Linux Audio Development: A Report from Karlsruhe

Updates on the latest plans for Linux audio functionality from the first developers' conference in Germany.

From March 14-16, the Zentrum für Kunst und Medientechnologie (ZKM) in Karlsruhe, Germany, hosted the first conference of Linux audio developers. Developers from more than a dozen countries attended this successful conference, representing organizations such as SuSE, Linux Audio Systems, Stanford University, IRCAM and Centro Tempo Reale. Topic discussions included in-depth presentations of the rapidly evolving Linux sound system, a look at the details of programming for professional audio standards and a survey of recent applications and audio-centric Linux distributions.

The first session took place on Friday evening, March 14, with two more sessions on Saturday and a final open session on Sunday, the 16th. All sessions were well-attended by developers and the public, and it is hoped that a second annual meeting will be planned for next year.

The New Linux Sound Architecture

Historically, the basic Linux sound system has been built on an API known most recently as OSS/Free. As of the 2.5 development series, the Linux kernel now officially deprecates the aging OSS/Free API and has replaced it with the Advanced Linux Sound Architecture (ALSA). ALSA provides a backwards-compatible layer for accommodating older applications designed for OSS/Free. But, its advanced API includes more interesting features, such as support for sound hardware from consumer-level sound cards to professional-grade digital audio boards, a fully modularized driver design, safe operation in SMP and threaded programming environments, and a user-space library (libasound) to simplify applications programming.

Conference participants included ALSA luminaries Jaroslav Kysela (founder and team leader), Takashi Iwai, Paul Davis, Frank van de Pol and Matthias Nagorni. Topic presentations included an in-depth analysis of the ALSA driver design, ALSA development in historical and technical perspective, an exposition of the JACK low-latency audio server/connector, details of the ALSA sequencer API and a demonstration of various ALSA-aware applications and utilities. As might be expected in this session, the level of discussion was quite technical at times, but all presentations were well-prepared and clearly delivered.

Some special mention must be made regarding JACK. This unique software provides a professional-grade audio server in a low-latency environment, making arbitrary audio signal routing possible, without dropouts or distortion. In a short period of time, JACK has been embraced enthusiastically by Linux audio applications developers, and the list of JACK-aware programs grows almost daily. JACK is not actually a part of ALSA, but its chief designer (Paul Davis) also has written some of ALSA's most significant drivers. Although it does not require ALSO specifically, JACK development closely follows ALSA's progress and, at this time, is best employed in an ALSA-based environment.

Takashi Iwai's presentation of the ALSA bake mix was another highlight, not soon to be forgotten by those who witnessed it. If his presentation was an indicator of new packaging trends, I believe we can expect some colorful innovations from Takashi and crew.

Programming the Ardour Hard-Disk Recorder and the LADSPA Effects Processors

Paul Davis's second presentation was titled "Some Things You Might Not Have Thought about When Writing an Audio Application", and it was a distillation of his experience programming the Ardour hard-disk recorder/digital audio workstation (DAW). Ardour has become a center of attention for those of us who wish to use Linux in a professional audio setting. As its development nears a first public release, anticipation and interest has become quite intense. Happily, Paul's presentation of the program's current status was most exciting, demonstrating features such as control automation, advanced editing procedures and effects processing using the LADSPA plugins. Ardour still has a way to go before reaching its 1.0 release, but it is already being tested in real-world scenarios with excellent results.

Ardour's development history has been of great importance to a new generation of Linux audio software programmers. As Paul points out, no road map exists for programming software like Ardour; that is, there is no existing code base for writing a professional-quality hard-disk recording system. Successful commercial DAW software manufacturers, such as Steinberg or Emagic, leave no open sources that could function as a guide to the construction of such a complex application. Thus, every important lesson learned by programmers in those commercial houses must be learned anew by the open-source developers. That Ardour has come so far and evolved so well is a testament to the talents and dedication of its programming crew. Thanks to Paul's efforts, along with those of many other Linux audio developers, the next generation of Linux audio software coders will find their way made easier and their labor less, well, arduous.

LADSPA stands for the Linux audio developers simple plugin architecture. The API was first proposed and designed by Richard W. E. Furse with the collaboration of other members of the Linux audio development community, but Steve Harris is probably the name most often associated with LADSPA plugins. Steve has authored the most popular collection of plugins and has consistently worked to improve not only his plugins but the LADSPA API as well. In his presentation at ZKM Steve demonstrated the ease with which LADSPA plugins can be written. He even managed to convince most of his audience that they too could become accomplished DSP programmers after only a few easy lessons, particularly if they employ Steve's XML-based plugin programming framework.


Similis sum folio de quo ludunt venti.


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Re: Linux Audio Development: A Report from Karlsruhe

Anonymous's picture

thats all good n a bag of beans. Now write a VST wrapper for the plugins and drivers... maybee then linux will be actually useful instead of lost in its own little crappy audio world like it is now.... Hell figure out a way to load windoze VST plugs via wine or sumptin.. Until then no one that produces will give a rats ass.

captchas suck. this implementation sucks more than most.

nonymous's picture

I had some valid points for both sides of the argument, but now that I am so irritated by the @*$&^#! captcha, I am just going to rant about that.

