[FFmpeg-user] ffmpeg concat issue

[Mark Hatch]

We use ffmpeg to concat a slate (mp4) to the end of a video file (mp4) and
most of the time it works great but occasionally, like 20% of the time, the
slate will have a video glitch 1 to 2 seconds into it. It appears to go
black for one frame, though the source slate does not have this issue.
Often if we add a frame to the precompressed file (first file) before
compressing and concatenating then it resolves the issue.

Here us ab example command:

ffmpeg -f concat -safe 0 -i <(printf "file $PWD/video.mp4\nfile
$PWD/slate.mp4") -an -codec copy -y ./output.mp4

Most of the time it works.

Any thoughts?