12-1. The data is an array of 4 uint32_t
      * where the first uint32_t describes how many (1-3) of the other timecodes are used.
      * The timecode format is described in the documentation of av_timecode_get_smpte_from_framenum()
      * function in libavutil/timecode.h.
      */
     AV_FRAME_DATA_S12M_TIMECODE,
 
     /**
      * HDR dynamic metadata associated with a video frame. The payload is
      * an AVDynamicHDRPlus type and contains information for color
      * volume transform - application 4 of SMPTE 2094-40:2016 standard.
      */
     AV_FRAME_DATA_DYNAMIC_HDR_PLUS,
 
     /**
      * Regions Of Interest, the data is an array of AVRegionOfInterest type, the number of
      * array element is implied by AVFrameSideData.size / AVRegionOfInterest.self_size.
      */
     AV_FRAME_DATA_REGIONS_OF_INTEREST,
 
     /**
      * Encoding parameters for a video frame, as described by AVVideoEncParams.
      */
     AV_FRAME_DATA_VIDEO_ENC_PARAMS,
 
     /**
      * User data unregistered metadata associated with a video frame.
      * This is the H.26[45] UDU SEI message, and shouldn't be used for any other purpose
      * The data is stored as uint8_t in AVFrameSideData.data which is 16 bytes of
      * uuid_iso_iec_11578 followed by AVFrameSideData.size - 16 bytes of user_data_payload_byte.
      */
     AV_FRAME_DATA_SEI_UNREGISTERED,
 
     /**
      * Film grain parameters for a frame, described by AVFilmGrainParams.
      * Must be present for every frame which should have film grain applied.
      *
      * May be present multiple times, for example when there are multiple
      * alternative parameter sets for different video signal characteristics.
      * The user should select the most appropriate set for the application.
      */
     AV_FRAME_DATA_FILM_GRAIN_PARAMS,
 
     /**
      * Bounding boxes for object detection and classification,
      * as described by AVDetectionBBoxHeader.
      */
     AV_FRAME_DATA_DETECTION_BBOXES,
 
     /**
      * Dolby Vision RPU raw data, suitable for passing to x265
      * or other libraries. Array of uint8_t, with NAL emulation
      * bytes intact.
      */
     AV_FRAME_DATA_DOVI_RPU_BUFFER,
 
     /**
      * Parsed Dolby Vision metadata, suitable for passing to a software
      * implementation. The payload is the AVDOVIMetadata struct defined in
      * libavutil/dovi_meta.h.
      */
     AV_FRAME_DATA_DOVI_METADATA,
 
     /**
      * HDR Vivid dynamic metadata associated with a video frame. The payload is
      * an AVDynamicHDRVivid type and contains information for color
      * volume transform - CUVA 005.1-2021.
      */
     AV_FRAME_DATA_DYNAMIC_HDR_VIVID,
 
     /**
      * Ambient viewing environment metadata, as defined by H.274.
      */
     AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT,
 
     /**
      * Provide encoder-specific hinting information about changed/unchanged
      * portions of a frame.  It can be used to pass information about which
      * macroblocks can be skipped because they didn't change from the
      * corresponding ones in the previous frame. This could be useful for
      * applications which know this information in advance to speed up
      * encoding.
      */
     AV_FRAME_DATA_VIDEO_HINT,
 };
 
 enum AVActiveFormatDescription {
     AV_AFD_SAME         = 8,
     AV_AFD_4_3          = 9,
     AV_AFD_16_9         = 10,
     AV_AFD_14_9         = 11,
     AV_AFD_4_3_SP_14_9  = 13,
     AV_AFD_16_9_SP_14_9 = 14,
     AV_AFD_SP_4_3       = 15,
 };
 
 
 /**
  * Structure to hold side data for an AVFrame.
  *
  * sizeof(AVFrameSideData) is not a part of the public ABI, so new fields may be added
  * to the end with a minor bump.
  */
 typedef struct AVFrameSideData {
     enum AVFrameSideDataType type;
     uint8_t *data;
     size_t   size;
     AVDictionary *metadata;
     AVBufferRef *buf;
 } AVFrameSideData;
 
