[FFmpeg-devel] [PATCH]Mention in the documentation that fieldmatch needs cfr input

[Calvin Walton]

On Sat, 2014-10-25 at 12:22 +0000, Carl Eugen Hoyos wrote:
> Clément Bœsch <u <at> pkh.me> writes:
> 
> > > +The filter only works for constant frame rate input. If your 
> > > input
> > > +has mixed telecined and progressive content with changing 
> > > framerate,
> > > +try the  <at> ref{pullup} filter.
> > 
> > Well I don't mind much but then... how is pullup making
> > any difference here actually
> 
> Just to sum it up:
> pullup works fine and is fast for all samples I have seen,
> it definitely misses many merging opportunities if the
> horizontal motion is very low (meaning some frames with
> artefacts remain for every real-world input).
> fieldmatch is very slow, it is apparently able to
> produce perfect output for badly cut input with constant
> (telecined) framerate but it fails completely for mixed
> content (as found on many DVD's).
> 
> Imo, fps=30000/1001,fieldmatch,decimate should fix this
> but decimate unfortunately does not drop the frame that
> fps inserted but a random (?) frame.
> (Or fieldmatch finds matches in progressive input?)

For content that was in mpeg2 with field flags set appropriate for 
display on an interlaced TV - which basically accounts for all DVD 
content - mplayer had a 'softpulldown' filter that used these flags to 
turn the video stream from mixed progressive+telecined+interlaced 
content with variable framerate (in NTSC, mixed 24/1001 frames/s and 
60/1001 fields/s) into a telecined+interlaced video with constant 
framerate (60/1001 fields/s).

I wonder if something similar would be useful in ffmpeg, to provide a 
constant fps stream that a detelecine filter could use as input.

-- 
Calvin Walton <calvin.walton at kepstin.ca>