[FFmpeg-user] Why does the 'detelecine' filter exist?

[Paul B Mahol]

On Wed, May 28, 2025 at 9:19 PM Mark Filipak <markfilipak.imdb at gmail.com>
wrote:

> On 28/05/2025 15.39, Alex Xu wrote:
> > I recently used the detelecine command in this thread:
> > https://ffmpeg.org/pipermail/ffmpeg-user/2025-May/059249.html
> >
> > I got strange results with the `fieldmatch+decimate` combo, where
> decimate
> > wasn't removing the correct frame.
> >
> > I also got strange results with the `pullup` filter.
> >
> > This may just be because my sample file was really exotic though.
>
> Yes, there are 'strange' telecines. I've seen 'NTSC' field sequences in
> which authors inserted
> varying telecined sequences at varying times (when bad timing became
> obvious to them) to maintain
> running time and sync with audio, and even 'PAL' that took cinema to 25
> fps via varying telecine,
> again to maintain running time and audio sync. I gave up trying to make
> them 24p in the usual ways
> and simply 'bobbed' them at 59.940p and 50p.
>
> None of those experiences justify keeping the 'detelecine' filter.
>
> I'm simply using 'detelecine' as a clear-cut example of all the filters
> that should be deprecated,
> or at least marked "obsolete". That would really help novices avoid
> headaches.
>
>
But user above just reported only single usecase where detelecine just
works for him.


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