MFC中FFMPEG+SDL播放音频的时候在主界面中播放有声音，创建线程去播放没有声音

[xbj6520044]

static Uint8 *audio_chunk;
static Uint32 audio_len;
static Uint8 *audio_pos;

/* 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
* 回调函数
*/
void fill_audio(void *udata,Uint8 *stream,int 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[])
{
AVFormatContext *pFormatCtx;
int i, audioStream;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;

char url[]="WavinFlag.aac";
//char url[]="WavinFlag.mp3";
//char url[]="72bian.wma";

av_register_all();
avformat_network_init();
pFormatCtx = avformat_alloc_context();
//Open
if(avformat_open_input(&pFormatCtx,url,NULL,NULL)!=0){
printf("Couldn't open input stream.\n");
return -1;
}
// Retrieve stream information
if(av_find_stream_info(pFormatCtx)<0){
printf("Couldn't find stream information.\n");
return -1;
}
// Dump valid information onto standard error
av_dump_format(pFormatCtx, 0, url, false);

// Find the first audio stream
audioStream=-1;
for(i=0; i < pFormatCtx->nb_streams; i++)
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){
audioStream=i;
break;
}

if(audioStream==-1){
printf("Didn't find a audio stream.\n");
return -1;
}

// Get a pointer to the codec context for the audio stream
pCodecCtx=pFormatCtx->streams[audioStream]->codec;

// Find the decoder for the audio stream
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL){
printf("Codec not found.\n");
return -1;
}

// Open codec
if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
printf("Could not open codec.\n");
return -1;
}

FILE *pFile=NULL;
#if OUTPUT_PCM
pFile=fopen("output.pcm", "wb");
#endif

AVPacket *packet=(AVPacket *)malloc(sizeof(AVPacket));
av_init_packet(packet);

//Out Audio Param
uint64_t out_channel_layout=AV_CH_LAYOUT_STEREO;
//AAC:1024 MP3:1152
int out_nb_samples=pCodecCtx->frame_size;
AVSampleFormat out_sample_fmt=AV_SAMPLE_FMT_S16;
int out_sample_rate=44100;
int out_channels=av_get_channel_layout_nb_channels(out_channel_layout);
//Out Buffer Size
int out_buffer_size=av_samples_get_buffer_size(NULL,out_channels ,out_nb_samples,out_sample_fmt, 1);

uint8_t *out_buffer=(uint8_t *)av_malloc(MAX_AUDIO_FRAME_SIZE*2);

AVFrame *pFrame;
pFrame=avcodec_alloc_frame();
//SDL------------------
#if USE_SDL
//Init
if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
printf( "Could not initialize SDL - %s\n", SDL_GetError());
return -1;
}
//SDL_AudioSpec
SDL_AudioSpec wanted_spec;
wanted_spec.freq = out_sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = out_channels;
wanted_spec.silence = 0;
wanted_spec.samples = out_nb_samples;
wanted_spec.callback = fill_audio;
wanted_spec.userdata = pCodecCtx;

if (SDL_OpenAudio(&wanted_spec, NULL)<0){
printf("can't open audio.\n");
return -1;
}
#endif
printf("Bitrate:\t %3d\n", pFormatCtx->bit_rate);
printf("Decoder Name:\t %s\n", pCodecCtx->codec->long_name);
printf("Channels:\t %d\n", pCodecCtx->channels);
printf("Sample per Second\t %d \n", pCodecCtx->sample_rate);

uint32_t ret,len = 0;
int got_picture;
int index = 0;
//FIX:Some Codec's Context Information is missing
int64_t in_channel_layout=av_get_default_channel_layout(pCodecCtx->channels);
//Swr
struct SwrContext *au_convert_ctx;
au_convert_ctx = swr_alloc();
au_convert_ctx=swr_alloc_set_opts(au_convert_ctx,out_channel_layout, out_sample_fmt, out_sample_rate,
in_channel_layout,pCodecCtx->sample_fmt , pCodecCtx->sample_rate,0, NULL);
swr_init(au_convert_ctx);

//Play
SDL_PauseAudio(0);

while(av_read_frame(pFormatCtx, packet)>=0){
if(packet->stream_index==audioStream){

ret = avcodec_decode_audio4( pCodecCtx, pFrame,&got_picture, packet);
if ( ret < 0 ) {
printf("Error in decoding audio frame.\n");
return -1;
}
if ( got_picture > 0 ){
swr_convert(au_convert_ctx,&out_buffer, MAX_AUDIO_FRAME_SIZE,(const uint8_t **)pFrame->data , pFrame->nb_samples);

printf("index:%5d\t pts:%lld\t packet size:%d\n",index,packet->pts,packet->size);

#if OUTPUT_PCM
//Write PCM
fwrite(out_buffer, 1, out_buffer_size, pFile);
#endif

index++;
}
//SDL------------------
#if USE_SDL
//Set audio buffer (PCM data)
audio_chunk = (Uint8 *) out_buffer;
//Audio buffer length
audio_len =out_buffer_size;

audio_pos = audio_chunk;

while(audio_len>0)//Wait until finish
SDL_Delay(1);
#endif
}
av_free_packet(packet);
}

swr_free(&au_convert_ctx);

#if USE_SDL
SDL_CloseAudio();//Close SDL
SDL_Quit();
#endif

#if OUTPUT_PCM
fclose(pFile);
#endif
av_free(out_buffer);
avcodec_close(pCodecCtx);
av_close_input_file(pFormatCtx);

return 0;
}

抄的这个例子，我把main函数中的东西放在线程中播不出声音是怎么回事呢，求大神！