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by W.A. Steer  PhD
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DVD playback hint

Are you finding DVD playback jerky (dropping frames) on your computer, despite owning a fast machine? I had this problem and eventually discovered that it is very common (often caused by a "bug" in Windows) and tracked down the solution.


DVD playback for some DVDs may be okay, but most will become jerky (drop frames) especially when the scene becomes "busy" e.g. when there's more action, pan-shots etc. If Task Manager is running, it shows that processor resources associated with the DVD player software rise (e.g. to >80%) during these "busy" times when frames are dropped. This can happen even with quite new, well specified PCs (e.g. 2GHz Pentium 4, 256MB memory...).

Common cause

Frequently newer versions of Windows (WinXP, Win2000, etc) cause the internal DVD drive interface to revert to "PIO Mode" (Programmed Input/Output - an old, slow, processor-intensive data transfer protocol) rather than "DMA Mode" (Direct Memory Access - transfers data directly from drive to memory without much processor intervention). This completely throttles data transfer from the DVD drive and causes dropped frames. A "bug" in Windows prevents the transfer mode being set back to DMA either automatically (e.g. on reboot), or by even vaguely user-friendly intervention!

This problem has been known about for over 2 years!
There is a hard-to-find Microsoft Knowledgebase article on it.

Open up Device Manager from the Windows Control Panel: (WinXP) - Start|Control Panel|Performance and Maintenance|See basic information about your computer, then select the Hardware tab, then press the Device Manager button. Expand the "IDE ATA/ATAPI" entry. At this point it helps to know whether your DVD drive is on the Primary or Secondary IDE channel (typically you might find that your hard disk(s) are on the Primary channel while your DVD and CD-ROM drives are on the Secondary). You can check by following the cables from the motherboard. Assuming for now that the DVD is on the Secondary channel... double-click that entry (or right-click and go to Properties). In the resulting dialog box, click the Advanced Settings tab:

IDE Channel Properties dialog box
[ On my computer, Device0 (top) is the DVD and Device1 (bottom) is the CD-RW ]

If instead any of those boxes say "PIO mode" and you have a reasonably-modern PC then you've probably got problems!

Unfortunately owing to this Windows "bug", just setting the transfer mode to "DMA if available" won't work, and won't "stick" on reboot.


Microsoft's official solution can be found in their Knowledgebase article Q817472. In my case (and most I've read on the Web), the easiest solution is to "Uninstall" the affected IDE channel from the Device Manager window, then reboot, allowing Windows to re-install the drivers and sort everything out from scratch!

uninstalling IDE channel

But don't just take my word for it (I want to be helpful, but I won't be responsible - nor can I answer a deluge of queries). Now you know what's going on, choose your own solution from the WWW.

This problem may be (is supposed to be?) fixed in Windows XP service pack 2 (SP2)

Created: December 2003
Last modified: 18 August 2004

Source: http://www.techmind.org/dvd/

©2004 William Andrew Steer