Not the Same Old STL

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Worldcast Systems APT has an extensive lineup of codecs, but the one I'll highlight is the Horizon. This is a 1RU full-duplex codec that supports linear coding and Apt-x. Probably its most interesting feature though is called Surestream, which basically sends two identical streams out on two different Ethernet ports, to two different networks. The underlying idea is that the public Internet isn't very reliable (which we all know) so making use of separate networks increases the robustness of the link. If you were to use the Horizon in conjunction with one of the radio links previously described you could opt to use one of the Ethernet ports for management on the LAN.

Tieline has introduced an IP codec called Genie, which is designed for high-reliability STL applications. Toward that end, it features two gigabit Ethernet ports and dual power supplies. Genie supports uncompressed PCM audio and E-Apt-x, LC-AAC, HE-AAC v1 and v2, MPEG Layer II, Tieline Music and Musicplus. It has integrated alarm management, and Tieline's G5 toolbox allows complete remote control of the device by IP. Finally, I think it's interesting to note that along with IPv4 support, that Genie will support IPv6 as well.

Musicam makes the Suprima, a 1RU full-duplex codec. It supports linear coding along with MPEG layers 2 and 3, AAC LC/LD/HE and ELD. This device also has two Ethernet ports, one of which can be used for management; it has an embedded Web browser, allowing full control and monitoring. It makes use of FEC for error correction, but also has an automatic jitter buffer (as deep as 10 seconds) along with error concealment to reduce audio dropouts from packet loss. Finally, the device will support multiple-unicast or multicast, as a means of serving audio to multiple locations simultaneously.

Telos offers the Z/IP One, a 1RU, full-duplex codec that supports long list of coding algorithms, including AAC-ELD, AAC-HE, AAC-LD, MPEG Layer 2, MPEG 4 AAC LC, MPEG 2 AAC LC, and linear PCM. The unit senses network conditions and adapts codec performance to provide the best audio for the circumstances. It has dual Ethernet ports for separate streaming and control, which is done via an embedded Web browser. Analog inputs and outputs are accessed via XLR connectors. It supports Livewire; it has an RS-232 channel for audio side channel or metadata, and an 8-bit parallel GPIO port for signaling and control.

It's important to note that the codecs I mentioned above would more than likely be used in a system where the program output from your studio is in an AES or analog format; but what if you use an AoIP sytem? In that event, you could select a radio link that could be configured as a LAN bridge, so that the far end of the link, as well as the near end, is on the same VLAN. In the case of Axia, you would then locate another node at the far end, or alternatively, a device that supports Livewire. In the case of Wheatstone, you would locate another blade at the far end, and take a digital or AES out from that blade to feed processing or perhaps your transmitter directly.

Several manufacturers make radios that have been proven to work with Wheatnet, for example Redline, Radwin, Dragonwave, Motorola Canopy, Ubiquiti Wifi Radio and Exalt. Likewise, many radio systems have been proven to work with Axia, namely Dragonwave (Horizon Quantum), Exalt EX-r, Harris RF7800, Motorola PTP600, RAD Airmux and Ubiquiti Nanobridge. Speak to your AoIP system provider to get the exact details before purchasing a system or even starting up the prior coordination process.

There are so many reasons to have network access at the transmitter site today - I can't really imagine being without it. What practically seemed like science fiction just five or so years ago is now just commonplace.

Irwin is transmission systems supervisor for Clear Channel NYC and chief engineer of WKTU, New York. Contact him at

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