[FFmpeg-devel] [PATCH 11/11] doc/filters.texi: update overlay_vaapi documentation

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Gyan Doshi
> Sent: Monday, October 10, 2022 1:08 PM
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 11/11] doc/filters.texi: update
> overlay_vaapi documentation
> 
> 
> 
> On 2022-10-10 04:24 pm, softworkz wrote:
> > From: softworkz <softworkz at hotmail.com>
> >
> > Signed-off-by: softworkz <softworkz at hotmail.com>
> > ---
> >   doc/filters.texi | 49 +++++++++++++++++++++++++++++++++++++------
> -----
> >   1 file changed, 38 insertions(+), 11 deletions(-)
> >
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index 2d0b5db909..5f4604a834 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -26271,30 +26271,57 @@ It takes two inputs and has one output.
> The first input is the "main" video on w
> >   The filter accepts the following options:
> >
> >   @table @option
> > -
> >   @item x
> > -Set the x coordinate of the overlaid video on the main video.
> > -Default value is @code{0}.
> > -
> >   @item y
> > -Set the y coordinate of the overlaid video on the main video.
> > -Default value is @code{0}.
> > +Set expressions for the x and y coordinates of the overlaid video
> > +on the main video.
> >
> > - at item w
> > -Set the width of the overlaid video on the main video.
> > -Default value is the width of input overlay video.
> > +Default value is "0" for both expressions.
> >
> > + at item w
> >   @item h
> > -Set the height of the overlaid video on the main video.
> > -Default value is the height of input overlay video.
> > +Set expressions for the width and height the overlaid video
> > +on the main video.
> 
> The default values should be mentioned here. And also what the
> default
> value means, if not trivial.
> 
> Regards,
> Gyan

Yea, you are hitting a point that I had left out because
I wasn't sure how detailed this should be explained:

The expression handling is done analog to overlay_qsv and I've taken
the same defaults which are:

    { "w", "Overlay width",      OFFSET(overlay_ow), AV_OPT_TYPE_STRING, { .str="overlay_iw"}, 0, 255, .flags = FLAGS},
    { "h", "Overlay height",     OFFSET(overlay_oh), AV_OPT_TYPE_STRING, { .str="overlay_ih*w/overlay_iw"}, 0, 255, .flags = FLAGS},


Essentially, the values are defaulting to the frame size of the
overlay input. This is because both, w and overlay_iw are initialized
to the overlay size. The default expression allows to set the width
only and have the height be adjusted proportionally.
But it doesn't work the other way round (setting h only), so 
I'm not sure whether it's a good default at all - I just wanted 
to have it equal to overlay_qsv..

Thanks,
softworkz