Scripting Language, My Shiny Metal Arse

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Scripting Language, My Shiny Metal Arse
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shtoom
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voice over IP, in python
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WARNING talk may contain rant
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and occasional cheap shots
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what's VoIP?
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telephony over the internet
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why is VoIP interesting?
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cheap calls
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use IP network for voice as well as data
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take the telephone network away from the telcos
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... it's not like they're doing much with it
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enable the next round of cool voice applications
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VoIP clients
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hardware phones
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software phones
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gateways
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VoIP protocols
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a short and biased summary
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first, there was H.323
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it sucks
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a lot
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don't let telcos design internet protocols
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this goes double for the ITU
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from cheapshot import X.400, X.500
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SIP
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IETF does telephony
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SIP is complex(the S isn't for Simple)
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the problem is complex
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fortunately, we don't need all of it
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UDP based, client-server(or client-server-client-
server)
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SIP is just for control
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setup, negotiation, call control
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RTP
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a little lump of audio in each UDP packet
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every 20ms
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multiple audio formats
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or video
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RTP is just the transport
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SIPRTP phone
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other protocols
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standards will win
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even if they're not all that good
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shtoom
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why on earth did I attempt this?
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a scriptable phone
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make my H.323 pain go away
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from cheapshot import c
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hopefully help stamp out ignorance
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it's just a scripting language
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only suitable for prototyping
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existing software phones not so good
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so write a better one
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other voice applications
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(voice applications ltgt voice recognition)
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why choose python?
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hopefully you all know the answers to that one
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a few additional reasons
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twisted
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nice UI toolkit
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many of them
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so why not use python?
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performance
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it's just a scripting language, after all
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timing and performance
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timing?
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an audio packet, every 20ms
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but PC clocks run at 100Hz
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miss by a fraction -gt 10ms delay
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this is very noticeable
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approaches to timing
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approach 1 setitimer
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approach 2 reset the timer
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approach 2b cheat
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approach 3 LoopingCall
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LoopingCall works, and works well
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performance?
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audio processing
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audio mixing
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a pile of mathematics
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raw python
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psyco
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numeric
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pyrex
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reimplement the performance critical bits
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duh...
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audioop
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use the standard library
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the best optimization is one that someone else
already wrote
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and the winner is...
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and again, for the managers
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but I prefer this one
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scripting language, my arse
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is this fast enough?
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audio encoding
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other people have done this already
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so use their work
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ULAW, GSM 06.10, G.72x, speex
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wrapping C code is easy
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yay (again) for Pyrex
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shtoom today
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second major release
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cross-platform
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kde/qt, gnome/gtk, tk, cocoa (soon), wx (soon),
command-line
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software phone usable
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firewall discovery and traversal
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(an aside UPnP)
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from cheapshot import Microsoft
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other applications
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doug, the application server
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conclusions
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python isn't just a scripting language
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python is fun
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VoIP is very cool right now
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VoIP in python is cool
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therefore, python is cool
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(No Transcript)
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no, really
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read the paper
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use the phone
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shtoom
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questions, abuse, anyone I forgot to insult?