2004.07_Alsa-Setting Up the Advanced Linux Sound Architecture.pdf

KNOW HOW

Alsa

Free Sound Dimensions

There are many good reasons

tions. If you are not forced

to use a specific sound

card, because your Win-

dows based music pro-

gram requires the specific

functionality of the card, a

cheap card and Alsa are

probably your best

options.

It is often possible

to use OSS-based ap-

plications, by installing

the compatibility library,

ALSA-oss , which is also

available from the Alsa

homepage [1].

The recommended

approach is to install the

Alsa packages supplied

with your distro first.

You can avoid downloads

and complicated modifi-

cations of your configuration in this way.

Once you have the drivers and audio

programs working to your satisfaction,

there is no real reason to update. As not

all Alsa tools and applications are

installed by default, you may need to

add one or two programs.

The current SuSE 9.0 and Mandrake

9.2 distributions have Alsa version 0.96 –

which was released in the fall of 2003 –

including a number of tools. 0.x versions

of Alsa are not under active develop-

ment. Currently, the Alsa homepage [1]

has a stable version 1.02 for kernel ver-

to install the Advanced Linux

Sound Architecture, Alsa, by

default on modern distribu-

tions. They include a variety of

Alsa-based audio applications

ranging from simple CD play-

ers to professional studio

programs.

BY WOLFGANG BONGERTZ

Figure 1: The Alsaplayer is versatile, and handles everything from MP3 files to

audio CDs as audio streams. It can also visualize signals. The spectral water-

fall (center of image) may be more appealing, but the spectrum analyzer

(bottom right) provides more information.

utions to opt for a GPL-licensed

software rather than a commercial

OSS. The first, and most obvious, advan-

tage is that the user does not need to

spend money just to install a sound card,

assuming that it has Alsa support. This is

true of many cards, including some quite

exotic models that you won’t find down

at your local hardware dealers. To find

out if Alsa supports your card, check out

the database at [1].

If your card is not listed, it doesn’t

automatically mean that you will be

unable to use it with Alsa, but it might

take a while to check what standards

your card supports and to tweak out the

best setings.

In many cases you might actually save

money by buying a new sound card,

rather than opting for a seemingly

inevitable OSS, as a surcharge may be

payable if you want to enable the card on

Linux. Yours truly first purchased an OSS

license for a sound card with the Aureal

Vortex chipset, only to discover that I

was expected to pay an additional fee for

enabling even the basic chipset func-

Box 1: Updating to Alsa from OSS

The first thing to do is to make sure that OSS

(if it is still installed) does not take command

of your sound card and is not automatically

loaded when you boot your machine. su to

root in the command line and halt the OSS

driver as follows:

soundoff

Then call soundconf to open the OSS config-

uration menu. Select the Disable automatic

startup at boot time option below Automatic

Boot Setup .You should see a message to the

effect that the OSS driver has been removed

successfully. Don’t forget to save and exit,

when quitting the configuration menu, to

prevent the OSS driver from launching auto-

matically in future.

Older OSS versions may use an entry in

/etc/init.d/boot.local to start the OSS driver.

In this case, remove the line with the

/usr/bin/local/soundon entry.

You can now use your distribution’s installa-

tion manager to install Alsa if you have not

already done so. After installing Alsa, you

should have a script called alsasound in your

/etc/init.d directory. Again working with

super user privileges, type

/etc/init.d/alsasound restart

in the command line to launch, or re-launch,

the driver.

Suse and Mandrake installation tools can

autodetect internal sound cards. If required,

you can finish off the configuration with

Ya ST on Suse 9.0 (see Figure 2), and with

draksound on Mandrake. The installation

procedure should also automatically start

the sound daemon.

If you installed the latest Alsa version from

the source code (see Box 2: Installing Alsa

from the Sources), avoid installing a sound

card via YaST or draksound as this would

overwrite the new drivers.

July 2004

www.linux-magazine.com

Alsa soundscapes, not just for musicians

I t seems quite logical for Linux distrib-

Alsa

KNOW HOW

sions 2.2, 2.4, and 2.6. Beta version 1.03

is just around the corner.

