From There to Hear: Audio Over IP

August 1, 2013


From there to hear

From time to time we review various products that are used to send program audio from point to point (or multipoint) via IP. Products evolve from year to year and new features get added, so it's worth seeing what's out there.

Tieline has introduced a version of its Genie codec known as Genie Distribution. What is special and unique about it is that it can become part of a WheatNet-IP studio facility. You can use Genie Distribution to connect two WheatNet-IP studio locations together, either via a private network or the public Internet, passing up to six channels of audio between endpoints. The device includes a purpose-built Tieline WheatNet audio card, and the rear panel provides a WheatNet LAN interface for connecting the codec directly to a WheatNet-IP network. After connecting it in that environment, the codec can deliver IP audio over LANs, WANs, the Internet, satellite IP, 3G, 4G, Wi-MAX and Wi-Fi.

Tieline Genie Distribution

Tieline Genie Distribution


Tieline's Toolbox, a browser-based GUI, is used to remotely control the device. If the Genie Distribution is connected to the WheatNet-IP environment, it becomes a node, and routing of WheatNet-IP sources and destinations can be performed using Wheatstone's Navigator software.

The Genie Distribution is not limited to being part of a WheatNet-IP facility though; you can use it for stereo audio distribution for up to 50 individual multi-unicast endpoints; as an STL system, or for IP multicasting (over WAN that supports multicast). Genie Distribution is capable of 24-bit/96kHz low latency linear PCM audio, but it also features the E-apt-X algorithm, as well as LC-AAC, HE-AAC v1 and v2, Opus, MPEG Layer II, Tieline Music and MusicPLUS, G.722 and G.711 algorithms.

Genie supports both IPv4 and IPv6 (Dual Stack) protocols, and the user can also connect over IP with any SIP-enabled IP codec brand that supports the EBU N/ACIP tech 3326 standard.

Telos Z/IP One

Telos Z/IP One


Telos has long been a standard-bearer in IP codecs. Its latest product is the Z/IP One, a 1RU, full-duplex codec that can also fulfill a role as an endpoint in an AoIP studio network. Aside from the typical balanced audio inputs (+4dBu or mic level, switchable) it also has a built-in Livewire interface -- thus allowing the Z/IP to become a source and destination in an Axia AoIP studio environment.

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The Z/IP One has many interesting and useful features. In its role connecting point A to point B, the user can configure it to use linear PCM or any of the following codecs: AAC-ELD; AAC-HE; AAC-LD; MPEG layer 2; MPEG 4 AAC LC; MPEG 2 AAC LC; and finally G.711 or G.722. It conforms to N/ACIP standards including SIP 2.0; it has a 'push' mode for one-way connectivity, and it will even talk with a Zephyr Xstream.

The Z/IP One comes with a Wi-fi stick and thus allows connectivity via Wi-fi, EVDO, and UMTS. Two Ethernet ports are standard, allowing control and streaming to be done via separate physical networks. Remote control and configuring are done via its embedded Web server. It includes RS-232, for passage of serial control or metadata; an 8-port GPIO is included as well, for purposes of end-to-end signaling.

When I write about Comrex typically it's about the Access -- but this time it's all about the BRIC-Link. BRIC (Broadcast Reliable Internet Codec) is proprietary Comrex technology, which (according to the company) "allows the system to perform well on the public Internet (using AAC compression modes)."

Comrex BRIC-Link

Comrex BRIC-Link


BRIC-Link is a small desktop package -- two go side-by-side in a 1RU package. It's a full-duplex codec, primarily meant to handle nailed-up connections over IP, whether transported over your LAN, a WAN, or the public Internet. BRIC incorporates a dynamic jitter buffer, increasing or decreasing its depth based upon the network performance. For QoS networks the buffer depth can be fixed.

BRIC-Link comes with professional level analog I/O on 1/4" TRS connectors, which can be switched to AES. The network connection is via a 10/100base-T Ethernet connector. Four GPIO connections, along with an RS-232 link, are provided via mini-DIN connectors. Audio levels are provided on the front panel via tri-color LEDs; these LEDs may be configured to show either the send or return levels. Another front-panel LED displays the Ethernet status.

BRIC-Link has its own built-in Web server, used to read connection status, to configure profiles for various connections, as well as for opening and closing said connections. Network diagnostics are available, as are audio level meters. Initial configuration is done via a windows-based setup utility run on the same network as the BRIC-Link; this same utility is used for applying software updates.

For audio transmission, BRIC-Link offers a stereo or mono linear mode, in addition to FLAC compression, as well as HE-AAC and HE-AACv2. When using AAC modes, BRIC-Link is capable of sending multiple one-way streams to other BRIC-Links, Comrex Access, or via IP-multicast (assuming network compatibility).

