[FFmpeg-devel] Politics

[Michael Niedermayer]

On Sat, Dec 18, 2021 at 08:41:09PM +0000, Soft Works wrote:
> 
> 
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Daniel
> > Cantarín
> > Sent: Saturday, December 18, 2021 9:05 PM
> > To: ffmpeg-devel at ffmpeg.org
> > Subject: Re: [FFmpeg-devel] Politics
> > 
> >  >
> >  > Then you have never seen anime translations where signage in the
> >  > videos are translated. If the subtitles are off even by one frame in
> >  > such a case, you will see it, especially when the translated sign is
> >  > moving with the video, and one new subtitle event is generated for
> >  > every video frame.
> >  > You can't sync to audio when the element you are translating is in the
> >  > video itself, and not audio.
> >  >
> >  > - Hendrik
> > 
> > This is correct, thank you.
> >    1. If you're translating visuals, you sync to video.
> >    2. If such visual is moving, you may move the translation in sync.
> > 
> > I've ignored those cases, and it's correct to remark them.
> > 
> > Yet, I understand this is done with video editing UIs, not ffmpeg filters,
> > specially as it requires to visually match XY coordinates.
> > 
> > Also, subtitle communities I know of use timings, not frames, even
> > when doing overlays: "overlay at X:Y:Z.000 time".
> > 
> > And a single frame means absolutelly nothing, even in this use cases.
> > 
> > So, overall, I fail to see the serious frame-perfect subtitle-video sync
> > problem with the patchset.
> 
> The more the focus is moving to "a single frame" doesn't matter,
> the more will that conversation create the impression that my patchset
> would be lacking precision.
> 
> In fact we're just talking about a fantasy subject instead of an 
> existing problem.
> 
> > But there's no need to so much debate: get us some such anime sub,
> > I get the original video somehow, do some tests, and post the results
> > here. I'm open to do the testing work, if others are willing to help me
> > with input examples.
> 
> I would also be interested in an example for this, even when it doesn't
> prove any issues.
> 
> I'd be really glad when somebody could provide a sample (even privately),
> it could be something I haven't seen yet.

playing devils advocate here, meaning iam not sure if the example below makes
sense as an argument in this debate but its a interresting case which was
not mentioned

consider a subtitle track
consider 2 video tracks for US 30000/1001 fps and EU 25 fps

the 6th frame in the US track is at  0.2002 sec, the 5th in the EU track at 0.2sec

if these differ and you want a subtitle to either stop displaying after the
earlier or begin displaying after the earlier reliably. Then you need a 
timebase that can represent points within each such close encounter of frame
times.

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct answer.
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