static void get_frame_defaults(AVFrame *frame)
{
    if (frame->extended_data != frame->data)
        av_freep(&frame->extended_data);

    memset(frame, 0, sizeof(*frame));

    frame->pts                   =
    frame->pkt_dts               =
    frame->pkt_pts               = AV_NOPTS_VALUE;
    av_frame_set_best_effort_timestamp(frame, AV_NOPTS_VALUE);
    av_frame_set_pkt_duration         (frame, 0);
    av_frame_set_pkt_pos              (frame, -1);
    av_frame_set_pkt_size             (frame, -1);
    frame->key_frame           = 1;
    frame->sample_aspect_ratio = (AVRational){ 0, 1 };
    frame->format              = -1; /* unknown */
    frame->colorspace          = AVCOL_SPC_UNSPECIFIED;
    frame->extended_data       = frame->data;
}