Your Complete Guide to VGA and VGA Capture
Whether your application involves creating IT instructional manuals, recording from high resolution security systems, sharing a presentation with people from around the world, or printing handouts directly from any computer screen, you are looking at VGA video capture or VGA signal capture as a mean to achieving these goals. This article will explain in-depth how VGA signal capture works and what you need to know in order to capture such a signal.
The VGA Plug
Unlike DVI or HDMI, which are both digital standards, a VGA signal is purely analog. The differences between VGA, DVI, and HDMI are described in detail in this article.
“VGA” is short for Video Graphics Array and has been the most common connector/plug for analog video on computer equipment and various electronics with an analog video output since the introduction of personal computers (PCs). VGA carries a RGB (red-green-blue) signal and is sometimes referred to as “D-Sub” due to its’ 15-pin “subminiature” connector. The term “VGA” also refers to the VGA standard graphics resolution – 640×480 pixels.
A detailed VGA pinout is shown below to help advanced users understand how VGA works. Source.
VGA Video Connector Pinout
| Pin # | Signal Name |
|---|---|
| 1 | Red |
| 2 | Green |
| 3 | Blue |
| 4 | No Connect |
| 5 | Ground |
| 6 | Ground |
| 7 | Ground |
| 8 | Ground |
| 9 | No Connect |
| 10 | Ground |
| 11 | No Connect |
| 12 | DDC DAT |
| 13 | Horizontal Synchronization |
| 14 | Vertical Synchronization |
| 15 | DDC Clock |
VGA Frame Grabbers and How They Work
The only true way to capture and record a VGA signal is through a VGA-compatible frame grabber. A VGA frame grabber can be defined as a device that proccesses analog VGA signals and converts them into digital signals readable by computer equipment. While frame grabbers are described in slightly higher detain in this Wikipedia article, these three main internal components determine a VGA frame grabber’s performance:
- ADC (analog-to-digital) converter. This is the circuit that transforms the analog signal coming from the source VGA signal into a digital stream that can be read by the target computer.
- RAM (random-access memory). Also referred to as buffer memory, this memory is vital in storing the captured image for a short period of time on board the actual frame grabber.
- FPGA (field-programmable gate array). This is the heart of the frame grabber and is analogous to a processor inside a PC. It is a part that is entirely programmed by the manufacturer of the frame grabber.
Some frame grabbers, like the PixelSmart VGA Master have no on-board RAM buffer memory. This fact alone, besides leading to a lower-quality image, lowers the maximum possible capture rate (also referred to as frame rate) achievable by the frame grabber. Frame grabbers without on-board RAM are sufficient for the capture of presentations with lots of static slides or any other static imagery, like capturing screenshots from the computer’s BIOS. On the other hand, if you are capturing a high-resolution image and/or are capturing from a source with a high frame rate, like a video game console (ie XBOX 360) or medical equipment (ie: ultrasound), a frame grabber with at least 16MB RAM would be preferred. The VGA2USB Pro by Epiphan Systems, for example, has 32MB RAM memory and is able to capture at a whopping 60 frames per second in some resolutions.
PixelSmart’s Internal PCI VGA-Master
Epiphan Systems’ external USB-based VGA2USB Pro frame grabber
While RAM is important in defining the characteristics of a frame grabber and the quality of the image it outputs, another important factor is the way that the FPGA, or processor, is programmed. You will notice that the higher-end frame grabbers, like the VGA2USB Pro pictured above, have built-in features that some of the more basic frame grabbers, like the PixelSmart, do not have. A quick look at the Epiphan Systems webpage reveals the following features programmed via the FPGA processor: On-board cropping, Color space conversion, USB Transfer Accelerator™, Compression Booster Filters™. All of these software/firmware features allow the frame grabber to achieve extremely high quality and transfer rates without increasing the frame grabber’s size.
Please refer to our complete Frame Grabber Specifications Comparison Table for detailed and complete specifications on every VGA frame grabber on the market.
Applications for Frame Grabbers
Frame Grabbers, while being a niche product, have many practical uses in today’s IT-oriented business environment. The five most common and prominent uses are described in detail in our Top 5 Uses for High Resolution Frame Grabbers You Should Know About article. From the gaming industry to the military, frame grabbers are used accross many fields related to computer technology. To give you a general idea, some industry-specific uses for high resolution VGA frame grabbers are described below.
Computer Console Gaming
Microsoft’s X-BOX 360 gaming console has the ability to output its images via VGA or DVI. This means that a VGA frame grabber can be used to capture and record the gameplay from this game console, and even broadcast the gameplay live over the internet for other viewers to see.
The diagram above explains how to connect an X-BOX 360 to a frame grabber for recording and broadcasting the gameplay. The X-BOX’s VGA cable is connected to a VGA splitter’s input, from which one VGA output goes to the TV, and the other to the frame grabber-equipped computer. The image can then be broadcasted to the internet using the computer.
Presentation, Conference Broadcasting and Recording
In today’s globalized business world, businesses often have partners in many different countries. When conducting an online meeting or presentation, the presenter often has the need to share his screen with viewers around the world. For this exact reason, VGA frame grabbers are useful. They allow the presenter to not only share an image from a projector, but also from a BIOS screen, an ATM machine, a RADAR device, a medical ultrasound device, a security system, or even an electronic microscope. Most of these VGA sources are not able to be broadcasted in real-time with the use of traditional software sources, and frame grabbers are the only way to properly create diagnostic-quality images and videos from these devices.
