[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 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).

Thanks,
softworkz