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102 lines
4.1 KiB
C
102 lines
4.1 KiB
C
/*
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* This example code creates an simple audio stream for playing sound, and
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* generates a sine wave sound effect for it to play as time goes on. This
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* is the simplest way to get up and running with procedural sound.
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*
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* This code is public domain. Feel free to use it for any purpose!
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*/
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#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
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#include <SDL3/SDL.h>
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#include <SDL3/SDL_main.h>
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/* We will use this renderer to draw into this window every frame. */
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static SDL_Window *window = NULL;
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static SDL_Renderer *renderer = NULL;
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static SDL_AudioStream *stream = NULL;
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static int total_samples_generated = 0;
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/* This function runs once at startup. */
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SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
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{
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SDL_AudioSpec spec;
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SDL_SetAppMetadata("Example Audio Simple Playback", "1.0", "com.example.audio-simple-playback");
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if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO)) {
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SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
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return SDL_APP_FAILURE;
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}
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/* we don't _need_ a window for audio-only things but it's good policy to have one. */
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if (!SDL_CreateWindowAndRenderer("examples/audio/simple-playback", 640, 480, 0, &window, &renderer)) {
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SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
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return SDL_APP_FAILURE;
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}
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/* We're just playing a single thing here, so we'll use the simplified option.
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We are always going to feed audio in as mono, float32 data at 8000Hz.
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The stream will convert it to whatever the hardware wants on the other side. */
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spec.channels = 1;
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spec.format = SDL_AUDIO_F32;
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spec.freq = 8000;
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stream = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &spec, NULL, NULL);
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if (!stream) {
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SDL_Log("Couldn't create audio stream: %s", SDL_GetError());
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return SDL_APP_FAILURE;
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}
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/* SDL_OpenAudioDeviceStream starts the device paused. You have to tell it to start! */
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SDL_ResumeAudioStreamDevice(stream);
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
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SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
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{
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if (event->type == SDL_EVENT_QUIT) {
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return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
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}
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs once per frame, and is the heart of the program. */
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SDL_AppResult SDL_AppIterate(void *appstate)
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{
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/* see if we need to feed the audio stream more data yet.
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We're being lazy here, but if there's less than half a second queued, generate more.
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A sine wave is unchanging audio--easy to stream--but for video games, you'll want
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to generate significantly _less_ audio ahead of time! */
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const int minimum_audio = (8000 * sizeof (float)) / 2; /* 8000 float samples per second. Half of that. */
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if (SDL_GetAudioStreamAvailable(stream) < minimum_audio) {
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static float samples[512]; /* this will feed 512 samples each frame until we get to our maximum. */
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int i;
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for (i = 0; i < SDL_arraysize(samples); i++) {
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/* You don't have to care about this math; we're just generating a simple sine wave as we go.
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https://en.wikipedia.org/wiki/Sine_wave */
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const float time = total_samples_generated / 8000.0f;
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const int sine_freq = 500; /* run the wave at 500Hz */
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samples[i] = SDL_sinf(6.283185f * sine_freq * time);
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total_samples_generated++;
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}
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/* feed the new data to the stream. It will queue at the end, and trickle out as the hardware needs more data. */
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SDL_PutAudioStreamData(stream, samples, sizeof (samples));
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}
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/* we're not doing anything with the renderer, so just blank it out. */
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SDL_RenderClear(renderer);
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SDL_RenderPresent(renderer);
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs once at shutdown. */
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void SDL_AppQuit(void *appstate, SDL_AppResult result)
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{
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/* SDL will clean up the window/renderer for us. */
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}
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