Microsoft KB Archive/99287

= VidCap: Double Buffering Causes Dropped Frames =

Article ID: 99287

Article Last Modified on 9/30/2003

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APPLIES TO


 * Microsoft Windows Sound System 1.0

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This article was previously published under Q99287



SUMMARY
When using VidCap to capture a live video sequence, you may drop an extraordinarily large number of frames if you have a line similar to the following in your CONFIG.SYS file:   DEVICE=C:\WINDOWS\SMARTDRV.EXE /DOUBLE_BUFFER



MORE INFORMATION
SMARTDrive 4.x provides the capability of caching both read and write operations. If this &quot;double-buffering&quot; is enabled, data is written to the SMARTDrive's buffer first, and from there to the hard disk. For optimal operation, VidCap tries to stream data continuously to the hard disk. If SMARTDrive is double-buffering, VidCap sends data to the buffer, and the data stream is then interrupted as SMARTDrive writes to the hard disk. This can result in either dropped frames throughout the video sequence, or all frames after a certain point to be dropped (depending on the size of SMARTDrive's cache.)

Double-buffering is required for proper Windows operation with some hard disk controllers, but is only suggested as a general performance enhancer with other controllers.

To reduce the number of dropped frames, you can try the following procedures:

  Comment out the following line from CONFIG.SYS and restart your computer:      DEVICE=C:\WINDOWS\SMARTDRV.EXE /DOUBLE_BUFFER For example, type the following to comment out the above line:      ;DEVICE=C:\WINDOWS\SMARTDRV.EXE /DOUBLE_BUFFER   If Windows fails to operate correctly after this line has been removed (unexpected system hangs, disk read errors, or Windows failing to start), try opening SYSTEM.INI in a text editor such as Notepad and add the following line to the [386enh] section:      VIRTUALHDIRQ=OFF   If Windows still does not operate properly, put the SMARTDrive double-buffering line back into CONFIG.SYS and modify the SMARTDrive line in AUTOEXEC.BAT to read:      C:\WINDOWS\SMARTDRV.EXE /L The &quot;/L&quot; causes SMARTDrive to keep the buffer size small, which results in smoother data streaming to the hard disk. 

Keywords: KB99287

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