PTS/DTS clearing in gcc sink pad

[Thibault Saunier]

Hi,

This is because the `rtpgccbwe` is doing the pacing[0], implying buffer
timestamps are meanigless after that point, in `webrtcbin` we
synchronize the streams upstream of that element we can thus remove the
timestamps so that downstream elements will not do any clock
synchronization anymore.

- Thibault

[0]
https://datatracker.ietf.org/doc/html/draft-ietf-rmcat-gcc-02#section-4

On Fri, 2023-01-13 at 22:12 +0800, Jun Xiao via gstreamer-devel wrote:
> Hi Mathieu,
> 
> In gcc/imp.rs, I found the sink pad is doing following:
>   mutbuf.set_pts(None);
>   mutbuf.set_dts(None);
> 
> I am curious what the purpose of this clearing is, and will DTS/PTS
> be re-provisioned by any subsequent element in a pipeline? Could you
> help to elaborate this.
> 
> Thanks,
> Jun