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I am very new in using the histogram filter. (http://ffmpeg.org/ffmpeg-filters.html#histogram)

Is it possible to dump the video level values from which the histogram graph is drawn into numeric values (textfile dump) to check if a video has levels inside the broadcast ranges (16-235/94-940)? Sorry if I misunderstand (and my knowledge about the question is definitely limited) but do you realise that valid (specification-compliant) broadcast-range video may contain values < 16 and > 235?

Carl Eugen

Hello Carl, no, I don´t. Can you explain this to me? I always thought that SD broadcast levels has to be >16 and <235. Best Regards Christoph

On 17/05/15 13:05, Carl Eugen Hoyos wrote:

Christoph Gerstbauer <christophgerstbauer <at> gmail.com> writes:

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do you realise that valid (specification-compliant) broadcast-range video may contain values < 16 and > 235?

Hello Carl, no, I don´t. Can you explain this to me? I always thought that SD broadcast levels has to be >16 and <235.

I cannot explain the relevant specifications (and I don't even know where to find them) to you but to the best of my knowledge: Just as "MPEG constant bitrate" does not mean constant frame size, so a stream containing video frames of different sizes is not necessarily "variable bitrate", you cannot judge a video stream as being non-"broadcast level" just because it contains values < 16 or > 235.

I would say a broadcast signal could quite reasonably contain values < 16 or > 235, that is the point of such values, it allows for over/undershoot transients resulting from analogue to digital conversion, or filtering. What you could reasonably say is that a broadcast signal to Rec601 or 709 etc has its black and white points defined at those values, and that anything outside that range should only be a transient, which those specs allow to be preserved in the interests of avoiding distortion.

Carl Eugen [..]

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