From: "Jeffrey W. Baker" <jwbaker@acm.org>
To: alsa-devel@lists.sourceforge.net
Subject: ALSA drivers for USB audio devices
Date: 19 Mar 2002 14:24:06 -0800 [thread overview]
Message-ID: <1016576646.23423.40.camel@heat> (raw)
Recently on this very list, Paul Barton-Davis proposed that one could
build a driver for a USB audio device entirely in user space. I think
this is an interesting idea, as I own an Edirol UA-5 USB audio device.
Naturally I would like to use it with ALSA to acheive the best
performance and lowest latency.
I hope someone on this list can describe how such a driver would work.
I am not aware of any user-space drivers for ALSA. If there is one,
that would be a nice example. Would the driver take the form of a
userspace daemon? How would the ALSA library communicate with the
daemon? Or, would the driver instead take the form of a shared library
which ALSA libraries would load?
In the daemon case, I have trouble imagining that a userspace
implementation would acheive low latency. The client application, say a
mixing board program, would have to write some data to the ALSA PCM
handle, then wait for the daemon to get scheduled. The latency would be
all over the place.
In the case of a library that ALSA loads, that scheduling problem would
not exist.
In any case, it seems almost MORE straightforward to write an kernel
driver like the other supported output devices use. A 24-bit/96KHz
stereo audio stream requires driving the USB bus at nearly full
throttle. I doubt a userspace implementation could deal with it.
Thoughts?
-jwb
PS: even at 16-bit/48KHz the USB audio device driver in Linux 2.4.18
taxes the CPU significantly.
_______________________________________________
Alsa-devel mailing list
Alsa-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/alsa-devel
next reply other threads:[~2002-03-19 22:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-19 22:24 Jeffrey W. Baker [this message]
2002-03-19 22:39 ` ALSA drivers for USB audio devices Paul Davis
2002-03-19 22:41 ` Dan Hollis
2002-03-19 22:48 ` Jeffrey W. Baker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1016576646.23423.40.camel@heat \
--to=jwbaker@acm.org \
--cc=alsa-devel@lists.sourceforge.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.