Microsoft KB Archive/139826

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AVI Video Authoring Tips & Compression Options Dialog Box

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Q139826

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The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK), version 3.5
 * Microsoft Video for Windows Development Kit (DK) version 1.1

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SUMMARY
This article provides tips you can use to help you compress AVI (audio- video interleaved) files. This article should help to clarify the information in the documentation. This article also provides hints concerning the settings for Interleave, Compression Quality, Key Frame Every, and Data Rate - all settings available in the Video Compression Options dialog box.

Authoring/Compression Tips

 * Don't capture on low or medium end equipment.
 * Avoid noise. Noise reduces the quality of the image and can effect the compression.
 * Use a low-pass filter such as the LOWPASS sample included with Visual C++ Graphics and MultiMedia samples and with the Win32 SDK to eliminate some of the audio noise.
 * Use a low-pass filter such as the LOWPASS sample included with Visual C++ version 2.x and with the Win32 SDK to get rid of some of the audio noise.
 * Avoid compressing the movie more than once. Edit your uncompressed bits of video together before doing any compression, and then compress the final product. Editing always works faster with uncompressed video.

Video Dimensions and Frame Rate
When authoring, consider that most display cards support up to 320x240x15 frames per second (fps). Larger images or faster frame rates increase the importance of testing on multiple machines with multiple configurations (CD- ROM drive speeds, video boards, display monitors, and so on).

Full Screen Playback
If your movie is 320x240 or less, you should get excellent full-screen playback that can handle 15 fps regardless of the video card. If your movie is bigger, it will play full screen, but performance may be poor. Test across multiple configurations to help identify the impact of stretching on various displays.

Video Compression Options
The following options are presented in the Compression Options dialog box. To gain access to this dialog box, on the File menu, click Save Options in SDK samples such as Aviedit and Aviview. Similar options are available in the Videdit utility from Video for Windows by clicking Save As on the File menu.

Interleave:

The interleave option places audio data physically between video frame data in the AVI file to ensure the best performance and synchronization. For example, with a 1:1 interleave setting, each frame of a 15 fps video would have 1/15 seconds of audio data. This setting does not matter when editing the file. When saving for playback, interleave every frame for best playback performance. Interleaving multiple audio streams is not possible using this option.

Compression Quality:

Use the highest quality number to get the best quality, but use the entire allowable data rate. A lower quality may take up less than the requested data rate.

Key Frame Every:

Normally, use the default key frame value for a particular codec. Fewer key frames could give a little better picture quality, but if your system can't keep up on playback, you'll stall for a longer time, and you won't degrade as gracefully. More key frames means fewer frames skipped when playback can't keep up.

Data Rate:

The minimum data rate that can be achieved on most computers is 100K/sec for single spin CD-ROM drives, and 225K/sec for double spin CD-ROM drives. Most computers can do more (150K and 300K for single and double speed respectively).