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[a! <a_guenther@xxxxxx>]

Just a short update:
Since my old computer brock down (more then 8 years old laptop), I have now a Thinkpad T450p. Running Kubuntu 14.10, as before my DAC is an Audiolab 8200CD. And this issue does not occur anymore, neither on the USB 2 nor USB 3 plug.
So might have been really an hardware issue somehow for me before.
Cheers!

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https://bugs.launchpad.net/bugs/1136110

Title:
  USB Audio Codec choppy playback

Status in linux package in Ubuntu:
  Fix Released

Bug description:
  1) The release of Ubuntu using
  Ubuntu 12.10 AMD64.
  Ubuntu 13.04 AMD64, daily build as new as 20130314.

  2) The version of the package used
  linux-image-3.5.0-26-generic
  linux-image-3.5.7-03050706-generic_3.5.7-03050706.201302221435_amd64.deb
  http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.5.7.6-quantal/
  linux-image-3.7.7-030707-generic_3.7.7-030707.201302111436_amd64.deb
  http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.7.7-raring/
  linux-image-3.8.0-030800rc7-generic_3.8.0-030800rc7.201302081635_amd64.deb
  http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.8-rc7-raring/

  This bug had been confirmed appearing after the following kernel upgrade step:
  v3.5.0-25 > v3.5.0-26 ~ v3.5.0-27
  v3.5.7.5 > v3.5.7.6 ~ v3.5.7.8
  v3.7.6 > v3.7.7 ~ v3.7.10
  v3.8.0-rc6 > v3.8.0-rc7 ~ v3.8.5
  The v3.9 branch has been affected since its very first release.
  v3.9-rc1, v3.9-rc2, v3.9-rc3 v3.9-rc4 are all affected.

  3) What you expected to happen
  When using a USB DAC to play audio, the audio should be played normally without any interruption.

  4) What happened instead
  This bug seems to affect only a certain kind of hardware, which is called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so called "Synchronous USB DAC", uses the clock hosted by the mother board, which is not affected by this bug.

  When this bug affects an asynchronous USB DAC, the audio played by the
  DAC is constantly interrupted. The playback itself does not stop, but
  the output becomes discontinous, filling with constant crackling
  noises, destroying everything the DAC plays.

  Using CLI command grep device.buffering to get the buffer from the
  devices, those affected kernels are reporting back a different number
  to the unaffected devices. The choppy noise is very similar to the
  situation when buffer size is not correctly set.

  I have tested four USB DACs, two Asynchronous and two Synchronous.
  Only the Asynchronous ones are affected by this bug.

  Affected Devices:
  Arce MDAC5
  Arce MDAC mini
  Ayre Acoustics QB-9
  Dragonfly USB DAC
  Musical Fidelity v2 DAC

  USB Audio Streaming Controller on affected devices:
  Texas Instrument TAS1020
  http://www.ti.com/product/tas1020

  Audio DAC on affected devices:
  Texas Instruments PCM1742
  http://www.ti.com/product/pcm1742

  This bug had been confirmed appearing after the following kernel upgrade step:
  3.5.0-25 > 3.5.0-26
  3.5.7.5 > 3.5.7.6 (and all 3.5.7.x above)
  3.7.6 > 3.7.7 (and all 3.7.x above)
  3.8.0-rc6 > 3.8.0-rc7 (and all 3.8.x above)
  I used Kdiff to find the similar patches, and find the following patches suspicous:
  USB: XHCI: fix memory leak of URB-private data
  (appeared in 3.5.7.6/3.7.7/3.8.0-rc7)
  USB: EHCI: fix for leaking isochronous data
  (appeared in 3.7.7/3.8.0-rc7)
  usb: Prevent dead ports when xhci is not enabled
  (appeared in 3.5.7.6/3.7.7/3.8.0-rc7)
  usb: Using correct way to clear usb3.0 device's remote wakeup feature
  (appeared in 3.5.7.6/3.7.7/3.8.0-rc7)
  USB: EHCI: remove ASS/PSS polling timeout
  (appeared in 3.7.7/3.8.0-rc7)
  USB: EHCI: unlink one async QH at a time
  (appeared in 3.7.7/3.8.0-rc7)
  USB: EHCI: fix timer bug affecting port resume
  (appeared in 3.5.7.6/3.7.7/3.8.0-rc7)
  USB: EHCI: fix bug in scheduling periodic split transfers
  (appeared in 3.5.7.6/3.7.7/3.8.0-rc7)

  Hope someone can look into this bug soon!

  ---
  ApportVersion: 2.6.1-0ubuntu10
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  tysontan   2117 F.... pulseaudio
   /dev/snd/controlC1:  tysontan   2117 F.... pulseaudio
   /dev/snd/pcmC1D0p:   tysontan   2117 F...m pulseaudio
  CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
  DistroRelease: Ubuntu 12.10
  HibernationDevice: RESUME=UUID=8545c3e2-caba-4eaa-8fa4-2fbebcc2d9bb
  InstallationDate: Installed on 2013-02-15 (14 days ago)
  InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
  IwConfig:
   eth0      no wireless extensions.

   lo        no wireless extensions.
  MachineType: LENOVO 0053A11
  MarkForUpload: True
  Package: linux 3.5.0.26.32
  PackageArchitecture: amd64
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-26-generic root=UUID=8c60a142-505f-4d74-afa0-37686558e86e ro quiet splash vt.handoff=7
  ProcVersionSignature: Ubuntu 3.5.0-26.40-generic 3.5.7.6
  RelatedPackageVersions:
   linux-restricted-modules-3.5.0-26-generic N/A
   linux-backports-modules-3.5.0-26-generic  N/A
   linux-firmware                            1.95
  RfKill:

  Tags: quantal package-from-proposed running-unity third-party-packages
  Uname: Linux 3.5.0-26-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
  dmi.bios.date: 10/11/2012
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 6QET70WW (1.40 )
  dmi.board.name: 0053A11
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Available
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvr6QET70WW(1.40):bd10/11/2012:svnLENOVO:pn0053A11:pvrThinkPadX201Tablet:rvnLENOVO:rn0053A11:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 0053A11
  dmi.product.version: ThinkPad X201 Tablet
  dmi.sys.vendor: LENOVO

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