[JyrkiAlakuijala]

I didn't try it out, but I don't see the 9 bit coming. I feel it gives about 7.5 bits.

Mixing two independent quantization sources will lead to more error.

Some decoding systems such as traditional jpeg does not specify results exactly so bit-perfect quantization-aware compensation is not going to be possible.

[kllrnohj]

The context of this thread is lossless webp, there aren't any compression artifacts to deal with.

Go try the math out, the theoretical is higher than 9 bits but 8.5-9 bit equivalent is very achievable in practice. With two lossless 8 bit sources this is absolutely adequate for current displays, especially since again you're not wasting bits on things like PQ's absurd range.

Will this be added to webp? Probably not, it seems like a dead format regardless. But 8 bit isn't the death knell for HDR support as is otherwise believed.

[JyrkiAlakuijala]

This depends on the quality you are aiming for.

You just cannot reach the best quality with 8 bits, not in SDR, not in HDR, not with gainmap HDR. Sometimes you don't care for a particular use case, and then 8 bits becomes acceptable. Many use cases remain where degradation by a compression system is unacceptable or creates too many complications.