[SPAM] Re: MSN Protocol documentation

Felipe Contreras felipe.contreras at gmail.com
Tue Feb 12 04:46:24 EST 2008

On Feb 12, 2008 6:58 AM, Youness Alaoui <kakaroto at kakaroto.homelinux.net> wrote:
> Hi,
> Thanks!
> There is actually an open source codec for both the ML20 video codec (libmimic thanks to Ole Andre) and for the Siren audio codec (libsiren
> thanks to myself :p) The audio can work without problems using the siren codec, and the webcam feature (unidirectional) works just fine with
> the ML20 codec.. the problem is with the bidirectional audio+video which uses WMV3.. libavcodec has an open source implementation of the WMV3
> codec, but it only has the decoder, not the encoder.
> Note that MSN has a lot of different v/v protocols..
> 1 - The 'old style' video call which uses a very old protocol and is still there only for interoperability with windows messenger (not WLM).
> That protocol is compatible with gnomemeeting.
> 2 - The 'Video Call' feature which is bidirectional audio and video and uses the new MSNP2P protocol for the signaling, WMV3 video codec and
> Siren audio codec
> 3 - The 'Computer Call' feature which is bidirectional audio and uses SIP/RTP and supports multiple different possible codecs (which are
> x-msrta, Siren, G722.1 (clock rate of 16000), x-msrta, AAL2-G726-32, G723, PCMA and PCMU (clock rate of 8000)).
> 4 - The 'Webcam' feature which is unidirectional video only, using MSNP2P for signaling and the ML20 codec
> 5 - the 'Voice clips' feature which is unidirectional audio, in form of 'clips' of a maximum of 15 seconds in length, uses MSNP2P and the
> Siren codec.
> (This should probably go into the wiki :p)
> So from all of these implementation, None of them worked for a long time, apart from the 'old style video call' which aMSN implemented
> using a modified version of linphone in the early 2001. Then we dropped it because it became impossible to maintain. Then Ole Andre reverse
> engineered the ML20 codec and made an open source library for it, then the webcam feature was added in some clients (like aMSN), then I
> reverse engineered the Siren codec and made an open source library for it, then voice clips were added into aMSN, and now. I was also able to
> get the 'Computer call' feature to work using SIP and PCMA as codec, but I never incorporated that into aMSN (because it depends on many libs
> and MSNP13). And now finally, I'm working on the 'Video Call' feature.
> In short, yes, there is already a solution for MSN video using aMSN and it works great on Mac, and it's been there for almost 3 years now.
> The Audio/Video codecs are open source, so you won't need mplayer or 'stolen' dlls...
> But you can't get a real-time audio conversation. For Audio, you can still use the 'voice clips', but that's annoying.. but hopefully, soon
> we'll be able to ship a working audio AND video implementation.
> Hope that helps!

Great stuff!

This should definitely go in the wiki :)

Felipe Contreras

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