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I'm running Xubuntu 13.10 "Saucy Salamander." It's a pretty recent install. I'm playing music over a bluetooth usb dongle on a home theater system. All of my sound goes through pulseaudio.

I've found that downloading files kills my sound -- it starts to stutter and lag to the point that it's pretty much unrecognizable. It's almost bearable around 200 KB/s but unusuable around 1-2 MB/s. My hard drive has a speed of 7200 RPM, so it seems unlikely to be an issue with the drive.

What's going wrong here? Is this just an issue with the linux disk scheduler? Do I need to patch my kernel with BFQ to fix it, or is there an easier way?

  • Is this an internal HDD, or a USB one? – derobert Nov 15 '13 at 15:52
  • Internal, the same HDD the operating system is installed on. – Patrick Collins Nov 15 '13 at 16:44
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Assuming you're playing music in compressed format (MP3, OGG or similar), there's no way for it to be a disk problem. A typical OGG file has the bitrate of 128-196 kbps, i.e. 16-24 KB/s, which is less than 0.5% of a typical HDD bandwidth. Plus, many players cache about 1 MB of a file they're playing which means once music has started playing, it can only be interrupted about once a minute because of poor HDD performance.

On the other hand, decoding compressed music requres some CPU time, and so does interfacing with the bluetooth dongle and channeling sound via pulse. My suggestion would be to check CPU usage with top during the stuttering sound conditions. If the CPU usage often peaks to 100%, the solution would be to run the downloader with nice.

Bonus: AND - auto nice daemon

  • I'm surprised to have finally gotten an answer on this question! Somewhere along the line (with two new versions of Xubuntu), this stopped being an issue. Now that you say it, I think it was a Bluetooth-related issue, via bluez. Bluez has caused me huge amounts of bizarre trouble, but it improved greatly when I switched from 4.X to 5.X. Probably the culprit. – Patrick Collins Sep 22 '15 at 8:50
  • Glad to hear it. I still experience sound stutter on weak hardware if my CPU-greedy jobs are not niced properly, so I hope my answer will help someone. – Dmitry Grigoryev Sep 22 '15 at 8:59

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