[FFmpeg-user] Rgbashift T value

[Paul B Mahol]

On Fri, Dec 22, 2023 at 10:43 PM emmanuel martin <ask.emmanuel at gmail.com>
wrote:

> Hello everyone,
>
> The rgbashift command is causing me some trouble when I refer to its
> documentation. Perhaps the issue stems from a misunderstanding. Here's the
> part that interests me:
>
> rgbashift AVOptions:
>    rh                <int>        ..FV.....T. shift red horizontally (from
> -255 to 255) (default 0)
>    rv                <int>        ..FV.....T. shift red vertically (from
> -255 to 255) (default 0)
>    gh                <int>        ..FV.....T. shift green horizontally
> (from -255 to 255) (default 0)
>    gv                <int>        ..FV.....T. shift green vertically (from
> -255 to 255) (default 0)
>    bh                <int>        ..FV.....T. shift blue horizontally
> (from -255 to 255) (default 0)
>    bv                <int>        ..FV.....T. shift blue vertically (from
> -255 to 255) (default 0)
>    ah                <int>        ..FV.....T. shift alpha horizontally
> (from -255 to 255) (default 0)
>    av                <int>        ..FV.....T. shift alpha vertically (from
> -255 to 255) (default 0)
>    edge              <int>        ..FV.....T. set edge operation (from 0
> to 1) (default smear)
>      smear           0            ..FV.....T.
>      wrap            1            ..FV.....T.
>
> If I understand correctly, 'T' indicates that the option can be set at the
> video filter level and over time, meaning the value can dynamically change
> based on the time in a video sequence. In other words, I can change the
> offset value of each color channel over time.
>
> The simple command below works perfectly:
>
> ffmpeg -i input.mp4 -vf "rgbashift=rh=20:bh=-20" -pix_fmt yuv420p
> output.mp4
>
> However, as soon as I integrate the 'T' parameter into the offset value, I
> get error messages. For example:
>
> ffmpeg -i input.mp4 -vf "rgbashift=rh='t*2':bh='t*-2'" -pix_fmt yuv420p
> output.mp4
>
> Error message:
>
> Undefined constant or missing '(' in 't*2' Unable to parse option value
> "t*2" Error applying option 'rh' to filter 'rgbashift': Invalid argument
>
> Do I have a misunderstanding of the documentation (ffmpeg -h
> filter=rgbashift) ? Or do I have a syntax problem somewhere?
>

Do you see anywhere in rgbashift documentation that it mentions
*explicitly* the _t_ parameter ?

Thank you very much.
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