linux-kernel - Re: USB-audio strange problems

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Date:	Thu, 20 Mar 2008 12:03:41 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Pavel Machek <pavel@....cz>
Cc:	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: USB-audio strange problems

At Wed, 19 Mar 2008 22:12:47 +0100,
Pavel Machek wrote:
> 
> Hi!
> 
> Ok, so it took me a year to get back to this bug. Oops.

Oh well, I don't remember what was the exactly problem...

> > Yep, let's fix it.  Just to make sure (ane debugging easy atm), could
> > you attach the following?
> > 
> > - content of /proc/asound/cards
> > - content of /proc/asound/card*/stream*
> > - the output of "lsusb -v"
> > - the generated file via "alsactl -f store somefile"
> > 
> > If I remember correctly, alsamixer at least doesn't break if you build
> > snd-usb-audio driver with IGNORE_CTL_ERR enabled, right?
> 
> I got the usb soundcard to work. I still have IGNORE_CTL_ERR enabled.
> 
> Problem was not mixer after all... somehow it expects me to play sound
> as 8-bit, and then I can play 16-bit mono and actually hear
> it. _Strange_.
> 
> So:
> 
> mplayer -ao alsa:device=hw=0 -af format=u8  KDE_Startup.wav
> mplayer -ao alsa:device=hw=0 -af format=s16le -af resample=48000  -af channels=1 KDE_Logout_1.ogg
> 
> ...plays both files. 
> 
> Forget about the first mplayer, and it will play nothing.

Dalls DS4201 has a known bug that it doesn't handle U8 format but only
S8 format.  The driver changes the supported format flags from U8 to
S8 when this USB ID is detected.  So you cannot play U8 format
natively.  (Still strange that it is accepted by mplayer.)


Takashi
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