I looked a the Video Waveform on both Linux and Windows and I see what Hudson555x shows above. I really like it because it has lines for broadcast safe plus can you mouse over it and see values. You can mouse over the histogram also and see values. That’s really good; very usable.
If it helps, here is a screenshot of the histogram from AVISynth (and Vapoursynth, they are identical). You can see the broadcast safe area. But you cannot mouse over this for values – that’s a nice touch in Shotcut. As you can see, there is a graph for all three YUV channels. But I don’t get much use out of the UV channels apart from centering the samples for white balancing – and there’s a function that just does that without having to look at the histogram anyway. And samples on the UV channels are never anywhere near the limits. Although, based on st599’s comments, perhaps that will be different with AVCHD. This particular histogram is from one of my MJPEG captures from an 8mm film scan.
