add waveform filter for video

[dave rice]

For video inspection it could be helpful to have a waveform filter for video. I can replicate this by using yuvdiag (​http://www.silicontrip.net/~mark/lavtools/yuvdiag.c) with mjpegtools and running:

ffmpeg -f lavfi -i mandelbrot -pix_fmt yuv420p -f yuv4mpegpipe - | ./yuvdiag -l | ffplay -i -

I'd recommend allowing options to select Y, U, and/or V individually to show either overlaid or in parade mode.

I uploaded an output of the above command here: www.youtube.com/watch?v=HXbLNbT8NRQ

[Elon Musk]

Implemented as histogram filter: "-vf histogram=mode=waveform:step=2:waveform_mode=column" gives same output as yuvdiag.

Do you really need u & v component in waveform mode? How should it be done?

[Elon Musk]

Ignore, I found far more useful explanation here ​http://documentation.apple.com/en/color/usermanual/index.html#chapter=8%26section=3%26tasks=true

Some stuff is done slightly different and some others are missing.
I will work on missing stuff and than close this bug.

[Elon Musk]

I do not consider separate/combination Y/U/V/R/G/B/A that important. I may eventually implement it anyway.