[FFmpeg-devel] [PATCH] avfilter/avfilter: Fix hardcoded input index

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Paul B Mahol
> Sent: Monday, 6 September 2021 08:48
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH] avfilter/avfilter: Fix hardcoded
> input index
> 
> On Mon, Sep 6, 2021 at 7:23 AM 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: Sunday, 5 September 2021 21:51
> > > To: FFmpeg development discussions and patches <ffmpeg-
> > > devel at ffmpeg.org>
> > > Subject: Re: [FFmpeg-devel] [PATCH] avfilter/avfilter: Fix
> hardcoded
> > > input index
> > >
> > > On Sun, Sep 5, 2021 at 9:44 PM Soft Works <softworkz at hotmail.com>
> > > wrote:
> > >
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On
> Behalf Of
> > > > > Soft Works
> > > > > Sent: Sunday, 5 September 2021 16:59
> > > > > To: FFmpeg development discussions and patches <ffmpeg-
> > > > > devel at ffmpeg.org>
> > > > > Subject: Re: [FFmpeg-devel] [PATCH] avfilter/avfilter: Fix
> > > hardcoded
> > > > > input index
> > > > >
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On
> Behalf
> > > Of
> > > > > > Paul B Mahol
> > > > > > Sent: Sunday, 5 September 2021 11:01
> > > > > > To: FFmpeg development discussions and patches <ffmpeg-
> > > > > > devel at ffmpeg.org>
> > > > > > Subject: Re: [FFmpeg-devel] [PATCH] avfilter/avfilter: Fix
> > > > > hardcoded
> > > > > > input index
> > > > > >
> > > > > > With what filters this happens?
> > > > > >
> > > > > > IIUC this is forbidden and such filters should use
> .activate
> > > > > instead.
> > > > >
> > > > > The hardcoded [0] is wrong, no matter what the use case is.
> > > > >
> > > > > But to answer your question: It's about a new
> overlay_textsubs
> > > filter
> > > > > where framesync cannot be used and incoming frames (video on
> > > input0,
> > > > > subs on input1) need to be processed independently: the
> subtitle
> > > > > events
> > > > > are fed into the ass library (you could practically feed all
> > > events
> > > > > in advance) while the overlay image generation is done based
> on a
> > > > > given
> > > > > time code.
> > > > > This works fine by having a separate .filter_frame function
> for
> > > each
> > > > > input (after applying this patch).
> > > >
> > > > BTW
> > > >
> > > > > > IIUC this is forbidden and such filters should use
> .activate
> > > >
> > > > The scale2ref filter is set up in the same way (two
> .filter_frame
> > > > functions, no .activate, no framesync), probably because - like
> in
> > > > my case - the filter must not sync frames across inputs.
> > > >
> > >
> > > FYI .activate does not sync frames across inputs.
> >
> > Using .activate helped to solve another issue I had, so thanks
> again
> > for the hint.
> >
> > Besides recommended usage patterns - would you disagree that this
> > patch is logically correct?
> >
> 
> Yes. Because .activate fixes numerous issues.
> I see that only scale2ref is still using old way with multiple
> inputs. It
> probably should be fixed,
> and after that assert should be added in this file so new filters do
> not
> expose same limitations and mistakes of the past.

Thanks for the explanation. I will use .activate instead.

softworkz