[FFmpeg-user] "Extracting" Alpha Channel

[Stefano Sabatini]

On date Thursday 2011-07-28 21:47:59 +1000, Dan Flett encoded:
[...]
> How about being able to do something like this?
> 
> format=yuva, lutyuv=y=a:u=minval:v=minval
> 
> Basically, being able to specify that the y (luma) channel output is equal
> to the a (alpha) channel of the input?
> 
> Being able to swap color channels around would be good:
> 
> format=rgb, lutrgb=r=b:g=r:b=g

Basically this won't be anymore a lut filter (for each input value,
lookup a pre-computed value in a table) but an eval filter (for each
input value, evaluate an expression depending on the current video
state).

mp=geq allows to do something similiar, but only works with yuv
formats, and I wrote an eval filter which was never applied, maybe
I'll find the time/inspiration to work on this...
-- 
ffmpeg-user random tip #5
FFmpeg documentation:
http://www.ffmpeg.org/documentation.html