Re: [FFmpeg-devel] [RFC] Moving edit list handling out of demuxers

["Tomas Härdin" <git@haerdin.se>]

fre 2025-06-13 klockan 16:21 +0200 skrev Michael Niedermayer:
> > 3) remove edit list hacks from all demuxers, especially mov.c
> 
> +1 (with ABI +2 bump)

I'm not sure why a (major?) bump would be necessary. Are removal of
options a major bump, not a minor one? Either way, we could make the
options ffmpeg.c ones rather than mov.c ones. There's going to be pain
either way, partly because doing this in the demuxer was the wrong
thing to do in the first place. Another case of "oh let's just do a
quick and dirty thing" coming back to bite us.

Come to think of this, perhaps hiding this behind a major bump is not
such a bad idea. That allows making more sweeping changes, including
behavioral ones.

> > The main issue I see with this is that it risks turning ffmpeg into
> > an
> > NLE tool,
> 
> If ffmpeg could do NLE, that would not be a bad thing
> And a full implementation of edit lists may be equivalent to this.
> I think thats a win not a loss

Fair enough. So long as I don't have to implement it or think
particularly much about it.

> > I haven't sketched out any API yet, but it would probably closely
> > mirror how elst works in MOV. Care should be taken that MXF
> > operational
> > pattern 3a can also fit into this API. Possibly even OP3c.
> > 
> > Thoughts?
> 
> it would be cool if someone implemented this, its not trivial as all
> sides need to support it. demuxer, muxer, player, ffmpeg

We don't need it everywhere immediately. But yeah, it's a lot. We
probably need a layer above lavf at some point. libavpresentation?
Probably with a cache. That's what libmlt does. It's also why I'm
skeptical of going too far with this, because that's dev time not spent
on libmlt.

I probably need to double-check that I can spend the time to implement
this on the demuxer side, and possibly in fftools, before I commit to
it. This being a blocker for getting segmented indexes working and
upstreamed might help. I'm assuming complete removal of elst support is
out of the question.

For now I'll probably dummy out elst support and the associated tests
just to make progress on segmented indexes.

/Tomas
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