ffmpeg解码视频流

//初始化、注册编解码器
avcodec_init();
av_register_all();
avformat_network_init();

//选取测试文件
char* FileName = "test.rmvb";
AVFormatContext *pFormatCtx;
if(av_open_input_file(&pFormatCtx, FileName, NULL, 0, NULL)!=0)
{
printf("打开文件失败\n");
return -1;
}
dump_format(pFormatCtx, 0, NULL, NULL);//打印相关参数

//寻找流信息，获取格式上下文信息
int err = av_find_stream_info(pFormatCtx);
if(err < 0)
{
printf("查看流信息失败");
return 0;
}

//找到所有的音频流和视频流
vector<int> v_video_index;
vector<int> v_audio_index;
for(unsigned int i = 0;i < pFormatCtx->nb_streams; i++)
{
if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
{
v_audio_index.push_back(i);
}
if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
v_video_index.push_back(i);
}
}

 AVCodecContext *pAVCodecCtx = pFormatCtx->streams[v_video_index[0]]->codec;
 AVCodec   *pAVCodec = avcodec_find_decoder(pAVCodecCtx->codec_id);  
 if(!pAVCodec)
 {
  printf("Unsupported codec!\n");
  return -1;
 }
 avcodec_open(pAVCodecCtx,pAVCodec); 


//初始化包
AVPacket packet;
av_init_packet(&packet);

int  got_picture_ptr=0;
int  len;
int  width;
int  height;
int  count=1;

//为每帧图像分配内存
AVFrame  *picture = avcodec_alloc_frame();
AVFrame  *pFrameRGB = avcodec_alloc_frame();   
if ( (picture == NULL)||(pFrameRGB == NULL) )   
{   
printf("avcodec alloc frame failed!\n");   
exit (1);   
}        

 //处理第一条视频流
while(av_read_frame(pFormatCtx,&packet)>=0)
{    
uint8_t* buff = (packet.data);
if(packet.stream_index==v_video_index[0])
{ 
  int iReadTime = 0; 
  while(packet.size > 0) 
  {
  iReadTime++;
  len = avcodec_decode_video2(pAVCodecCtx, picture, &got_picture_ptr, &packet);
  if(len==0)  
  {
  got_picture_ptr=0;
  }
  if(len<0)
  {
  break;
  }
  if(got_picture_ptr)
  { 
  #if 1     
  if(picture->key_frame==1)
  {
  printf("关键帧\n");
  }
  else
  {
  printf("非关键帧\n");
  }
  #endif

  #if 1        //判断I B P 帧
  if(FF_I_TYPE == picture->pict_type)
  {
  o<<"I Frame:"<<"packet.dts:"<<packet.dts<<"        "<<"packet.pts:"<<packet.pts<<endl;
  }
  else if(FF_B_TYPE==picture->pict_type)
  {
  o<<"B Frame:"<<"packet.dts:"<<packet.dts<<"        "<<"packet.pts:"<<packet.pts<<endl;
  }
  else
  {
  o<<"P Frame:"<<"packet.dts:"<<packet.dts<<"        "<<"packet.pts:"<<packet.pts<<endl;
  }
  #endif

  width = pAVCodecCtx->width;
  height = pAVCodecCtx->height;
if(count)
 {
  //保存YUV
  #if 1   
  int  dstwidth = 800;
  int  dstheight = 600;
  //uint8_t *BufferForSws = (uint8_t*)av_malloc(MAX_FRAME_SIZE);
  int size = avpicture_get_size(PIX_FMT_YUV420P, dstwidth, dstheight);
  uint8_t *BufferForSwsCtx = (uint8_t*)av_malloc(size);
  AVFrame     *dstframe = avcodec_alloc_frame();                  
  avpicture_fill((AVPicture*)dstframe, BufferForSwsCtx, PIX_FMT_YUV420P, dstwidth, dstheight);   
  SwsContext* pSwsCtx = sws_getContext(pAVCodecCtx->width, pAVCodecCtx->height, pAVCodecCtx->pix_fmt, dstwidth, dstheight, PIX_FMT_YUV420P, SWS_BILINEAR,NULL,NULL,NULL);                   
  int ret = sws_scale(pSwsCtx,picture->data, picture->linesize, 0, pAVCodecCtx->height, dstframe->data, dstframe->linesize);
  dstframe->width = dstwidth;
  dstframe->height = dstheight;
  SaveYUV(dstframe, dstwidth, dstheight, count);
  av_free(dstframe);
  sws_freeContext(pSwsCtx);
  #endif 
}  
  count++;
  break;
  }
  packet.size -= len;
  packet.data += len;
   }
   if(packet.data != NULL)
   {
 av_free_packet(&packet);
   }
}
}
 av_free(picture);
 av_free(pFrameRGB);

 avcodec_close(pAVCodecCtx);
 av_close_input_file(pFormatCtx);