Create audio from packet dumps located in a spooldir

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If you need to get audio from a SIP and RTP packets dump stored in spooldir by voipmonitor sniffer, continue reading.


to have full RTP+SIP captures in a spooldir you get this with following options voipmonitor.conf


You can also use capture rules in a GUI to get full RTP captures only for some IPs/Telnums


Get (SIP+RTP) pcaps and merge them to single file

you need to locate SIP+RTP packet dumps in a spooldir using DATE and HH:MM and call-id header of the call's SIP session

Locate and untar SIP and RTP

Example is for the call with call-id: ad856a3587b477e2f8edc21856c6f2e1 (done at 2021-03-30 14:44) from spooldir with default compression settings

tar --wildcards -xOf '/var/spool/voipmonitor/2021-03-30/14/44/RTP/rtp_2021-03-30-14-44.tar' 'ad856a3587b477e2f8edc21856c6f2e1.pcap*' > tmp/aa/ad856a3587b477e2f8edc21856c6f2e1_RTP_lzo.pcap
tar --wildcards -C /tmp/aa -xzf '/var/spool/voipmonitor/2021-03-30/14/44/SIP/sip_2021-03-30-14-44.tar.gz' 'ad856a3587b477e2f8edc21856c6f2e1.pcap*'

Decompress LZO

you need to decompress RTP packet dump using sniffer binary (by default the RTP packet dumps are additionally compressed with internal fast LZO compression tool)

voipmonitor -kc --unlzo-gui='/tmp/aa/ad856a3587b477e2f8edc21856c6f2e1_RTP_lzo.pcap /tmp/aa/ad856a3587b477e2f8edc21856c6f2e1_RTP.pcap'

Merge SIP and RTP packets together

mergecap /tmp/aa/ad856a3587b477e2f8edc21856c6f2e1_RTP.pcap /tmp/aa/ad856a3587b477e2f8edc21856c6f2e1.pcap -w /tmp/aa/merged.pcap

Use sniffer binary and GUI's codecs binary to generate the audio file

you need to put link of vmcodecs binary into PATH and prepare config file for audio create

create link to vmcodecs binary

to create the link to vmcodecs binary located in ./bin subfolder of voipmonitor's GUI - this is necessary to allow to create audio also from other then g711 codecs (requires working GUI license and GUI installation)

ln -s /var/www/html/bin/vmcodecs /sbin/vmcodecs

create the new config file for audio create

Example content of a file /etc/voipmonitorcliwav.conf file:

ogg_quality = 0.1
saveaudio_afterconnect = yes


the CLI command for generate the audio

voipmonitor --config-file /etc/voipmonitorcliwav.conf -k -v0 -r /tmp/aa/merged.pcap  --json_config='[{"saveaudio":"wav"},{"spooldir":"/tmp/testAu"}]'

Note: the settings done in /etc/voipmonitorcliwav.conf is overriden with the --json-config option, above command will results in wav file in /tmp/testAu folder.