SDL+FFMPEG 音頻解碼和播放流程

1.設定音頻參數和相應的回呼函數，當聲音裝置需要資料時SDL會自動調用該回呼函數，填充該結構體。

typedef struct SDL_AudioSpec {int freq;/**< DSP frequency -- samples per second */Uint16 format;/**< Audio data format */Uint8  channels;/**< Number of channels: 1 mono, 2 stereo */Uint8  silence;/**< Audio buffer silence value (calculated) */Uint16 samples;/**< Audio buffer size in samples (power of 2) */Uint16 padding;/**< Necessary for some compile environments */Uint32 size;/**< Audio buffer size in bytes (calculated) *//** *  This function is called when the audio device needs more data. * *  @param[out] streamA pointer to the audio data buffer *  @param[in]  lenThe length of the audio buffer in bytes. * *  Once the callback returns, the buffer will no longer be valid. *  Stereo samples are stored in a LRLRLR ordering. */void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len);void  *userdata;} SDL_AudioSpec;

2.開啟聲音裝置

SDL_OpenAudio(&wanted_spec, &spec)

3.開始播放

SDL_PauseAudio(0);

4.在回呼函數中解碼音頻流，將解碼後的buffer複製到stream中

void audio_callback(void *userdata, Uint8 *stream, int len) {  //從檔案中讀取資料包，解碼到audio_buf中  .....  memcpy(stream, (uint8_t *)audio_buf + audio_buf_index, len1);  .....}