[mythtv-users] Video jitter possibly cased by low cpu usage

[Marius Schrecker]

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On Monday, December 16, 2013 12:22 CET, Stuart Morgan <stuart at tase.co.uk> wrote:
 On Monday 16 Dec 2013 12:07:05 Marius Schrecker wrote:
> Hi,
>
> After recenrt updates (I'm not sure what) I'm noticing slightly more
> jerkyness and jitter on some videos and (possibly unrelated) wandering
> audio sync on others.
>
> System is a dual core opteron with nvidia 620 video adapter doing vdpau
> rendering and jitterometer tells me that when playing affected full
> 1080 at 25p content frame rate varies at +- 1-2 Hz of 25 and both CPU cores
> are running at around 15% capacity. One of my recent changes was upgrading
> the Nvidia driver from 304 to 310 and google tells me that teghre was a
> substantial performance increase bertween these two drivers. Something that
> might be causing my CPU usage and bus speed to drop so much that I'm
> getting throughput errors.
>
> What's the best way to test the hypothesis?

Change the minimum cpu speed.

sudo echo {valid_speed} >
/sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

Where {valid_speed} is something above the minimum from
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

You may need to try different values to find the best one, assuming it works at
all.

These are the scripts I use to automatically boost my cpu speed during
playback of video with vdpau, with them I get stutter/jitter issues.

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

frequencyup.sh

#!/bin/bash

echo 1800000 | sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
> /dev/null

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

frequencydown.sh

#!/bin/bash

echo 1000000 | sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
> /dev/null

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

This is in my /etc/sudoers file
{username} ALL=(ALL) PASSWD: ALL, NOPASSWD: /usr/bin/tee
/sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

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

Finally I trigger the scripts with the "Playback started" and "Playback
stopped" system events. I also trigger the slower clockspeed when paused, and
unpaused but that bit's optional.
--
Stuart Morgan
MythTV
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Brilliant Stuart!  That's just what I wanted.

I may ask for help triggeringb from system events but will adjust the speeds manually first and see if that solves my problems.

Cheers!

Marius