It took me like 10 tries to get the first one right. Now I have to enter another one to actually post?

An indication of whether it's case-sensitive would probably have eliminated the first 3-4 fails. Then I just got unreadable ones. Yes I can read, but the display is excessively ambiguous at 1600x1200 on my 21" CRT.

A dhtml function to just regenerate the image would be slightly less annoying than having to resubmit the whole page.

I have wasted valuable time which would have been better spent helping create/improve software for the benefit of all humanity, and I daresay that is a higher negative cost than suffering the theoretical spam it is intended to prevent. (Yes, I could have cut those losses by just bailing out immediately, but I believe crusading for usability is every software designer's duty.)

Please improve on this situation!

> Now write a VST wrapper

Anonymous's picture

> Now write a VST wrapper for the plugins and drivers...
> maybee then linux will be actually useful instead of lost
> in its own little crappy audio world like it is now

For those unable to parse this, let me translate it for you. It actually means:

"I am a thoroughly brainwashed Microsoftie unable to do anything without my decorative little WinXP desktop in the background, and so totally tied to my VST plugins that I can't even make a cup of coffee because my kettle has no VST interface. So, because you Linux lot cannot accomodate my myopic view of the world, you are all obviously irrelevant and unprofessional. Oh, and Leenucks sux and XP r0x0rs!!"

There, that should be a bit clearer.

Re: Linux Audio Development: A Report from Karlsruhe

Anonymous's picture

Possibly windows-vst-plugins (and macintosh-plugins on PPC-linux) can be embedded to a linux-host-application natively. AFAIK, over 90% of all plugins are not linked against any operating system library. They came with own widgetsets and all using api functions come from the host application.

Re: Linux Audio Development: A Report from Karlsruhe (author res

Anonymous's picture

Not that I want a rat's ass, but FYI Kjetil Matheussen's VSTserver provides VST support for LADSPA plugins and Pd. It's very cool, I've experimented with up to a dozen or more VST plugins activated in a Pd patch. Btw, Kjetil did indeed utilize some WINE capabilities to achieve his software.

Also, Paul Davis recently experimented with JACK + VST. If all goes well I think we might expect VST support from JACK. More cool...

Regarding drivers: ALSA has evolved into a splendid audio system, it's doubtful we'd get much of a technical "win" by attempting ASIO support (if that's what you're talking about).

== dp

Re: Linux Audio Development: A Report from Karlsruhe (author res

Anonymous's picture

Jack supports ASIO under Linux, just start it with the -a option. It's just a way of defining the data size sent to the PCI card, not a way of getting low latency etc. Some cards support this transfer mode, some don't.

All these things, ASIO, VST, Direct Monitoring, Rewire etc etc are just brand names. They don't guarantee good performance or sound, just a particular standard and way of achieving a goal.
We would have VST native in Ardour now if the header files were re-distributable, the technical side is not hard. (Emulating windows gui is another matter...)

You can do the same things under Linux, but they are called JACK, ALSA, LADSPA etc etc.

Re: Linux Audio Development: A Report from Karlsruhe (author res

Anonymous's picture

you're no producer, just a kid who uses pirated copies of windows audio software he found on kazzaa and dreams of being the next drum&bass "star"... get off the crystal, stop snorting ketamine, take a bath and maybe we'll take you seriously.

Re: Linux Audio Development: A Report from Karlsruhe

Anonymous's picture

Open your eyes and get informed. Most studios don't tell you which

operating system they use. Upon close inspection, you may find

out some interesting facts. Or the, maybe not. You see what you want to see.

Re: Linux Audio Development: A Report from Karlsruhe

Anonymous's picture

I just wish and hope that the ALSA drivers will start working better than the OSS ones soon. I have tried them with three different sound boards, and had to revert to the OSS drivers on the grounds that they seem to behave better.

It's not MP3 just because its compressed audio

Anonymous's picture

> Pictures and MP3s from the conference are available on-line.

Anyone else upset that about MP3 being the Kleenex of audio? Those are ogg/vorbis, not MP3.

Re: It's not MP3 just because its compressed audio (author respo

Anonymous's picture

Another oops. My bad, sorry about that.

== dp

Oops, I forgot to mention SuSE

Anonymous's picture

I should have mentioned that thanks also go to SuSE for their support. The general Linux community owes SuSE big thanks for directly supporting the ALSA project, it's the kind of project that benefits everyone.

== dp


Anonymous's picture

Hey Dave.
great summary. That'll show my M$-loving friends how far we are and what is to expect.

Maybe Linuxjournal should always append a picture like
that one of yours to show what shiny happy people we are.

All I long for now is a Linux-Audio-User-and-Docu-hacking-Convention.
Thanks to Lukas, Francois, Julien and Joern for the little jamming you/we did! Had a great time!

Cheers, tobias.

Re: yep.

Anonymous's picture


Re: Linux Audio Development: A Report from Karlsruhe

Anonymous's picture

Wonderful summary, Dave, that captures especially well the nice spirit and friendly vibe surrounding the LAD conference. Maybe next year, I have enough Pd patches ready to host a whole dance night ;)



Frank Barknecht