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VGA Capture Processing: Review and Guidelines

VGA together with its supersets and extensions forms the basis of most video cards used in PCs. Many video cards support color modes and resolutions which are far beyond what VGA really is, but, for compatibility, they also support the original VGA modes. The VGA output is used in a wide range of devices applied in various spheres of human activity – science, medicine, education, engineering, etc. It is important for the most users dealing with this equipment to capture images. Time-critical tasks often need to be carried out with the assistance of image processing. The images can be recorded, broadcasted to the web, viewed and edited remotely. It would not be overstating the case to say that digitizing of the captured images is an irreplaceable function for the equipment users. One should make its choice among the solutions available on the market depending on the needs and used equipment.

Converters and Graphic Boards

Among the great number of VGA capture solutions currently available on the market at the lower end of the price range there are video converters. VGA converters are external solutions connecting VGA source output to the video input on your TV. VGA2Video from Svideo allows a user to watch video from the computer on a TV and VGA monitor at the same time. The unit is powered through the computer’s USB socket. Similar functionality is provided by Sewell’s PC-to-TV converter. If you are looking for low-cost solutions for capturing video signal, you may choose any graphics board with video capture support – capture video cards. These internal solutions are offered by all main manufacturers (NVIDIA, ATI, Matrox, ASUS, etc.). For example, ATI Radeon VIVO card features 64 MB of video memory and 3D resolutions (32-bit color) at a very competitive price. External conversion units allow users to connect analog video equipment to the computers for video editing. ADVC110 from Grass Valley connects to all analog and digital cameras. It has no drivers to install and requires no power supply.

Frame Grabbers: Internal and External Solutions

Very often low-quality video capture is not convenient for the users due to multiple reasons. Let’s assume a situation where a user needs to capture video from cameras with high data rates or multi-camera systems with overall data rates in excess of 100Mbyte/s. If capture should be performed from scientific or military equipment just to name a few, life-like quality and high resolution rates are required. And it is here that the frame grabbers come up trumps. Frame grabbers are rather expensive solutions that provide VGA capture to USB. They capture or “grab” video signal, and convert it into a digital stream. Currently there are a lot of VGA and DVI frame grabbers on the market, with their advantages and disadvantages.

As frame grabbers generally deliver a wide range of functions, sometimes they are by nature more complex to operate. Usually two main groups are distinguished: internal and external frame grabbers. Generally, internal frame grabbers are PCI cards installed in the computer. These solutions grab video signal through VGA port and convert it into a video file or a series of images which are then saved in a proper format. Usually the VGA capture cards are supplied with specialized software but sometimes they support third-party applications.

VGA-Master from PixelSmart is an internal PCI card featuring resolution up to 1280x1024. The card is supplied with its own software that allows snapping screenshots. The card supports Windows 2000.
Datapath VisionRGB-PRO1 captures the VGA output and displays it as an independent application. This card uses specialized dual-port video memory ensuring high performance. It captures data at maximum resolution 1600x1200.
TopDomain XI102AE video capture card allows saving captured data in different formats (WM9, REAL, MPEG4) and supports resolution up to 1920x1440. This PCI-E card supports multiple cards operation in a single PC and allows for streaming or broadcasting over PAL/NTSC network.
XtremeRGB-Ex1 by EMS-Imaging is a PCI-Express card that captures images either form VGA or DVI sources. It has input mode detection, supports seven RBG modes and features maximum analog RGB capture resolution of 2048x1536 and on-card processor for sync detection and real-time mode. Using a special option you can choose between transferring data to the card via system memory affecting performance or directly.
PC2-Vision Express from Dalsa is a PCIe image acquisition board. It interfaces with standard (RS-170 and CCIR), nonstandard (progressive scan), RGB and dual-channel analog cameras. PC2-Vision Express features six inputs and high digitization rates.
Digitizer DCC 3.1 Card from NCast features VGA, DVI, S-Video and Composite Video inputs and works with both Windows 2000/XP and Linux PC desktops.

External frame grabbers are standalone solutions providing VGA capture to USB. They are less frequently offered by manufacturers. External frame grabbers can be connected to PCs via USB input or directly to the Ethernet allowing remote users to view the captured stream and record it on PC. Currently Epiphan Systems is the only manufacturer of the high-quality external VGA frame grabbers.

VRmFAVC-1OEM frame grabber from VRmagic is available both in internal and external versions and features 64 MB ring buffer to prevent loss of image data. Its maximum resolution is 720x576.
iPORT Connectivity Solution streams imaging or video data from analog cameras in real time over Ethernet. It converts the data to IP packets and pumps it onto the GigE link. Packets are transported continuously to PC connected to Ethernet. This device requires installing several software packages on the PC. Microvision’s MV-U2000 external frame grabber box is a portable USB color/monochrome frame grabber box with resolution up to 768x576.
Epiphan Systems’ VGA2USB frame grabber captures VGA signal from any sources – workstations running under Windows, Mac OS, Linux and all kinds of equipment featuring VGA output. Its main advantage is possibility to capture video at an extremely high resolution up to 2048x1536. VGA2USB supports 13 VGA modes with frame rates up to 28.0. VGA2USB software allows for viewing and saving captured data in a real time or copying captured data to a clipboard. It is compatible with DirectShow on Windows and QuickTime on Mac OS X.

Which One Should be Preferred?

The selection of an appropriate VGA capture solution is dependent on the following considerations. First of all, for what purposes video signal will be captured and up to what extent will the captured image quality be principal? If the quality does not matter and the resolution provided by video converters and capture video cards is sufficient for the user, there is no need to look for more expensive solutions than those at the lower end of the price range. If you need a solution for capturing high-quality images, then frame grabbers are worth the cost. Internal frame grabbers are suitable for home and consumer needs. As they are once fitted in the PC’s motherboard, it will not be suitable for the cases where portable equipment is preferred. You will have to open up the PC each time you need to install the frame grabber – it often causes end users a certain amount of concern. If you work in scientific, military, industrial, secure environments you will most likely need a standalone, lightweight and easy pluggable external frame grabber, such as Epiphan VGA2USB. Frame grabber’s installation does not require a modification of a source device providing total security of VGA capturing process. This equipment has its place for tasks that require high levels of data reliability. It is broadly used for streaming media, webcasting, digital multimedia recording security and surveillance, and remote viewing applications.