21 Using FFMpeg - bootstrap code for decoding

main.c

// a very simplified FFMPEG decoding bootstrap code (without any error handling...)

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>

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

  // init format context and open the file
  AVFormatContext *pFormatContext = avformat_alloc_context();
  avformat_open_input(&pFormatContext, argv[1], NULL, NULL);

  // find the video stream from streams in a file, and init codec
  AVCodec *pCodec = NULL;
  int video_stream_index = av_find_best_stream(pFormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, &pCodec, 0);
  AVCodecParameters *pCodecParameters = pFormatContext->streams[video_stream_index]->codecpar;

  // init codec context
  AVCodecContext *pCodecContext = avcodec_alloc_context3(pCodec);
  avcodec_parameters_to_context(pCodecContext, pCodecParameters);
  avcodec_open2(pCodecContext, pCodec, NULL);

  // alloc frame and packet
  AVFrame *pFrame = av_frame_alloc();
  AVPacket *pPacket = av_packet_alloc();

  int response = 0;
  int how_many_packets_to_process = 8;

  // call read frame in a loop
  while (av_read_frame(pFormatContext, pPacket) >= 0 && how_many_packets_to_process > 0)
  {
    if (pPacket->stream_index == video_stream_index) {
      // send packet
      avcodec_send_packet(pCodecContext, pPacket);
      how_many_packets_to_process--;

      // attempting to receive frame
      while(avcodec_receive_frame(pCodecContext, pFrame) >= 0) {
        // do something with decoded frame here...
        printf("%"PRId64, pFrame->pts);
        printf("\n");
      }
    }
    // clear up packet buffer for next frame
    av_packet_unref(pPacket);
  }

  // free memory
  avformat_close_input(&pFormatContext);
  avformat_free_context(pFormatContext);
  av_packet_free(&pPacket);
  av_frame_free(&pFrame);
  avcodec_free_context(&pCodecContext);
  return 0;
}