A User's Guide to ALSA
Figure 4 shows off the envy24control mixer in a JACK environment. JACK is an audio connections manager designed to professional specifications for low-latency communication between the JACK server and its clients. JACK requires a native system audio driver, which for Linux can be a dummy driver, an OSS driver, PortAudio or, most typically, ALSA. I will present the JACK system in detail in a future article.
It is no exaggeration to state that all contemporary major Linux audio software wants ALSA's special services. MIDI programs enjoy the connectivity of the ALSA sequencer, digital audio systems make use of ALSA's drivers for pro-audio hardware and thorough support is provided for common desktop audio/video activities. Figures 5 and 6 represent some screens commonly seen on my desktop, thanks to ALSA.
From the normal user's point of view, ALSA's most obvious weakness is in its lack of GUI front ends for the various tools and utilities that make up so much of the system's power: a configuration panel, complete with options for configuring and reordering your installed cards, loading the virtual MIDI driver, selecting plugins for .asoundrc and generating a new file, operating alsactl and so forth. ALSA is indeed feature-rich, but too many of its excellent features are available only to those of us willing to write scripts and resource files.
Fortunately, there is an abundance of ALSA documentation and information for users of all levels. I already mentioned the man pages for the ALSA utilities. The ALSA Web site includes many resources for basic and advanced use of the system. Also,the alsa-user and alsa-devel mail lists are founts of wisdom and assistance, as is the excellent ALSA Wiki.
The project always needs programmers, but it also needs graphics artists, technical writers and beta testers, so even if you can't code, your skills might still be valuable to the project. Donations of hardware and cash also are cheerfully accepted; please see the ALSA Web site for appropriate contact details.
The average user can expect to see more cards supported, with more features available to the user. Hopefully, card configuration will become easier: getting the most from ALSA can be a simple matter or it can be a difficult thing. It is true that what is difficult is not impossible, and the payoff certainly can be worth the effort. Hopefully, though, we also will see some more accessible tools for user-level configuration.
The author thanks Jaroslav Kysela and Takashi Iwai for their vast patience and excellent assistance over the years I've been using ALSA. Thanks also to all members of the ALSA development team, past, present and future, for this great gift to the world of Linux sound. Finally, thanks to Len Moskowitz for the extended loan of his outstanding Core Sound PDAudioCF card.
Resources for this article: /article/8324.
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 Book of Linux Music & Sound, as well as numerous articles in Linux Journal.
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Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
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