basic_decoder.c

int main(int argc, const char *argv[])
{
  av_register_all();

  AVFormatContext *pFormatContext = avformat_alloc_context();
  avformat_open_input(&pFormatContext, argv[1], NULL, NULL);
  avformat_find_stream_info(pFormatContext, NULL);
  AVCodec *pCodec = NULL;
  AVStream *pStream = NULL;
  int video_stream_index = -1;

  // find the first video stream
  for (int i = 0; i < pFormatContext->nb_streams; i++)
  {
    video_stream_index = i;
    pStream = pFormatContext->streams[i];
    AVCodecParameters *pCodecParameters =  pStream->codecpar;

    if (pCodecParameters->codec_type == AVMEDIA_TYPE_VIDEO) {
      pCodec = avcodec_find_decoder(pCodecParameters->codec_id);
      break;
    }
  }

  AVCodecContext *pCodecContext = avcodec_alloc_context3(pCodec);
  avcodec_open2(pCodecContext, pCodec, NULL);
  AVFrame *pFrame = av_frame_alloc();
  AVPacket *pPacket = av_packet_alloc();

  while (av_read_frame(pFormatContext, pPacket) >= 0) {

    int response = avcodec_send_packet(pCodecContext, pPacket);
    if (response < 0) {
      printf("error sending packet");
      return -1;
    }

    while (response >= 0) {
      response = avcodec_receive_frame(pCodecContext, pFrame);

      if (response == AVERROR(EAGAIN) || response == AVERROR_EOF) {
        printf("error receiving frame");
        return -1;
      } else if (response < 0) {
        printf("Error during decoding\n");
        return -1;
      }
      printf("saving frame %3d\n", pCodecContext->frame_number);
    }
  }
}