Win/TV and Full Motion Video Capture

Motion Video Capture

All Win/TV boards have the ability to capture a stream of video to your PC's hard disk. There are a number of names that are used for this capability: clip capture, digital movies, motion video capture and AVI capture. AVI is the file type used on PCs for identifying motion video. You'll notice these files on your hard disk drive by their .AVI file extension. There is another standard which has been popular, Apple's QuickTime for Windows. The Win/TV cannot create QuickTime files directly, but you can convert an AVI file into a QuickTime by using software distributed free by Apple.

Microsoft's Audio/Video Interleaved (AVI) was one of the first standards for putting together digital movies on PCs, and in 1993 Hauppauge Computer introduced software that allowed our Win/TV digital video board to create a digital movie in an AVI file format. We have continued the development of AVI capture drivers and today, all Win/TV boards support this useful feature.

AVI clip capture is important for several reasons. It is the basis for creating multimedia presentations for computer based training and corporate presentations. It is also used for many of the CD-ROMs that include full motion video, CD-ROMs like the Encarta multimedia encyclopedia. And AVI is used as the basis for many of the new desktop video conferencing systems coming to market, which will allow in the not-too distant future the home or business user to "video communicate" with a friend or colleague from their own PC. Motion videos are also fun to create and the process of digitally editing your motion video really shows off the capabilities of your PC!

The AVI clip capture perfomance of Win/TV's differs between board types. Here is a chart that shows the maximum performance that can be achieved:

                  window size     frames/sec   compression ratio
======================================================================================
Win/Motion60          640x480          30      6:1 up to 50:1
Win/TV-HighQ          320x240          24      3:1
Win/TV-Celebrity      320x240          15      3:1
Win/TV-Cinema95       320x240          15      3:1
Win/TV-Prism          160x120          15      none

If you would like to convert your AVI videos into MPEG video for playback to one of the popular MPEG cards such as the Sigma ReelMagic, there are a few software packages on the market that will do this. Two of these packages are from Xing Technology and from U-Lead.

Steps to create motion videos

There are three steps typically used for making motion videos. Actually, only the first step is required, since you can play back raw AVI files immediately, but lets see a complete set of steps.

First, you need to capture the raw motion video. You can do this with any Win/TV board, creating an AVI file on your hard disk. We include a program called "WIN/TV-CAP" with all Win/TV boards so that you can easily create motion videos onto your hard disk. WIN/TV-CAP has three icons in the toolbar: live video, capture video, play back video. This makes WIN/TV-CAP very easy to use. You can capture video, then immediately play the motion video back from disk so that you can see what you have captured. Click here to see a WIN/TV-CAP window.
Next, you can edit the AVI clip. There are several popular AVI motion video edit packages on the market including Adobe's Premiere and U-Lead MediaStudio. Editing is like cutting and pasting text, but you are working with video sequences instead of words.
Lastly, you can compress and convert your motion video into a AVI type that can be played on PCs that do not have a Win/TV board. For example, if you are making a CD-ROM, you need an AVI type that runs on 386, 486 and Pentium PCs that do not have a Win/TV installed. We'll give you some tips here on creating AVI types that can be played on allmost all PCs.

Capturing Raw AVI Video

The live video you are seeing in the Win/TV window is a digitized version of what is called "analog" video. Analog video is what comes out of your VCR when it is playing or the video that you see on your TV set when watching television. Actually, almost all video we are used to is analog video. The Win/TV digitizes the analog video coming from your VCR or cable TV and then puts the digitized video in a window on your PC screen. When you want to capture motion video to your hard disk, the digitized video is simply moved from the Win/TV board into your PCs memory, mixed with the audio (if you are capturing audio at the same time as the video), modified into the AVI file format and then written to the hard disk.

When capturing motion video, you can specify the size of the video image and the number of frames per second that is captured. The full video image size is normally the size of your PC screen, 640x480, while a quarter screen image is 320x240. In the U.S. the number of frames per second that is standard for broadcast TV is 30 frames per second while in Europe it is 50 frames per second.

