最简单的视音频播放示例9：SDL2播放PCM

int SDLCALL SDL_Init(Uint32 flags)

int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired, SDL_AudioSpec * obtained);

typedef struct SDL_AudioSpec { int freq; /**< DSP frequency -- samples per second */ SDL_AudioFormat 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) */ SDL_AudioCallback callback; void *userdata; } SDL_AudioSpec;

void (SDLCALL * SDL_AudioCallback) (void *userdata, Uint8 * stream, int len);

void SDLCALL SDL_PauseAudio(int pause_on)

/** * 最简单的SDL2播放音频的例子（SDL2播放PCM） * Simplest Audio Play SDL2 (SDL2 play PCM) * * 雷霄骅 Lei Xiaohua * leixiaohua1020@126.com * 中国传媒大学/数字电视技术 * Communication University of China / Digital TV Technology * http://blog.csdn.net/leixiaohua1020 * * 本程序使用SDL2播放PCM音频采样数据。SDL实际上是对底层绘图 * API（Direct3D，OpenGL）的封装，使用起来明显简单于直接调用底层 * API。 * * 函数调用步骤以下: * * [初始化] * SDL_Init(): 初始化SDL。 * SDL_OpenAudio(): 根据参数（存储于SDL_AudioSpec）打开音频装备。 * * [循环播放数据] * SDL_PauseAudio(): 播放音频数据。 * SDL_Delay(): 延时等待播放完成。 * * This software plays PCM raw audio data using SDL2. * SDL is a wrapper of low-level API (DirectSound). * Use SDL is much easier than directly call these low-level API. * * The process is shown as follows: * * [Init] * SDL_Init(): Init SDL. * SDL_OpenAudio(): Opens the audio device with the desired * parameters (In SDL_AudioSpec). * * [Loop to play data] * SDL_PauseAudio(): Play Audio. * SDL_Delay(): Wait for completetion of playback. */ #include <stdio.h> #include <tchar.h> extern "C" { #include "sdl/SDL.h" }; //Buffer: //|-----------|-------------| //chunk-------pos---len-----| static Uint8 *audio_chunk; static Uint32 audio_len; static Uint8 *audio_pos; /* Audio Callback * The audio function callback takes the following parameters: * stream: A pointer to the audio buffer to be filled * len: The length (in bytes) of the audio buffer * */ void fill_audio(void *udata,Uint8 *stream,int len){ //SDL 2.0 SDL_memset(stream, 0, len); if(audio_len==0) /* Only play if we have data left */ return; len=(len>audio_len?audio_len:len); /* Mix as much data as possible */ SDL_MixAudio(stream,audio_pos,len,SDL_MIX_MAXVOLUME); audio_pos += len; audio_len -= len; } int main(int argc, char* argv[]) { //Init if(SDL_Init(SDL_INIT_AUDIO | SDL_INIT_TIMER)) { printf( "Could not initialize SDL - %s ", SDL_GetError()); return ⑴; } //SDL_AudioSpec SDL_AudioSpec wanted_spec; wanted_spec.freq = 44100; wanted_spec.format = AUDIO_S16SYS; wanted_spec.channels = 2; wanted_spec.silence = 0; wanted_spec.samples = 1024; wanted_spec.callback = fill_audio; if (SDL_OpenAudio(&wanted_spec, NULL)<0){ printf("can't open audio. "); return ⑴; } FILE *fp=fopen("../NocturneNo2inEflat_44.1k_s16le.pcm","rb+"); if(fp==NULL){ printf("cannot open this file "); return ⑴; } //For YUV420P int pcm_buffer_size=4096; char *pcm_buffer=(char *)malloc(pcm_buffer_size); int data_count=0; while(1){ if (fread(pcm_buffer, 1, pcm_buffer_size, fp) != pcm_buffer_size){ // Loop fseek(fp, 0, SEEK_SET); fread(pcm_buffer, 1, pcm_buffer_size, fp); data_count=0; } printf("Now Playing %10d Bytes data. ",data_count); data_count+=pcm_buffer_size; //Set audio buffer (PCM data) audio_chunk = (Uint8 *) pcm_buffer; //Audio buffer length audio_len =pcm_buffer_size; audio_pos = audio_chunk; //Play SDL_PauseAudio(0); while(audio_len>0)//Wait until finish SDL_Delay(1); } return 0; }