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

[Paul B Mahol]

On Sun, Sep 5, 2021 at 9:56 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: 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?
>

Numerous examples across code base, grep for .activate.


> Thanks,
> softworkz
>
>
>
>
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