On 17/05/15 13:05, Carl Eugen Hoyos wrote:
Christoph Gerstbauer <christophgerstbauer <at> gmail.com> writes:
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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