[FFmpeg-user] Why histogram filter mode levels cannot use h|vstack filter inputed rgb(a) source?

[Moritz Barsnick]

Hi,

On Thu, Oct 01, 2015 at 05:42:41 -0700, nicolab wrote:
> I am using  histogram <https://ffmpeg.org/ffmpeg-filters.html#histogram>  
> filter mode levels is error but color, color2 and waveform mode is OK.

The mandelbrot source seems to output RGBA, but histogram does not
support RGBA (nor any RGB, AFAICT). So inserting the format filter is
the right thing, but perhaps using "format=gbrap" may be more lossless.
(I admit I don't have a lot of expertise when it comes to formats.)

I checked the sources to see that histogram supports gbrap (and gbrp
and gbrp9 and ...).

Moritz