[vlc] Re: Choppy video and audio in Red Hat Linux

[Marco Sanguinetti]

I'm using kernel version 2.4.  I tried Paul Allen's suggestion and was
able to turn DMA on for /dev/hdd:

.bashrc complete.
[mps]~
$ cd /dev
[mps]/dev
$ kernelversion
2.4
[mps]/dev
$ ls -l hd[a-e]
brw-rw----    1 root     disk       3,   0 Aug 30 19:31 hda
brw-rw----    1 root     disk       3,  64 Aug 30 19:31 hdb
brw-------    1 mps      disk      22,   0 Aug 30 19:31 hdc
brw-rw----    1 root     disk      22,  64 Aug 30 19:31 hdd
brw-rw----    1 root     disk      33,   0 Aug 30 19:31 hde
[mps]/dev
$ hdparm -d1 hdc

hdc:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Permission denied  (WOOPS! I need to
 using_dma    =  0 (off)                  be superuser)
[mps]/dev
$ su
Password: 

.bashrc complete.
[root]/dev
$ hdparm -d1 hdc

hdc:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)
[root]/dev
$ hdparm -d1 hdd

hdd:
 setting using_dma to 1 (on)
 using_dma    =  1 (on)
[root]/dev
$ 

*********** END-OF-LOG ******************

After having turned DMA on for /dev/hdd (which has major number 22
corresponding to the secondary IDE controller) I still get the same
choppy video and audio.  (I also tried "hdparm -X34 -d1 /dev/hdd" but
that didn't work either).

-Marco Sanguinetti

----------------------------------------------------------------


On Fri, 2003-01-03 at 08:41, Sam Hocevar wrote:
> On Thu, Jan 02, 2003, Marco Sanguinetti wrote:
> 
> >      hdparm -X34 -d1 /dev/dvd
> > 
> > /dev/dvd:
> >  setting using_dma to 1 (on)
> >  HDIO_SET_DMA failed: Operation not permitted
> 
>    Which kernel version are you using? Is CONFIG_BLK_DEV_IDEDMA set in
> your .config? If not, try to reconfigure your kernel with this option.
> 
> -- 
> Sam.
> -- 
> This is the vlc mailing-list, see http://www.videolan.org/vlc/
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> 


----------------------------------------------------------------


On Thursday, 2003-01-02  Paul Allen wrote:
Turning DMA mode on fixes this problem.  Without it, the channel to the
drive hasn't got enough bandwidth.  On my dual 550MHz Celeron box, I
have this line in /etc/rc.d/rc.local:

        /sbin/hdparm -d1 /dev/hdd

If I run that command manually, I get this output:

[root at granite rc.d]# /sbin/hdparm -d1 /dev/hdd

/dev/hdd:
 setting using_dma to 1 (on)
 using_dma    =  1 (on)
[root at granite rc.d]#

My DVD/CD-RW is the slave on the second IDE channel.  I use /dev/hdd in
the above command because /dev/dvd is a symlink to /dev/scd0, which is
serviced by the SCSI generic driver and doesn't know what DMA mode is.
With DMA mode enabled in the underlying IDE driver, DVD's play
flawlessly on my system.  Before I figured out that was the problem, I
had the same symptom you're seeing.

If pointing hdparm at the IDE device doesn't help, you might try leaving
the -X34 option off the command.  Possibly the drive doesn't like being
explicitly set to that transfer mode.  I'm just letting the drive use
its default DMA transfer mode, and both it and I are happy as clams.

Good luck!

Paul Allen

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