Am 14.09.2022 um 11:21 schrieb Dan:
Using the latest 5.1.1 "essentials build" by www.gyan.dev.
Hi all, I'm a beginner to ffmpeg so I'm having a hard time believing
that a utility so old and so widely used has such a fundamental bug,
but the evidence is staring me in the face and leads me to no other
conclusion.
It's incredibly easy to replicate thankfully. I want to convert
numerous frames to make an animation, but thankfully, I've simplified
the problem to even using a single image to make a '1 frame video' for
the purposes of debugging.
Simply perform this command line:
ffmpeg.exe -i original.png -crf 0 -vcodec libx264 output.mp4
...With this "original.png" ("fC2Tj") image:
https://i.stack.imgur.com/5jkct.png
And this command line:
ffmpeg.exe -i doubleHeight.png -crf 0 -vcodec libx264 output.mp4
...On this "doubleHeight" ("RGIvA") image:
https://i.stack.imgur.com/PLdsb.png
The double height version is darker than it should be. I've checked
the resulting video in both Media Player Classic and Chrome.
The issue can be reproduced without input images as follows:
ffmpeg -f lavfi -i color=0x19be0f:s=400x576 -crf 0 -vcodec libx264 -t 5
-y out1.mp4
ffmpeg -f lavfi -i color=0x19be0f:s=400x578 -crf 0 -vcodec libx264 -t 5
-y out2.mp4
The color seems to be brighter if the height is 576 or smaller, and
darker if the height is 578 or larger.
It's clearly visible if you play both videos side by side. I did test
with VLC Player and FFplay. I don't see how zscale could fix this issue.
Michael
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