[alsa-devel] Problem with DoP mode in Chord 2qute USB audio

[Pavel Hofman]

Hello,

I am working with owner of Chord 2qute on the following problem (FYI 
long discussion at 
http://www.diyaudio.com/forums/pc-based/310578-chord-2qute-dop-challenge.html):

Regular 176.4/24 PCM plays OK, however 176.4/24 DoP produces random 1-2 
sec sound interruptions every several tens of seconds. Tested players - 
squeezelite, MPD. The soundcard has its own power supply.

I googled out several reports of simlar problem with this soundcard, 
mostly on linux (did not see any problem report for OSX).

alsainfo: http://www.fyn13.dk/diy/alsa_output_chord_2qute_4.4.0-62.txt

lsusb -v : http://www.fyn13.dk/diy/chord_lsusb.txt

hw_params and stream0 files are identical for both 176.4/24 PCM and DoP:

/proc/asound/card1/pcm0p/sub0/hw_params:
access: RW_INTERLEAVED
format: S32_LE
subformat: STD
channels: 2
rate: 176400 (176400/1)
period_size: 1764
buffer_size: 7056

/proc/asound/card1/stream0:
Chord Electronics Ltd 2Qute at usb-0000:00:14.0-2, high speed : USB Audio
Playback:
   Status: Running
     Interface = 2
     Altset = 1
     Packet Size = 224
     Momentary freq = 176402 Hz (0x16.0ce0)
     Feedback Format = 16.16
   Interface 2
     Altset 1
     Format: S32_LE
     Channels: 2
     Endpoint: 5 OUT (ASYNC)
     Rates: 32000, 44100, 48000, 88200, 96000, 176400, 192000, 352800, 
384000
     Data packet interval: 125 us

We checked for XRUNs, none were produced during the interruption in DoP 
playback.

Powerful 4-core CPU Intel Pentium 4405U @ 2.10GHz, idle > 99% of time in 
DoP playback.

However, the IRQs rate of the onboard XHCI controller is 8k/s for both 
PCM and DoP playback which corresponds to 1 IRQ every 125us frame. The 
rate drops to almost zero when playback is stopped in the player - 
clearly it is related to the soundcard.  Could this perhaps be a sign of 
the problem? Please is there a way to lower the rate, like the old 
removed param nrpacks of the usb-audio driver?

I suspect a buggy XMOS firmware. I very much appreciate any suggestion 
or help, either with fixing in software, or further diagnostics to 
support potential claim to the manufacturer.

Thank you very much. With regards,


Pavel.