Bug 98863

Summary:	USB audio gives continous heavily distorted sound (random bug) (Alesis core 1)
Product:	PulseAudio	Reporter:	trondsg+bugzilla+freedesktop
Component:	core	Assignee:	pulseaudio-bugs
Status:	RESOLVED MOVED	QA Contact:	pulseaudio-bugs
Severity:	normal
Priority:	medium	CC:	lennart
Version:	unspecified
Hardware:	x86-64 (AMD64)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:

Description trondsg+bugzilla+freedesktop 2016-11-26 19:54:09 UTC

I just bought an Alesis Core 1. (USB audio interface.)

A few times I have returned to the computer and found that the sound output has become heavily! distorted / metallic / crackling. There is silence (as it should be) when no sound is playing.

After unplugging the usb cable and plugging it back in, the sound is OK.

This is PulseAudio 4.0 on Ubuntu Studio 14.04.

Comment 1 trondsg+bugzilla+freedesktop 2016-11-29 19:41:06 UTC

Actually, this happens even when I'm using the computer, but then the crackle/distortion is lighter. So maybe it isn't related to screen dpms.

Comment 2 trondsg+bugzilla+freedesktop 2016-12-20 23:44:29 UTC

Intuitively, this may be a timing issue, where the timer of the soundcard and pulseaudio are drifting apart. Just guessing.

Comment 3 Tanu Kaskinen 2016-12-21 14:53:15 UTC

I don't think it's a clock drift issue. Pulseaudio runs at the sound card rate. When the system clock is used, the usage is adapted to any differences compared to the sound card clock.

The audio may become corrupted if pulseaudio writes too close to the point in memory where the hardware is reading. (An aside: I don't understand the mechanism of that - I would understand a single glitch, but I don't understand how the audio can become permanently corrupted, and the resulting distortion is weird.) I don't know if you have this problem, but "metallic" sounds similar to what I've experienced on an internal HDA card long time ago.

When this happens, you could record from the sink's monitor source to verify that the recorded audio is clean. If it's clean, the distortion happens in lower layers of the audio stack. Here's the command to use (all on one line):

parecord --device=alsa_output.usb-Alesis_Core_1-00-C1.analog-stereo.monitor --fix-rate --fix-format --fix-channels > test.wav

(I got the device name from the "pactl list" output in your other bug, 99112.)

Comment 4 trondsg+bugzilla+freedesktop 2016-12-22 14:53:05 UTC

I got lots of light-to-medium crackles (sounds like buffer underruns) from html5 playback in Chrome. I captured the sound using the command line you gave me, except it had to be parec. The sound on the recording was fine.

Comment 5 GitLab Migration User 2018-07-30 10:04:46 UTC

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/issues/199.

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