The following sections assume that

you have a working Alsa driver installa-

tion. Users moving from OSS should

check out the notes in the boxes. Box 2

provides instructions on installing Alsa

from the sources.

a Jack interface. In this case,

Jack controls the synthe-

sizer indirectly, as the MIDI

sequencer which controlling

the synthesizer is running

as a Jack client – synchro-

nously with the multi-track

recorder client.

Thanks to the efforts of a

continually growing com-

munity of audio developers,

most of whom work with

Alsa applications, there is a

large selection of “jackified”

software available, and the

collection continues to

grow. Box 3: Applications,

lists a number of programs that rely on

Jack functionality.

Jack Connects

The Jack Audio Connection Kit (Jack)

[3] allows multiple applications to work

with the Alsa audio drivers at the same

time. Jack is included with most current

distributions, and will automatically be

installed if you set up an application

such as alsaplayer .

Jack is an audio server that connects

various audio applications to the hard-

ware and makes sure that applications

can exchange data. See Figure 3. For

example, a MIDI sequencer simply

records control data which are fed to a

sound generator on the sound card, or

an external instrument, which in turn

takes care of producing the required

sounds. If you want to add an echo, Alsa

Figure 2: Suse Linux uses YaST to for Alsa sound configuration.

Users can set the volume at the same time.

will transport your midi data to the chip

that generates the sound, and Jack will

take the sound produced by the chip to

the echo processor, and hand it back to

the sound card. It can even take a detour

via a software based audio mixer, if

required.

Of course, this assumes that the appli-

cations are “jackified”. Figure 4 shows a

software synthesizer that does not have

LADSPA versus VST

LADSPA (Linux Audio Developers Sim-

ple Plugin Architecture) is the Open

Source equivalent of Steinberg’s VST

standard for audio plug-ins in Cubase or

Nuendo. Synthesizers, sequencers, audio

workstations, and a multitude of pro-

Box 2: Installing Alsa from the Sources

Before you start, make sure that the kernel

source code is installed to fulfill all of the

Alsa drivers’ dependencies. Then you need to

type

modinfo soundcore

If the response tells you that this module is

available, you can assume that you will not

need to re-compile the kernel. The database

of supported cards on the Alsa hompage [1]

typically has detailed guidelines on individ-

ual cards, and links to distribution specific

tutorials.

Packages that you downloaded from the

homepage need to be unpacked in separate

directories. They include both the drivers,

and a collection of libraries, tools, and mod-

ules for special cards like the Aureal Vortex,

Tur tle Beach Multisound Pinnacle/Fuji,

Sek’D/Marian Prodif Plus, or Advantage.

After unpacking the archive files in /opt, for

example, you should have a few subdirecto-

ries called alsa-driver , alsa-lib , alsa-firmware ,

alsa-oss , alsa-utils , and alsa-tools plus the

version number suffix for the version you are

installing.

Step by Step

The following example is for a Terratec

128iPCI card, which uses a es1938 driver mod-

ule. This driver is referred to by its module

name during configuration and when added

to the kernel. You may need to refer to the

installation guide on the Alsa homepage [1]

to find out the module name for your sound

card.

In a command line window, change to the

driver directory

cd /opt/alsa-driver-xx

and then type the following

./configure -with-sequencer= U

yes with--isapnp=no; U

make; make install

to build the software in a single operation.

configure options always start with --with

and are located in the INSTALL file. In this

case, we simply enabled sequencer support,

and removed ISA PnP sound card support,

which we will not need. If you prefer, you can

tell configure to configure the driver module

for your card by stipulating --with-cards=

es1938 .Alsa versions prior to 0.94 need to

run a script to be able to assign privileges for

snddevices.

Before you turn to the lib package, first type

chmod a+rw /dev/mixer U

/dev/dsp /dev/sequencer /dev/mid

Then working in the /opt/alsa-lib-xx direc-

tory, follow the normal steps to complete the

install: /configure; make; make install .Follow

the same approach for the utilities and OSS

compatibility packages in /alsa-utils-xx , and

/alsa-oss-xx . Change to the directory, config-

ure, compile, and install all in a single quick

action.

