Cycling 74 » Topic: Epiphan DVI2USB via jit.qt.grab

Epiphan DVI2USB via jit.qt.grab

Jesse — Tue, 06 Apr 2010 07:36:13 +0000

Just wanted to let everyone know that I’ve had my hands on an Epiphan DVI2USB box for the last few days, and it works perfectly as an input to Max/MSP/Jitter on OSX. Epiphan provides a QT component and jit.qt.grab recognizes it immediately.

http://www.epiphan.com/products/dvi-frame-grabbers/dvi2usb/

My test setup was grabbing 1280 x 720 frames over the DVI connection – framerate was around 85fps on a MacBook Pro, 2.8Ghz Core2 Duo, OS 10.5.8. (Note that this number is NOT referring to recording to disk, just the raw framerate coming out of jit.qt.grab.)

I didn’t do much with the frames but they looked pristine – they are uncompressed 24bit RGB.

This definitely is a nice option for multi-computer rigs and for recording patches rendered in GL without “rendering,” but the device is a bit pricey. The “DVI2USB Solo” is cheaper, but lacks the ability to capture from VGA sources. Both connect to the host via USB 2.0, so they can be used easily with laptops.

Have not tested with Max on Windows, but will report back when I do.

Re: Epiphan DVI2USB via jit.qt.grab

Andrew Benson — Tue, 06 Apr 2010 21:05:59 +0000

Thanks for reporting. An important test would be to try @unique 1 on jit.qt.grab and see what FPS you get. I have a suspicion that the 80fps you are getting is misleading. Either way, it shows promise that USB-based solutions will continue to get better/cheaper.

Re: Epiphan DVI2USB via jit.qt.grab

Jesse — Mon, 12 Apr 2010 22:29:59 +0000

I will test with the @unique attribute set to 1 and report back.

In the meantime, this may be of interest:

http://www.blackmagic-design.com/press/detail.asp?pressID=191

Hopefully Apple will get the hint and begin supporting USB 3.0.

Re: Epiphan DVI2USB via jit.qt.grab

Jesse — Thu, 15 Apr 2010 18:19:47 +0000

I can confirm that the frame rate drops with @unique set to 1. The default setting is for 30fps, which is steadily achieved in my patch. I went into the settings dialog and set the frame rate to 60, which also was steady in the patch. The frame rate did appear to drop slightly with large inter-frame changes on the input signal, but it never appeared to dip below 45fps.

Not bad for 1280 x 720 uncompressed…

I tried a higher resolution as well – 1680 x 1050. This only managed 10fps, with very high CPU usage.

Re: Epiphan DVI2USB via jit.qt.grab

Andrew Benson — Thu, 15 Apr 2010 22:47:01 +0000

That’s good to hear, and about probably as good as could be expected. The BlackMagic box is definitely an intriguing product, although USB3 is still conspicuously missing from most current generation computers. Once there is wider adoption of the USB3 hardware, it looks to have some significant benefits for live interactive video, especially not having to deal with expresscard-based or PCI-based solutions for capture. Will also be interesting to see how fast USB3-based HD-enclosures compare with eSata,GBit ethernet, and FW800.

Thanks for the report.