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

[Marton Balint]

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.

Regards,
Marton