[Libav-user] Overlay filter has incorrect frame rate

[Brian C. Wiles]

Hi,


  I am trying to programmatically overlay one video onto another, and
the top (overlaid) video plays at half it's normal frame rate.  If I use
the ffmpeg command, it works fine.


  I started with the doc/examples/transcoding.c example and changed the
filter initialization.  Here's how I create the filters:


static int init_filters(char *source, char *source_type)
{
    char filter_spec[2000];
    unsigned int i;
    int ret;
    filter_ctx = av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
    if (!filter_ctx)
        return AVERROR(ENOMEM);

    for (i = 0; i < ifmt_ctx->nb_streams; i++)
    {
        filter_ctx[i].buffersrc_ctx = NULL;
        filter_ctx[i].buffersink_ctx = NULL;
        filter_ctx[i].filter_graph = NULL;
        if (!(ifmt_ctx->streams[i]->codecpar->codec_type ==
                  AVMEDIA_TYPE_AUDIO ||
              ifmt_ctx->streams[i]->codecpar->codec_type ==
AVMEDIA_TYPE_VIDEO))
            continue;

        if (ifmt_ctx->streams[i]->codecpar->codec_type ==
AVMEDIA_TYPE_VIDEO)
        {
            sprintf(
                filter_spec,
                "movie='anim.mp4', "
                "scale=w='min(250\\, iw*3/2):h=-1' [wm]; "
                "[in][wm]
overlay=x=main_w-overlay_w-50:y='main_h-overlay_h-50'"
                ":enable='between(t,5,10)' [out]");
        }
        else
        {
            strcpy(filter_spec,
                   "anull"); /* passthrough (dummy) filter for audio */
        }

        ret = init_filter(&filter_ctx[i], stream_ctx[i].dec_ctx,
                          stream_ctx[i].enc_ctx, filter_spec);
        if (ret)
            return ret;
    }
    return 0;
}

  I have tried using the fps and setpts filters, but that seems like a
hack to get it to honor the actual frame rate in the file.  Let me know
if you need more info.  I appreciate any help someone can give me.  Thanks!


-Brian