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 Attero Tech LLC 2013 Page 14 614-00002-07
4.2.1 – Notes on Transmit Bundles
Setting the correct bundle number for the mode is vitally important. The bundle number should be set based on the
transmission type. If the bundle is going to be unicast or multi-unicast, the bundle number should be between 256 and
65279. For multicast bundles, the bundle number should be between 1 and 255. Using a multicast bundle with a bundle
number higher than 255, or using a unicast bundle with a bundle number less than 256, may result in the audio not being
transmitted across the network.
Transmitter submap assignments in bundles should always be populated in the bundle starting with submap Ch1 and
working down. The values in transmitter submap represent the audio from a particular CobraNet output. A value zero
represents no audio. A value of 1 represents the audio from CobraNet output 1. A value of 2 represents the audio from
CobraNet output 2 and so on. Each output audio stream can be allocated as many times as required in as many bundles as
required. This means the audio can be duplicated multiple times in the same bundle (normally not done as a single copy of
the audio is normally enough but may be required given a particular application). It also means the same audio can also be
used in more than one bundle too.
Whilst the values 1 through 32 are valid numbers, the actual usable channels on a device will depend on the device being
set up. Some devices have up to 32 CobraNet output channels while others are only capable of 2 (refer to the device’s user
manual for information on what CobraNet output channels are available for that device). Care should be taken when
allocating channels to submaps to ensure only usable audio channels are included in bundles.
The subcount should also be set based on the number of channels actually needed. Setting up a bundle with a subcount of
8 and only placing four active channels in it with the remaining channels being either being set to zero or a non-used audio
channel will still result in eight channels worth of data being sent across the network. The unused channels with simply
contain zeros or random data (depending on exactly how the bundle is set up and what CobraNet output audio the device
has available). This wastes network bandwidth and under certain conditions, may cause audio issues due to excessive
network bandwidth usage.
Another point to note is that the default settings of 5.33ms latency and 20-bit audio allows the full 8 channels of audio to
be used. Changing the bit depth and/or the latency affects the number of channels a bundle may hold. A bundle can never
hold more than eight audio channels but adding more bits/sample or decreasing the latency can restrict the maximum
number of channels in a bundle to less than 8. More details on the restrictions and how these settings affect the channels
count in a bundle can be found if the reference documents noted in APPENDIX B.
There can also be bandwidth-related consequences and added congestion when adding Multicast traffic to the network. See
Bundle Assignment White Paper at http://www.cobranet.info/support/design/bundle_assignments.