 /**
  * Structure describing a single Region Of Interest.
  *
  * When multiple regions are defined in a single side-data block, they
  * should be ordered from most to least important - some encoders are only
  * capable of supporting a limited number of distinct regions, so will have
  * to truncate the list.
  *
  * When overlapping regions are defined, the first region containing a given
  * area of the frame applies.
  */
 typedef struct AVRegionOfInterest {
     /**
      * Must be set to the size of this data structure (that is,
      * sizeof(AVRegionOfInterest)).
      */
     uint32_t self_size;
     /**
      * Distance in pixels from the top edge of the frame to the top and
      * bottom edges and from the left edge of the frame to the left and
      * right edges of the rectangle defining this region of interest.
      *
      * The constraints on a region are encoder dependent, so the region
      * actually affected may be slightly larger for alignment or other
      * reasons.
      */
     int top;
     int bottom;
     int left;
     int right;
     /**
      * Quantisation offset.
      *
      * Must be in the range -1 to +1.  A value of zero indicates no quality
      * change.  A negative value asks for better quality (less quantisation),
      * while a positive value asks for worse quality (greater quantisation).
      *
      * The range is calibrated so that the extreme values indicate the
      * largest possible offset - if the rest of the frame is encoded with the
      * worst possible quality, an offset of -1 indicates that this region
      * should be encoded with the best possible quality anyway.  Intermediate
      * values are then interpolated in some codec-dependent way.
      *
      * For example, in 10-bit H.264 the quantisation parameter varies between
      * -12 and 51.  A typical qoffset value of -1/10 therefore indicates that
      * this region should be encoded with a QP around one-tenth of the full
      * range better than the rest of the frame.  So, if most of the frame
      * were to be encoded with a QP of around 30, this region would get a QP
      * of around 24 (an offset of approximately -1/10 * (51 - -12) = -6.3).
      * An extreme value of -1 would indicate that this region should be
      * encoded with the best possible quality regardless of the treatment of
      * the rest of the frame - that is, should be encoded at a QP of -12.
      */
     AVRational qoffset;
 } AVRegionOfInterest;
 
 /**
  * This structure describes decoded (raw) audio or video data.
  *
  * AVFrame must be allocated using av_frame_alloc(). Note that this only
  * allocates the AVFrame itself, the buffers for the data must be managed
  * through other means (see below).
  * AVFrame must be freed with av_frame_free().
  *
  * AVFrame is typically allocated once and then reused multiple times to hold
  * different data (e.g. a single AVFrame to hold frames received from a
  * decoder). In such a case, av_frame_unref() will free any references held by
  * the frame and reset it to its original clean state before it
  * is reused again.
  *
  * The data described by an AVFrame is usually reference counted through the
  * AVBuffer API. The underlying buffer references are stored in AVFrame.buf /
  * AVFrame.extended_buf. An AVFrame is considered to be reference counted if at
  * least one reference is set, i.e. if AVFrame.buf[0] != NULL. In such a case,
  * every single data plane must be contained in one of the buffers in
  * AVFrame.buf or AVFrame.extended_buf.
  * There may be a single buffer for all the data, or one separate buffer for
  * each plane, or anything in between.
  *
  * sizeof(AVFrame) is not a part of the public ABI, so new fields may be added
  * to the end with a minor bump.
  *
  * Fields can be accessed through AVOptions, the name string used, matches the
  * C structure field name for fields accessible through AVOptions. The AVClass
  * for AVFrame can be obtained from avcodec_get_frame_class()
  */
 typedef struct AVFrame {
 #define AV_NUM_DATA_POINTERS 8
     /**
      * pointer to the picture/channel planes.
      * This might be different from the first allocated byte. For video,
      * it could even point to the end of the image data.
      *
      * All pointers in data and extended_data must point into one of the
      * AVBufferRef in buf or extended_buf.
      *
      * Some decoders access areas outside 0,0 - width,height, please
      * see avcodec_align_dimensions2(). Some filters and swscale can read
      * up to 16 bytes beyond the planes, if these filters are to be used,
      * then 16 extra bytes must be allocated.
      *
      * NOTE: Pointers not needed by the format MUST be set to NULL.
      *
      * @attention In case of video, the data[] pointers can point to the
      * end of image data in order to reverse line order, when used in
      * combination with negative values in the linesize[] array.
      */
     uint8_t *data[AV_NUM_DATA_POINTERS];
 
