Filter expression syntax is undocumented

[jason]

Multiple filters take a mathematical expression as a parameter, for example 'setpts' and 'select'.

The syntax of this expression is completely undocumented, despite its heavy use. For example, what functions are available? Are boolean combinations allowable and if so, what are the operators? What other mathematical operators are available? Are there equality comparison operators?

Afaict there is no hint in any of the documentation of the format of an "expression".

If it does exist, it should be made available under a more obvious documentation section heading, and possibly moved towards the beginning of the filter docs with the rest of the general common filter info.

[Cigaes]

https://ffmpeg.org/ffmpeg-all.html#Expression-Evaluation

I grant you FFmpeg's documentation is lacking in the department of internal links, but you cannot say that expressions are not documented.

[jason]

Replying to Cigaes:

https://ffmpeg.org/ffmpeg-all.html#Expression-Evaluation

I grant you FFmpeg's documentation is lacking in the department of internal links, but you cannot say that expressions are not documented.

Thank you, much appreciated. I just found the same and actually came here to close this report.

These expression docs are really good, actually.

[jason]

Docs exist! And are pretty good, too. https://ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation