[TESTING] Vero V: IPT colour space conversion

With recent developments, it is now possible for Vero V to perform on the fly tonemapping of the IPT colour space in to HDR10 as well as SDR.

ICtCp is a colour space implementation for HDR. It is also known as Dolby Vision Profile 5. This profile is used by a number of streaming services and does not have an HDR fallback layer. As a result, playing such content on a device which cannot handle this colour space correctly results in magenta and green colours. The content is effectively unwatchable.

Vero V is now able to tonemap this content and output it in a compatible HDR format. One advantage of this is that a user does not need a Dolby Vision compliant sink (AVR, TV), to be able to watch Dolby Vision Profile 5 content.

Another is that a user does not need to store content with a ‘fallback’ HDR layer, as Vero can calculate the appropriate transformations on the fly. This reduces the filesize of the media and improves compatibility. With all of the tonemapping improvements we’ve released over the years, the goal is to allow Vero to play and provide the best possible output regardless of the display. This is yet another step in this direction.

This is still experimental and feedback is wanted and needed. I’ve added some instructions on how to test here: [TESTING] Vero V: IPT colour space conversion - #39 by sam_nazarko




Does an mkv that is DV work for this testing scenario? If so I can help test

Also are you looking for testing on a DV capable TV, projector or both?

I’ve tried this and it works with mp4 or mkv. Doesn’t need a DV capable TV.

I can help wih some tesing of this new tone mapping functionality.

I’m using PC > Wifi > Vero-V > Yamaha RX-A2A > LG OLED48CX6LB .

So on a DV TV you don’t need it to trigger DV on the tv for it to work properly. I know for the projector you don’t as it goes through the SDR conversion. It’s the same for the TV?

Your DV TV will play it as HDR10 (or SDR if you choose that option in Settings->Player). If your PJ doesn’t do HDR10 the output will be SDR.

I can help test. Vero V, Denon AVR, Sony ZD9

What does Vero V do if mkv includes DV and HDR fallback?

This conversion only applies to profile 5 which never has any fallback. For other DV profiles, the HDR fallback will be output.

Ah, good to know. Thanks for enlightenment!

Will this feature come to Vero 4K+ as well?

1 Like

Unfortunately this is not possible

I can test this.
Just let me know if you need extra testing.

Great news - though presumably this is mapping the Dolby Vision IPTPQc2 to the YCrCb colour space that other formats (like Rec 601, Rec 709 etc. used) but there’s no colour gamut or EOTF conversion needed ?

Isn’t Dolby Vision IPTPQc2 content already in the same Rec 2020 gamut that HDR10 content uses, and the same PQ ST.2084 EOTF? (Or does Dolby use different gamuts and EOTFs?)

I think you are confusing two scenarios. Not helped by Dolby Vision (*) meaning different things in different scenarios.

  1. HDR10/HDR10+ YCbCr compatible main base layer with DV RPUs (and possibly EL - Enhancement Layers ) (As used on UHD Blu-ray)
  2. IPTPQc2 Dolby Vision (as used on streaming services) which is a Dolby Vision ‘native’ file and incompatible with other WCG HDR standards.

Situations 1. and 2. are two totally different scenarios.

  1. Plays already - albeit in HDR10 (as it’s a single file designed to be compatible with HDR10 players and to add Dolby Vision dynamic metadata, and increased bit depth, when played on a Dolby Vision player)
  2. Will currently decode but you get green and magenta video because this is purely a Dolby Vision file, with no backwards compatibility, as it’s encoded in IPTPQc2 instead of YCbCr colour-space. Sam’s new system should allow this to be remapped to YCbCr Rec 2020 PQ - i.e. PQ10 (don’t know if it also includes static metadata that turns PQ10 to HDR10) which will play correctly.

Sam’s point about fallbacks is that if you have video in format 2. for DV-friendly devices, you no longer need to also have a second copy in format 1 (or another format that plays) (I’m not aware that people actually encode a single file with both the 1. and 2. streams in them though - they are usually two separate files I believe?)

(Worth noting that there are a lot of ‘Hybrid’ HDR10+DV RPU encodes kicking around that are taking Dolby Vision RPUs -i.e. DV Metadata about each scene - from one source, and adding them to HDR10 encodes from a different source. These may make a DV light come on on some platforms - but that doesn’t mean they are giving you anything representative of the original DV as it assumes the same metadata can be applied to two different encodes and there’s no guarantee that’s the case)

(*) Like Dolby Atmos - which can be used with both Dolby True HD and Dolby Digital Plus/E-AC3 - Dolby Vision can be deployed in very different ways.


Will DV HLG now work?

Do you mean DV Profile 8 - which is YCbCr Rec 2020 with an HLG EOTF (aka ARIB STD-B67) rather than PQ EOTF (i.e. ST.2084) combined with DV metadata RPUs? (i.e. Apple iPhone HDR video)

I wasn’t aware that didn’t play correctly currently - albeit in Rec 2020 HLG without the RPUs?

1 Like

Yes. People seem to be ripping the RPUs out of profile 5 files and stitching them into HDR10 base layers and calling them DV profile 8. The assumption seems to be that IPTPQc2, once converted to YUV, is equivalent to a HDR10 release of the same title, which I would have thought … doubtful.

DV HLG as output by iPhones for example has always worked. I don’t think there’s much if any DV fairy dust in those.

1 Like

Some sources say Dolby have ‘custom primaries’ but I think this project for Vero V just uses BT2020 and we don’t get gross hue shifts on typical material.