     /**
      * For video, a positive or negative value, which is typically indicating
      * the size in bytes of each picture line, but it can also be:
      * - the negative byte size of lines for vertical flipping
      *   (with data[n] pointing to the end of the data
      * - a positive or negative multiple of the byte size as for accessing
      *   even and odd fields of a frame (possibly flipped)
      *
      * For audio, only linesize[0] may be set. For planar audio, each channel
      * plane must be the same size.
      *
      * For video the linesizes should be multiples of the CPUs alignment
      * preference, this is 16 or 32 for modern desktop CPUs.
      * Some code requires such alignment other code can be slower without
      * correct alignment, for yet other it makes no difference.
      *
      * @note The linesize may be larger than the size of usable data -- there
      * may be extra padding present for performance reasons.
      *
      * @attention In case of video, line size values can be negative to achieve
      * a vertically inverted iteration over image lines.
      */
     int linesize[AV_NUM_DATA_POINTERS];
 
     /**
      * pointers to the data planes/channels.
      *
      * For video, this should simply point to data[].
      *
      * For planar audio, each channel has a separate data pointer, and
      * linesize[0] contains the size of each channel buffer.
      * For packed audio, there is just one data pointer, and linesize[0]
      * contains the total size of the buffer for all channels.
      *
      * Note: Both data and extended_data should always be set in a valid frame,
      * but for planar audio with more channels that can fit in data,
      * extended_data must be used in order to access all channels.
      */
     uint8_t **extended_data;
 
     /**
      * @name Video dimensions
      * Video frames only. The coded dimensions (in pixels) of the video frame,
      * i.e. the size of the rectangle that contains some well-defined values.
      *
      * @note The part of the frame intended for display/presentation is further
      * restricted by the @ref cropping "Cropping rectangle".
      * @{
      */
     int width, height;
     /**
      * @}
      */
 
     /**
      * number of audio samples (per channel) described by this frame
      */
     int nb_samples;
 
     /**
      * format of the frame, -1 if unknown or unset
      * Values correspond to enum AVPixelFormat for video frames,
      * enum AVSampleFormat for audio)
      */
     int format;
 
 #if FF_API_FRAME_KEY
     /**
      * 1 -> keyframe, 0-> not
      *
      * @deprecated Use AV_FRAME_FLAG_KEY instead
      */
     attribute_deprecated
     int key_frame;
 #endif
 
     /**
      * Picture type of the frame.
      */
     enum AVPictureType pict_type;
 
     /**
      * Sample aspect ratio for the video frame, 0/1 if unknown/unspecified.
      */
     AVRational sample_aspect_ratio;
 
     /**
      * Presentation timestamp in time_base units (time when frame should be shown to user).
      */
     int64_t pts;
 
     /**
      * DTS copied from the AVPacket that triggered returning this frame. (if frame threading isn't used)
      * This is also the Presentation time of this AVFrame calculated from
      * only AVPacket.dts values without pts values.
      */
     int64_t pkt_dts;
 
     /**
      * Time base for the timestamps in this frame.
      * In the future, this field may be set on frames output by decoders or
      * filters, but its value will be by default ignored on input to encoders
      * or filters.
      */
     AVRational time_base;
 
     /**
      * quality (between 1 (good) and FF_LAMBDA_MAX (bad))
      */
     int quality;
 
