[FFmpeg-devel] [PATCH 4/9] avfilter/overlay_subs: Add overlay_subs filter

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Paul B
> Mahol
> Sent: Thursday, 19 August 2021 09:58
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 4/9] avfilter/overlay_subs: Add
> overlay_subs filter
> 
> Reuse old code and just put new/changed stuff into vf_overlay.c


The primary problem I have is that the regular overlay filter just 
enforces an overlay format that matches the primary input video format:

e.g.: when the primary video is yuv420p, it requests yuva420p for
the overlay input which causes a format filter to be inserted automatically.

That's not possible in this case because we have subtitle frames as 
input. Ideally, there wouldn't happen any format conversion up-front.
Neither for the main video, nor for the overlay rects.
What I mean is, that only the pixels of the overlay area would be touched,
like for example: convert yuv to rgb, blend with rgba overlay, convert
back rgb to yuv.

Does that make sense?

softworkz