Re: [FFmpeg-devel] [PATCH v3] area changed: scdet filter

[<radu.taraibuta@gmail.com>]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Tobias
> Rapp
> Sent: joi, 13 iunie 2024 12:52
> To: ffmpeg-devel@ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH v3] area changed: scdet filter
> 
> On 12/06/2024 21:51, radu.taraibuta@gmail.com wrote:
> 
> [...]
> 
> > diff --git a/doc/filters.texi b/doc/filters.texi index
> > bfa8ccec8b..53814e003b 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -21797,6 +21797,22 @@ Default value is @code{10.}.
> >  @item sc_pass, s
> >  Set the flag to pass scene change frames to the next filter. Default
> > value is @code{0}
> >  You can enable it if you want to get snapshot of scene change frames
> > only.
> > +
> > +@item mode
> > +Set the scene change detection method. Default value is @code{-1}
> > +Available values are:
> > +
> > +@table @samp
> > +@item -1
> > +Legacy mode for sum of absolute linear differences. Compare frame
> > with previous only and no delay.
> > +
> > +@item 0
> > +Sum of absolute linear differences. Compare frame with both previous
> > and next which introduces a 1 frame delay.
> > +
> > +@item 1
> > +Sum of mean of cubic root differences. Compare frame with both
> > previous and next which introduces a 1 frame delay.
> > +
> > +@end table
> >  @end table
> >
> >  @anchor{selectivecolor}
> 
> Out of curiosity: How do these three modes roughly compare (CPU)
> performance wise?

Mode -1 is virtually equal with mode 0 (no frame clone speedup of mode 0 is mostly theoretical). Mode 1 is roughly 40% slower, depending on input, it could benefit from ASM.

> I'd prefer if mode "-1" could be used for the default case, and the three modes
> get explicit values 0/1/2. 

So you want four possible values for mode where the default -1 is the same as one of the others?

>Regarding naming I think that the "Legacy" mode still
> has its usecases in the future. Naming it something like "simple" would not
> imply that it is deprecated in general, but rather that it has lower precision
> (and is possibly faster).
> 
OK, I will rename "Legacy" mode so it doesn't look deprecated to somebody that can't allow 1 frame delay. Otherwise it shouldn't be used.


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