     /**
      * Frame owner's private data.
      *
      * This field may be set by the code that allocates/owns the frame data.
      * It is then not touched by any library functions, except:
      * - it is copied to other references by av_frame_copy_props() (and hence by
      *   av_frame_ref());
      * - it is set to NULL when the frame is cleared by av_frame_unref()
      * - on the caller's explicit request. E.g. libavcodec encoders/decoders
      *   will copy this field to/from @ref AVPacket "AVPackets" if the caller sets
      *   @ref AV_CODEC_FLAG_COPY_OPAQUE.
      *
      * @see opaque_ref the reference-counted analogue
      */
     void *opaque;
 
     /**
      * Number of fields in this frame which should be repeated, i.e. the total
      * duration of this frame should be repeat_pict + 2 normal field durations.
      *
      * For interlaced frames this field may be set to 1, which signals that this
      * frame should be presented as 3 fields: beginning with the first field (as
      * determined by AV_FRAME_FLAG_TOP_FIELD_FIRST being set or not), followed
      * by the second field, and then the first field again.
      *
      * For progressive frames this field may be set to a multiple of 2, which
      * signals that this frame's duration should be (repeat_pict + 2) / 2
      * normal frame durations.
      *
      * @note This field is computed from MPEG2 repeat_first_field flag and its
      * associated flags, H.264 pic_struct from picture timing SEI, and
      * their analogues in other codecs. Typically it should only be used when
      * higher-layer timing information is not available.
      */
     int repeat_pict;
 
 #if FF_API_INTERLACED_FRAME
     /**
      * The content of the picture is interlaced.
      *
      * @deprecated Use AV_FRAME_FLAG_INTERLACED instead
      */
     attribute_deprecated
     int interlaced_frame;
 
     /**
      * If the content is interlaced, is top field displayed first.
      *
      * @deprecated Use AV_FRAME_FLAG_TOP_FIELD_FIRST instead
      */
     attribute_deprecated
     int top_field_first;
 #endif
 
 #if FF_API_PALETTE_HAS_CHANGED
     /**
      * Tell user application that palette has changed from previous frame.
      */
     attribute_deprecated
     int palette_has_changed;
 #endif
 
     /**
      * Sample rate of the audio data.
      */
     int sample_rate;
 
     /**
      * AVBuffer references backing the data for this frame. All the pointers in
      * data and extended_data must point inside one of the buffers in buf or
      * extended_buf. This array must be filled contiguously -- if buf[i] is
      * non-NULL then buf[j] must also be non-NULL for all j < i.
      *
      * There may be at most one AVBuffer per data plane, so for video this array
      * always contains all the references. For planar audio with more than
      * AV_NUM_DATA_POINTERS channels, there may be more buffers than can fit in
      * this array. Then the extra AVBufferRef pointers are stored in the
      * extended_buf array.
      */
     AVBufferRef *buf[AV_NUM_DATA_POINTERS];
 
     /**
      * For planar audio which requires more than AV_NUM_DATA_POINTERS
      * AVBufferRef pointers, this array will hold all the references which
      * cannot fit into AVFrame.buf.
      *
      * Note that this is different from AVFrame.extended_data, which always
      * contains all the pointers. This array only contains the extra pointers,
      * which cannot fit into AVFrame.buf.
      *
      * This array is always allocated using av_malloc() by whoever constructs
      * the frame. It is freed in av_frame_unref().
      */
     AVBufferRef **extended_buf;
     /**
      * Number of elements in extended_buf.
      */
     int        nb_extended_buf;
 
     AVFrameSideData **side_data;
     int            nb_side_data;
 
 /**
  * @defgroup lavu_frame_flags AV_FRAME_FLAGS
  * @ingroup lavu_frame
  * Flags describing additional frame properties.
  *
  * @{
  */
 
 /**
  * The frame data may be corrupted, e.g. due to decoding errors.
  */
 #define AV_FRAME_FLAG_CORRUPT       (1 << 0)
 /**
  * A flag to mark frames that are keyframes.
  */
 #define AV_FRAME_FLAG_KEY (1 << 1)
 /**
  * A flag to mark the frames which need to be decoded, but shouldn't be output.
  */
 #define AV_FRAME_FLAG_DISCARD   (1 << 2)
 /**
  * A flag to mark frames whose content is interlaced.
  */
 #define AV_FRAME_FLAG_INTERLACED (1 << 3)
 /**
  * A flag to mark frames where the top field is displayed first if the content
  * is interlaced.
  */
 #define AV_FRAME_FLAG_TOP_FIELD_FIRST (1 << 4)
 /**
  * @}
  */
 
