[JyrkiAlakuijala]

Gainmaps don't solve 8-bit mach banding. If anything you get more banding: two bandings, one banding from each of the two 8-bit fields multiplied together.

Gainmaps "solve" the problem of computing a local tone mapping by declaring that it needs to be done at server side or at image creation time rather than at viewing time.

My prediction: Gainmaps are going to be too complex of a solution for us as a community and we are going to find something else that is easier. Perhaps we could end up standardizing a small set of local tone mapping algorithms applied at viewing time.

[kllrnohj]

> Gainmaps "solve" the problem of computing a local tone mapping by declaring that it needs to be done at server side or at image creation time rather than at viewing time.

Which was already the case. A huge amount of phone camera quality is from advanced processing, not sensor improveds. Trying to get that same level of investment in all downstream clients is both unrealistic and significantly harder. A big aspect of why DolbyVision looks better is just Dolby forces everyone to use their tone mapping, and client consistency is critical.

Gainmaps also avoid the proprietary metadata disaster that plaugues HLG/PQ video content.

> If anything you get more banding: two bandings, one banding from each of the two 8-bit fields multiplied together.

The math works out such that you get the equivalent of something like 9 bits of depth but you're also not wasting bits on colors and luminance ranges you aren't using like you are with bt2020 hlg or PQ

[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.