[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: 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.

Thanks for the information, I wasn't aware of that; so far I had always
seen it used in combination with framesync, do you know an example
where it's being used without framesync?

Thanks,
softworkz