     /**
      * Frame flags, a combination of @ref lavu_frame_flags
      */
     int flags;
 
     /**
      * MPEG vs JPEG YUV range.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVColorRange color_range;
 
     enum AVColorPrimaries color_primaries;
 
     enum AVColorTransferCharacteristic color_trc;
 
     /**
      * YUV colorspace type.
      * - encoding: Set by user
      * - decoding: Set by libavcodec
      */
     enum AVColorSpace colorspace;
 
     enum AVChromaLocation chroma_location;
 
     /**
      * frame timestamp estimated using various heuristics, in stream time base
      * - encoding: unused
      * - decoding: set by libavcodec, read by user.
      */
     int64_t best_effort_timestamp;
 
 #if FF_API_FRAME_PKT
     /**
      * reordered pos from the last AVPacket that has been input into the decoder
      * - encoding: unused
      * - decoding: Read by user.
      * @deprecated use AV_CODEC_FLAG_COPY_OPAQUE to pass through arbitrary user
      *             data from packets to frames
      */
     attribute_deprecated
     int64_t pkt_pos;
 #endif
 
     /**
      * metadata.
      * - encoding: Set by user.
      * - decoding: Set by libavcodec.
      */
     AVDictionary *metadata;
 
     /**
      * decode error flags of the frame, set to a combination of
      * FF_DECODE_ERROR_xxx flags if the decoder produced a frame, but there
      * were errors during the decoding.
      * - encoding: unused
      * - decoding: set by libavcodec, read by user.
      */
     int decode_error_flags;
 #define FF_DECODE_ERROR_INVALID_BITSTREAM   1
 #define FF_DECODE_ERROR_MISSING_REFERENCE   2
 #define FF_DECODE_ERROR_CONCEALMENT_ACTIVE  4
 #define FF_DECODE_ERROR_DECODE_SLICES       8
 
 #if FF_API_FRAME_PKT
     /**
      * size of the corresponding packet containing the compressed
      * frame.
      * It is set to a negative value if unknown.
      * - encoding: unused
      * - decoding: set by libavcodec, read by user.
      * @deprecated use AV_CODEC_FLAG_COPY_OPAQUE to pass through arbitrary user
      *             data from packets to frames
      */
     attribute_deprecated
     int pkt_size;
 #endif
 
     /**
      * For hwaccel-format frames, this should be a reference to the
      * AVHWFramesContext describing the frame.
      */
     AVBufferRef *hw_frames_ctx;
 
     /**
      * Frame owner's private data.
      *
      * This field may be set by the code that allocates/owns the frame data.
      * It is then not touched by any library functions, except:
      * - a new reference to the underlying buffer is propagated by
      *   av_frame_copy_props() (and hence by av_frame_ref());
      * - it is unreferenced in av_frame_unref();
      * - on the caller's explicit request. E.g. libavcodec encoders/decoders
      *   will propagate a new reference to/from @ref AVPacket "AVPackets" if the
      *   caller sets @ref AV_CODEC_FLAG_COPY_OPAQUE.
      *
      * @see opaque the plain pointer analogue
      */
     AVBufferRef *opaque_ref;
 
     /**
      * @anchor cropping
      * @name Cropping
      * Video frames only. The number of pixels to discard from the the
      * top/bottom/left/right border of the frame to obtain the sub-rectangle of
      * the frame intended for presentation.
      * @{
      */
     size_t crop_top;
     size_t crop_bottom;
     size_t crop_left;
     size_t crop_right;
     /**
      * @}
      */
 
