RTMMoIP RTMMoIP

Alfredo Terzoli / Mosioua TsietsiAlfredo Terzoli / Mosioua Tsietsi

A conversation becomes A conversation becomes DATADATA

And it is tranported…And it is tranported…

Another view!Another view!

VoIP bandwith VoIP bandwith calculationcalculation

• Let’s get more specific on B/W Let’s get more specific on B/W usage, for AUDIO transmissionusage, for AUDIO transmission

• Two families of CODECS: Two families of CODECS: – wave coding wave coding

• unrestricted, any sound (sound engineering)unrestricted, any sound (sound engineering)

– vocoding vocoding • good for voice, can reach very low bitratesgood for voice, can reach very low bitrates

• kbps: kilo bits per second (here kbps: kilo bits per second (here kilo=1000, not 1024!) kilo=1000, not 1024!)

‘‘Vocoders’ for Videos?Vocoders’ for Videos?

Voice Synthesisers & Voice Synthesisers & VocodersVocoders

• A voice synthesiser includes a A voice synthesiser includes a vocoder of some type, naturallyvocoder of some type, naturally

• In fact, using a voice synthesiser one In fact, using a voice synthesiser one can substantially reduce the can substantially reduce the bandwidth needed for the bandwidth needed for the transmission of voice. HOW?transmission of voice. HOW?

• (BTW, who knows how MIDI works?)(BTW, who knows how MIDI works?)

B/W consumption of a few B/W consumption of a few codecscodecs

VoIP bandwith VoIP bandwith calculationcalculation

VoIP bandwith VoIP bandwith calculationcalculation

• Bandwidth calculators at:Bandwidth calculators at:– http://www.newport-networks.com/http://www.newport-networks.com/

pages/voip-bandwidth-calculator.html pages/voip-bandwidth-calculator.html (btw, the white paper distributed to you on b/w calculation (btw, the white paper distributed to you on b/w calculation

comes from newport-networks)comes from newport-networks)

– http://www.packetizer.com/voip/http://www.packetizer.com/voip/diagnostics/bandcalc.htmldiagnostics/bandcalc.html

Reducing overheadReducing overhead

• cRTP compact RTP (RFC 2508):cRTP compact RTP (RFC 2508):– From 40 to 2 to 4 bytes, substantialFrom 40 to 2 to 4 bytes, substantial

• Trunking: same packet transport Trunking: same packet transport more than one conversation (of more than one conversation (of course, can be used only if on a course, can be used only if on a trunk)trunk)

Questions?Questions?