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Four HDMI signals into one PC

PostPosted: Fri Apr 10, 2015 8:16 am
by Jesper Taxbøl
Hi Guys,

I am writing a OpenFrameworks application where I need to work on four HD streams in realtime.

I have worked on two before using a setup consisting of a MacMini with two thunderbolt ports and two BlackMagic Ultrastudio Mini Recorders.

I am wondering how I would be able to add two more recorders in my setup as I am limited to two thunderbolt ports.

Do you have a suggestion for how I would be able to do this? Does there exist a hub of some sort or a different product that can do this?

Kind regards


Re: Four HDMI signals into one PC

PostPosted: Sat Apr 11, 2015 6:04 am
by Fred Rodrigues
You will need to use

Either a thunderbolt to PCI expansion box - you may find one with 4 slots and try for 4 x cheap HDMI cards or you can use a quad card with HDMI to SDI inputs

You can switch to 2x ultrastudio 4k as these have support for stereo (2x HDSDI inputs simultaneously)

You can also try to mix USB 3 and thunderbolt products- your computer is doing a lot of work with the USB 3 but it

I assume you are using one of the OF addons that leverages the SDK, not through QTKit or AVFoundation- you will have a lot of trouble with these.

Re: Four HDMI signals into one PC

PostPosted: Mon May 04, 2015 8:18 am
by Jesper Taxbøl
I ended up buying a PC with four PCI-E slots. On top of that I have purchased four Blackmagic Mini Recorder PCI-E.

I am hooking four Gopro Hero4 Black edition into these, but I cant seem to lock on the signal in a stable way. The signal drops in and out.

I have tried both The NTSC and PAL setting which outputs 1080p29.97 or 1080p25. I cant lock to both signal types.

The funny thing is that I am able to lock onto the GoPro hero3 signals without problems. That signal is 1080p24

I have tried both Windows 7 and Ubuntu, where teh behavior is the same.

I am using the latest firmware on both the Blackmagic Recorders and the GoPro cameras.

Any ideas on how to proceed, as I dont have budget to buy other cameras.

Kind regards

Jesper Taxbøl

Re: Four HDMI signals into one PC

PostPosted: Sun May 10, 2015 6:01 am
by Fred Rodrigues
Head over to the live production section of this forum for some advice and search go pro hdmi

Here are some things that can go wrong. The HDMI output of the gopros is unreliable and does not always go to the setting you would expect. There is a chart somewhere of what setting gives what output and it is strange (it could be you need to send an interlaced not progressive signal but I cannot see what the image looks like). You will have to find the common functioning HDMI setting for all cameras.

How long are your HDMI cables- HDMI is a pretty terrible format and good for about 2-5m over that you can do some strange things to get it stable (like using an active splitter next to your input) but it is pretty annoying. If you are using cables over 2m try shorter ones (again a lot of info in the live production setting).

If the cables are short my guess is you need to run the output at 1080i50.