The Rivendell Hardware Paradigm

In addition to the core computer hardware (CPU, motherboard, etc), each Rivendell host typically interacts with specialized hardware required to accomplish the task at hand. Three main categories of such 'special' hardware are of interest to us here, the three being audio adapters, serial ports and GPIO/switcher devices. We'll cover each below.

Audio Adapters

An audio adapter in Rivendell is simply a device or facility for getting audio into and/or out of a host on a realtime basis. Most commonly this will be a sound card, although other, more exotic possibilities (using TCP/IP networking or direct routing to other audio applications) also exist. The three main classes of audio adapters supported by Rivendell are:

Advanced Linux Sound Architecture (ALSA)

The standard Linux sound card driver starting with the 2.6.x kernel series, ALSA supports a huge array of commercially available sound cards, ranging from entry level 'game' cards to high-end cards aimed at professional audio uses. More information, including a current list of supported cards, is available at the ALSA web site,

HPI Adapters

These are high-performance sound cards manufactured by AudioScience Corporation. Designed and built specifically for broadcast automation applications, many feature advanced capabilities (such as onboard MPEG codecs and AES3 i/o) specially aimed for use in that setting. They are so-called because Rivendell uses AudioScience's special 'HPI' driver to access and control them. More information is available at AudioScience's web site,

JACK Audio Interconnect Kit

JACK is not a particular set of hardware devices, but rather an audio 'framework' that allows compliant applications to share audio resources and route audio in realtime amongst themselves. JACK is different from similar efforts within the Linux realm in that it was designed from the ground up for professional audio work, with particular focus upon low-latency operation and synchronous execution of all clients. More information can be found at the JACK web site,

Serial Ports

Commonly known in the DOS/Windows world as 'COM ports', serial ports are often used to communicate with outboard gear, such as satellite receivers and audio switchers. Up to eight serial ports can be accessed simultaneously by each Rivendell host.

GPIO/Switcher Devices

Because these capabilities are often (although not always) bundled together in the same device, Rivendell lumps GPIO and switcher devices together within the same class. 'GPIO' stands for 'General Purpose Input Output'. As the name implies, these devices can be used to interface to a huge variety of outboard equipment by means of control lines. GPI (General Purpose Input) lines can be used to sense changes in an outboard system's state (and Rivendell programmed to take various actions on the basis of that), while GPO (General Purpose Output) lines can be used to send commands to an outboard system. The actual physical interfacing of GPIO devices is complex and generally beyond the scope of this document. Readers are encouraged to consult a good handbook on radio engineering for more information. A current list of GPIO/Switcher devices supported by Rivendell can be found in 'docs/GPIO.txt' file in the Rivendell sources.

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