Mini Converter processes LUTs wrong

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Pepijn Klijs

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Mini Converter processes LUTs wrong

PostMon Nov 02, 2020 4:52 pm

I had a bit of a surprise today, trying to calibrate a display that was hooked up to a Mini Converter SDI TO HDMI 6G, serving as a calibration lutbox.

The calibration LUT I created was first tested in Lightspace and also in Resolve. Everything looked ok. But when I installed the LUT in the lutbox I immediately saw gamut errors (the gamut looked bigger then the intended gamut).

Now I think the only thing that could cause this is if the lut is processed in video range inside the mini converter. BUt mind you, BMD's own manual suggests that 'you can use Resolve to create LUTs for the MIni Converter', however, Resolve's luts are lways full range LUTs and there's no way around it.

Even more confusing, BMD's Teranex Mini can also hold a calibration LUT and that one does get full range processing.

I hope someone at BMD can explain me what's going on. I'm also wondering if other users have had more succes with the lut function inside the mini converters then me.
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davo_me

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Re: Mini Converter processes LUTs wrong

PostWed Dec 09, 2020 5:07 pm

Pepijn Klijs wrote:I had a bit of a surprise today, trying to calibrate a display that was hooked up to a Mini Converter SDI TO HDMI 6G, serving as a calibration lutbox.

The calibration LUT I created was first tested in Lightspace and also in Resolve. Everything looked ok. But when I installed the LUT in the lutbox I immediately saw gamut errors (the gamut looked bigger then the intended gamut).

Now I think the only thing that could cause this is if the lut is processed in video range inside the mini converter. BUt mind you, BMD's own manual suggests that 'you can use Resolve to create LUTs for the MIni Converter', however, Resolve's luts are lways full range LUTs and there's no way around it.

Even more confusing, BMD's Teranex Mini can also hold a calibration LUT and that one does get full range processing.

I hope someone at BMD can explain me what's going on. I'm also wondering if other users have had more succes with the lut function inside the mini converters then me.



Hi Blackmagic – can anyone comment on this?

I'm about to buy a 6G SDI to HDMI to use the LUT features, and it would be good to get clarity on this before I do so.

Thanks
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davo_me

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Re: Mini Converter processes LUTs wrong

PostThu Jan 07, 2021 1:55 pm

Hello, is anyone at Blackmagic able to address this please? Thanks
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tristansummers

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Re: Mini Converter processes LUTs wrong

PostFri Jan 08, 2021 11:56 am

curious about this.
Have you asked on Colourspace forums?
If you only need HD you could go for the 3G which is newer and might work?
Which I was going to do...
I get confused if using Resolve as generator, as I think it does not make full range signals, Get the Raspberry Pi 3+ generator for full range.

Sounds like it could be a resolve set up issue?
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Larry Towers

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Re: Mini Converter processes LUTs wrong

PostMon Jan 11, 2021 11:22 pm

"The calibration LUT I created was first tested in Lightspace and also in Resolve. Everything looked ok. But when I installed the LUT in the lutbox I immediately saw gamut errors (the gamut looked bigger then the intended gamut)."

Where did everything look OK? What was the signal chain? If everything looked ok at the output before you inserted the lutbox, that's because you are adding a LUT to something that already looked OK. Probably because your monitor setup already had a LUT in place. A LUT is to correct or transform something. cascading corrections should be done with care.
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ConnecTED

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Re: Mini Converter processes LUTs wrong

PostTue Jan 12, 2021 12:16 am

Pepijn Klijs wrote:I had a bit of a surprise today, trying to calibrate a display that was hooked up to a Mini Converter SDI TO HDMI 6G, serving as a calibration lutbox.

The calibration LUT I created was first tested in Lightspace and also in Resolve. Everything looked ok. But when I installed the LUT in the lutbox I immediately saw gamut errors (the gamut looked bigger then the intended gamut).

Now I think the only thing that could cause this is if the lut is processed in video range inside the mini converter. BUt mind you, BMD's own manual suggests that 'you can use Resolve to create LUTs for the MIni Converter', however, Resolve's luts are lways full range LUTs and there's no way around it.

Even more confusing, BMD's Teranex Mini can also hold a calibration LUT and that one does get full range processing.

