[ARMedslack] Improving USB audio sound quality on the Dockstar

[Thorsten Mühlfelder]

Am Thursday 05 May 2011 10:32:52 schrieb Thorsten Mühlfelder:
> Hi,
>
> I'm using a high quality USB audio device (Burr-Brown Japan PCM2702) with
> my Dockstar. I've configured mpd to use the hardware interface without dmix
> because dmix seems to be broken on the ARM platform.
>
> But there is one problem left: sometimes clicks and pops can be heard. They
> appear randomly up to 2 times a minute. My impression is that hard disk
> data transfer causes them, because using "hdparm -t" makes the situation
> worse. On the Dockstar all USB devices are connected via hub to the same
> USB controller:
> # lsusb
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
> Bus 001 Device 003: ID 0bc2:2120 Seagate RSS LLC
> Bus 001 Device 005: ID 08bb:2702 Texas Instruments Japan Speakers
>
> Is it possible to give the USB audio data transfers a higher priority?

Another idea is that network traffic may cause this because eth0 has higher 
priority IRQ than USB:
thorsten at dreamtheater:~$ cat /proc/interrupts 
           CPU0
  1:   68571661   orion_irq  orion_tick
  5:          2   orion_irq  mv_xor.0
  6:          2   orion_irq  mv_xor.1
  7:          2   orion_irq  mv_xor.2
  8:          2   orion_irq  mv_xor.3
 11:   94038944   orion_irq  eth0
 19:   37108202   orion_irq  ehci_hcd:usb1
 22:          0   orion_irq  mv_crypto
 33:        290   orion_irq  serial
 46:         25   orion_irq  mv643xx_eth
Err:          0



-- 
Thorsten Mühlfelder
Salix OS: www.salixos.org