VVC MP4 Decoding Issue - Frames Are Missing

[Rupert_Williamson]

Summary of the bug:

Attempting to extract frames from a vvenc-encoded .mp4 file does not extract all the frames.

How to reproduce:

Encode with:
% ffmpeg -r 60 -ss 0 -i silver.mov -t 4 -y -c:v libvvenc vvc.mp4

Then decode with:
ffmpeg -r 60 -i vvc.mp4 out/out_%04d.png

ffmpeg version 2024-10-10-git-0f5592cfc7-full_build-www.gyan.dev Copyright (c) 2000-2024 the FFmpeg developers

Rather than getting 240 frames as I would expect (4 seconds of 60.000 fps input), I only get 209 frames out.

In this case the input file is a lossless 8bpc RGB 60fps 4K uncompressed .mov file. However I have this issue with other files too, such as 16 bit .nut files or even 16bpc .tif sequences.

Gyan thinks it "notionally appears to be a bug in the mp4 muxer" and sees an "editlist setting the start of the video track output from ~half-second."

For more details, you can see a post I made here:
​https://www.reddit.com/r/ffmpeg/comments/1g684mo/vvc_decoding_issue_frames_are_missing/