[FFmpeg-devel] [PATCH] libavcodec: add editpts bitstream filter [v4]

[Paul B Mahol]

On 9/3/19, Marton Balint <cus at passwd.hu> wrote:
>
>
> On Tue, 3 Sep 2019, Andreas Håkon wrote:
>
>> Hi,
>>
>> Ping, ping! (another time).
>>
>> Please take note of these three points:
>>
>> 1. Lip-Syncing is a relevant topic in the AV editing area. Almost all
>> professional video editors have
>> the functionality to realign audio with video. And at time the ffmpeg
>> project lacks for a lipsync
>> bitstream filter. For this reason, this new filter is relevant. Although
>> it can also be used for other purposes.
>>
>> 2. This is the fourth iteration of the patch, and it incorporates all
>> suggested requests. So it's ready
>> for review and acceptance.
>>
>> 3. Although the current implementation can be improved (using, for
>> example, values expressed in
>> nano-seconds), it's preferable to first add it and then improve it.
>
> Some things can't be improved later, because they become part of the
> public interface so we can no longer just remove them, we'd have to
> deprecate them first.
>
> Also ffmpeg tries to be consistent with other parts of the code, use names
> based on the same logic, or use similar concepts throughout the libraries.
>
> Avoiding duplicated functionality is also a strong requirement for us, if
> something can be implemented in a more generic way (even if that takes a
> little more work), we should aim for that.
>
> That is why I suggest you implement a more generic approach, a setpts like
> filter (setts) with evaluation. As others pointed out, you typically need
> to modify both PTS and DTS, so the expression should affect both.
> Additional parameters can be introduced if somebody wants different
> expressions for PTS and DTS.

Agree with Marton here, looking at source code of bitstream filter it
is very limited in functionality.

>
> Regards,
> Marton
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