Public bug reported:
About 12 times a second the captured analog audio switches channels. The
resulting noise depends upon how much separation there happens to be in
the source channels. There are further channel switches happening as
well, usually lasting 48 audio samples (1 millisecond). The device
samples audio a rate of 48000 (LE16 stereo).
The easiest way to hear this is to use TV input 1 (composite--v4l2-ctl
-i 1) and disconnect one of the audio channels.
I was able to see the channel switch with Audacity against captured
audio.
I tracked this problem down with a usb trace to the fact that the device
is sending urb's each millisecond, and they split the left and right
channels between urb's simultaneous to when the channels switch,
including regular 1/12 second intervals.
sound/usb/usbaudio.c is coded to expect the urb's data to contain an
integral number of audio slots (each containing both left and right
channel samples). This current driver behaviour is helpful to recovery
where data is damaged during transit over the bus, but violation of the
assumption by the device causes the loss of one channels sample, and
therefore loss of left/right synchronization between the device and the
driver.
ProblemType: Bug
AplayDevices:
**** List of PLAYBACK Hardware Devices ****
card 0: SB [HDA ATI SB], device 0: ALC268 Analog [ALC268 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
Architecture: i386
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: gruber 2116 F.... pulseaudio
/dev/snd/controlC0: gruber 2116 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
Card hw:0 'SB'/'HDA ATI SB at 0xce400000 irq 16'
Mixer name : 'Realtek ALC268'
Components : 'HDA:11c11040,11790001,00100200
HDA:10ec0268,1179ff68,00100003'
Controls : 17
Simple ctrls : 11
Card1.Amixer.info:
Card hw:1 'U0x20400x7200'/'USB Device 0x2040:0x7200 at usb-0000:00:13.5-2,
high speed'
Mixer name : 'USB Mixer'
Components : 'USB2040:7200'
Controls : 1
Simple ctrls : 1
Card1.Amixer.values:
Simple mixer control 'PCM',0
Capabilities: cswitch cswitch-joined
Capture channels: Mono
Mono: Capture [on]
Date: Fri Dec 11 21:36:10 2009
DistroRelease: Ubuntu 9.10
HibernationDevice: RESUME=UUID=14b4ed98-22c8-4708-96e3-c1a23a289650
MachineType: TOSHIBA Satellite L355D
Package: linux-image-2.6.31-15-generic 2.6.31-15.50
ProcCmdLine: root=/dev/sda9 ro
ProcEnviron:
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-15.50-generic
RelatedPackageVersions:
linux-backports-modules-2.6.31-15-generic N/A
linux-firmware 1.25
RfKill:
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
SourcePackage: linux
Uname: Linux 2.6.31-15-generic i686
XsessionErrors:
(gnome-settings-daemon:2129): GLib-CRITICAL **: g_propagate_error: assertion
`src != NULL' failed
(gnome-settings-daemon:2129): GLib-CRITICAL **: g_propagate_error: assertion
`src != NULL' failed
(nautilus:2164): Eel-CRITICAL **: eel_preferences_get_boolean: assertion
`preferences_is_initialized ()' failed
(polkit-gnome-authentication-agent-1:2193): GLib-CRITICAL **:
g_once_init_leave: assertion `initialization_value != 0' failed
dmi.bios.date: 09/16/2008
dmi.bios.vendor: Insyde Corp.
dmi.bios.version: 1.70
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.vendor: TOSHIBA
dmi.board.version: Base Board Version
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias:
dmi:bvnInsydeCorp.:bvr1.70:bd09/16/2008:svnTOSHIBA:pnSatelliteL355D:pvrPSLE0U-01000R:rvnTOSHIBA:rn:rvrBaseBoardVersion:cvnChassisManufacturer:ct10:cvrChassisVersion:
dmi.product.name: Satellite L355D
dmi.product.version: PSLE0U-01000R
dmi.sys.vendor: TOSHIBA
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: John S. Gruber (jsjgruber)
Status: New
** Tags: alsa apport-bug i386
--
Distorted Captured Analog Stereo Audio with Hauppauge HVR-950Q
https://bugs.launchpad.net/bugs/495745
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