wrong frames generated by overlay filter when y is negative and dynamic

[Taner Sener]

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 \
-filter_complex "[0:v]scale=400:400,[1:v]overlay=0:'-h+t/1*600*2',trim=duration=1[video]" \
-map [video] -c:v mpeg4 output.mp4

ffmpeg version N-92590-gf7faaa8c18 Copyright (c) 2000-2018 the FFmpeg developers
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.

[Taner Sener]

Output video generated by this command using ffmpeg from git-master

[Taner Sener]

Input file used in testing

[Taner Sener]

ffmpeg log report

[Taner Sener]

Output video generated by this command using ffmpeg from 3.4.x branch

[Elon Musk]

add threads=1 as workaround.

[Taner Sener]

add threads=1 as workaround.

Adding -threads 1 didn't make any difference for me.

[Elon Musk]

Replying to tanersener:

add threads=1 as workaround.

Adding -threads 1 didn't make any difference for me.

threads=1 is filter option not flag.. read what i wrote would you?

[Taner Sener]

Output video generated by test command and threads=1 option using ffmpeg from git-master

[Taner Sener]

Replying to richardpl:

Replying to tanersener:

add threads=1 as workaround.

Adding -threads 1 didn't make any difference for me.

threads=1 is filter option not flag.. read what i wrote would you?

Using threads=1 option improves output a little but doesn't fix the issue. You can see the output file ​failure_with_threads_1.mp4.

By the way, thanks for trying to help me but I never used threads option before and FFmpeg Filters Documentation does not list any threads option for filters used so I googled your threads=1 recommendation. All search results from first page corrected threads=1 as -threads 1. This is why I tried using -threads 1. Just wanted to let you know.

[Elon Musk]

threads=1 option works fine. Post full uncut ffmpeg output.

[Taner Sener]

Replying to richardpl:

threads=1 option works fine. Post full uncut ffmpeg output.

You're right, workaround works fine, my mistake, ignore failure_with_threads_1.mp4.

[Elon Musk]

Fixed in 8440835dbe93ef9972ceb940af9bda9bc0e178e7.