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PulseAudio - Tune your setting and prevent glitching

Posted: Fri Mar 26, 2010 7:48 am
by kwevej
I had some problems with glitches & drop-outs during playback...
Yesterday, I've found the solution*. Here it is:

*In case it looks too complicated, or you still experience glitches at high CPU usage, look for # section down here.
  1. (1) Find out your audio device parameters
    1. 1st, you'll need PA verbose logging:

      Code: Select all

      echo autospawn = no >> ~/.pulse/client.conf
      killall pulseaudio
      LANG=C pulseaudio -vvvv > ~/pulseverbose.log 2>&1
      Run the code above, press Ctrl+C.

      Code: Select all

      rm ~/.pulse/client.conf
    • run:

      Code: Select all

      grep device.buffering -m2 ~/pulseverbose.log
      You should see something like:

      Code: Select all

      : sink.c:     device.buffering.buffer_size = "352800"
      : sink.c:     device.buffering.fragment_size = "176400"
      (those are values of my NuForce uDAC)

      Write down the values. Proceed to step (2)
  • (2) Calculate your fragment size in msecs and number of fragments
    1. For my configuration I do use the standard sampling rate and bit depth ( 44,1 kHz @ 16bit )

      That means, that I need 44100*16 = 705600 bits per second. That's 1411200 bps for stereo.
      Let's take a look at the parameters we've found in the previous step:
    • device.buffering.buffer_size = "352800" => 352800/1411200 = 0,25s = 250 msecs
      device.buffering.fragment_size = "176400" => 176400/1411200 = 0,125s = 125 msecs

      Now, I got the values in secs, regarding to the sampling rate & bith depth.
      (source: me)
  • (3) Modify PA daemon configuration
    1. The config file is located at /etc/pulse/daemon.conf

      Code: Select all

      sudo gedit /etc/pulse/daemon.conf
    • Locate & uncomment (remove leading semicolons) these lines:

      Code: Select all

      ; default-fragments = X
      ; default-fragment-size-msec = Y
    • What are those parameters for?
      Some hardware drivers require the hardware playback buffer to be subdivided into several fragments.
      default-fragments= The default number of fragments. Defaults to 4.
      default-fragment-size-msec=The duration of a single fragment. Defaults to 25ms (i.e. the total buffer is thus 100ms long).
      (see man of pulse-daemon.conf)
    • Let's fill them in.
      In the part (2), We've calculated the fragment size parameter.
      Number of fragments is simply buffer_size/fragment_size. That's, in my case, 2.

      Code: Select all

      default-fragment-size-msec = 125
      default-fragments = 2
      While you're doing that, you should set also those:

      Code: Select all

      default-sample-format = s16le
      default-sample-rate = 44100
      default-sample-channels = 2
  • (4) Restart PA daemon
    1. Code: Select all

      pulseaudio -k
      pulseaudio --start
  • (5) Test
    1. Listen your favorite music & hit your PC with some load. I find Fink, to be fine test music ;)
  • (6) Still not satisfied? Let's tune the PA priority & scheduling
    1. in the PA conf, you can find params like:

      Code: Select all

      ; high-priority = yes
      ; nice-level = -20
      ; realtime-scheduling = yes
      ; realtime-priority = 1
      That's what we need, but there is a bug ( ... bug/265010) which prevents us to use them in the standard way.
    • At the link above, you can find a solution written by Oliver Joos:

      PA daemon can gain high-priority and realtime scheduling by editing "/etc/security/limits.conf". For each desktop user add the following 2 lines:

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      <$USER> - nice -11 # values from -20 upto 19 allowed
      <$USER> - rtprio 9 # values from 1 upto 99 allowed
      Substitute <$USER> with your login name.

