High Quality mode - is HDR output possible? | v6 Beta

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subpixel
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High Quality mode - is HDR output possible? | v6 Beta

Post by subpixel »

If High Quality mode is calculated with 16bit colour and alpha channels, is HDR output possible, or are the Composition and output devices (screens, Spout, virtual devices, NDI, whatever) always downsampled back to 8bits per channel (eg by a value >> 8 kind of operation)?

If it is possible to get more than 8bit output, what hardware examples are there of this actually known to work, and what are some of the details (eg bit depth, any kind of HDR scheme used such as PQ or HLG)?

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Re: High Quality mode - is HDR output possible? | v6 Beta

Post by Menno »

Nope we're not doing any HDR whatsoever. The high quality mode only affects the precision of the calculations we're doing on the video. And yes, actual outputs (virtual devices aren't outputs) get converted to the lower precision 8bpc format.

The precision affects pretty much everything, but gets more interresting if you're using more effects and mixers etc.
Imagine a color channel of value 233/255 being passed through two 10% opacity mixers.
In normal quality you'll end up with a color channel value of 2, rather than 2.33, a deviation of 16.5% of where it should be at.
In a high quality environment the same color channel value would be 59882/65536. After two 10% opacity mixers you'll end up with a color channel of 599 instead of 598.82 which is a deviation of only 0.03%.

Obviously if this high precision texture is then output to a physical device we're right back to 8bpc so we have the same deviation, but if this texture is inserted into another effect or mixer you can imagine these imprecisions will add up to a different result eventually.

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Re: High Quality mode - is HDR output possible? | v6 Beta

Post by drazkers »

What if your using a quadro or FirePro card that supports 10 or 12bit colour?

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subpixel
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Re: High Quality mode - is HDR output possible? | v6 Beta

Post by subpixel »

I'm really interested in being able to get a 10bit colour signal to video projectors for a special projection trick I devised, and also to start experimenting with high bit depth colour for LED wall panels (which can apparently also do 10 bit colour, and obviously very high brightness).

drazkers, can you tell me anything about using high bit depth outputs? Do they show up as Displays in the usual Windows Settings > Displays control panel? Or does only certain software send to it?

Possible workaround for the 8bit output situation: make an FFGL plugin that exports the 16bit texture to wherever it is needed. I wonder if Spout can do that.

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