by August 10, 2001 0 comments



ALSA (Advanced Linux Sound Architecture) is an alternate set of sound drivers for Linux, which comes with the Linux kernel is the OSS/Free driver set. You might wonder why you need to bother with ALSA at all. First, if your sound card isn’t supported or couldn’t be configured properly with OSS, ALSA may solve the problem. ALSA is also faster to come out with drivers for new sound cards. It has native ISA PnP support for those pesky ISA sound cards that you have lying around. Also, ALSA has much more advanced MIDI support for a lot of sound cards. It has full-duplex support for all sound cards that support it. And ALSA is totally open source under the GNU GPL license. 
Convinced already? Let’s get on with the install.

Installation

Before you actually proceed to install ALSA, you have to upgrade your kernel to the one provided on the CD. This is needed because the ALSA driver’s rpm contains modules which are compiled for this specific kernel version. In this case, the readymade modules we have shipped on the CD are for kernel 2.4.3-12 that is included on the CD.

If you need some other kernel, then you will have to compile the ALSA modules manually. To install ALSA, login as root and mount the PCQuest CD with the command ‘mount /mnt/cdrom’ and then go to the directory containing the RPMs:
cd /mnt/cdrom/cdrom/linux/desktop/audio/alsa/
Now install the RPMS in that directory:
rpm -ivh *.rpm

This installs the ALSA drivers, libraries, utilities and configuration program. Run the configuration utility ‘alsaconf’. Alsaconf first tries to detect your card, and if it can’t detect it, it presents you with a list of cards supported. Select your card from among the list. Then it asks you for certain parameters about the card. If you’re not sure about something which is asked for, just leave it blank and proceed to the next one. (If you have an ISA card, it’ll ask you for the I/O address, IRQ and DMAs, so make sure you have that information ready). Say ‘Yes’ when it asks you whether it should modify /etc/modules. conf. After all this, it tries to load the ALSA sound modules, and if everything went well you’ll hear Linus Torvalds’ voice!

Now you can run any normal program which runs on the OSS drivers, thanks to the OSS emulation offered by ALSA. There are also quite a few native ALSA applications available, and others which support both ALSA and OSS but perform much better under
ALSA.

There are a few utilities which are included in the alsa-utils package which you may want to use. Alsactl is a utility which stores and restores sound-card settings (this is done automatically when shutting down and starting up). Aplay and arecord are utilities to play back and record audio files. There are also two mixers provided–alsamixer is an ncurses based mixer, and amixer is command-line based. You can of course, use any ordinary OSS-based mixer like aumix since ALSA is OSS-compatible. If you want to learn more about ALSA, visit the website www.alsa-project.org, which also has a complete matrix of supported sound cards.

Mrinal Kalakrishnan is a trainee consultant with
Exocore Consulting www.exocore.com

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