static void print_sdp(void)
{
    char sdp[16384];
    int i;
    AVFormatContext **avc = av_malloc(sizeof(*avc) * nb_output_files);

    if (!avc)
        exit_program(1);
    for (i = 0; i < nb_output_files; i++)
        avc[i] = output_files[i]->ctx;

    av_sdp_create(avc, nb_output_files, sdp, sizeof(sdp));
    printf("SDP:\n%s\n", sdp);
    fflush(stdout);
    av_freep(&avc);
}