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

[Robert Krüger]

On Tue, Jul 2, 2013 at 11:55 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> 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
>   ^^^^^^
Oh, reading that again, I must say this was misleading. I did not mean
to say that ffplay does not play the file as that is not what I
tested.

>> 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.
That's good to know and good news. I will test this.

>
> 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 am not quite sure what you mean by that. I do not want to insert
anything either. I probably did not express myself correctly.

> 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
Do you mean Ticket #2602?

> libraries, it should be trivial to detect (just look at the
> timestamps). I am not convinced that another default behaviour
OK, thanks, I will try that.

> will suddenly solve all problems, just run your stream through
Neither proposing, implying nor expecting that.

> 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.)
I would guess nothing that makes sense. Is this combination used anywhere?

Thanks a lot! Your comments have helped me quite a bit.

Robert