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[20071113] pad(4) - pseudo audio device driver
Jared McNeill has committed his pseudo audio device driver, pad(4): ``With this pseudo-device, audio played back via the standard audio interfaces is redirected back to userland as raw PCM data on /dev/padN.

One example usage is to stream audio to an AirTunes compatible device using rtunes (http://www.nazgul.ch/dev_rtunes.html), ie: 

$ rtunes - < /dev/pad0
$ mpg123 -a /dev/sound1 blah.mp3
Another option is to capture audio output from eg. Real Player, by simply instructing Real Player to output to /dev/sound1, and running: 
$ cat /dev/pad0 > blah.pcm''

To find out what /dev/sound* device to use, use dmesg(8) output - Jared tells me that ``/dev/soundN and /dev/audioN are the same device; the only difference is behaviour on open -- /dev/audioN emulates traditional Sun audio behaviour and resets the device to a known configuration, whereas /dev/soundN uses the previous device state.

There is nothing yet to discover the attachment apart from dmesg: 

$ dmesg | grep pad0
pad0: Pseudo Audio Device
pad0: outputs: 44100Hz, 16-bit, stereo
audio1 at pad0: half duplex''


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[20050901] Real-Time Audio Servers on BSD Unix Derivatives
As mentioned on Undeadly.org, Juha Erkkilä has managed to bring the topics of real-time processing in operating systems and audio servers together in his master's thesis "Real-Time Audio Servers on BSD Unix Derivatives": `` This paper covers real-time and interprocess communication features of 4.4BSD Unix derived operating systems, and especially their applicability for real-time audio servers. The research ground of bringing real-time properties to traditional Unix operating systems (such as 4.4BSD) is covered. Included are some design ideas used in BSD-variants, such as using multithreaded kernels, and schedulers that can provide real-time guarantees to processes. Factors affecting the design of real-time audio servers are considered, especially the suitability of various interprocess communication facilities as mechanisms to pass audio data between applications. ''. The thesis then describes how to implement things for OpenBSD, but it may still be of interest to NetBSD to some extent. [more]

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[20050829] Presentation on the future of NetBSD's audio system
Tamura Kent is working on the NetBSD audio system for some time now, and he gave a presentation about past, present and future at the NetBSD BOF in Tokyo the other day. The in-kernel rate conversion code is useful infrastructure, but of course we are all looking forward for in-kernel audio mixing. Which may be some time off, due to audio.c needing some massive work for that. For all the details, see the presentation slides.

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[20041214] Article: NetBSD: Ideas on Audio Framework
Well, Tamura Kent wrote to tech-kern@ a few days ago, proposing changes to the NetBSD audio system. Aparently kerneltrap.org picked it up and made an article with an interview out of it.

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