DVD playback for some DVDs may be okay, but most will become jerky(drop frames) especially when the scene becomes "busy" e.g. whenthere's more action, pan-shots etc. If Task Manager is running, itshows that processor resources associated with the DVD player softwarerise (e.g. to >80%) during these "busy" times when frames aredropped. This can happen even with quite new, well specified PCs (e.g.2GHz Pentium 4, 256MB memory...).
Common causeFrequently newer versions of Windows (WinXP,Win2000, etc) cause the internal DVD drive interface to revert to "PIOMode" (Programmed Input/Output - an old, slow, processor-intensive datatransfer protocol) rather than "DMA Mode" (Direct Memory Access -transfers data directly from drive to memory without much processorintervention). This completely throttles data transfer from the DVDdrive and causes dropped frames. A "bug" in Windows prevents thetransfer mode being set back to DMA either automatically (e.g. onreboot), 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 informationabout your computer, then select the Hardware tab, then press theDevice Manager button. Expand the "IDE ATA/ATAPI" entry. At this pointit helps to know whether your DVD drive is on the Primary or SecondaryIDE channel (typically you might find that your hard disk(s) are on thePrimary channel while your DVD and CD-ROM drives are on the Secondary).You can check by following the cables from the motherboard. Assumingfor now that the DVD is on the Secondary channel... double-click thatentry (or right-click and go to Properties). In the resulting dialogbox, click the Advanced Settings tab:
[ 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 thetransfer mode to "DMA if available" won't work, and won't "stick" onreboot.
SolutionMicrosoft'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 sorteverything out from scratch!