Ventuz Forum

Hi,
we are having some color clipping issues in one project were we need a HDMI Signal.
We're running 4x Full HD Outputs on an AMD FirePro with Displayport to Single-Link DVI converters and DVI to HDMI adapter-cable (necessary, because the card only supports 2 passive DP to HDMI adapters)

The Problem with this Setup is color clipping, e.g. dark gray will appear black and light gray -> white.
After some research we came to the conclusion that we need an HDMI signal with REC709-Range instead of RGB.

1) Is there a way to render said REC709 Color Range?
2) Is it possible to set RGB Format from 8bit to 32bit in AMD/Nvidia Graphics Adapter Output? (Advanced Settings only show in "Newtek iVGA" and "Off-Screen")

Greetings,
Dennis

This sounds suspiciously like a non-software issue to me - are you only getting clipping in Ventuz, or is it happening on, say, the windows desktop also?

First step should be to use the color calibration tools of your graphics cards and display device (screen/projector etc).

But to answer your questions:

1) This is a slightly different discussion if we are talking about SDI out, where Gamut and broadcast safe colors apply, but if you are using standard HDMI, that should not apply to you on the Ventuz side.
2) Ventuz can indeed internally render at 32bit RGBA, but no device currently supports that. 10bit or even 16bit color would be theoretically possible, but do you really have a 10bit display or projector - given that most display devices these days arent even 8bit?

Hi Erik, thanks for your reply.

Sorry, it wasn't supposed to sound like a Ventuz Problem, I was hoping that I can fix it within Ventuz :P

The clipping applies to the whole output, in the GPU driver there is an option to use the REC709 range, but this applies exclusively to video rendering (e.g. VLC Player) and not DirectX.

We tried using a custom shader that raises the Black Level to 16 (in the 0-255 range), which helps a bit, but is not perfect. We were hoping that the 32bit Format could smooth this out since the shader has more data to convert from (if this even makes sense).

No worries!

You can set a render target to be 32bit RGBA in order to process a shader, but bear in mind the computational cost...

Also, is there any reason for the DVI cable, as opposed to going from DP to HDMI directly?

-E

You can set a render target to be 32bit RGBA in order to process a shader, but bear in mind the computational cost...

Thanks! Will try that. I hope there's a bit more CPU/GPU time available since you improved the video engine (We're converting from a Ventuz 3 Project and had micro stuttering in video playback)

In V4.00.00.442 the colors are a bit scrambled :P

Also, is there any reason for the DVI cable, as opposed to going from DP to HDMI directly?

We had no active DP to HDMI adapters, but we are going to order some Club3D dongles.