[FFmpeg-user] ffmpeg MP4/x264 output colours change when input source is different resolution (bug?)

[Paul B Mahol]

On 9/14/22, Paul B Mahol <onemda at gmail.com> wrote:
> On 9/14/22, Dan <twinbee42 at skytopia.com> wrote:
>> On Wed, 14 Sep 2022 21:26:59 +0100, Carl Zwanzig <cpz at tuunq.com> wrote:
>>
>>> On 9/14/2022 8:01 AM, Paul B Mahol wrote:
>>>> The reason of scale behavior is known and legacy.
>>>
>>> Is it documented with the filter? I don't see anything obvious about it
>>> at
>>> https://ffmpeg.org/ffmpeg-filters.html#toc-scale-1, where can a person
>>> find
>>> about this otherwise-known behavior?
>>
>> To be fair, Paul did suggest the use of the zscale filter instead of
>> using
>> scale.
>> I actually managed to get the line to run in the end. I just needed to
>> put
>> the
>> "zscale=w=-1:h=-1" bit at the end like this:
>>
>> ffmpeg.exe -i "input.bmp" -crf 0 -vcodec libx264 -t 5 -y "output.mp4" -vf
>> zscale=w=-1:h=-1
>>
>> Unfortunately, I'm still getting the same darkening problem. The second
>> mp4
>> is darker
>> than the first.
>>
>> Even tried using Michael's direct colour technique combined with zscale:
>>
>> ffmpeg.exe -f lavfi -i color=0x19be0f:s=400x576 -crf 0 -vcodec libx264
>> -vf
>> zscale=w=-1:h=-1 -t 5 -y "576.mp4"
>> ffmpeg.exe -f lavfi -i color=0x19be0f:s=400x578 -crf 0 -vcodec libx264
>> -vf
>> zscale=w=-1:h=-1 -t 5 -y "578.mp4"
>>
>> Again, no luck. Second is darker.
>>
>> Unless I'm somehow misusing zscale (which is a possibility), it would
>> seem
>> as if the
>> problem lies elsewhere.
>
> If you do not use format filter after zscale it will not work correctly.

Also please state player you use/ how you inspect hex values.
It is important what you use to decode output of ffmpeg.

>
>>
>> Dan
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>