[FFmpeg-devel] [RFC] vfilters (germinal) docs

[Vitor Sessak]

Hi!

V?ctor Paesa wrote:
> Hi,
> 
> This could be an starting point for the video filters documentation.
> The paragraphs stolen from the README, vf_setpts.c, vsrc_movie.c
> would be removed from these files as part of the doc commit.
> The idea is that the README remains would contain the
> developer info, and this vfilters.texi the user level info.
> 
> Please feel free to comment/correct/polish/flesh it out.

Just a few comments:

> @chapter Introduction
> 
> The substitute of 'vhooks' is 'libavfilter', the result of our 'Video Filter API'
> Google Summer of Code project.

I'd prefer starting by defining libavfilter a bit differently:

Libavfilter is the filtering API of FFmpeg. It is the substitute of the 
now deprecated 'vhooks' and started as a Google Summer of Code project.

> @section format
> 
> @example
> ./ffmpeg -i in.avi -vfilters "format=yuv420p" out.avi
> @end example
> 
> Set the list of supported formats on all inputs to a set of chosen pixel formats.

Convert video to one of the specified filters formats (libavfilter will 
try to pick one that is supported as an input to the next filter).

> @section noformat
> 
> @example
> ./ffmpeg -i in.avi -vfilters "noformat=yuv420p" out.avi
> @end example
> 
> Set the list of supported formats on all inputs to any pixel formats except the chosen ones.

Force libavfilter not to send any of the specified pixel formats to the 
next filter.

> @section scale
> 
> @example
> ./ffmpeg -i in.avi -vfilters "scale=200:100:sws_flags=bicubic" out.avi
> @end example
> 
> Scale to new width/height and/or convert colorspace.

I'd prefer s/colorspace/pixel format/

> @section slicify
> 
> @example
> ./ffmpeg -i in.avi -vfilters "slicify=32" out.avi
> @end example
> 
> Pass on input video to next video filter as multiple slices.
> The parameter is the slice height (16 if not specified).

Add:

Adding this in the beginning of filter chains should make filtering 
faster due to the better use of the memory cache.

> @section buffer
> 
> This filter is used by ffmpeg to feed frames to the filter graph.

This input filter is used by the client application to feed pictures to 
the filter chain. See ffmpeg.c for an usage example.

> @section movie

This input filter decodes a file using libavcodec and libavformats and 
output the decoded frames.

-Vitor