Radio Free Linux

You would have a difficult time today finding a radio station that was all-live and did not have some kind of computerized, automated means of storing and playing audio.

In a bygone era, hands-on media management of records and tape cartridges ("carts") was the way of the world. Through the years, turntables, CD players and "cart decks" gave way to mechanized playback of content by banks of reel-to-reel machines under crude sequential control. The earliest fully computerized "audio on hard drive" systems for radio stations and networks ran generally under DOS, evolving into the elaborate Windows-based systems in use everywhere today.

So What about Linux?

Do a web search for "Linux radio station", and the pickings are slim indeed, with most sites promoting instead ham radio software or streaming audio players, and a handful devoted to setting up a streaming web radio station—including one such optimistic article in Linux Journal some 15 years ago (see "Running a Net Radio Station with Open-Source Software", January 2001).

Unfortunately, much of this documented interest took place a decade or more in the past via domains like that are no longer with us. A few projects persevere, but a good number of postings are similarly dated. The fact is, there are more Linux-based ways to stream and listen to radio stations than there actually are the means to broadcast and control them.

Fortunately, the choices today are getting better. Transmitter manufacturer Nautel incorporates Linux in its AUI. Broadcast automation and media management systems, such as Airtime and DIY-DJ, were designed around Linux from the start. Many Windows-based commercial automation systems seem happy when networked with Linux servers. But, as for in-studio hands-on control of program execution, there still is a way to go.

Off to Washington

In and around the nation's capital, actual over-the-air radio programming driven by Penguin power is a reality, and you already may be listening to it wherever you are.

Back around 2002, Fred Gleason, then the director of engineering for the Salem Communications radio cluster in Arlington, Virginia, saw the need for an open-source radio automation system: one that was nimble enough to handle the turn-on-a-dime demands of radio station programming, flexible enough to be modified and rewritten as the demands on it grew, and as crash-proof as possible to keep the music flowing and the commercials rolling. Working with partner and automation expert Scott Spillers, the two planted the seeds for what became the Rivendell radio automation suite. Rivendell is now under the banner of Paravel Systems, with Gleason as President and Chief Developer, and co-founder Spillers holding the VP reins. The company offers Rivendell as custom-built turnkey hardware, with a free software version as a downloadable iso file.

Rivendell originally was crafted for SUSE Linux but now runs under CentOS. It is an artistic mix of custom code and popular existing libraries and applications. Gleason used the Qt Toolkit to create the user interface, allowing it to run on anything right down to a Raspberry Pi; MySQL to maintain and manage the audio database; the Apache Web Server, ID3Lib, a couple CD rippers and the X11 Window System, among its many components.

Gleason's handcrafted code includes the GlassSuite collection of audio tools for Icecast and HTTP Live Streaming (HLS), and what he calls "a slew of code" to perform audio format conversions whenever new audio is imported into the station's audio library. Early in the development of Rivendell, SOX handled the format conversion, but Gleason noticed a slowdown due to "limited process control with the multi-stage command pipeline. This was before SOX had its library interface." His code performs the format conversions natively, without any shell outs.

Today, there are three major broadcast operations based in Washington, DC, that employ Rivendell—Radio America Network, Salem Communications DC and Radio Free Asia—with listeners everywhere in both Eastern and Western hemispheres. This is not to say that Rivendell is available only to major players. Many smaller users have come to depend on Rivendell as well. High school educational radio station WKHS-FM in Worton, Maryland, has been a Rivendell user since 2012, opting for a 32-bit Ubuntu-based appliance distro called RRABUNTU. A recent count showed more than 40 US AM and FM radio stations with a Rivendell installation in operation. A dozen miles south of DC, "Rolling Valley Radio", a low-power license-free community station uses the 64-bit CentOS version to broadcast its short-range signal to a small enclave of four or five suburban blocks.


Alan Peterson is a DC-based broadcaster, writer, audio engineer and has been advocate of Linux in radio broadcasting since 2007.