[Libav-user] Video overlay only overlays first frame

Kenneth Gibson kennethjjgibson at gmail.com
Thu Feb 16 01:58:46 CET 2012

I found this somewhere:

"The first frame of one of the videos will also be repeated in the
beginning if the videos that have different initial timestamps."

I guess that was what was happening, even though I was attempting to set
both initial timestamps to 0. Just as a test I changed the overlay setpts
to -10 and now it plays the video properly, although I don't really
understand why.

On Thu, Feb 16, 2012 at 12:28 PM, Kenneth Gibson
<kennethjjgibson at gmail.com>wrote:

> Hi,
> I'm trying to overlay a .mp4 on top of another .mp4 programmatically.
> This is my filter description:
> "movie=myvid.mp4, setpts=PTS-STARTPTS [movie]; [in] setpts=PTS-STARTPTS,
> [movie] overlay=0:0 [out]"
> This results in only the first frame of myvid.mp4 being overlaid on my
> video. And the first frame persists for the length of the video, like it is
> a static image.
> My code is basically identical to that of filtering.c<http://ffmpeg.org/doxygen/trunk/filtering_8c-source.html> (the
> difference being that I output the result into a .mp4)
> What would cause the filter to only overlay the first frame?
> Cheers
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