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

void print_packet_frame_pts(AVFormatContext *pFormatCtx, int StreamIndex)
{
    AVCodecContext* pCodecCtx = pFormatCtx->streams[StreamIndex]->codec;
    avcodec_open2(pCodecCtx, avcodec_find_decoder(pCodecCtx->codec_id), NULL);
    AVFrame *pFrameSource = avcodec_alloc_frame();
    AVPacket packet;

    int finished = 0;

    // read all packets
    while(!av_read_frame(pFormatCtx, &packet))
    {
        // only process packets from video stream
        if(packet.stream_index == StreamIndex)
        {
            // decode packet into frame
            if(avcodec_decode_video2(pCodecCtx, pFrameSource, &finished, &packet) > 0)
            {
                // check if frame is completely decoded
                if(finished)
                {
                    printf("  packet.pts=%lu => frame.pts=%lu\n", packet.pts, pFrameSource->pkt_pts);
                }
                else
                {
                    printf("  packet.pts=%lu => FRAME NOT FINISHED\n", packet.pts);
                }
            }
        }
        av_free_packet(&packet);
    }
    av_free(pFrameSource);
    pCodecCtx = NULL;

    // go back to frame 0
    av_seek_frame(pFormatCtx, 0, 0, AVSEEK_FLAG_BACKWARD);
    avcodec_flush_buffers(pFormatCtx->streams[0]->codec);
}

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

    AVFormatContext *pFormatCtx = NULL;

    // open file "test.avi"
    if(avformat_open_input(&pFormatCtx, "test.avi", NULL, NULL) == 0)
    {
        // read all packets and print pts, also decode corresponding frames and print pts
        printf("\n# BEFORE avformat_find_stream_info()\n\n");
        print_packet_frame_pts(pFormatCtx, 0);

        // try to get info by decoding some frames
        avformat_find_stream_info(pFormatCtx, NULL);

        // FIXME: insert fix here so packet/frame pts will not be corrupted after avformat_find_stream_info()
        // flush internal packet buffer ?

        // read all packets and print pts, also decode corresponding frames and print pts
        printf("\n# AFTER avformat_find_stream_info()\n\n");
        print_packet_frame_pts(pFormatCtx, 0);
    }

    // close file
    if(pFormatCtx != NULL)
    {
        avformat_close_input(&pFormatCtx);
        pFormatCtx = NULL;
        printf("\n");
    }

    return 0;
}