Come in Just17, calling Just17
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By Jack Wallen - March 4, 2013,
Jack Wallen takes on PulseAudio and runs head first into an issue that has been around since 2008. With Steam gaining ground, sound is going to become a crucial element for Linux. Can the PulseAudio developers solve this troubling issue?
I don’t usually have a case to go off on a Linux or an open source project. But in the case of PulseAudio — I do.
Let me set this stage.
One of my other, many jobs, is recording audio books. For this job I use Audacity — it’s a perfect solution for the task. I use Audacity on Ubuntu 12.10. Since purchasing a new computer (one with an Intel i5 chip), I’ve had nothing but issues with skipping sound (which caused ‘hiccups’ in the system and in my recordings). And I have gone through a long list of troubleshooting steps:
Replaced motherboard
Ran memtest86
Replaced hard drive
Tested CPU
Installed three flavors of Linux (Ubuntu Studio, Linux Mint, Ubuntu 12.10)
Installed three different kernels (3.7, 3.8, and low-latency)
Tried various multimedia players
Tweaked PulseAudio settings
Read more about sound than I thought I ever would
Turns out — the issue has been around for some time and is still a problem. Now, before I lay blame on a single project, I understand it’s a challenge. The PulseAudio developers have to deal with multiple hardware, many distributions, desktops, and applications. It would be a daunting task for anyone. But — and here’s where the sympathy leaves the building for me — prior to PulseAudio, this wasn’t an issue (and the developers of Esound, OSS, and Alsa had the same pressures on their shoulders).
I should also say that some of my tweaking had better results (I’ll share what I did in a moment); but, in the end, the skipping persists. I have to say this: Get it together PulseAudio! I’ve scoured countless forums to find posts dating back to 2008, posts complaining of the same problem. Countless bugs have been filed, but the pleas for help seem to fall on deaf ears.
Here’s the problem: When PulseAudio works well, it’s a dream. But when it starts causing problems, it’s a nightmare. Removing PulseAudio isn’t the solution — as too many distributions are now in deep with this sound system. Ultimately, the solution is for the skipping audio to be fully, and completely, addressed.
My optimizations
I’ve managed to get my skipping down to a bare minimum. I’ve tried quite a lot of tweaks and changes, but ultimately, what has worked the best for me, is the following:
kernel 3.8.1 - generic
using Audacious to listen to sound (making sure to choose PulseAudio for the output settings)
The following tweaks need to be made in the /etc/pulse/daemon.conf file:
Uncomment the following lines: realtime-scheduling = yes
realtime-priority = 5
Uncomment the following lines: default-sample-format = s16le
default-sample-rate = 44100
default-sample-channels = 2
Set the following*: default-fragment-size-msec = 125
default-fragments = 2
* The above numbers were derived from the following steps (done from a terminal window): echo autospawn = no >> ~/.pulse/client.conf
killall pulseaudio
LANG=C pulseaudio -vvvv > ~/pulseverbose.log 2>&1
Hit Ctrl-c to return to your prompt. Now run the following commands: rm ~/.pulse/client.conf
grep device.buffering -m2 ~/pulseverbose.log
The second command should present to you something like:: sink.c: device.buffering.buffer_size = “352800″
: sink.c: device.buffering.fragment_size = “176400″
The calculations for the settings are: 352800/1411200 = 0,25s = 250 msecs
176400/1411200 = 0,125s = 125 msecs
Once you’ve added those settings to /etc/pulse/daemon.conf, restart PulseAudio with the command pulseaudio -k. You should now enjoy less (but not zero) skipping.
http://www.techrepublic.com/blog/opensource/pulseaudio-an-achilles-heel-that-needs-repair/4202
