int main()
{

    av_register_all();


    AVFormatContext *ps = avformat_alloc_context();

    AVFormatContext *ps2 = avformat_alloc_context();
    AVOutputFormat *oF = av_guess_format("mp4", NULL, "video/mp4");
    avformat_alloc_output_context2(&ps2, oF, NULL, "vid2.mp4");

    if(avformat_open_input(&ps, "vid.mp4", NULL, NULL) != 0)
    {
        printf("Failed to open input file.\n");
        return -1;
    }

    avio_open(&ps2->pb, "vid2.mp4", AVIO_FLAG_WRITE);

    avformat_find_stream_info(ps, NULL);

   // AVStream *iStream;
    //AVStream *oStream;

    AVCodecContext *pC, *p2C;
    //AVCodec *encoder;

    AVStream *oStream = NULL;
    AVStream *iStream = NULL;

    AVCodec *encoder = NULL;

    for(unsigned int i = 0; i < ps->nb_streams; i++)
    {
        oStream = avformat_new_stream(ps2, NULL);
        iStream = ps->streams[i];

        pC = iStream->codec;
        avcodec_parameters_copy(oStream->codecpar, iStream->codecpar);

        if(pC->codec_type == AVMEDIA_TYPE_VIDEO || pC->codec_type == AVMEDIA_TYPE_AUDIO)
        {
            encoder = avcodec_find_encoder(pC->codec_id);

            avcodec_parameters_to_context(p2C, iStream->codecpar);

            avcodec_open2(p2C, encoder, NULL);
            avcodec_open2(pC, avcodec_find_decoder(pC->codec_id), NULL);


        }
    }

    avformat_write_header(ps2, NULL);

    printf("Fine\n");

    AVFrame *rawFrame = av_frame_alloc();

    AVPacket *pkts = av_packet_alloc();
    av_init_packet(pkts);
    AVPacket *pktr = av_packet_alloc();
    av_init_packet(pktr);


    while(av_read_frame(ps, pkts) == 0)
    {
        //decoding
        int ret1 = avcodec_send_packet(pC, pkts);
        int ret2 = avcodec_receive_frame(pC, rawFrame);

        //encoding
        avcodec_send_frame(p2C, rawFrame);
        avcodec_receive_packet(p2C, pktr);

        int ret = av_interleaved_write_frame(ps2, pktr);
    }


}