[FFmpeg-user] How to set histogram size?

Dave Rice dave at dericed.com
Tue Apr 7 16:08:33 CEST 2015

> On Apr 7, 2015, at 9:38 AM, Moritz Barsnick <barsnick at gmx.net> wrote:
> On Mon, Apr 06, 2015 at 20:01:49 -0400, Dave Rice wrote:
>>> On Apr 6, 2015, at 4:32 PM, Pedro <ffmpeg at 11.to> wrote:
>>> *ffmpeg -y -report -i input.mp4 -vf "split[a][b];[a]format=gray,histogram=mode=waveform:waveform_mode=column,vflip,split[c][d];[b]pad=iw:ih+256[padded];[c]geq=g=1:b=1[red];[d]geq=r=1:b=1,crop=in_w:220:0:16[mid];[red][mid]overlay=0:16[wave];[padded][wave]overlay=0:H-h" output.mp4*
>> Maybe unrelated, but you're forcing [a] to grayscale and then splitting that to [c] and [d], then using geq to extract red from [c] and green from [d]. Taking red and green from a grayscale image should give the same result. Can you explain what you are hoping to achieve?
> I believe Pedro took that very code from the example on the given wiki
> page:
> https://trac.ffmpeg.org/wiki/FancyFilteringExamples#waveform
> I too had my problem understanding what it's supposed to do, and why.
> ;-) Perhaps a clean-up would be nice. Step by step instructions of how
> a filter chain was built up would be nice, but are apparently not
> within the scope of that page.

Ack, I realized that that was my code after responding to Pedro. I’ll assign myself rewriting this. Initially I was using that code while trying to set analog levels of video piped through bmdtools to ffmpeg.
Dave Rice

> Moritz
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