Time to add the modules to the kernel. The

Alsa hardware database at [1] tells you the

right module(s) for your sound card(s). This is

snd-es-1938 for the Terratec 128i PCI in our

case:

modprobe /dev/snd-es1938; U

modprobe /dev/snd-mixer; U

modprobe /dev/snd-seq-oss

After completing the install, you may find

that the volume controllers for the sound

card are muted. You can use the alsamixer

from the utilities package to set the volume.

Assuming that the install worked out OK,

you should also be able to use other mixers

such as gamix or kmix .

You can use the user-specific .asoundrc file to

update plug-ins for converting PCM formats

or routing to distribution specific variants for

Alsa. Alsa will work perfectly well without

.asoundrc ,but it does give you more control

over your own soundcard(s). Check out the

tutorial [2] for more info on generating an

.asoundrc .

www.linux-magazine.com

July 2004

KNOW HOW

Alsa

Figure 4: amSynth brings back the classical sound

of analog synthesizers. You need to twiddle but-

tons to control it, just like on a true analog

synthesizer.

Figure 3: This diagram by Jörn Nettingsmeier shows how Jack works.The jackd daemon hovers like a spi-

der in its web, and provides stable routing of the audio streams in the background.

INFO

grams for musicians and sound engi-

neers all work with LADSPA plug-ins. In

fact, there are any number of quite

impressive plug-ins available from vari-

ous sources.

The Agnula project distributions,

which are tailored to meet the needs of

musicians and studio owners, all rely

heavily on a combination of Trio Alsa,

Jack, and LADSPA.

self-installing and configuring versions,

DeMuDi and ReHMuDi, were due to be

completed on 31.3.2004. the Agnula

homepage had a downloadable ISO CD

image of both distributions ready by the

deadline. Unfortunately, neither of the

CDs was bootable, and both lacked a

simple installation routine. The packages

these distros contain are older than those

provided by generic distributions in most

cases.

This said, the approach is interesting.

The Agnula distributions provide a col-

lection of apps for musicians and sound

engineers, and this gives DeMuDi and

ReHMuDi a fighting chance against com-

mercial applications for Mac and

Windows in this professional market.

[1] The Alsa project: http://alsa-project.org

[2] Tutorial .asoundrc: http://alsa-project.

org/alsa-doc/doc-php/asoundrc.php3

[3] Jack homepage:

http://jackit.sourceforge.net/

[4] Introduction to Alsa, Jack, and LADSPA:

http://www.agnula.org/documentation/

dp_tutorials/alsa_jack_ladspa/

[5] Alsa applications:

http://alsa-project.org/applications.php3

[6] Jazz++ MIDI sequencer: http://www.

jazzware.com/cgi-bin/Zope.cgi/jazzware

[7] Amsynth synthesizer: http://amsynthe.

sourceforge.net/amSynth/

[8] Ardour homepage: http://ardour.org/

[9] Simsam MIDI Sample Player:

http://simsam.sourceforge.net

[10] MusE “Professional Music Maker” Linux

Magazine, Issue 37, December 2003, p20

[11] The BEAST: http://beast.gtk.org/

[12] AlsaModularSynth:

http://alsamodular.sourceforge.net/

[13] FluidSynth: http://www.fluidsynth.org/

[14] Rosegarden “On a Bed of Roses” Linux

Magazine, Issue 37, December 2003, p25

Agnula and EU Sponsorship

The European Commission invested 1.7

million Euro over a period of two years

in the Agnula project [4], giving the pro-

ject the task of developing a customized,

Debian and Red Hat-based Linux distrib-

ution for audio applications. The

■

Box 3: Applications

Free and commercial applications for Alsa

and Jack can easily hold their sway with

more established audio applications. Check

out the list of applications and short descrip-

tions later on in this article. For a more

detailed list, check out the Applications sec-

tion [5] on the Alsa hompage.

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