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IP multicast is a technique for one-to-many communication over an IP network. The transmitter sends out packets to a specific multicast IP address. Any node (phone) listening on this IP address will receive the stream and play it in handsfree mode.
Currently any Snom phone can use up to 10 multicast addresses. The index of the addresses is equivalent to the stream priority: 1 is lowest, 10 is highest.
Streams with higher priorities will overlap those with lower priority. This description deals with firmware version 8.x.
The Multicast configuration can be found in the phones web interface on Advanced → SIP/RTP.
The default codec used by the phone when sending multicast is pcmu, with a packet-size of 20 milliseconds. Starting with version 8.6.6, you can edit these values using the following settings:
Starting with version 8.7.3.26, you can setup the multicast address with additional options:
mc_address1=239.255.255.230:5555,speaker=1,interrupt=1,volmax=1,priority=9,name=Sales
interrupt | A call is active and multicast comes in | Multicast is active and a call comes in | Multicast is active and the user makes an outgoing call |
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0 (default) |
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1 |
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It is possible to stream an audio file directly to the snom phones via multicast. This can be used to start pre-recorded audio announcements or automated audio warning messages. Depending on which file format your audio file is, a different streaming tool has to be used.
ffmpeg works for both wav and mp3 files but vlc only works for wav files.
On the receiving phone configure:
multicast_listen=on mc_address1=239.255.255.244:5555
On the PC or MAC in the terminal window type:
PATH/TO/VLC PATH/TO/WAVFILE --sout "#transcode{acodec=ulaw,ab=16,scale=1,channels=1,samplerate=8000}:rtp{dst=239.255.255.244,port-audio=5555}"
g711u
PATH/TO/FFMPEG -re -i PATH/TO/MP3FILE -filter_complex 'aresample=8000,asetnsamples=n=160' -acodec pcm_mulaw -ac 1 -f rtp udp://239.255.255.244:5555
g722
PATH/TO/FFMPEG -re -i PATH/TO/MP3FILE -filter_complex 'aresample=16000,asetnsamples=n=160' -acodec g722 -ac 1 -f rtp udp://239.255.255.244:5555
FW Version <=10.1.42.14 - D717, D735 and D335 only support g711u properly (ulaw option in vlc and mulaw option in ffmpeg). All other phones support g722 as well.
FW Version >= 10.1.42.14 - All phones support g711 as well as g722
The snom phones D3xx, D7xx, PA1 and MP are able to generate a muticast stream. You need to setup a function key for that.
Example
Starting with version 8.9.3.58 incoming multicast audio will be displayed by an icon in the title bar on phones with monochrome displays.
Example monochrome display:
On all other phones the text "PA" will be shown in the status message line.
The concept of Multicast Zones is introduced in version 10.1.x. The configuration is done on the web interface the same as before, with the addition of Zone names.
A new keyevent type F_ZONES is added, so that a function key can be configured for the Multicast Zone feature, using the web interface as shown below.
An example showing the idle screen of D375:
The above softkey will bring up the Multicast Zones screen on the phone interface.
The user can select the zone on which to start the outbound multicast stream. The first number is the zone number, and corresponds to the keypad shortcut. For example, user presses 2 to select Zone 2.
Note: key 0 corresponds to zone 10.
Further Information
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