Codec2 voice over DML

Mime type: application/dml-codec2

DML header: none, Codec2 does not have codec specific data.

DML data packet:

0 - 7 8 - 15 16 - 23 24 - 31 32 - 39 40 - 47 48 - 55 56 - 63 64 -
64 bit header Codec2 data
48 bit address 8 bit Codec2 mode 8 bit Level Codec2 data octets
In mode 0 (3200 bps) a typical packet will contain 8 data octets encoding 20ms of audio. When the sending station wants to change the state a packet consisting of only a header is allowed. The 48 bit address field contains the callsign of the sending station. In case of digital voice systems this is the callsign of the actual sender. In case of a system where this info is not known (such as an analog voice repeater) the callsign of the receiving station is used. It is recommended to set the multicast bit in the address for such setups.

Mode 65 is used for A-Law encoding. This is not an actuall codec2 mode. However it is usefull if the sending node has no practical bandwidth limit and the data is not already encoded.

The signal level is encoded in a single byte. values 1 through 255 represent levels -127dBm through 0dBm. (Zero is regarded as -Infinite dBm)