If watching a DVD seems a bit choppy (stops and starts) then perhaps
the CD/DVD IDE device needs some tuning. First check to see what the
current settings are (e.g., on Belinos (101.3) where the DVD driver
is /dev/hda):
$ hdparm /dev/hda
/dev/hda:
IO_support = 0 (default 16-bit)
unmaskirq = 0 (off)
using_dma = 0 (off)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
HDIO_GETGEO failed: Invalid argument
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For a DVD, setting the readahead to 8 (-a8) seems to fix
it. Turning unmask on (-u1) also might help:
$ sudo hdparm -d1 -a8 -u1 /dev/hda
/dev/hda:
setting fs readahead to 8
setting unmaskirq to 1 (on)
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
unmaskirq = 1 (on)
using_dma = 0 (off)
readahead = 8 (on)
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To have this tuning survive a reboot add something like the following
into /etc/hdparm.conf:
/dev/hda {
read_ahead_sect = 8
interrupt_unmask = on
}
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This needs to be run on boot after the appropraite modules for the
CD/DVD have been loaded, so following the instructions in the README
file:
$ wajig readme hdparm | most
$ sudo editor /etc/hdparm.conf
ROOT=/dev/sda
$ sudo ln -s /etc/init.d/hdparm /etc/rcS.d/S39hdparm.second
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The instructions suggest S29 but that did not work for me.
If you have any problem rebooting after making these changes, use the
nohdparm boot parameter and this will inhibit
hdparm from doing anything.
Visit https://www.mplayerhq.hu/DOCS/HTML/en/drives.html for a
collection of tuning suggestions.
Turning DMA on (-d1) fails on many DVDs. According to the
Red Hat Linux Release Notes
(https://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/release-notes/x86/)
DMA is often disabled on CD-ROM drives because they are often not
capable of IDE DMA. If you are sure that your CD-ROM drive is capable
of IDE DMA you can do the following:
# rmmod ide_cd
# modprobe ide-cd dma=1
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