Re: [FFmpeg-devel] [PATCH] avformat/movenc: fix VVC encoding with leading pictures

[Nuo Mi <nuomi2021@gmail.com>]

On Fri, May 16, 2025 at 7:05 PM Gabriel Hege <g+ffmpeg@hege.cc> wrote:

> This is a resubmission with a corrected commit message.
>
>
> The default behavior for VVenC (since v1.10.0) is to create an IDR with
> leading pictures for the first picture in decoding order (POC 32). This
> leads to FFmpeg generating an edit list with an empty entry, skipping
> the leading pictures.
>
> This patch fixes the calculation for the start_pts, while the DTS is
> negative (as produced by libvvenc).
>
>
> How to reproduce the issue (needs --enable-libvvenc and a recent
> libvvenc, e.g. v1.13):
>
Hi Gabriel,
Thank you for your patch. It addresses the MP4 issue, but it looks like MKV
has the same problem as well.

Hi @James Almer <jamrial@gmail.com> ,
Could you please take a look at the patch when you have a moment? You've
been the most active contributor to this file recently.

>
> Encode VVC directly into MP4 container:
> ./ffmpeg -i /data/YUV/foreman_352x288_30Hz_i420_8.y4m -an -preset faster
> -vcodec vvc test.mp4
>
>    -> encodes 300 frames.
>
> Decode to YUV (or play back using ffplay):
> ./ffmpeg -i test.mp4 test.yuv
>
>    -> outputs 271 frames
>
> When dumping the mp4-structure using 'MP4Box -diso test.mp4', I see the
> following EditListBox, which skips the first couple of
> frames:<EditListBox Size="40" Type="elst" Version="0" Flags="0"
> Specification="p12" Container="edts" EntryCount="2">
> <EditListEntry Duration="1033" MediaTime="-1" MediaRate="1"/>
> <EditListEntry Duration="8967" MediaTime="18432" MediaRate="1"/>
> </EditListBox>
>
>
> With the fix applied 300 frames are decoded as expected and the
> EditListBox looks like this:
> <EditListBox Size="28" Type="elst" Version="0" Flags="0"
> Specification="p12" Container="edts" EntryCount="1">
> <EditListEntry Duration="10000" MediaTime="2560" MediaRate="1"/>
> </EditListBox>
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