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Subject: Re: [alsa-devel] Roland/Edirol M-16DX
From: Tim Camp <timc@wnsp.com>
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To: James Trevelyan <james@jamestrev.com>
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	alsa-devel@alsa-project.org, clemens@ladisch.de, james@jamestrevelyan.com
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Date: Fri, 14 Nov 2008 08:59:19 -0600
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James,

Reading your email I was struck by something.
I also have a digital I/O connected to the mixer from the pc.
I wonder if this is allowing the clocks to sync?

Just a thought.

Tim

On Fri, 2008-11-14 at 00:55 +0000, James Trevelyan wrote:
> On Thu, 2008-11-13 at 20:12 +0200, Lasse Kärkkäinen wrote:
> > Has anyone been able to solve the distortion problem yet?
> > 
> > It seems like a broken ringbuffer implementation. The distortion itself 
> > seems to be just the signal itself in different phase. I tested this 
> > with a 441 Hz (100 samples) sine wave played thru the device and 
> > recorded back. The recording is here:
> > http://zi.fi/debug/M16DX-bug.flac
> 
> I haven't solved it yet, though I exchanged emails with Tim Camp who
> reported that he had this working when the device was set to 44.1khz (I
> haven't had a chance to try this)
> 
> I had previously done something similar to Lasse in re-recording a test
> signal and noticed the same interesting patterns.  However, I also did
> some usb-logging, and when I reassembled the data stream being sent to
> the device it was as it should be, i.e. uncorrupted, suggesting that the
> distortion is being caused in the device, and the driver isn't sending a
> corrupted data stream (though obviously something in the way it is sent
> is upsetting the device)
> 
> I also did some usb-logging under Windows (where it works) and
> disappointingly couldn't see any obvious difference in the way the data
> was sent.  I played around with things like the size of the urbs in the
> driver to try to make the raw usb data look the same, but it had no
> effect.
> 
> However, what I did notice is that in all circumstances the windows
> driver was capturing at the same time as playback, even when I was not
> asking it to record.  This suggests to me that the comment in the driver
> source about synchronising playback to capture has some relevance ...
> 
> James
> 

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