What does the FFmpeg warning "Missing picture in access unit with size x" mean?

I’ve recently updated to the most recent version of ffmpeg and now every time I edit a flv, I always get endless warnings:

[Null @ 002de180] Missing Missing picture in access unit with size xxxx (size varies per file)

[Null @ 002de180] AVC: nal size xxxx (size also varies per file)

.....

...

I’ve checked other versions too and it seems like any version above 2.1.4 will start giving these warnings.

The command I'm using is ffmpeg.exe -t 0:03:00 -y -i "C:\test.flv" -vcodec copy -acodec copy "C:\Desktop\newvid.flv" to cut sections of a video.

Even with these warnings, the output file plays fine and the video seems to be in sync. The file size is also the same as if I edit the vid with ffmpeg 2.1.4. But the versions with these warnings take much longer to encode. Any idea what is happening or what these warnings mean?

1 Answer

This is a known bug until version 2.4.2. It's already solved. For more details see here