     /**
      * AVBufferRef for internal use by a single libav* library.
      * Must not be used to transfer data between libraries.
      * Has to be NULL when ownership of the frame leaves the respective library.
      *
      * Code outside the FFmpeg libs should never check or change the contents of the buffer ref.
      *
      * FFmpeg calls av_buffer_unref() on it when the frame is unreferenced.
      * av_frame_copy_props() calls create a new reference with av_buffer_ref()
      * for the target frame's private_ref field.
      */
     AVBufferRef *private_ref;
 
     /**
      * Channel layout of the audio data.
      */
     AVChannelLayout ch_layout;
 
     /**
      * Duration of the frame, in the same units as pts. 0 if unknown.
      */
     int64_t duration;
 } AVFrame;
 
 
 /**
  * Allocate an AVFrame and set its fields to default values.  The resulting
  * struct must be freed using av_frame_free().
  *
  * @return An AVFrame filled with default values or NULL on failure.
  *
  * @note this only allocates the AVFrame itself, not the data buffers. Those
  * must be allocated through other means, e.g. with av_frame_get_buffer() or
  * manually.
  */
 AVFrame *av_frame_alloc(void);
 
 /**
  * Free the frame and any dynamically allocated objects in it,
  * e.g. extended_data. If the frame is reference counted, it will be
  * unreferenced first.
  *
  * @param frame frame to be freed. The pointer will be set to NULL.
  */
 void av_frame_free(AVFrame **frame);
 
 /**
  * Set up a new reference to the data described by the source frame.
  *
  * Copy frame properties from src to dst and create a new reference for each
  * AVBufferRef from src.
  *
  * If src is not reference counted, new buffers are allocated and the data is
  * copied.
  *
  * @warning: dst MUST have been either unreferenced with av_frame_unref(dst),
  *           or newly allocated with av_frame_alloc() before calling this
  *           function, or undefined behavior will occur.
  *
  * @return 0 on success, a negative AVERROR on error
  */
 int av_frame_ref(AVFrame *dst, const AVFrame *src);
 
 /**
  * Ensure the destination frame refers to the same data described by the source
  * frame, either by creating a new reference for each AVBufferRef from src if
  * they differ from those in dst, by allocating new buffers and copying data if
  * src is not reference counted, or by unrefencing it if src is empty.
  *
  * Frame properties on dst will be replaced by those from src.
  *
  * @return 0 on success, a negative AVERROR on error. On error, dst is
  *         unreferenced.
  */
 int av_frame_replace(AVFrame *dst, const AVFrame *src);
 
 /**
  * Create a new frame that references the same data as src.
  *
  * This is a shortcut for av_frame_alloc()+av_frame_ref().
  *
  * @return newly created AVFrame on success, NULL on error.
  */
 AVFrame *av_frame_clone(const AVFrame *src);
 
 /**
  * Unreference all the buffers referenced by frame and reset the frame fields.
  */
 void av_frame_unref(AVFrame *frame);
 
 /**
  * Move everything contained in src to dst and reset src.
  *
  * @warning: dst is not unreferenced, but directly overwritten without reading
  *           or deallocating its contents. Call av_frame_unref(dst) manually
  *           before calling this function to ensure that no memory is leaked.
  */
 void av_frame_move_ref(AVFrame *dst, AVFrame *src);
 
 /**
  * Allocate new buffer(s) for audio or video data.
  *
  * The following fields must be set on frame before calling this function:
  * - format (pixel format for video, sample format for audio)
  * - width and height for video
  * - nb_samples and ch_layout for audio
  *
  * This function will fill AVFrame.data and AVFrame.buf arrays and, if
  * necessary, allocate and fill AVFrame.extended_data and AVFrame.extended_buf.
  * For planar formats, one buffer will be allocated for each plane.
  *
  * @warning: if frame already has been allocated, calling this function will
  *           leak memory. In addition, undefined behavior can occur in certain
  *           cases.
  *
  * @param frame frame in which to store the new buffers.
  * @param align Required buffer size alignment. If equal to 0, alignment will be
  *              chosen automatically for the current CPU. It is highly
  *              recommended to pass 0 here unless you know what you are doing.
  *
  * @return 0 on success, a negative AVERROR on error.
  */
 int av_frame_get_buffer(AVFrame *frame, int align);
 
