[FFmpeg-user] Confusion about fieldmatch, decimate and framerate (now with yadif)

Nicholas Robbins nickrobbins at yahoo.com
Sat Dec 21 15:59:32 CET 2013

I double checked, and it did have the 3-3 pattern you suggested. I don't know what could cause that. I looked around on the internet and couldn't find a Telecine process that would produce a 3-3 pattern. I decided to just do yadif. In this case the fps filter is unneeded. The resulting file thinks it has a different fps but it plays correctly. I use yadif=deint=interlaced and it worked fine.

Thanks for your help.


> On Thursday, December 19, 2013 11:11 AM, L. Lee <llee040 at sbcglobal.net> wrote:
> > 
> On 12/18/13, 8:02 PM, "Nicholas Robbins" <nickrobbins at yahoo.com> 
> wrote:
>>>>  fps=fps=30000/1001,fieldmatch,decimate,yadif (which will yadif
>>>  I would surely like to get a sample. I shouldn¹t need more than 20-30
>>>  seconds to see what results I¹m able to produce. You might be able to
>>>  email me such an excerpt. I don¹t see how any conversion to 
> deinterlaced
>>>  30 fps would result in optimal output. Nearly any smooth horizontal
>>>  panning is like getting slapped in the face 6 times per second. If
>>> output
>>>  is deinterlaced, all 4th and 5th frames are duplicates. If not
>>>  deinterlaced, those frames are interlaced complements which still take
>>>  twice as long as a normal frame to play. Thanks.
>>>  Laine Lee
>> I will see about sending you a snippet offline. I can't seem to edit the
>> file as a vob without starting at the beginning and there aren't really
>> good problems at that point.  So I've remuxed it into a mkv using
>> mkvmerge.
>> Also, I don't think you are quite understanding the filters.
>> fps=30000/1001 is actually just relabeling things. If you've been
>> following the thread, the video file actually has this man frames, but
>> the container things is has 60000/1001 fps. So that first filter just
>> labels the file correctly. The second filter should replace the 30 fps
>> telecined with  ABCDD non-telecinded originals. Decimate will then remove
>> every fifth frame. At least that is how it is supposed to work. However,
>> it doesn't always work, some frames sometimes are missed, sometimes due
>> to editing after telecining for instance. These frames are supposed to me
>> marked as interlaced by fieldmatch and then yadif can de-comb them, which
>> isn't ideal, but the information to do the ideal thing is on the cutting
>> room floor presumably.
>> However, yadif=deint=interlaced isn't noticing any interlaced frames. So
>> if I want to remove the combing, I have to yadif everything.
>> In any case, I'll send you the file and you can play with it.
> Thanks for the 0:30 sample file. Yes, some are interlaced, but not in the
> pattern I would expect for telecined video. If you open it in mplayer, you
> can pause it at any point by pressing space, then advance frame by frame
> using ³.². What I see for the interlacing is the pattern of 3 frames
> interlaced followed by 3 frames non-interlaced. Please try that and let me
> know if you agree. Pulldown would be interlaced frames 4 and 5 of every 5,
> I believe. Here¹s a yadif filter chain that did the same thing as the one
> I mailed you privately using -deinterlace, except probably better. Thanks
> again.
> ffmpeg -i test1.mkv -pix_fmt yuv420p -c:v libx264 -vf
> ³yadif=0,fps=fps=30000/1001" -preset slower -crf 18 -x264opts
> keyint=40:bitrate=1800:qpmin=8:qpmax=28:qpstep=4 test1.m4v
> Laine Lee
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