[clug] Choppy video on Dell XPS laptop / Ubuntu 10.04 (linux Digest, Vol 97, Issue 1, Message 1)

Grant Morphett grant at gmorph.com
Sun Jan 16 15:27:18 MST 2011

Ben, I have the same laptop as you.  I currently don't have any problems
with choppy playback.  A couple of things could be going on.

Firstly pulseaudio.  I've had no end of trouble with it sucking down
resources.  I am now running Ubuntu 10.10 having continuously upgraded from
7.10 and I recently uninstalled all the pulseaudio I could (sudo apt-get
remove --purge pulseaudio) and then installed it again.  Seems to have
helped.  If you run "top" whilst playing your video you will see if
pulseaudio is using way too much CPU.

Secondly I've had a major issue with my CPU scaling.  Make sure you add CPU
scaling monitor to your panel and keep an eye on your clock frequencies.  If
your playing your video, its choppy and you notice your clock is low then
you too may have the same problem.  I "think" its caused by my BIOS lying to
the OS about the max clock speed for some reason.  When its stuffed the
output of cpufreq-info is

analyzing CPU 1:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1
  CPUs which need to have their frequency coordinated by software: 1
  maximum transition latency: 10.0 us.
  hardware limits: 800 MHz - 2.20 GHz
  available frequency steps: 2.20 GHz, 2.20 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave,
  current policy: frequency should be within 800 MHz and 800 MHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.
  cpufreq stats: 2.20 GHz:15.41%, 2.20 GHz:0.29%, 1.60 GHz:0.34%, 1.20
GHz:0.20%, 800 MHz:83.77%  (119983)

Notice that on the line "current policy: frequency should be within 800 MHz
and 800 MHz" the min and max are both the same i.e. 800 MHz.  It didn't
matter what commands I tried to adjust this (and I tried them all) it didn't
help.  I finally found this post
On my system the file bios_limit was present sometimes and it did indeed
have the 800MHz frequency in it so I assumed this was my issue.  I added the
processor.ignore_ppc=1 to my kernel boot parameter list in grub and the
issue seems to be resolved.  The cpufreq-info output now has the line
"current policy: frequency should be within 800 MHz and 2.20 GHz." as it

Let us know how you go.


On 3 January 2011 11:41, Ben Davies <ben.davies at anu.edu.au> wrote:

> I'm having a problem with choppy video playback, so was wondering if anyone
>>> has
>>> any ideas.
>>> I was trying to play a full HD/H264 codec video on a Dell Intel Core2 Duo
>>> 2GHz
>> ...
>>   Hm, What kind of graphics device does the laptop have? I would have
>> expected that the XPS series of laptops have discrete NVIDIA or
>> ATI/AMD  graphics devices. But you never know, you might have an
>> "integrated" (or "less discrete") Intel "GMAxxx" graphics device.
> Ooops, forgot to add the graphics card specs before :(
> The system is a XPS M1330, with an NVIDIA GeForce 8400M GS & with 128mb of
> GDDR3 memory. I've been using the NVIDIA binary driver (version according to
> synaptic is 195.36.24-0ubuntu1~10.04), which gives the same choppy result.
> IIRC, it isn't limited to HD content either, once or twice I've had really
> choppy playback on smaller, lower res video. I'd post the link but it has
> been removed: the production company seems to had it up for a limited time.
> For some basic tests, I tried some HD demo vids (~3 mins) and these worked
> fine.
>    If you've got the much more likely discrete graphics, they should be
>> physically able to do HD content, however you'll need to ensure you
>> have the blessed appropriate XV/XVMC module loaded (run xdpyinfo and
>> look for the "XVideo" extension or run xvinfo and see what that tells
>> you)
> xdpyinfo reports that the XVideo extension is present :-)
> cheers,
> Ben
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