Datapath X4 with Resolume for Screen Blend

[DeanPelton]

I have a quick question if the Datapath X4 is the right product to use for screen blends with Resolume. Since dual link DVI maximum resolution is 2560×1600 I actually can't do a 2 screen blend with 1920 x 1080 projectors can I?

For example a 30 x 10 screen would be 3240 x 1080 but the Mac won't spit out that resolution using a display port to dvi adaptor.

Do I have this correct and just need the Matrox product?

Thanks!

-Dean

[Oaktown]

That's not quite the way it works. DL-DVI's maximum clock frequency is 330Mhz (2x165Mhz) and data rate is 7.92 Gbit/s (2x3.96 Gbit/s) so whatever you can fit within these parameters will work.

Furthermore in the Datapath X4 UI, you have access to various timing methods to tweak the throughput such as:

• • VESA CVT (Coordinated Video Timing)
  • VESA CVT Reduced Blanking
  • SMPTE (for HD modes) (Society of Motion Picture and Television Engineers
  • VESA GTF (Generalized Timing Formula)
  • Custom

The maximum standard resolution you can use is 2560x1600 @60Hz but you can use 3840x2160 @ 30Hz (4 @ 1920x1080) in CVT Reduced Blanking with the X4 no problems. Here is a quick list of resolution that'd work with the X4 to give you a sense of what you can use:

• 3840x2160@30Hz in CVT Reduced Blanking: 262.75Mhz
  3840x2400@30Hz in CVT Reduced Blanking: 292Mhz
  4096x3072@24Hz in CVT Reduced Blanking: 317.25Mhz - That means you could use one Datapath Dl8 with 4 Datapath X4 to send signal to 16 XGA projectors with one DL-DVI output!

You would then retime your outputs to whatever you need for your projectors such as 50Hz, 59.94Hz or 60Hz. I use the Datapath X4s to blend 4 HD projectors using Resolume Arena all the time and it works perfectly so you're on the right path!

[DeanPelton]

Thank you so much for this detailed response. This is starting to make sense.

Would the correct way to do this would be to set the preferred EDID to the specs you mentioned?
For example, "3840x2160@30Hz in CVT Reduced Blanking: 262.75Mhz" would allow my macbook to see the X4 as an external display capable of that resolution? Then I can tweet the outputs to make them projection friendly? This would be for a 2x2 array but if I want a 2x1 array do I need to change this up or is it fine to just leave it in this state? A 2x1 array would be 3840 x 1080....I'm not sure how to calculate the frequency for this resolution or if the app does it for me so any additional help there appreciated.

I won't have my hands on the unit again until later this week when I come off the road and looking forward to getting past this last hurdle.....pleased to not have to be using the Matrox product....it causes my mouse to freeze every 4 seconds because of some HDCP issue.....very annoying!

[DeanPelton]

Can someone provide the math equation or modeline calculator used to get these clock values?

From what I have found on google the timings are calculated by multiplying HxVxfrequency but they just are not adding up correctly for me.

For example "3840x2160@30Hz in CVT Reduced Blanking: 262.75Mhz" I get 3840x2160x30=248.8Mhz so where am I going wrong?

Thanks!

[Zoltán]

you are missing the sync (blanking) timings.

here is for example a screenshot from switchresx, notice the total pixels and lines, which multiplied with the refresh rate(59.990Hz ) gives the pixel clock.

[Oaktown]

This would be for a 2x2 array but if I want a 2x1 array do I need to change this up or is it fine to just leave it in this state? A 2x1 array would be 3840 x 1080....I'm not sure how to calculate the frequency for this resolution or if the app does it for me so any additional help there appreciated.

You can set the Datapath any way you want as long as it fit within a 4Kx4K so you could easily set it to 3840x1080 and have input 1 & 2 set to be Left and Right and have input 3 & 4 set to be test patterns from the internal UI (that's what I do so that I can test projectors) or not used.

Can someone provide the math equation or modeline calculator used to get these clock values?

Calculating clock frequency is a complex equation with many variables and most of it are things you probably won't even care to know what they are so why don't you use the UI from the Datapath X4?

[DeanPelton]

Great! Thank you very much...

-Dean

[Scratchpole]

.....and just to be sure you need the usb powered dual dvi adapter from apple to get your desired resolution.

[Oaktown]

It doesn't have to be the Apple brand necessarily (another good one is the Accell B087B-003J) but If you use the Apple adapter, make sure the one you buy has firmware v1.03.

Firmware v1.03 was released back in late 2011 so if you get a new older adapter that's been sitting on a shelf send it back and get a different one.

I power my DL-DVI adapters from an external USB power source instead of using the computer USB ports.

Also if you're going to be using a Datapath X4, do yourself a favor and invest $30 in SwitchResX to manage your display settings.

[DeanPelton]

Thanks again.. I have this working now! Once I set the preferred EDID on the X4 the Mac allowed me to set the resolution to match with zero issues. If this is working well whats the advantage of the additional layer of software to make the magic happen? I'll buy whats needed but is there a chance that sometimes the mac won't always let me set the resolution that is setup in the X4? If so....$30 well spent....I just like to keep things simple.

You guys were a tremendous help with this and all makes perfect sense now...I just didn't understand the non-standard resolution trick with the lower refresh rate.