How Does a Video Capture Card Work?

By Jack Gerard

Purpose of Video Capture Cards

Video capture cards are used to allow you to take screenshots or record video files on your computer from an external video source. Most video capture cards are installed into an expansion slot on your computer's motherboard; PCI, PCI-Express, and PCI-Express 2.0 models are available in order to ensure compatibility with different expansion slot types. The source of the video can differ depending on the input types that your specific video capture card features; a majority of cards will allow any source that has standard video and audio-out cables to be connected to it, meaning that you can capture stills and video from your VCR, DVD player, camcorder, and a number of other common video devices. For those wishing to capture video from digital sources, many video capture cards also allow input using s-video cables and some even allow HDMI or other high-definition video input as well. The video capture card transfers the video into a format that is useable by the software which accompanies it, with the software providing the interface for you to decide how you want to capture your screenshots and video from your source.

Video Capture with TV Tuner Cards

In addition to the video input options available with standard video capture cards, some cards also allow you to capture video from cable or satellite television signals due to the inclusion of a TV tuner on the card. The TV tuner allows you to connect a coaxial cable to the video capture card in addition to other video input types, allowing your cable or satellite television signal to be received by your computer much as it would be by your television. The video capture software will include a television descrambler in addition to its standard video capture options, allowing you to not only capture screenshots and video from live television, but also letting you watch TV on your computer just as you would on your television.

External Video Capture Cards

While most video capture cards plug in to a PCI or PCI-Express expansion slot on your motherboard, some cards are contained within external enclosures that connect to your computer via a USB cable. This allows you to connect your video capture card only when you need it and also makes it more easily portable from one computer to another; this can be especially useful if you plan on using it both at work and at home or if you wish to be able to use the card with a laptop computer. External video capture cards generally do not contain TV tuner functions and may be slightly slower in transferring video information than internal PCI-Express or PCI-Express 2.0 cards, but they otherwise will perform many if not all of the same functions as more expensive internal cards.