We’re asked to deliver a project that’s in HLG & Rec2020, in NotchLC.
With Notch being a 10bit codec and HLG being a fairly “mild”, static HDR, there’s no limitation from rendering such HDR video in Notch — my question is more about metadata to process the files properly in Premiere, AE, and Notch Playback.
I can’t find any reference ever anywhere about NotchLC and HDR.
While After Effects allows overriding Notch clips’ color profile, Premiere does not.
Tests I ran today to transcode from an HLG HDR ProRes to Notch, in Premiere/Media Encoder, appear to suggest that it thinks it has to be a Rec709 destination and auto-converts it to SDR. It definitely doesn’t tag those Notch MOVs as HLG the way it does ProRes.
NotchLC support High Bit Depth content, but not HDR content - content with a wider colour gamut will be clipped outside the 0-1 range. You could try to squeeze the colour range into the 0-1 range and then separate it again in post, but you’ll lose a lot of colour depth trying to do so.
As someone who implemented NotchLC playback and also wonders about this:
Shouldn’t it “just” be possible, by convention, to honor the COLR atom in the MOV container, at least the Primaries and Transfer Characteristics parts? (Matrix would probably always be set to 0 because the decoder outputs RGB directly)
That way you wouldn’t have to change anything in the codec itself; for HDR you’d choose eg. Rec2020 primaries and the SMPTE2084 or HLG curves, and all values would still be between 0 and 1.
This is what codecs like AVC/HEVC/AV1 etc do, too, so I’d reckon that most software on both the encoder and decoder side that wants to support different color spaces should be equipped to handle these curves. (eg. for us it would be adding literally one line to our code to tell the next shader downstream what color space to expect )
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