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Working with Epiphan DVI2PCIe

While preparing this review, we had some doubts whether we would be able to do any practical tests with our Epiphan DVI2PCIe. The card is so easy to use that it's hard to tell anything about that. The algorithm is simple: you put the DVI2PCIe into your PC, install its software and drivers, reboot, and connect external video sources for it to capture. Capturing is performed with the included Epiphan Capture Tool or third-party software that can receive video signal via DirectShow. The card and its accompanying software are optimized by Epiphan, so there’s not a single problem on the way from installation to usage. Everything works well even at the default settings: the card automatically identifies the resolution of the incoming video, so you don't really need to change any settings for basic tasks. You must only have the necessary cables and adapters to connect your video source to the card's DVI-I connector.

The resulting image quality is blameless. If the video source is connected to the DVI2PCIe via digital interface, the transmission is absolutely accurate without any loss or distortion. The resulting screenshot will always show exactly what is to be displayed on the monitor.

In order to check out the quality of the DVI2PCIe we connected our testbed to its input via DVI and selected Full-HD resolution (1920x1080) with a color depth of 32 bpp. The pictures below include screenshots captured right on the PC and identical screenshots captured via the Epiphan DVI2PCIe card.

Original image Grabbed with Epiphan DVI2PCIe
(digital connection)





It’s easy to see that the screenshots captured with the Epiphan DVI2PCIe are absolutely identical to the originals. Well, it must be noted that the Epiphan card lowers the color depth to TrueColor (24 bpp) but you cannot really see this in practice.

When it comes to analog video sources, the DVI2PCIe of course introduces certain distortions on the analog-to-digital conversion stage. To check them out in practice, we carried out another test after connecting the testbed to the DVI2PCIe with a standard VGA cable with D-Sub connectors. We used a DVI↔D-Sub adapter for the DVI2PCIe’s DVI input.

Original image Grabbed with Epiphan DVI2PCIe
(analog connection)





Well, it is hard to see any distortions even with the analog connection. The DVI2PCIe is very good at analog-digital conversion, so we can’t spot any visual artifacts typical of consumer-class video capture devices. In other words, the Epiphan solution confirms its high professional status in this test, too.

The lack of distortions and quality loss while capturing still images doesn’t mean that the card is that good with dynamic video, too. Besides image quality, the frame rate must also be taken into account here. Maintaining an acceptable frame rate calls for high performance from the video capture device.

Well, the DVI2PCIe is equipped to cope with that task, too. It uses PCI Express x4 whose bandwidth should be enough to transmit Full-HD video with a high frame rate. Besides, the DVI2PCIe additionally uses some lossless compression that helps improve its performance if video frames are similar to each other.

So, Epiphan claims that the DVI2PCIe card can capture Full-HD video with a frame rate up to 35 fps. We decided to check this out by capturing dynamic video with different resolution. Our testbed playing a movie was the video source. It was connected to the DVI2PCIe card via digital DVI interface.

The video capture performance was recorded with drivers version RC. You must keep it in mind that the driver has a great effect on the capture card’s performance since it contains the basic firmware which is loaded into the FPGA. It means that the DVI2PCIe may get faster with driver updates since Epiphan is constantly working on improving the driver.

Well, the DVI2PCIe is quite good even with the driver it already has, surpassing its own specifications. The capturing speed is limited by the refresh rate generated by the computer’s graphics card at resolutions up to 1600x900 pixels. In other words, the DVI2PCIe captures video at 1600x900 and lower resolutions without any loss. Every frame sent by the video source is successfully received by the DVI2PCIe.

At higher resolutions the number of captured frames is limited by the card. Notwithstanding the compression algorithms, the correlation between video capturing performance and video content isn’t strong.

By the way, if the frame rate is your priority, Epiphan Capture Tool offers a compromise. For example, you can increase it to the maximum of 60 fps even for Full-HD video by simply reducing the card’s color depth settings. The image quality will deteriorate, of course, but it won’t lose its sharpness.

Summing it up, the Epiphan DVI2PCIe is capable of delivering acceptable frame rate and image quality even at the Full-HD resolution. Moreover, it won’t be easy, if possible at all, to find solutions that offer higher performance, so the DVI2PCIe is indispensable for capturing HD video. External frame grabbers with USB interface cannot ensure such speed because the USB interface doesn’t provide enough bandwidth.

The video quality is beyond criticism again. The lack of distortions when capturing still frames refers to the entire video, which makes the DVI2PCIe an excellent tool if high frame rate must be accompanied with high image quality.

As an example of a video captured with the Epiphan DVI2PCIe we suggest that you take a look at the following clip which shows our testbed (equipped with a GeForce GTX 680) running the Unigine Heaven 3.0 benchmark.

Besides proving the high quality of Full-HD video capturing, this clip helps understand the purpose of products like the Epiphan DVI2PCIe for hardware reviewers. If we used some software tools to record the video, the testbed’s performance would be affected, distorting the benchmark results. But when the video is made by a standalone device, we can report accurate benchmarking results and even show the full process of our testing.

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