In the diagram above, the VGA source is connected directly to a frame grabber-equipped PC with access to the internet. Using any web broadcasting software, the user is able to relay the images and video captured by the frame grabber to his or her audience.
Security System Surveillance Recording and Broadcasting
Today’s security systems and cameras are able to support digital formats as well as high resolutions required for complex security solutions. Of course, as solution is needed to record the outputs from the security system, store it in a digital format, and provide access to the files from remote locations. All of this can be accomplished with VGA frame grabber-based technology, such as the VGA Recorder, which have ample space for recording video files (up to 500GB), are able to directly transmit recordings to a remote FTP location, and give access to the recorded files through a web interface.
The diagram above, borrowed from the Epiphan Systems website, shows how easy it is to hook up a security system’s VGA output to the VGA Recorder. Everything can be set up in minutes, and the VGA Recorder is able to archive hundreds of hours of digital compressed video data to its internal hard drive.
Telemedicine and Remote Guidance
Telemedicine, also known as Remote Guidance, is an expanding field in which doctors are able to, through the internet, diagnose patients and provide advice. Telemedicine has many practical applications but some of the more notable ones are the delivery of expertise to areas in which it is not practical to have a qualified doctor at all times. For example, lets suppose that a player on a sports team gets a knee injury. Through telemedicine, the coach can use a portable ultrasound device like the Logiq Book XP and, with the aid of a frame grabber, relay the images from the Logiq Book directly to a qualified radiologist who can then make a decision on the severety of the injury.
The diagram above shows how any equipment with a VGA output, such as the ultrasound device, can be connected to a frame grabber, and the a computer. The images are then relayed to the qualified radiologist or doctor through the internet or a satellite uplink. If you would like to find out more about the field of remote guidance, then this website is a good start.
Summary
The VGA signal is the most common format used on today’s electronics and computer-based equipment. When this equipment is coupled with a VGA frame grabber, the possibilities are endless. Using a frame grabber, which is a relatively inexpensive device, organizations can not only significantly cut costs, but can also improve their productivity.
DVI Image and Video Capture – The Basics
Almost all computer equipment sold these days supports DVI. This can range from modern computers and projectors to game consoles like the Microsoft X-Box. Of course, this means that high end hardware solutions for DVI capture are now becoming readily available.
The first thing that you must determine is whether your DVI signal is a true digital video signal or a traditional analog source. The easiest way to tell if a digital or analog signal is running through your DVI port is to look at he connector that you are using and match it with the diagram of the DVI connector below.
If either your DVI plug or connector are DVI-D (DVI-Digital), this means that a 100% digital signal is being used. For this kind of signal, you absolutely need to use a DVI frame grabber.
If the connector or plug is of the DVI-A (DVI-Analog) flavor, then you’d be able to use a DVI to VGA adapter and a VGA frame grabber. DVI-A supports analog signals only is and is identical to VGA but with a different pin placement.
If the plug is DVI-I (DVI-Integrated), this means that it is capable of running both an analog and digital signal along the cable. Thus, unless you know if the signal is analog or digital, you would need a DVI-capable frame grabber to capture the signal.
As stated earlier, a VGA frame grabber would do the job for DVI-A and analog-only DVI-I signals. Before a VGA grabber can be used, the DVI signal needs to be converted to a VGA one using a DVI-to-VGA adapter, which costs roughly $10 (pictured below).
You can now follow the same procedure as you would when recording a VGA signal with your VGA frame grabber.
Digital Signals (DVI-D and DVI-I)
If you have determined that you have a digital DVI signal that needs to be captured, a DVI-specific frame grabber must be used. Before choosing a suitable frame grabber, you must determine if the DVI signal is single link or dual link.
A single link DVI signal can support, at a refresh rate of 60 Hz, a maximum resolution of 1915 x 1436. If your DVI cable supports a higher resolution at a refresh rate of 60 Hz, then you are running a dual link signal. Dual link DVI is used primarily on large LCD monitors, such as the Apple monitor or the 25″+ Dell monitors.
If you need to capture a dual link DVI signal, then your choice of frame grabber is limited to one model, the Epiphan Systems DVI2USB Duo (pictured below), which captures single and dual link digital DVI signals only.
Unfortunately, the DVI2USB Duo is a very specific high-end frame grabber that does not have the ability to capture an analog or VGA video signal. However, the DVI2USB Duo is a blessing for those with dual link DVI capture requirements. You can see how the DVI2USB Duo stacks up against its competition in this table.
If, however, you need to capture a single link DVI signal, then your choices are much greater. If you are looking for a PCI-based card, then you have a choice of the EMS Imaging Xtreme RGB, NCast DCC 3.1 or the Unigraf UFG-03. If you are into external USB-based solutions, then Epiphan Systems offers the DVI2USB, which is an external dual-mode VGA and DVI frame grabber or the DVI2USB Solo, which can capture a single link DVI signal only.
There is no one ideal frame grabber that does everything. Your choice of a DVI capturing device should depend on your needs, as outlined above. If you wish to find the specifications of each frame grabber featured in this article, then this would be a good place to start.
