IDE settings (WAS: [MPlayer-users] DVD playback)

[Sven Hartge]

Um 11:12 Uhr am 22.11.01 schrieb Frank Boehme:

> Actually, I found that on my system the proper IDE flags have more
> influence than -cache, especially when playing DVD. So hdparm helps,
> until I get a dma timeout or some other event which resets the IDE
> device. After such a soft reset, dma access and unmasking other IRQs is
> disabled and the movie begins to jerk.

Well, I have only seen DMA-timeouts with buggy/crappy hardware, most times
way too long IDE cables. So check if you have one of those 1m cables build
in an replace them with proper ones, each no longer than 40cm.

> Now, hdparm has the -k parameter which tells the device to keep its
> flags over a soft reset but my CDROM does not adhere this. So I think,
> I will try to set up some sort of watchdog that watches
> /proc/ide/mydevice/settings for changes or catches the kernel messages
> (hdx: dma timeout...) and fires up hdparm with the right switches
> whenever this happens.

Prepare for data loss. All DMA-Modes below UDMA66 _do not use error
correction_, so if you *force* UDMA33 for example, even if the kernel
insists switching it off, you may introduce errors into the date read or
written.

I have seen this some time ago, one day the pictures (from a webcam) on
the disk were fine, but the next day, after they have been copied to
another directory for archiving, there were errors, some bits changed.
Reason was a too long IDE cable.

So be careful, the kernel has a reason to switch DMA off.

S!