[AVT] summary for draft-lazzaro-avt-mwpp-midi-nmp-00.txt
John Lazzaro <lazzaro@CS.Berkeley.EDU> Fri, 07 December 2001 19:19 UTC
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Date: Fri, 07 Dec 2001 11:17:26 -0800
From: John Lazzaro <lazzaro@CS.Berkeley.EDU>
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To: avt@ietf.org
Subject: [AVT] summary for draft-lazzaro-avt-mwpp-midi-nmp-00.txt
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Hi everyone, Sorry for the delay, this is the summary for draft-lazzaro-avt-mwpp-midi-nmp-00.txt, I'll be presenting in the Monday PM session. --- summary begins here --- MWPP (the MIDI Wire Packetization Protocol, draft-lazzaro-avt-mwpp-midi-nmp-00.txt) is an RTP packetization to support "band practice over the Internet" applications, where musicians located in different locations perform together as if they were in the same room. The "M" in MWPP is MIDI, a control stream that electronic musical instruments generate to describe physical gestures musicians make (press down piano keys, release them, etc). We've prototyped MWPP in sfront, our freely-redistributable softsynth: http://www.cs.berkeley.edu/~lazzaro/sa/ http://www.cs.berkeley.edu/~lazzaro/nmp/ so Linux users can download sfront and play around with demos based on MWPP. We also presented a "case for NMP" paper at NOSSDAV this summer, that describes how MWPP works in practice: http://www.cs.berkeley.edu/~lazzaro/sa/pubs/pdf/nossdav01.pdf The presentation in SLC will hit the following points: o A few slides introducing the application. o MWPP controversies surrounding time: unlike most audio packetizations, playout buffering for jitter removal is infeasible for MWPP, because end-to-end latency needs to be quite low for musical performance to work. MWPP is designed for MIDI commands to be executable on receipt by the receiver -- the receiver models the nominal latency of the link, and uses its knowledge of the semantics of each type of MIDI command to "do the right thing" if a packet is "late." o MWPP controversies surrounding resiliency: MIDI is a very fragile command language -- a single lost command is indefinitely catastrophic (think of what happens if the "turn this note off" command is lost -- the note "hangs" and plays forever!). MWPP has a FEC-like reliability system built into the protocol to address this issue, which is multicast compatible, and only uses the standard RTCP SR/RR reports. o MWPP controversies surrounding MPEG: MWPP was designed for use with MPEG 4 Structured Audio (a normative softsynth that is part of MPEG 4 Audio, which our sfront prototype uses). However, we envision most users of MWPP to be non-MPEG-4 softsynth users, since in practice Structured Audio has not taken off in the softsynth marketplace yet. So, MWPP supports two types of underlying transport: "RFC-generic" for MPEG 4 Structured Audio folks, and raw RTP for non-MPEG folks. Finally, the presentation doesn't exist yet -- I'm starting it as soon as I send this summary off to the list :-). So, if you have requests for topics to cover, or if you think these topics above are not appropriate, send me email and I'll adapt the talk to suit the needs of the WG. Thanks! --john lazzaro lazzaro@cs.berkeley.edu _______________________________________________ Audio/Video Transport Working Group avt@ietf.org http://www1.ietf.org/mailman/listinfo/avt
- [AVT] summary for draft-lazzaro-avt-mwpp-midi-nmp… John Lazzaro