Re: [FFmpeg-devel] [PATCH] avfilter: add vf_yazf filter

[Quentin RENARD <asticode@gmail.com>]

> If this filter is meant to be same as existing zoompan but more precise, 
> then you should modify the original filter with a mode option for FP use.

Thing is I hesitated modifying the existing zoompan but there are a few things that don’t fit my use case and I didn’t want to update too many things:

- frame’s PTS is rewritten
- configurable output size is not dynamic (and is not evaluated in frame mode)
- if output aspect ratio is different than input aspect ratio, output image will be stretched

I can:

- add an option to enable PTS passthrough
- add “w” and “h” options on top of “s” options that would allow dynamic output size
- make sure computed crop size respect output aspect ratio

Would that be ok?

> I would suggest to add a 2nd FFFilter entry to
> libavfilter/vf_perspective.c
>
> with a zoompan user interface to access the already existing interpolation code
> in vf_perspective.c
>
> we have bilinear and bicubic interpolation there and it should form a
> better basis for the implementation

Reusing vf_perspective.c interpolation implementations seems like a really great idea, I didn’t know they existed.

However I don’t understand the way you suggest I should do it.

Are you suggesting I should add “const FFFilter ff_vf_yazp = {}” in “vf_perspective.c” and move the zoompan logic there? If not, maybe what you’re suggesting has already been implemented in another filter and I can use it as an example to understand and reproduce it better?

Cheers
Quentin



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