Linux Audio Development: A Report from Karlsruhe

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 ArchitectureHistorically, 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 ProcessorsPaul 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.Applications and DistributionsThe last session focused on the actual programs LAD people
have written and new means of packaging and distribution. As the
possible interactions between applications become more complex,
some development efforts have taken on the task of ensuring that
the new user finds a ready-made integrated environment that
includes a system prepared for low-latency, high-priority
performance. The environment needs a selection of applications that
can take advantage of the new Linux sound system.Francois Dechelle demonstrated recent free software
developments taking place at IRCAM in Paris. The jMax software is
already quite well-known and has evolved into one of the most
sophisticated audio production and processing environments
available for Linux. jMax can be thought of as a synthesizer, a
sample playback machine, a DSP engine, an audio/video composition
and processing environment or even a LADSPA plugin. Although
Francois's demonstration was plagued by technical difficulties, it
was enough to be able to glimpse jMax's enormous flexibility.
Francois also presented news regarding the OpenMusic project,
another free software development sponsored by IRCAM. OpenMusic is
targeted for composers; that is, it is essentially music
composition software, very advanced in its features and
capabilities. Alas, the port to Linux is incomplete, but a
dedicated team at IRCAM continues the work. We can expect wonderful
things when we finally see OpenMusic 1.0 for Linux.Andrea Glorioso reported on the efforts of the AGNULA team,
of which I am proud to be a member. AGNULA stands for "a GNU/Linux
audio" distribution, and it has been designed to provide turnkey
systems for new Linux users who especially want to work with audio
and video software. AGNULA plans to release two complete
distributions, one based on Debian and another based on Red Hat.
These distributions are complete systems, not crippled in any way,
with enhancements such as a kernel patched for low-latency and a
collection of entirely free software (free in the sense described
by the FSF). A 0.9 release of the Debian distribution (Demudi)
should be ready this summer.The PlanetCCRMA suite is another response to the need for a
system targeted at new users interested in the possibilities of
Linux audio and video software. Developer Fernando Pablo
Lopez-Lezcano described PlanetCCRMA's evolution in historical and
technical perspective. Fernando also described the system's use of
the apt-get utility so familiar to Debian users. With apt-get and a
fast network connection, a user can download, install and update
the entire PlanetCCRMA system over the Internet. Alternatively, she
can download CD ISO images and install the system off-line. Unlike
AGNULA, PlanetCCRMA is not an actual distribution. Instead, it
depends on an existing Red Hat installation (7.x, 8.x) and replaces
the default kernel with a kernel optimized for multimedia
performance (low-latency, capabilities-enabled, high-priority
scheduling). It also adds the ALSA drivers to your system and, of
course, provides an excellent bundle of selected audio/video
applications for Linux.My own presentation was a rather rambling account of issues
I've encountered while documenting Linux audio software. The lack
of release dates, the constant evolution of the software described
and the rapid pace of system development all conspire to make the
doc writer's work difficult, particularly if he is trying to write
tutorial documentation for normal users. Other documentation issues
include standardized bug report and test forms, the need to
distinguish between reference and instructional documentation and
the predictable difficulty of writing simple and clear user-level
introductions and tutorials.The WrapThe open session on Sunday was quite exciting; applications
were demonstrated, code was viewed and shared, conversation and
discussion thrived and many pictures were taken. Memorable moments
included Torben Hohn's demonstration of the gAlan
synthesis/processing network environment, Stefen Westerfeld's
presentation of the BEAST synthesis/composition software, Fernando
Lopez-Lezcano's composition for quad-speaker playback and Frank
Barknecht's awesome demo of Pd-as-techno-machine.Informal discussions took place throughout the conference,
over breakfast and dinner, while sampling the excellent beer and in
apartments and hotel rooms until the wee hours. I think I averaged
about four hours of sleep per night, and by Monday morning I was
exhausted and exhilarated. Nevertheless, on my flight back to the
US I found myself wishing for another few days in Karlsruhe. I was
told that the city and its environs include many lovely sights, but
involvement with the conference was so intense that none of us got
to be tourists. Perhaps next year's meeting will be a little
longer, and we'll be able to see more of Karlsruhe, visit
Heidelberg or take a bicycle ride along the Rhein and into the
Schwarzwald.AcknowledgementsFirst thanks must go to Frank Neumann, Matthias Nagorni and
Götz Dipper. They managed a large and diverse group of
developers arriving from various points at various times, ensuring
everyone's comfort and well-being. For a first-time effort
organizing a conference of this size, they all deserve the highest
praise and thanks. The directorate and staff at ZKM also must
receive great gratitude for their hospitality and financial
assistance. The Zentrum is an awesome place to hold such a
conference, and I recommend it to anyone visiting Karlsruhe. Thanks
also to Jörn Nettingsmeier for managing the live internet feed
and for helping in so many other ways.Finally, vast thanks to the developers themselves who have
done so much and given so freely. They are true heroes, persevering
to create a unique phenomenon: powerful software freely available
to musicians and sound people the world over, running on the
world's most free and powerful operating system. What an amazing
group, what remarkable accomplishments!ResourcesPictures and MP3s from the conference are
available
on-line.More information about ZKM may be found at
www.zkm.de.Information regarding the Linux Audio Developers group is at
www.linuxdj.com/audio/lad/.More general information about Linux sound and music software
can be found at
linux-sound.org.Dave Phillips is a musician,
teacher and writer living in Findlay, Ohio. He has been an active
member of the Linux audio community since his first contact with
Linux in 1995. He is the author of The Linux Book of
Music & Sound.

email: dlphilp@bright.net