[FFmpeg-user] Rgbashift T value

[emmanuel martin]

I used this command in the terminal to have some details on how to use it :

ffmpeg -h filter=rgbashift

Because I couldn’t find informations I asked to Chat GPT what ..FV.....T. means and here is the answer : 

The string ..FV.....T. provides information about the capabilities and options of the filter. Each character in the string represents a specific feature or attribute of the filter. Here's the breakdown:

. (dot): Placeholder for a feature that is not applicable or not available.
F: The filter supports frame-level multithreading, meaning it can process multiple frames concurrently.
V: The filter supports slice-level multithreading, which allows for parallel processing of different slices of a frame.
T: The filter supports temporal multithreading, indicating that it can take advantage of temporal dependencies between frames.
So, in the case of ..FV.....T., the filter supports frame-level multithreading (F), slice-level multithreading (V), and temporal multithreading (T). The dots in other positions suggest that some features might not be applicable or available for this specific filter.

> Le 22 déc. 2023 à 22:45, Paul B Mahol <onemda at gmail.com> a écrit :
> 
> On Fri, Dec 22, 2023 at 10:43 PM emmanuel martin <ask.emmanuel at gmail.com <mailto: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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