 /**
  * Check if the frame data is writable.
  *
  * @return A positive value if the frame data is writable (which is true if and
  * only if each of the underlying buffers has only one reference, namely the one
  * stored in this frame). Return 0 otherwise.
  *
  * If 1 is returned the answer is valid until av_buffer_ref() is called on any
  * of the underlying AVBufferRefs (e.g. through av_frame_ref() or directly).
  *
  * @see av_frame_make_writable(), av_buffer_is_writable()
  */
 int av_frame_is_writable(AVFrame *frame);
 
 /**
  * Ensure that the frame data is writable, avoiding data copy if possible.
  *
  * Do nothing if the frame is writable, allocate new buffers and copy the data
  * if it is not. Non-refcounted frames behave as non-writable, i.e. a copy
  * is always made.
  *
  * @return 0 on success, a negative AVERROR on error.
  *
  * @see av_frame_is_writable(), av_buffer_is_writable(),
  * av_buffer_make_writable()
  */
 int av_frame_make_writable(AVFrame *frame);
 
 /**
  * Copy the frame data from src to dst.
  *
  * This function does not allocate anything, dst must be already initialized and
  * allocated with the same parameters as src.
  *
  * This function only copies the frame data (i.e. the contents of the data /
  * extended data arrays), not any other properties.
  *
  * @return >= 0 on success, a negative AVERROR on error.
  */
 int av_frame_copy(AVFrame *dst, const AVFrame *src);
 
 /**
  * Copy only "metadata" fields from src to dst.
  *
  * Metadata for the purpose of this function are those fields that do not affect
  * the data layout in the buffers.  E.g. pts, sample rate (for audio) or sample
  * aspect ratio (for video), but not width/height or channel layout.
  * Side data is also copied.
  */
 int av_frame_copy_props(AVFrame *dst, const AVFrame *src);
 
 /**
  * Get the buffer reference a given data plane is stored in.
  *
  * @param frame the frame to get the plane's buffer from
  * @param plane index of the data plane of interest in frame->extended_data.
  *
  * @return the buffer reference that contains the plane or NULL if the input
  * frame is not valid.
  */
 AVBufferRef *av_frame_get_plane_buffer(const AVFrame *frame, int plane);
 
 /**
  * Add a new side data to a frame.
  *
  * @param frame a frame to which the side data should be added
  * @param type type of the added side data
  * @param size size of the side data
  *
  * @return newly added side data on success, NULL on error
  */
 AVFrameSideData *av_frame_new_side_data(AVFrame *frame,
                                         enum AVFrameSideDataType type,
                                         size_t size);
 
 /**
  * Add a new side data to a frame from an existing AVBufferRef
  *
  * @param frame a frame to which the side data should be added
  * @param type  the type of the added side data
  * @param buf   an AVBufferRef to add as side data. The ownership of
  *              the reference is transferred to the frame.
  *
  * @return newly added side data on success, NULL on error. On failure
  *         the frame is unchanged and the AVBufferRef remains owned by
  *         the caller.
  */
 AVFrameSideData *av_frame_new_side_data_from_buf(AVFrame *frame,
                                                  enum AVFrameSideDataType type,
                                                  AVBufferRef *buf);
 
 /**
  * @return a pointer to the side data of a given type on success, NULL if there
  * is no side data with such type in this frame.
  */
 AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
                                         enum AVFrameSideDataType type);
 
 /**
  * Remove and free all side data instances of the given type.
  */
 void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);
 
 
 /**
  * Flags for frame cropping.
  */
 enum {
     /**
      * Apply the maximum possible cropping, even if it requires setting the
      * AVFrame.data[] entries to unaligned pointers. Passing unaligned data
      * to FFmpeg API is generally not allowed, and causes undefined behavior
      * (such as crashes). You can pass unaligned data only to FFmpeg APIs that
      * are explicitly documented to accept it. Use this flag only if you
      * absolutely know what you are doing.
      */
     AV_FRAME_CROP_UNALIGNED     = 1 << 0,
 };
 
