[FFmpeg-devel] [PATCH v4 13/18] avfilter/overlay_graphicsubs: Add overlay_graphicsubs and graphicsub2video filters

[Paul B Mahol]

On Sat, Sep 11, 2021 at 8:42 PM Soft Works <softworkz at hotmail.com> wrote:

>
>
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> > Paul B Mahol
> > Sent: Saturday, 11 September 2021 12:49
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel at ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH v4 13/18]
> > avfilter/overlay_graphicsubs: Add overlay_graphicsubs and
> > graphicsub2video filters
> >
> > You are still duplicating core overlaying code from overlay filter,
> > among
> > other things.
> >
> > Filter should be in same file as vf_overlay filter, this is more
> > demanding
> > to do because its harder than code extraction/copy&paste and adding
> > defines
> > and extra variables/functions for different paths.
>
> I've been afraid to do that because there are significant differences:
>
> - The functions in vf_overlay are based on both images having the
>   same planes/layout, but in overlay_graphicsubs, the overlay image
>   is always PAL8, even when overlaying on something like yuv420p
>
> - For overlaying the PAL8 over YUV, it's most efficient to convert
>   the palette to YUV first, and then lookup in the converted palette
>   while overlaying
>
> Wouldn't you think that changing the code in vf_overlay to accommodate
> for those cases, would add a bit too much complication? IMO, it would
> make the resulting code hard to read and maintain.
>
> I can still do it - are you sure I should?
>

With some refactoring it could be done. But if subtitle stuff is always
PAL8 than
not needed to do it into vf_overlay.

But some stuff is still duplicated... So refactoring could/should be done.


>
> Thanks,
> softworkz
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