LHi and RGB

[Gary Adcock]

[Keith Pratt] “Can the LHi access RGB from the graphics card when working in Color (i.e. prior to the graphics card converting it to YCbCr), then output as RGB over HDMI? “

OK.

The LHi card cannot access anything on the graphics card that came with your computer.

It can output its HDMI as RGB, that is a function of the later HDMI specs. If you are working in an RGB space note that the Frame Raster limit on this card is 1920×1080 at 60fps.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

Check out
https://www.aja.com/kiprotour/

Inside look at the IoHD
https://library.creativecow.net/articles/adcock_gary/AJAIOHD.php

[Keith Pratt]

Thanks for the reply.

I’m wondering if we’d got our wires crossed when you said “the LHi cannot access anything from the graphics card that came with your computer.”

The easiest way to state my question might be in the form of a scenario:

I need output over HDMI to be RGB (for reasons that would only serve to complicate matters if explained).

Say I am editing ProRes in FCP. Can I instruct the LHi to turn that YCbCr into RGB for HDMI viewing output?

I then send the ProRes timeline to Color. With Color using the GPU to do its work, can the LHi access that image in its RGB form, rather than letting the GPU convert back to YCbCr and the LHi then converting it back to RGB for output?

And a similar question if I was working with (1920×1080) DPX files in Color — would I get bona fide RGB, rather than RGB (DPX files) converted to YCbCr by the GPU, then converted to RGB again by the LHi?

[Ramona Howard]

Keith,

This will be a little off topic but all relative.

What you are asking is a feature we have designed into our new RaveDi. Since we have written our own driver for the AJA hardware and our own code for the application we can do things like pass data between the AJA and GPU easily, in fact we do this all the time. This is a real time process, actually faster because we have to account for other things.

We can stay in a 16bit work space (so no wishy washy 10/12/16bit to 8bit going on). If your in RGB, that is what you pass and stay in. We have not done anything with the Lhi yet as all our current customers need SDI and all the options of the Kona3, but our driver is designed to work with any AJA board.

I know AJA makes a HDMI to SDI converter (we use this for showing off another product we make), is there one the other way? If so, and if it supports a newer HDMI spec, then there you go, problem solved.

I have not dug too deep into Nvidias HDMI implementation to see what spec they are supporting so I can’t suggest using a graphics board that has HDMI on it just yet. But if it does we could go from AJA straight to Nvidia out.

Cheers,
Ramona

Play hard today, it may be raining tomorrow!

[Walter Biscardi]

[Ramona Howard] “I know AJA makes a HDMI to SDI converter (we use this for showing off another product we make), is there one the other way? If so, and if it supports a newer HDMI spec, then there you go, problem solved. “

Hi-5

https://www.aja.com/products/converters/converters-hd-hi5.php

Not sure which HDMI standard this is, but there you go.

Walter Biscardi, Jr.
Biscardi Creative Media
HD and SD Production for Broadcast and Independent Productions.

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[Ramona Howard]

well there you go.

There are still many devices that need SDI, which would be a good reason to go with a converter vs a fixed HDMI solution. Not limiting yourself to HDMI only would be a smart approach.

Ramona

Play hard today, it may be raining tomorrow!

[Gary Adcock]

[Keith Pratt] “Say I am editing ProRes in FCP. Can I instruct the LHi to turn that YCbCr into RGB for HDMI viewing output? “

YES is does.

[Keith Pratt] “ith Color using the GPU to do its work, can the LHi access that image in its RGB form, rather than letting the GPU convert back to YCbCr and the LHi then converting it back to RGB for output? “

This is much tricker, since the GPU processing is being done on your Graphics card and therefor only the rendered content can then played out via the LHi (a Video Card) and that would rely on the individual application and how it communicates that info to the Kona Card.

where as you use send to color and it returns the files to FCP – does it return as RGB or YUV? FCP is not know for it’s RGB capabilities.

[Keith Pratt] “nd a similar question if I was working with (1920×1080) DPX files in Color — would I get bona fide RGB, rather than RGB (DPX files) converted to YCbCr by the GPU, then converted to RGB again by the LHi?”

Ah read my mind.

DPX files captured at the camera are usually RGB, and stay RGB only on Video output do the file get converted to YUV and that would depend on your workflow.

I Note that you are awfully worried about maintaining the signal as RGB- what is your output and is it RGB, Video usually by default is always YUV for delivery and RGB only during production.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

Check out
https://www.aja.com/kiprotour/

Inside look at the IoHD
https://library.creativecow.net/articles/adcock_gary/AJAIOHD.php

[Keith Pratt]

Thanks again.

Delivery will often be DPX 1920×1080. I’m looking at a Gluetools workflow for this. I’ve not done much in Color and am currently also looking into whether the program itself handles black and white points or whether the LHi would.

I will also be doing some work in YCbCr, but need to monitor in RGB due to a quirk with my monitor. But that’s no problem if the LHi can convert the YCbCr to RGB on the fly.

[Keith Pratt]

Thanks for your replies.

The LHi has 3Gb/s HD-SDI as well, but the specs seem only to suggest can do 50/60p YCbCr with the added bandwidth. They are quite explicit that it does RGB over HDMI, but “RGB” is a term absent when they talk HD-SDI. I’ve sent them an e-mail, but not yet had a reply, so not sure.

I do already have a Blackmagic DeckLink, so a convertor like the new AJA Hi5 3G (3Gb/s HD-SDI and RGB) would be an option, but I thought it more likely that the LHi would be able to convert YCbCr to RGB on the fly.

[Gary Adcock]

[Keith Pratt] “I thought it more likely that the LHi would be able to convert YCbCr to RGB on the fly.”

OK
every alarm just went off.

Is there is a balloon in the frame that say “MIRACLE HAPPENS HERE”

its not about color space as much as it is about bit depth.

I will take some thing “10bit” over “RGB” in a heartbeat. Without knowing why you are doing this, I am concerned about going farther into an explanation what you are trying to do.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

Check out
https://www.aja.com/kiprotour/

Inside look at the IoHD
https://library.creativecow.net/articles/adcock_gary/AJAIOHD.php

[Keith Pratt]

There’s no need for alarm.

I’m using an HP DreamColor LP2480zx to monitor. There’s no HD-SDI (only HDMI) but it can handle all common frame rates and has user-selectable colour spaces ranging from Rec.601 to DCI-P3 — the caveat being that the “DreamColor engine” it uses to manage colour space only works with a progressive RGB signal. If you feed it interlaced YCbCr it will display it but with the monitor at full gamut and god-know-what gamma, giving a hugely saturated and wildly inaccurate look. But it’s an excellent display, and a genuine 10-bit panel to boot. So, that’s where the RGB obsession comes in.

Like I said, a lot of my work will be on DPX files, so for that I’m looking for a pathway for RGB right the way through, from file, through software, capture card and to display. For YCbCr stuff I need something that will do the conversion to RGB before the signal reaches the monitor. And that’s 10-bit YCbCr to 10-bit RGB.

The LHi may well be able to do all I want, but there are certain areas of vagueness I wanted to clear up before believing I’d found the Holy Grail.