 /**
  * Crop the given video AVFrame according to its crop_left/crop_top/crop_right/
  * crop_bottom fields. If cropping is successful, the function will adjust the
  * data pointers and the width/height fields, and set the crop fields to 0.
  *
  * In all cases, the cropping boundaries will be rounded to the inherent
  * alignment of the pixel format. In some cases, such as for opaque hwaccel
  * formats, the left/top cropping is ignored. The crop fields are set to 0 even
  * if the cropping was rounded or ignored.
  *
  * @param frame the frame which should be cropped
  * @param flags Some combination of AV_FRAME_CROP_* flags, or 0.
  *
  * @return >= 0 on success, a negative AVERROR on error. If the cropping fields
  * were invalid, AVERROR(ERANGE) is returned, and nothing is changed.
  */
 int av_frame_apply_cropping(AVFrame *frame, int flags);
 
 /**
  * @return a string identifying the side data type
  */
 const char *av_frame_side_data_name(enum AVFrameSideDataType type);
 
 /**
  * Free all side data entries and their contents, then zeroes out the
  * values which the pointers are pointing to.
  *
  * @param sd    pointer to array of side data to free. Will be set to NULL
  *              upon return.
  * @param nb_sd pointer to an integer containing the number of entries in
  *              the array. Will be set to 0 upon return.
  */
 void av_frame_side_data_free(AVFrameSideData ***sd, int *nb_sd);
 
 #define AV_FRAME_SIDE_DATA_FLAG_UNIQUE (1 << 0)
 
 /**
  * Add new side data entry to an array.
  *
  * @param sd    pointer to array of side data to which to add another entry,
  *              or to NULL in order to start a new array.
  * @param nb_sd pointer to an integer containing the number of entries in
  *              the array.
  * @param type  type of the added side data
  * @param size  size of the side data
  * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
  *
  * @return newly added side data on success, NULL on error. In case of
  *         AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of matching
  *         AVFrameSideDataType will be removed before the addition is
  *         attempted.
  */
 AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
                                         enum AVFrameSideDataType type,
                                         size_t size, unsigned int flags);
 
 /**
  * Add a new side data entry to an array based on existing side data, taking
  * a reference towards the contained AVBufferRef.
  *
  * @param sd    pointer to array of side data to which to add another entry,
  *              or to NULL in order to start a new array.
  * @param nb_sd pointer to an integer containing the number of entries in
  *              the array.
  * @param src   side data to be cloned, with a new reference utilized
  *              for the buffer.
  * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
  *
  * @return negative error code on failure, >=0 on success. In case of
  *         AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of matching
  *         AVFrameSideDataType will be removed before the addition is
  *         attempted.
  */
 int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
                              const AVFrameSideData *src, unsigned int flags);
 
 /**
  * Get a side data entry of a specific type from an array.
  *
  * @param sd    array of side data.
  * @param nb_sd integer containing the number of entries in the array.
  * @param type  type of side data to be queried
  *
  * @return a pointer to the side data of a given type on success, NULL if there
  *         is no side data with such type in this set.
  */
 const AVFrameSideData *av_frame_side_data_get_c(const AVFrameSideData * const *sd,
                                                 const int nb_sd,
                                                 enum AVFrameSideDataType type);
 
 /**
  * Wrapper around av_frame_side_data_get_c() to workaround the limitation
  * that for any type T the conversion from T * const * to const T * const *
  * is not performed automatically in C.
  * @see av_frame_side_data_get_c()
  */
 static inline
 const AVFrameSideData *av_frame_side_data_get(AVFrameSideData * const *sd,
                                               const int nb_sd,
                                               enum AVFrameSideDataType type)
 {
     return av_frame_side_data_get_c((const AVFrameSideData * const *)sd,
                                     nb_sd, type);
 }
 
 /**
  * @}
  */
 
 #endif /* AVUTIL_FRAME_H */