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GOING DIGITAL: Video Frame Grabbing
In my previous article I indicated I would get into discussions about frame grabbing and scanning. Let's start with the frame grabbing concepts and go from there.
A note of interest
A typical video image will produce a fairly low resolution digital image. (The term "resolution" in this discussion refers to the level of detail in an image. The higher the resolution of an image, the more detail there will be.) Each video frame is made up of a limited number of horizontal lines that are painted on to a TV screen one at a time. This painting happens fast enough to fool the brain into seeing a complete image. A screen full of these horizontal lines can be frozen, captured and translated to digital information, however the image resolution is limited to the number of those lines. Most computer monitors can display images at a much higher resolution than TV screens so when viewed full-screen on a PC monitor, individual video frames can look a bit sketchy.
Frame grabbing
Frame grabbing is another way of describing the capture of individual pictures from a video source. Video is made up of a series of individual images displayed in rapid succession so that apparent motion and transition are smooth and flowing. Typically, full motion video runs at around 30 frames per second. Camcorders, VCRs and cable TV signals run at about this rate. This means there's a lot of individual pictures available from even short lengths of video. Once captured. you can use computer software to convert these images to digital format files that you can save, view, send via e-mail or place on a web site.
Frame grabbing can be accomplished in a number of ways. The methods vary depending on the type of video source you're interested in. Possible video sources include:
- PC based video cameras
- Devices with a video output connector such as
- Camcorders
- VCRs
- TV sets
- and cable boxes
- Computer video files
Seo Software
All video sources, with the exception of computer video files, need to be "hooked up" to a PC. Newer mid-level and up PCs may come with video input cards already installed. If your PC isn't equipped with one on these, some installation work may be necessary. This is usually pretty easy to do, but requires a little confidence and the patience to carefully read and follow directions. Some retail PC suppliers offer installation services that come in handy for this sort of project if you feel this would push you beyond your comfort range. As an alternative, there are adapter devices that simply plug into the printer connection port on your PC and don't require invasive surgery to install. Once any installation work is complete, getting video into the PC is usually a simple matter of connecting a video cable from your source to the video input card or adapter device.
PC based video cameras
PC based video cameras are pretty easy to deal with. These are the little cameras that connect directly to a PC and let you video conference with someone at a remote PC. Usually, the software that comes with these cameras will give you the ability to freeze frame a single image. The frozen frame can then be saved as an image file. That's pretty simple!
Devices with a video output
Devices with a video output connector can be connected to your PC after you've installed a video input device. The connection process is usually pretty straight forward. Whatever your video source, you'll need to attach a small cable between it and your video input device. Other than that, its a matter of turning on the power to the video source and running the software on your PC.
NOTE: If you are working with a VCR or a camcorder in VCR mode, you'll have to put it in "play" to start the video moving to your PC. Usually, you can reverse and forward the tape to find just the right image to capture. Some of the recorders and cameras have a "slow" feature that makes life even easier.
If you're working with a live video source such as a "video out" signal from a TV or cable box, the "hook up" connection is the same. The difference here is that you don't have the option of searching around for the perfect image. When you see it you have to grab it. In these days when VCRs outnumber the pets in the USA, you may choose to record live video and then feed it to your PC from your recorder. You'll have a better chance of grabbing the images you want this way.
Computer video files
Computer video files offer an opportunity to grab frames also. This doesn't require any additional equipment, but does mean you'll need some graphics software that will allow you to view and save individual frames from a video file. Since most computer video files produce relatively small low resolution images, their usefulness is somewhat limited.
The software that accompanies a video input device may allow you to perform a wide range of activities. Study the options and try them out. A little time spent here will reward you with success more often than frustration. That's a plus when it comes to PCs.
The simple video adapter device that plugs into your printer port will allow you to "play" video to your PC and let you grab an image frame on-the-run. These devices generally let you grab one frame at a time. The accompanying software provides you with a basic set of tools for capturing, editing and saving your pictures. The incoming video is displayed on your PC screen and you perform a simple mouse click when you see an image you want to capture. The image is now yours .
Video input cards
The installed video input cards generally let you grab multiple frames and will improve your chances of capturing the best images. Video input card systems vary considerably from inexpensive (under $100) entry level to fairly sophisticated. A full video editing "system" will allow studio like capabilities complete with titling, sound, and the ability to send video back out to a recorder or TV. These systems can run into hundreds of dollars but may offer you the tools you want to get really creative. For simple frame grabbing purposes, just about any of these devices will do fine.
PC television cards
PC television cards are a separate class of video processing equipment that you can get for a PC and there are some available that are cable ready and have frame grabbing capabilities. It took me a couple years to move up to a home computer that didn't require using the family TV as a monitor. I guess that's why I've avoided turning my PC back into a TV. It somehow feels like regression. But for those of you interested in combining the two worlds, you can capture images of your favorite TV heroes or heroines.
The webmaster for this site was hoping I could finish up the frame grabbing and scanning discussions in this article, but the tyrant limited the number of pages to less than this discussion has taken. I'll get to scanning in my next article.
Until next time...
Ken McBee
Going Digital: Cameras
Going Digital: Video Frame Grabbing
Going Digital: Image Scanning
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