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Another well-known maker of IP codecs is Musicam, and its Suprima has had some recent improvements. Suprima is a 1RU, two-channel, full-duplex IP codec that has some unique features. It has balanced analog inputs and outputs, as well as AES ins and outs (will sync externally or generate its own clock). It has a single Ethernet port that is used for control and the actual stream (TCP or UDP); control is done via its internal Web server. The Suprima also supports multicast over compatible networks. Seven GPIO connections are included, and it will support an auxiliary data stream if operating in MPEG mode or standard Apt-X modes. The unit will support linear PCM and codecs supported are G.711, G.722, Musicam ISO MPEG1/2 L2, ISO MPEG1/2 L3, MPEG2/4 AAC-LC, MPEG4 AAC-LD, MPEG4 AAC-HE, Standard and Enhanced Apt-x(64,128kb/s; mono, dual, j-stereo). It will also support Dolby E when the AES input is used, with the codec set in transparent mode.

Musicam Suprima

Musicam Suprima


The device has seen recent improvements to its network management, including better FEC, jitter and buffer control. Also, the Suprima has its own methodology for using two IP links, called Solid Stream. This feature permits two Suprimas to connect via two different IP data paths. Finally, the Suprima can pull down audio files from a USB stick, and play them out in the event that it detects an IP connection failure.

Another established player in IP codecs is Worldcast Systems, which took over the APT line of hardware codecs several years ago. It makes several IP codec products, but the one I chose to highlight is the Horizon NextGen (previous page). This is also a 1RU, two-channel, full-duplex codec that features dual-Ethernet connections on its rear apron, one of which can be used for a LAN connection while the other is used for the streaming output. IP transport is accomplished via RTP/UDP or SIP/SDP, and not surprisingly, Horizon Nextgen is fully N/ACIP compliant. The device supports unicast, multiple-unicast and multicast (assuming a compatible network).

Worldcast Systems APT Horizon NextGen

Worldcast Systems APT Horizon NextGen


Audio inputs and outputs are accomplished via XLR connectors, analog or AES. Four optically coupled inputs, along with four relay outputs, are included for GPIO (DB15 connector).

In addition to linear PCM, the unit supports Enhanced Apt-x. As an option, you can include MPEG 4 HE-AAC versions 1 and 2.

Control can be done from the front panel LCD screen and keypad or via its network connection using the Worldcast Network management software, or simply via its embedded webserver. SNMP support is provided as well.

SureStream is the name of the Worldcast feature that allows the Horizon NextGen to make user of two IP links to the far end device, thus providing extra reliability, especially over the public Internet. If you intend to use an IP codec over a trunked system (i.e., multiple VLANs) you'll be interested to know that the Horizon NextGen supports VLAN tagging.

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Barix is a well-known name in IP codecs. Many are familiar with the Instreamer/Exstreamer pairs, but the company also makes codecs, such as the Exstreamer 500. This device comes with balanced analog inputs and outputs, 4 GPIO inputs and outputs, as well as a USB port for audio fail-over from a storage device. Algorithms available are MP3 (variable bit rate, between 8 and 320kb/s, and sample rates between 8 and 48kHz), PCM, and AAC-LC, HE-AAC, and HE-AAC v2.

Barix Exstreamer 500

Barix Exstreamer 500


Another brand of IP codecs that sees some use is AEQ. It makes several different units, but we'll look at the Phoenix Venus. This is a 1RU, full-duplex codec that will handle two stereo pairs (or four mono) simultaneously. The two AES ins/outs are available on DB15 connectors, with SRC, and will individually sync between 16 and 96kHz. Analog ins/outs are available via XLR connectors. The unit has a single 10/100baseT Ethernet (RJ-45) port.

AEQ Phoenix Venus

AEQ Phoenix Venus


Phoenix Venus was designed to meet the N/ACIP EBU Tech3326 standard and includes the option of an adaptive buffer in order to absorb network jitter; DHCP allowing the automatic configuration of the IP Network parameters; and FEC and automatic reference clock adjustment in order to synchronize both ends of the communications link. Audio algorithms include G.711, G.722, PCM, MP2, and optionally AAC-LC and AAC-LD. The unit also includes AEQ-LD, which is AEQ's proprietary codec.

The delivery of audio from point A to point B via IP, whether over your LAN, a WAN, or the Internet, has become commonplace nowadays. While it may not be imminent, the demise of ISDN is certainly on the horizon, so now is the time (if you haven't already) to learn something about audio over IP.


Irwin is RF engineer/project manager for Clear Channel Los Angeles. Contact him at doug@dougirwin.net.



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