      Each user who wants high-priority and/or realtime scheduling may put config into his ~/.pulse

      Code: Select all

      high-priority = yes         # default no
      rlimit-nice = 31            # default 31, values higher than 31 are interpreted as 31!
      nice-level = -11            # default -11, lowest value allowed: (20 - rlimit-nice), lower means more CPU-%
      realtime-scheduling = yes   # default no
      rlimit-rtprio = 9           # default 9, values from -20 upto 19 allowed
      realtime-priority = 9       # default 5, highest value allowed: rlimit-rtprio, higher means more priority
      ; log-level = info          # uncomment only to check if it works. this will spam syslog a lot!
      (Download at
  • (7) Reboot
  • (8) Pleasure your ears with some fine tunes from NinjaTunes
# Glitches @ high CPU usage (

Since 0.9.14, the PulseAudio sound server has been rewritten to use timer-based audio scheduling instead of the traditional interrupt-driven approach. Timer-based scheduling may expose issues in some Alsa drivers. To turn timer-based scheduling off, replace the line:

Code: Select all

load-module module-udev-detect 
in /etc/pulse/ by:

Code: Select all

load-module module-udev-detect tsched=0

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Fri Mar 26, 2010 8:00 am
by Aging Technogeek
Very useful How-to considering the number of users posting with audio problems.

Nice job.

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Sat Feb 08, 2014 11:28 am
by robert leleu
I use this configuration, thanks.

It made the situation much better. In case of glitches, I restarted Mint.

Edit : one month later I can say there is no more glitches

Unfortunately on march 25 2014 glitches are again here. I checked the config which did not change.

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Mon Mar 10, 2014 9:45 pm
by theAntiBob
What's wrong with this solution for pulseaudio crackling?
found on these common pages: ... _crackling

changing the fragments and fragment size of the buffer in daemon.conf won't do anything without timer-based scheduling being disabled in by adding tsched=0 to the end of the line load-module module-udev-detect

what's more, the device.buffering strings in the verbose info from pulseaudio (-vvvv) are merely stating what the buffer fragments and size have been set to

what's even more, the grep argument -m2 allows only 2 instances of the filter string "device.buffering" to be annunciated which usually means you're looking at buffer the information for your microphone

grep -C 5 should give you enough info to see what device the buffer info is for...

what's even morer is that default-fragments and default-fragment-size-msec are changed to the nearest usable settings depending on what the audio device will accept, which varies from device to device


don't just ask the first pulseaudio device that comes along what it's buffer info is and then try to make that info your default buffer setting

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Sat Mar 29, 2014 12:25 pm
by robert leleu
I just tried to fix these glitches (which came back on March 25, perhaps after an update) following informations in the above post, and the links it gives. No success.
I checked that the bug occurs also, on the same machine, with a Mint16 or Lubuntu 12.10 live CD. BTW Lubuntu runs smoothly on another machine.

I'm now considering trying other OS (non ubuntu ones) which could be free of the bug. If anyone knows such an OS (save Windows), thanks !

Hurrah ! I found ... gProcedure and applied, see ... ion/246272

The sound is back, no glitches.

/etc/pulse/daemon.conf shows the values calculated according to the first post of this thread.

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Mon Apr 21, 2014 9:45 am
by robert leleu
But the sound disappeared around the 13th of april.

I recover it on the 21st morning by installing the trusty pavucontrol debian package on my Mint16 MATE=saucy

Then I uninstall/reinstall project-neon (a daily upgrading of KDE unstable master)....the sound had disappeared...from my MATE session, which doesn't use the project-neon packages.
I (only) uninstalled this project-neon, and the sound was back......

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Mon May 19, 2014 12:18 pm
by robert leleu
One week ago glitches came back. Perhaps with an update, sinc I update very often to follow project neon which is now my standard session. Came back only in project neon MATE sound is OK !
I go on alternating MATE and NEON sessions.....

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Tue May 20, 2014 5:56 am
by robert leleu
... and now play smoothly in both sessions, MATE and NEON

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Thu Jul 03, 2014 5:46 am
by robert leleu
Theycame back on july 2d, all the day session long. They were there at the beginning of the july 3d session, but just for half an hour, and disappeared.
…… and returned around 2 pm, while the computer was inactive.....

I searched for pulse in the logs, but saw nothing which seemed relevant

Re: PulseAudio - Tune your setting and prevent glitching

Posted: Tue Aug 12, 2014 2:28 am
by xenopeek
This tutorial is more than 4 years old. Don't post support questions here; post a new topic in one of the support forums instead. And while PulseAudio in its first few releases was problematic, don't assume any audio problems you have are caused by PulseAudio these days--it's been stable and problem free for many years now. If you have audio problems, approach it with an open mind as to what may be the cause.