[FFmpeg-trac] #4990(avfilter:new): fieldmatch+decimate duplicate frames with yuv

FFmpeg trac at avcodec.org
Fri Nov 6 00:56:53 CET 2015


#4990: fieldmatch+decimate duplicate frames with yuv
-------------------------------------+-------------------------------------
             Reporter:  nullb        |                     Type:  defect
               Status:  new          |                 Priority:  critical
            Component:  avfilter     |                  Version:  git-
             Keywords:  decimate     |  master
  duplicate frames bug               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 FFMPEG cannot currently fieldmatch and decimate a yuv input correctly.
 Resulting in duplicate frames from either mismatched fields or a failure
 to apply a proper decimate pattern.

 The following AVS script using the same source which I've attached for
 your convenience does produce a correct result without duplicate frames,
 as fieldmatch+decimate are meant to be based on TIVTC I was expecting the
 same fault but the AVS script succeeds.

 {{{
 LoadPlugin("rawsource.dll")
 LoadPlugin("TIVTC.dll")

 RawSource("bugged.yuv", 1920, 1080,
 "I420").AssumeFPS("ntsc_video").AssumeTFF()
 TFM().TDecimate()
 }}}

 Plugins for AVS are:
 http://www.avisynth.nl/users/warpenterprises/files/rawsource_5F25_dll_20060728.zip
 http://bengal.missouri.edu/~kes25c/TIVTCv105.zip

 Source in yuv format:
 https://drive.google.com/file/d/0B2keH696oskMYWVNSW5McFRxTTA/view?usp=sharing

 How to reproduce:
 {{{
 % ffmpeg -pix_fmt yuv420p -s 1920x1080 -r 30000/1001 -i bugged.yuv -vf
 "setfield=mode=tff,fieldmatch,decimate" test.mkv

 You will find duplicate frames on frames 2,3 - The first frame is also
 incorrect as you'll see in comparison to AVS.
 I have only attached a small sample as yuv frames are obviously quite
 large but on the complete yuv dump multiple duplicate frames appear.
 It still happens even with the use of a stronger set of filter parameters
 e.g: fieldmatch=order=tff:combmatch=full,yadif=deint=interlaced,decimate

 Bug is present on the git-master and all versions of ffmpeg since
 fieldmatch+decimate was added, unfortunately I'm not familiar enough with
 the avfilter to create a solution, hopefully somebody here can.
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4990>
FFmpeg <https://ffmpeg.org>
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