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Old 20th October 2017, 18:16   #5654  |  Link
benwaggoner
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Join Date: Jan 2006
Location: Portland, OR
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Quote:
Originally Posted by d3rd3vil View Post
If I have an m2ts file with 2 layers and HDR10 PLUS Dolby Vision but the TV only recognizes HDR10, is there a way to force Dolby Vision somehow?
Wow, a lot of Dolby Vision questions!

First off, there aren't any extant Dolby Vision titles that use HDR10 as a base layer. The two modes you'll see in streaming or discs today are:

SDR base layer + enhancement layer + dynamic metadata
Non-backwards compatible base layer + dynamic metadata

The enhancement layer is quarter res of the base layer, so a 2160p title would have a 1080p base layer.

The non-backwards compatible base layer dynamically shifts the code values to make maximal use of the 10-bit space, and is in ICtCp. Playing it back as itself would be very trippy, but sub VideoCD quality.

In both cases, the layers and metadata are combined to render a 12-bit ICtCp frame. From there it gets tone mapped to the actual display's characteristics using yet more metadata. Lots of science and tricks go into the playback process, including dynamic backlight control for non-OLED displays.

As far as reusing or reencoding these streams, that would require a LOT of tooling. There's a lot of metadata (both for rendering out the source to the intermediate space, and then rendering from that to the current display) that needs to get transferred correctly for DoVi playback. And you'd need to be able to feed that content back into a DoVi player.

Reencoding is going to be even more fraught. By default DoVi uses ICtCp instead of Y'CbCr color space; that's what the non-backwards compatible stream is in. And for dual layer, the enhancement layer is its own thing that doesn't look like natural images at all. So reencoding using traditional psychovisual tuning may result in...issues.

Dolby Vision has a whole lot of other modes, some implemented in shipping devices, some not. But AFAIK everything available to consumers today uses one of the above.

If 12-bit decoders become broadly available in CE devices someday (NVidia starting with Pascal is the only thing I know of doing it today), then DoVi could just use 12-bit ICtCp + playback metadata, which would make for simpler implementations. The content would already be in the intermediate format, leaving the (highly complex) tone mapping to display stage.

I don't know if anything particularly interesting or useful could be done with DoVi today without licensing the Dolby Vision SDK.
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