Re: AW: usb quattro

[Patrick Shirkey <pshirkey@boosthardware.com>]

Takashi Iwai wrote:
> At Sat, 07 Sep 2002 05:40:02 +0900,
> Patrick Shirkey wrote:
> 
>>Takashi Iwai wrote:
>>
>>
>>>>the Tascam US-428 driver (copied / changed from snd-usb-audio ) showed a
>>>>similar problem.
>>>>I worked around it by not using ASYNC_UNLINKing of the urbs.
>>>
>>> 
>>>yes, this could be the problem.
>>>this happend once and i thought it fixed on the alsa side, but it
>>>seems that there is something wrong on usb driver itself.
>>>why it happened on jack is because jack caused xrun - and the driver
>>>tries to stop the stream and unlinks urbs with ASYNC_UNLINK flag.
>>>
>>>anyway, i changed the code on cvs to use SYNC unlink mode as default.
>>>this may have a drawback that the urbs still exist even if the driver
>>>stops the stream after detection of xrun.  but usually this doesn't
>>>matter so much.
>>>
>>>i've tested normal playbacks and it seems working.
>>>
>>>
>>
>>I have actually managed to get a stream from alsaplayer through without 
>>a hang but the sound is choppy.
>>
>>I will make a test signal  so you can hear what I am getting. It's 
>>similar to what was happening before the driver was fixed last time.
>>
>>I got this output from jackd. this happened after I started jack and 
>>didn't connect any other apps. Maybe it timed out but I don't think it 
>>is supposed to.
>>
>>----
>>$ jackd -v -d alsa -d q4
>>jackd 0.37.1
>>Copyright 2001-2002 Paul Davis and others.
>>jackd comes with ABSOLUTELY NO WARRANTY
>>This is free software, and you are welcome to redistribute it
>>under certain conditions; see the file COPYING for details
>>
>>512 waiting for signals
>>creating alsa driver ... q4|1024|2|48000|swmon
> 
> 
> the resolution of usb-audio device is 1ms.  this value is fixed.
> thus you need to adjust the period size according to the sample rate
> if you want to achieve the real-time response with a small period
> size.
> 
> that means:
> - the sample rate should be 48kHz (or 32kHz), which can be divided by
>   1000, and should not be 44.1kHz.
> - the period size should be aligned to (rate / 1000).
>   in the case of 48kHz, the period size should be 48, 96, 192, ...
> 
> please try this combination.
> 
> 

Takashi you little beauty :)

The sound is infinitely better.

I'll add a note to the docs.

Hmm. Now I have no excuses when people ask to hear my music though ;)

-- 
Patrick Shirkey - Boost Hardware Ltd.
For the discerning hardware connoisseur
Http://www.boosthardware.com
Http://www.boosthardware.com/LAU/guide/
========================================

"Um...symbol_get and symbol_put... They're
kindof like does anyone remember like get_symbol
and put_symbol I think we used to have..."
- Rusty Russell in his talk on the module subsystem



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