[bcm2835 - bcm2835 ALSA, playback] Underruns, dropouts or crackling sound

Bug #1563112 reported by David Chatterton on 2016-03-28
This bug affects 3 people
Affects Status Importance Assigned to Milestone
alsa-driver (Ubuntu)

Bug Description

This bug can be reproduced by using the Speaker Testing for bcm2835 ALSA window from the Sound Preferences > Hardware > Test Speakers button. Clicking the Front Left or the Front Right Test buttons causes the bug to be demonstrated.

The bug prevents apps that produce sound from working correctly.

This bug has been mentioned recently on Google+ by David Johnson although probably not reported through the Ubuntu bug reporting system.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: alsa-base 1.0.25+dfsg-0ubuntu5
Uname: Linux 4.1.18-v7+ armv7l
ApportVersion: 2.19.1-0ubuntu5
Architecture: armhf
 /dev/snd/controlC0: david 895 F.... pulseaudio
CurrentDesktop: MATE
Date: Tue Mar 29 00:16:18 2016
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:ALSA successful
Symptom_Card: bcm2835 ALSA - bcm2835 ALSA
Symptom_PulsePlaybackTest: PulseAudio playback test successful
Symptom_Type: Underruns, dropouts, or "crackling" sound
Title: [bcm2835 - bcm2835 ALSA, playback] Underruns, dropouts or crackling sound
UpgradeStatus: No upgrade log present (probably fresh install)

David Chatterton (dmchatterton) wrote :
David Chatterton (dmchatterton) wrote :

Just in case it is not obvious from the data collected, this relates to the version of Ubuntu MATE 15.10 running on a Raspberry Pi 3

David Chatterton (dmchatterton) wrote :

The bug also exists on Ubuntu MATE 15.10 running on the Raspberry Pi 2.

David Johnson (dj53144) wrote :

I have experienced the problem on Raspberry PI 2 using Ubuntu MATE 15.10 Under raspbian the same hardware works correctly.

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in alsa-driver (Ubuntu):
status: New → Confirmed
Changed in alsa-driver (Ubuntu):
importance: Undecided → Medium
David Chatterton (dmchatterton) wrote :

Having upgraded the Raspberry Pi (2 & 3) to Ubuntu MATE 16.04 Beta 2, the bug is still present and can be demonstrated adequately by attempting the built-in Speaker Test.

Interestingly, the Raspberry Pi s are capable of attempting to run the Software Defined Radio app Gqrx. This app has instability issues of its own, reported elsewhere. However, when it does run (for up to 2 minutes before crashing), it is capable of outputting decent quality stereo sound via the speakers although the sound sequence always seems to begin with a broken sound stream. Whether the handshake between the app and ALSA or its breakdown is the cause of the app crashing is another matter but since the app is capable of receiving good quality broadcast stereo sound via the VHF band, this sound is capable of being reproduced at high quality via ALSA and the HDMI interface to the monitor (with speakers) whilst the app is running.

As soon as I can upgrade to Ubuntu MATE 16.04, I shall report back with further observations.

David Chatterton (dmchatterton) wrote :
David Chatterton (dmchatterton) wrote :

Despite the crackling on the Speaker Test, I have managed to get YouTube videos to play with un-distorted sound using Firefox.

Obviously, Firefox's input to the sound system appears to work as expected.

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