Which size of video image you can capture and the number of frames per second you can capture is dependant upon the performance of your PC and the model of Win/TV board you are using. Here is a list of some of the things that you need to look into to optimize the perfomance of video capture in your PC:

Make sure you are not using DoubleSpace or other type of disk compression. These kill hard disk perfomance!
The more system RAM you have, the better. When capturing AVI files the motion video is stored temporarily in your PCs RAM where it is converted into the AVI format. In general, system RAM can help compensate for a slower hard disk drive.
Use a faster hard disk. Though a fast hard disk is not the complete solution to capturing bigger and faster motion video, it is one of the most important. We have found that running a program like SpeedDisk from Norton or Optimize which is in Windows 95 really helps speed up your hard disk for motion video capture. There are some new hard disks coming to market which are called "A/V Hard Disks". These disks are optimized for motion video capture, and include the Conner FilePro, the IBM UltraStor XP and the Seagate Elite. All of these disks use a SCSI-2 interface for fast moving of data from the PCs memory to the hard disk. Another way of making your hard disk drives faster is to use an array of inexpensive IDE disk drives.
Turn off screen savers. These programs use a portion of the CPU to check the system timer and it is important to give your CPU as much unencumbered time as possible. Also turn off any TSRs that might kick in during motion video capture.
Disable your network. Like screen savers, connection to a network will take performance away from video motion capture.
Capture audio seperately. Most professional video editors record audio as a seperate track, then lay down the track during the edit stage. Capturing audio takes a siginificant amount of CPU horsepower away from capturing motion video.
If you have a second hard disk in your PC that is used just for video capture, there are a number of things that can be done to optimize video motion capture. First, turn off Smartdrive (found in either CONFIG.SYS or AUTOEXEC.BAT) for this drive and make sure 32-bit access is enabled (in Windows ControlPanel under 386 Enhanced). Turn on Double Buffering for the drive. Make sure the permanent swap file is not on the hard disk used for motion video capture. Since PCs can have up to two IDE disk drive controllers installed, use a second disk controller for the disk drive being used for motion video capture.

Editing Your Video Clips

There are a number of PC based digital video editing software packages on the market. They all use AVI files created by the Win/TV boards as the source for the video to be edited. Some of the popular editing pacakges are: Adobe's Premiere, U-Lead MediaStudio, the Razor package and Splice from Asymetrix. Each package has the ability to cut and paste video clips, overdub audio tracks, and add special effects. There are significant differences between these packages, and you might want to use more than one to edit your video clips.

Compressing the Motion Video for Playback on PCs

Once your motion video has been edited and a sound track has been added, its now time to think about the PC that the video will be played back on. This will affect the type of compression that you will use when putting your final digital video cut onto disk.

If you are creating a multimedia presentation and plan to play back the motion video on the PC that has the Win/TV board, you are almost done. There is no need to compress the video since the Win/TV has built in hardware to playback AVI files that were recorded with the Win/TV. You might want to choose another video image size but there is no need to compress the edited video.

If you are going to distribute the video clip on CD-ROM, you should choose one of the popular compressors like Cinepak or Indeo. These compression schemes will give good playback speed coming from CD-ROM even if they are being played back an 386 PCs. If the PC that is being played back on has an VGA card with an accelerated videoplayback, then Cinepak or Indeo will playback even faster. This is due to two hardware features in these VGA cards that helps the performance of motion video play back: color space conversion and hardware zoom.

If you want to target your video playback for MPEG, you can use either hardware or software playback. Software playback has been gaining in popularity lately, but it still is slower and uses smaller image sizes than hardware assisted MPEG. So if you want to target for software playback you might want to start with 320x240 video clips. If you have hardware playback you can start with 640x480 video clips. Whichever MPEG playback you use, the Xing or U-Lead software can take your AVI files and convert them to MPEG.

Back to Home Page | Back to the Tips page

Questions, comments, or problems regarding this service?

Copyright © 1999 Hauppauge Computer Works, Inc. All rights reserved.
The Hauppauge logo and WinTV are registered trademarks of Hauppauge Computer Works, Inc. Windows and WebTV are trademarks of Microsoft. Corp. Company logos are trademarks of their respective companies.