Appendix a Configuring Cobranet | JBL Professional DP SERIES

APPENDIX A: CONFIGURING COBRANET

General

CobraNet is a licensed technology developed by Peak Audio, Inc. consisting of proprietary communications protocol, ﬁrmware and hardware. It allows reliable, deterministic (i.e. real-time) transmission of high quality (i.e. un-compressed) digital audio over standard 100Base-T Fast-Ethernet network. CobraNet will also oper- ate on faster versions of Ethernet (e.g. Giga-bit and 10Giga-bit).

A CobraNet system is comprised of CobraNet devices and the Ethernet network that connects them. PCs or other system controllers may also be connected to the network for setup but are not required for operation.

Ethernet

Ethernet is a hardware and signaling speciﬁcation developed by Xerox in 1970 for data networking.The IEEE (Institute of Electrical and Electronics Engineers) standardized the technology in the IEEE 802.3 standard and its variants.

With over 50 million nodes installed, Ethernet is easily the most dominant data networking technology in use today. It is carried over inexpensive CAT-5 UTP cables or ﬁber.Typical Ethernet cabling limitations are: 100 meters over CAT-5 copper cable, 2 kilometers over multimode ﬁber.

The CobraNet™ Device

Each CobraNet device embeds specialized hardware and ﬁrmware. The hardware includes a standard 100MB Fast-Ethernet interface along with custom high-speed DSP chips and clock circuitry.The DSP and its embedded software are used to encode and decode the Ethernet network messages using the propri- etary protocol.The clock circuitry is used to accurately decode the system master clock timing needed for high-quality real-time audio delivery.

Audio Specs

All CobraNet devices operate at a ﬁxed sample rate of 48kHz.The audio data may be transmitted at 16, 20 or 24 bit data as desired. For reliable operation, each CobraNet device must implement transmit and receive buffering.This buffering is ﬁxed at 256 samples and results in a minimum audio network latency of 5.333ms. (256 samples at 1/48kHz per sample)

Bundles and Audio Channels

Routing of digital audio between CobraNet devices is accomplished through Bundles. A Bundle is the name given to the proprietary encoded message (a.k.a.“packet”) transmitted between CobraNet devices that in- clude multiple channels of digital audio. Each CobraNet device can transmit and receive up to four Bundles. Each Bundle includes up to 8 Audio Channels.Therefore, each device is capable of transmitting and receiv- ing up to 32 Audio Channels to and from the network.

Bundles can be transmitted using Ethernet multicast or Ethernet unicast methods. Multicast Bundles are sent to all CobraNet devices on the network, while unicast Bundles are sent to one and only one CobraNet device. Since each device can send and receive four Bundles, great ﬂexibility is allowed in the routing of audio over the network. Up to 8 multicast Bundles (64 Audio Channels) can be transmitted on a simple re- peater based Ethernet network. Up to 4 multicast Bundles (32 Audio Channels) along with up to 421 unicast Bundles (>3000 Audio Channels) can be transmitted simultaneously on a full-duplex switch-based CobraNet network.

Assignment of Bundles is accomplished through the selection of a Bundle number. Bundles between 1-255 are always multicast, while Bundles between 256 - 65,279 are unicast. Bundle assignments must not be duplicated. Only one CobraNet transmitter is allowed per bundle.

The Conductor

On a CobraNet network, the Conductor coordinates transmission of audio packets throughout the entire network. When two or more CobraNet devices are interconnected properly, one of them will be selected the Conductor based on their respective Conductor.

JBL Professional DP SERIES, VT4887ADP-CN, VT4887ADP-AN, VT4881ADP Appendix a Configuring Cobranet