[BUG] Vapoursynth: Image Stream Luma TV Range not working correctly (??)

[The_Tinkerer]

These are the options I have for image stream input (Hybrid Dev 2020.07.20.1):



I selected "bt709"; before I was selecting "unknown" but it was just using bt709 so I'm guessing that's why "unknown" was removed.

When I do that and set the Luma range to "tv", it looks correct in AviSynth preview and outputs correctly. It looks wrong in Vapoursynth preview and outputs incorrectly, unless I enable that levels filter.

I didn't need a histogram... I selected "save snapshot" from Vapoursynth preview, then opened it in an Irfanview window, then opened the original .png of the same frame in another Ifranview window, then toggled between them. It's definitely different!

I attached the png's I'm using in an archive on Zippyshare above if you have time to try and see if it happens to you.


From above:

Source png frame (resized):


Vapoursynth preview snapshot save (resized):

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If I open the .png's via Image Stream as PC instead of TV, it looks correct in Vapoursynth, but will output a PC range video file. It looks incorrect in AviSynth (too dark).

If on the Vapoursynth "Color" tab at the very bottom of the filter list, I select "Range Conversion" -> "full to limited (pc -> tv)", it stays looking correct, but it will not output a TV range video file... the video file output will be at the PC range.

This "feels" like a bug. But I'm not sure!