I hope someone at BMD can explain me what's going on. I'm also wondering if other users have had more succes with the lut function inside the mini converters then me.


Hey Pepijn,

When the gamut is larger when the LUT is handled by that BMD device, it means that the device needs video LUT, but video inside a full range LUT (as a container).

After the LUT generation with ColourSpace, apply a pass black video scale filter and then export it.

After the videoscale, the LUT will be mapped to the 64-940 of the 0-1023 LUT. Let me know if it will work.
Ted's LightSpace CMS Calibration Disk

S/W: ColourSpace INF, LightSpace CMS, SpaceMan ICC, SpaceMatch DCM, CalMAN, ChromaPure, ControlCAL​
V/P: eeColor 3D LUT Box - P/G: Murideo Six-G, DVDO AVLab TPG​
Meters: JETI Specbos 1211, Klein K-10A
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ConnecTED

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Re: Mini Converter processes LUTs wrong

PostTue Jan 12, 2021 12:38 am

tristansummers wrote:curious about this.
Have you asked on Colourspace forums?
If you only need HD you could go for the 3G which is newer and might work?
Which I was going to do...
I get confused if using Resolve as generator, as I think it does not make full range signals, Get the Raspberry Pi 3+ generator for full range.

Sounds like it could be a resolve set up issue?


Hi Tris,


Something I figured out last night and verified with external scopes also.

When you are using iTPG of Resolve controlled from ColourSpace via DeckLink output SDI/HDMI, with a video data timeline and ColourSpace patchscale 0-255, an LG OLED will receive 64-940 (video level patterns).

If we want to talk specifically, using a DeckLink Monitor 4K HDMI output with 2160p24 video timeline, LG will receive RGB 10-bit (or 12) when the SDI4:4:4 is ticked, and YCbCr 4:2:2 10bit with SDI4:4:4 unticked, when TV HDMI black level is at LOW.

LG OLEDs internally have 64-1023 LUTs.

So to generate these patterns, it will require PGenenerator or an external RGB bit-perfect generator.

However, I have found a method, which has verified with external scopes also to send 64-1023 patches from Resolve iTPG, but it will work only with a DeckLink card with HDMI output and only when its enabled the RGB output of the Decklink.

It will not work when you will use DeckLink SDI and then a Convertor to HDMI.

For DeckLink to able to send RGB, it will require to tick the SDI4:4:4 setting.

You can confirm that LG gets RGB using HDMI Diagnosis hidden menu.

When you want to calibrate LG internal LUT, ideally, you need to use RGB 64-1023 patch generation to match the internal LUT range.

For Resolve iTPG, to able to send 64-1023 patches, you have to set PC levels the timeline and add from ColourSpace as an offset to patchscale 16-255. (TV HDMI black level is at LOW.)

So iTPG of Resolve will work in 0-1023, and the ColorSpace will add the offset for the LG to receive 64-1023 patches.

The procedure us to pre-calibrate the LG with 64-1023 patches (Resolve SDI 4:4:4 ticked, Data Levels timeline + ColourSpace patchscale 16-255) and profile also. (TV HDMI black level is at LOW.)

After loading the 3D LUT correction to the TV, you can change the resolve timeline to Video levels, allow sub-black, and use ColourSpace patchscale 0-255, so the verification will be performed to 64-940 range. (TV HDMI black level is at LOW.)

Note, it will work only with DeckLink with native HDMI output without convertors, only with an RGB output, not YCbCr.

About HDMI Diagnostics Hidden Menu: https://www.avsforum.com/threads/2019-l ... t-58775690
Ted's LightSpace CMS Calibration Disk

S/W: ColourSpace INF, LightSpace CMS, SpaceMan ICC, SpaceMatch DCM, CalMAN, ChromaPure, ControlCAL​
V/P: eeColor 3D LUT Box - P/G: Murideo Six-G, DVDO AVLab TPG​
Meters: JETI Specbos 1211, Klein K-10A
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Marc Wielage

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Re: Mini Converter processes LUTs wrong

PostWed Jan 13, 2021 12:29 pm

Ah, I just figured out that "iTPG" = LG's Internal Patch Generator. (Sometimes, you need footnotes to read this forum.)
marc wielage, csi • VP/color & workflow • chroma | hollywood

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