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Date:      Fri, 9 Jun 2000 14:45:58 -0500
From:      "Richard Seaman, Jr." <dick@tar.com>
To:        Brian Somers <brian@Awfulhak.org>
Cc:        Maxim Sobolev <sobomax@FreeBSD.org>, Kenneth Wayne Culver <culverk@wam.umd.edu>, Chris Piazza <cpiazza@jaxon.net>, Cameron Grant <cg@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, brian@hak.lan.Awfulhak.org
Subject:   Re: cvs commit: src/sys/dev/sound/pcm channel.c
Message-ID:  <20000609144558.B566@tar.com>
In-Reply-To: <20000609141129.A566@tar.com>; from dick@tar.com on Fri, Jun 09, 2000 at 02:11:29PM -0500
References:  <dick@tar.com> <200006091630.RAA01120@hak.lan.Awfulhak.org> <20000609141129.A566@tar.com>

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On Fri, Jun 09, 2000 at 02:11:29PM -0500, Richard Seaman, Jr. wrote:

> > If I just cat a .au file into /dev/audio, I get about 1/4 of a second 
> > of plan and then silence, with & without the patch.
> 
> Your symptoms are different then.  Don't know if the cause is the
> same.

Thinking about this some more, and as a followup to my last message, here's
what I'm guessing is happening to you.

You fill the device buffers very rapidly.  Since chn_wrintr is not getting
called as dma activity occurs, the only time the dma pointers can get updated
and therefore indicate that the buffers aren't full is when you write to
the buffers -- but you can't because they're already marked full.  ie.
you're deadlocked. The sound you hear is the dma buffers emptying, but your
app never knows it happened because the buffers are still marked full.

My case is the opposite side of the problem.  My app doesn't always fill the
buffers fast enough, and the dma pointers get corruped.

I'd guess that those that don't have problems either a) are getting
dma interrupts, or b) manage to fill the buffers at a rate that is
neither too fast nor too slow.

-- 
Richard Seaman, Jr.        email:    dick@tar.com
5182 N. Maple Lane         phone:    262-367-5450
Nashotah WI 53058            fax:    262-367-5852


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