[FFmpeg-trac] #7583(avfilter:new): wrong frames generated by overlay filter when y is negative and dynamic

FFmpeg trac at avcodec.org
Sun Dec 2 18:48:43 EET 2018

#7583: wrong frames generated by overlay filter when y is negative and dynamic
             Reporter:  tanersener  |                     Type:  defect
               Status:  new         |                 Priority:  normal
            Component:  avfilter    |                  Version:  git-master
             Keywords:  overlay     |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
 '''Summary of the bug:'''

 I want to create a vertically moving photo using overlay filter. If I
 start with a negative y and increase it by time, photo is expected to
 slide down from the top of the screen slowly. But unfortunately input
 photo is not rendered correctly and some parts are missing from the photo.

 This technique works brilliantly when applied horizontally on x but when y
 is used this technique fails.

 '''How to reproduce:'''

 Any photo can be used as input.

 % ffmpeg \
 -loop 1 -i input.jpg \
 -f lavfi -i color=black:s=600x600 \
 -map [video] -c:v mpeg4 output.mp4

 ffmpeg version N-92590-gf7faaa8c18 Copyright (c) 2000-2018 the FFmpeg
 built with gcc 7 (Ubuntu 7.3.0-27ubuntu1~18.04)

 '''Affected versions:'''

 According to my analysis, commit d54014d1573ec6e958e9c9e802e613c73c7f7ba5
 breaks something about overlay filter. Test command provided above works
 on all releases without this commit: 2.8.x, 3.4.x, 4.0.x. But 4.1 and
 master, which has d54014d1573ec6e958e9c9e802e613c73c7f7ba5, is not working
 as expected.

Ticket URL: <https://trac.ffmpeg.org/ticket/7583>
FFmpeg <https://ffmpeg.org>
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