Webinar FAQ

Capturing a VGA signal, or even a DVI signal, in order to save it to a computer for archiving, editing, or even broadcasting requires a device called a framegrabber, or frame grabber. Whether you are looking for a VGA frame grabber or a DVI frame grabber, there are several choices that must be looked into before being able to make an informed decision about a purchase which this article will briefly discuss.

The first step is to determine what needs to be captured with the frame grabber. Framegrabbers are very versatile units and have the ability to capture from any VGA or DVI outputs. These devices are critical in many medical applications, such as creating digital archives of X-Ray imagery or ultrasound, military applications where frame grabbers are used to capture output from radar, and research applications where the output from scientific equipment is captured in real-time using a frame grabber. What’s more, all of these applications require an external solution due to size and security constraints. As long as a functioning VGA or DVI port is present, there is a frame grabber that will capture it. Thus, depending on what is being captured, the capture rate (frame rate) and resolution requirements need to be determined. The user also needs to determine if he/she is capturing a VGA signal or DVI signal.

Based on different characteristics, this article will analyze and compare digital and analog VGA and DVI frame grabbers from the following major manufacturers: Epiphan Systems, EMS Imaging, Foresight Imaging, Ncast, PixelSmart, and Unigraf.

Portability

Besides Epiphan Systems, all the manufacturers listed in the previous paragraph make PCI-based devices. What this means is that the frame grabber is bound to the computer in which it is enclosed. What’s more, a PCI frame grabber may not be used in conjunction with a laptop (notebook computer). Epiphan Systems takes a different approach to their frame grabbers, making them all external and using the common USB bus. This gives the user a significant advantage over PCI-based frame grabbers, as a USB-based device can be easily moved around between different devices and locations.

It would also be important to note that the USB to VGA frame grabbers from Epiphan are the only ones that are compatible with Windows, Linux, and Mac OS X.

Resolution

Knowing the highest resolution that will need to be captured is imperative in choosing the right image/video grabber. A frame grabber that can only capture resolutions of up to 1280 x 1024 will not be able to capture the 1600 x 1200 resolution. As frame grabbers can get pretty expensive depending on their specifications, it is recommended that you purchase a device that will for sure meet your present and future resolution requirements. Below is a quick summary of maximum resolution specifications from the different manufacturers:

Manufacturer, Maximum Resolution

Epiphan Systems, 2048 x 2048

EMS Imaging, 2048 x 1536

Foresight Imaging,1600 x 1200

NCast, 1920 x 1200

PixelSmart, 1280 x 1024

Unigraf, 1600 x 1200

Epiphan Systems’ external frame grabbers are capable of processing the highest resolutions, with EMS Imaging’s devices being able to capture slightly less. PixelSmart seems to be the only manufacturer with a very low maximum resolution by today’s standards.

Capture Rate

Capture rate is also known as “frame rate,” and it represents the amount of times per second that the picture on the output changes. A high capture rate is not required for images that are rather static (ie.: radar). On the other hand, if the image being captured is very dynamic, such as from a high resolution camera, the capture rate plays a big role in the final quality of the recording. For the purpose of this review, the common resolution of 1280 x 1024, being in the middle, will be taken in order to compare capture rates across manufacturers.

Manufacturer, Capture Rate at 1280 x 1024

Epiphan Systems, 51 fps

EMS Imaging, 40 fps

Foresight Imaging, 42 fps

NCast, 50 fps

PixelSmart, 15 fps

Unigraf, 42 fps

Epiphan Systems’ USB-based frame grabbers are first in this category as well, being able to achieve capture rates of 51 fps. NCast’s PCI frame grabbers are only 1 frame per second behind Epiphan’s external solution.

Based on the portability, resolution, and capture rate capabilities of different frame grabbers, Epiphan’s line of VGA2USB and DVI2USB devices seem to be the leader in every category. What’s more, these tiny devices are designed to be used with PC sources as well as non-PC sources, making them perfect for medical, military, scientific, industrial, and legal applications. Unless there is a specific situation where a USB-based device cannot be used, due to their versatility and characteristics, employing frame grabbers from Epiphan Systems’ line of VGA2USB and DVI2USB devices would be the best choice for those that desire a quality picture from a solid and reputable manufacturer in the field.