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

[Gabriel Hege]

On 25.05.25 04:08, Nuo Mi wrote:
> On Thu, May 22, 2025 at 4:35 PM Gabriel Hege <g+ffmpeg at hege.cc> wrote:
> 
>>
>> On 17.05.25 04:26, Nuo Mi wrote:
>>> On Fri, May 16, 2025 at 7:05 PM Gabriel Hege <g+ffmpeg at 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 Nuo Mi,
>>
>> I'm sorry I don't really have an understanding of the MKV format. I had
>> a quick look at the code, but the processing seems quite different and I
>> didn't really find the corresponding code locations to fix the problem
>> there.
>>
> Hi Gabriel,
> Thank you for checking.
> Could you help create a similar issue for MKV? Someone familiar with MKV
> might pick it up.

I filed a bug report: https://trac.ffmpeg.org/ticket/11611


> Hi  James and all,
> If no one objects, I’ll push this.
> 
> Thank you.
> 
>>
>>
>>> Hi @James Almer <jamrial at 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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