Flash plugin skips and lags intermittently while using other programs and browser tabs

[Jon C]

After upgrading Ubuntu from 10.04 to 12.04, I have been using Pandora (pandora.com) for listening to streaming music. Sometimes, the music is skipping, repeating, or lagging.

The problem occurs most while either running another program besides the web browser or when the browser is downloading web pages. The problem is NOT worsened by interacting with the launcher or Dash, except that the mouse movements also skip or lag at the same time as the audio. A few times during these periods of incident, as the symptoms were at a max, Pandora stopped trying to play the current song and switched to the next song. Web page scrolling is also affected during the skipping.

I have been watching the system monitor graphs and both CPU and memory are well below 100%. I have experienced this both in Firefox and Chrome.

I asked for help in the #ubuntu IRC channel and was told to report this here as a possible bug. I have also looked at the question at the link below, but the answer does not seem like a full solution since it requires the user to manually choose a CPU level, requiring knowledge of which setting is right, such that the user could choose a setting that overclocks the processor.
http://askubuntu.com/questions/128848/high-cpu-usage-while-playing-flash-on-ubuntu-12-04-amd64

Pandora and audio playback were working perfectly right before the upgrade to Ubuntu 12.04. I update my system daily. Rebooting did not help.

Full list of steps:
1. Install Ubuntu 12.04 and nvidia driver.
2. Use Unity 2d.
3. In Firefox or Chrome, log into pandora.com and play music.
4. While music is playing, open several other pages in other tabs. Also, open software center and search for various packages. Listen for music to skip, repeat, or lag, and for mouse to skip and lag.

Thank you for the assistance.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: firefox 12.0+build1-0ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic-pae 3.2.14
Uname: Linux 3.2.0-24-generic-pae i686
NonfreeKernelModules: nvidia
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: jon 1655 F.... pulseaudio
 /dev/snd/pcmC0D0p: jon 1655 F...m pulseaudio
BuildID: 20120423122624
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xdfffc000 irq 46'
   Mixer name : 'SigmaTel STAC9200'
   Components : 'HDA:83847690,102801cc,00102201'
   Controls : 14
   Simple ctrls : 7
Channel: release
Date: Sat May 5 00:41:47 2012
ExecutablePath: /usr/lib/firefox/plugin-container
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
IpRoute:
 default via 192.168.0.1 dev wlan0 proto static
 169.254.0.0/16 dev wlan0 scope link metric 1000
 192.168.0.0/24 dev wlan0 proto kernel scope link src 192.168.0.5 metric 2
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=12.0/20120423122624 (Running)
RunningIncompatibleAddons: False
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/23/2006
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A01
dmi.board.name: 0JF242
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA01:bd03/23/2006:svnDellInc.:pnLatitudeD820:pvr:rvnDellInc.:rn0JF242:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude D820
dmi.sys.vendor: Dell Inc.

[Jon C (jon180)]

This additional information might be related.

Today, Flash (pandora) was playing just fine until I opened the Ubuntu Software Center. I found that my CPU suddenly jumped to 100% sustained utilization, all programs were locking up, and the music was skipping severly. I checked system monitor and found that I was also being affected by the bug linked below (the update-apt-xapian-index process was consuming 100% CPU).
https://bugs.launchpad.net/ubuntu/+source/apt-xapian-index/+bug/655831

After closing software center and update manager, CPU usage dropped to below 50% in both cores and under 50% memory sustained, but the music continued to skip every few seconds, less severe than before. It is as if the other bug is triggering this but Flash is unable to recover after CPU is back to normal until I reboot.

So, steps to reproduce:
1. In Chrome or Firefox, go to pandora.com and play music.
2. While music is playing, open Ubuntu Software Center. Ensure that update-apt-xapian-index is running (not sure when it runs).
3. Use system monitor or top command to see if CPU is at 100%. If so, check which processes are consuming the CPU.
4. Close software center.
5. Check that CPU is back to normal.
6. Check if pandora is still skipping.

[Jon C (jon180)]

I tried a few more things. Killing the Flash process and trying again did not help.

I also opened the sound settings from the system settings manager. Under Output > Play sound through, I switched from "headphones" to "digital output" and then switched back. This seems to have fixed the problem, at least temporarily. I will wait and see if this fixes it permanently.

[Jon C (jon180)]

The problem has not occurred again after I reset my settings for pulseaudio mentioned above. Someone can probably close this and update it as an issue with pulseaudio while upgrading to 12.04.

[Launchpad Janitor (janitor)]

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

[Austin Macdade (austinian)]

This bug affects me when only using chrome or firefox, and not just pandora, but affects all flash... apps? youtube, pandora, vimeo, facebook and google chat among them.