[LAU] Strange change of sample rate upon connecting mixing desk

Peter P. p8rpp at aol.com
Fri Jan 31 23:59:30 UTC 2014


Dear list, 
allow me to post a question here that I already sent to alsa-user, but
without any response so far, thank you!

----------8<-----------

Hi all, now here is one of the weirdest problems I have come across in
the past years. Actually it is halting my current production even, but
I am primarily interested how this error is caused (and how it can be
solved):

The sampling rate of my RME HDSP Card is set from "Internal 44.1k" to
"Internal 48k" upon connecting a Yamaha DM1000 mixing console via usb!

The console does not provide a USB audio interface, but several midi
ports over USB, using the snd_usb_audio module.

cat /proc/asound/cards:

 0 [Intel          ]: HDA-Intel - HDA Intel
                      HDA Intel at 0xf2520000 irq 43
 1 [DSP            ]: H-DSP - Hammerfall DSP
                      RME Hammerfall DSP + Multiface at 0xf0000000,
                        irq 19
 2 [DM1000         ]: USB-Audio - DM1000
                      Yamaha DM1000 at usb-0000:00:1d.0-1.2, full
                        speed
29 [ThinkPadEC     ]: ThinkPad EC - ThinkPad Console Audio Control
                      ThinkPad Console Audio Control at EC reg 0x30,
                        fw 6QHT26WW-1.07

>From HDSP's alsamixer I can see that upon connecting the DM1000 the
control "Sample Clock Source Locking" gets set to [Off], and the
sample rate is set to 48k as described above.

The change is also reflected in the 'hdspconf' software that
configures some properties of the card.

cat /proc/asound/pcm does not list the DM1000:
        00-00: CONEXANT Analog : CONEXANT Analog : playback 1 : capture 1
        00-03: HDMI 0 : HDMI 0 : playback 1
        01-00: RME Hammerfall DSP + Multiface : RME Hammerfall DSP + Multiface : playback 1 : capture 1

This is on a Debian box runnig kernel 3.2.0-4-rt-amd64

Let me add here, that upon starting any audio application using the                                                    
same card under alsa can (re)set the sampling rate to the correct                                                      
value.                                                                                                                 
If the mixer is re-connected, after that audio application was                                                         
launched, the sampling rate of the HDSP card is changed to 48k,                                                        
causing an audible transposition.

Can anyone imagine what causes this strange behavior?

Thank you so much for all hints

best, P


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