[FFmpeg-user] Detecting 24 FPS pulldown in MPEG-2 DVD streams

Carl Eugen Hoyos cehoyos at ag.or.at
Tue Jul 2 11:55:09 CEST 2013

Robert Krüger <krueger <at> lesspain.de> writes:

> > But otoh, it is a known limitation that FFmpeg does
> > not handle soft-pulldown very well, so the output
> > will not give a lot of information, I just wanted
> > to describe a possibility to show the issue esily.

> Quicktime does not play the pulldown file correctly 
> either and it was created/processed by Apple tools in 
> every step of the workflow .

I realise now that what I wrote above was quite misleading:
I suspect that ffplay plays your program stream with 
(soft) pulldown fine and that ffmpeg -i file -qscale 2 out.avi 
produces a file without A/V desync.
Additionally, ffmpeg -i file -vf fps=24000/1001 -qscale 2 out.avi
produces a file with no repeated frames (I'd expect).
Everything else would be a bug that is unknown afaik.

To insert telecined frames (you called them "interlaced" 
frames in your original mails) automatically would be the 
worst thing to do imo, you can get that effect with the 
telecine filter.
I just wanted to write above that ffmpeg does not explicitly 
tell you about soft telecine and it does not allow you to 
create such streams (this is an open ticket) but using the 
libraries, it should be trivial to detect (just look at the 
timestamps). I am not convinced that another default behaviour 
will suddenly solve all problems, just run your stream through 
the usual inverse telecine chain, that should fix the output.

(Or in other words: I wonder what mediainfo says about 
streams with mixed soft and hard pulldown.)

Carl Eugen

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