[alsa-devel] ice1712 and jack

Takashi Iwai tiwai at suse.de
Wed Jan 7 12:49:00 CET 2009

At Mon, 29 Dec 2008 23:22:54 +0000,
mike start wrote:
> I've been having difficulty getting an ews88MT (ice1712 chipset) to work 
> in full duplex using the jack audio server (jackd).  Capture only mode 
> works fine, even down to 64 samples latency, Playback only mode works 
> fine down to 64 samples latency.  Duplex mode causes 'xruns' at even 
> 2048 samples latency.  Looking at the interrupt handler, if I add some 
> diagnostics to tell me the difference between the capture and playback 
> DMA counters timing out I see what appears to be clock drift between the 
>   playback and capture halves of the ice1712.  I also added some debug 
> messages to show what sample rate the alsa driver was setting the 
> hardware to and it agrees with the rate set in my jackd invocation 
> (jackd -R -d alsa -n 2 -p 1024 - r 48000 -d hw:0,0)
> Also adding diagnostics to jackd to show the time spent in poll waiting 
> for the capture and playback interrupts shows that they start in sync 
> and gradually drift until an 'xrun' occurs when they are '-p' samples 
> apart.  According to the ice1712 data sheet the 'professional' 
> multitrack part of this chip (the part my soundcard is using) runs its 
> inputs and outputs from the same master clock so I'm puzzled as to why 
> they are drifting.

I'm puzzled, too.  Not only clock but also sample rates are shared
(must be identical) both for playback and capture on ICE1712...

>  Does anybody have any more information relating to 
> the ews88mt?  - I think the drivers are working fine but the problems 
> are being caused by the capture and playback not being quite in sync 
> which renders it almost useless for professional recording.  Anyone have 
> any suggestions?

How did you check the DMA counter value?  From the raw register read
or on jackd?


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