[FFmpeg-trac] #6590(undetermined:new): weave filter produces video with incorrect field order

FFmpeg trac at avcodec.org
Wed Aug 16 13:43:03 EEST 2017

#6590: weave filter produces video with incorrect field order
             Reporter:  alexz         |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  undetermined  |                  Version:  3.2.4
             Keywords:                |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
 Summary of the bug:

 weave filter produces interlaced video with an incorrect field order

 How to reproduce:

 1. Create sample video (horizontally moving box) with a double frame rate
 ffmpeg -f lavfi -i "color=color=blue:size=352x288:rate=50:duration=3" \
     -vf "color=white at 1:size=50x50:rate=50:duration=3 [box]; [in][box]
 overlay=n*hsub:10" \
     -codec:v ffv1 -level 3 output-50p.mkv

 2. Make an interlaced video with the first field top using weave filter
 ffmpeg -i output-50p.mkv -aspect 4/3 \
     -vf "weave=first_field=t" \
     -codec:v ffv1 -level 3 output-25i.mkv

 Despite mediainfo correctly identifies the resulting video (output-
 25i.mkv) as interlaced with the top field first, video playes "jerky".
 This is points to an incorrect field order.

 Also the incorrect field order is visible in the frame's pictures,
 extracted with
 ffmpeg -i output-25i.mkv %03d.png

 Attached patch fixes the issue.

Ticket URL: <https://trac.ffmpeg.org/ticket/6590>
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