An Implementation Guide for RTP MIDI
RFC 4696
Network Working Group J. Lazzaro
Request for Comments: 4696 J. Wawrzynek
Category: Informational UC Berkeley
November 2006
An Implementation Guide for RTP MIDI
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2006).
Abstract
This memo offers non-normative implementation guidance for the Real-
time Protocol (RTP) MIDI (Musical Instrument Digital Interface)
payload format. The memo presents its advice in the context of a
network musical performance application. In this application two
musicians, located in different physical locations, interact over a
network to perform as they would if located in the same room.
Underlying the performances are RTP MIDI sessions over unicast UDP.
Algorithms for sending and receiving recovery journals (the
resiliency structure for the payload format) are described in detail.
Although the memo focuses on network musical performance, the
presented implementation advice is relevant to other RTP MIDI
applications.
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RFC 4696 An Implementation Guide for RTP MIDI November 2006
Table of Contents
1. Introduction ....................................................2
2. Starting the Session ............................................3
3. Session Management: Session Housekeeping ........................6
4. Sending Streams: General Considerations .........................7
4.1. Queuing and Coding Incoming MIDI Data .....................11
4.2. Sending Packets with Empty MIDI Lists .....................12
4.3. Congestion Control and Bandwidth Management ...............13
5. Sending Streams: The Recovery Journal ..........................14
5.1. Initializing the RJSS .....................................16
5.2. Traversing the RJSS .......................................19
5.3. Updating the RJSS .........................................19
5.4. Trimming the RJSS .........................................20
5.5. Implementation Notes ......................................21
6. Receiving Streams: General Considerations ......................21
6.1 The NMP Receiver Design ....................................22
6.2 High-Jitter Networks, Local Area Networks ..................24
7. Receiving Streams: The Recovery Journal ........................25
7.1. Chapter W: MIDI Pitch Wheel (0xE) .........................30
7.2. Chapter N: MIDI NoteOn (0x8) and NoteOff (0x9) ............30
7.3. Chapter C: MIDI Control Change (0xB) ......................32
7.4. Chapter P: MIDI Program Change (0xC) ......................34
8. Security Considerations ........................................35
9. IANA Considerations ............................................35
10. Acknowledgements ..............................................35
11. References ....................................................35
11.1. Normative References .....................................35
11.2. Informative References ...................................36
1. Introduction
[RFC4695] normatively defines a Real-time Transport Protocol (RTP,
[RFC3550]) payload format for the MIDI (Musical Instrument Digital
Interface) command language [MIDI], for use under any applicable RTP
profile, such as the Audio/Visual Profile (AVP, [RFC3551]).
However, [RFC4695] does not define algorithms for sending and
receiving MIDI streams. Implementors are free to use any sending or
receiving algorithm that conforms to the normative text in [RFC4695],
[RFC3550], [RFC3551], and [MIDI].
In this memo, we offer implementation guidance on sending and
receiving MIDI RTP streams. Unlike [RFC4695], this memo is not
normative.
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RFC 4696 An Implementation Guide for RTP MIDI November 2006
RTP is a mature protocol, and excellent RTP reference materials are
available [RTPBOOK]. This memo aims to complement the existing
literature by focusing on issues that are specific to the MIDI
payload format.
The memo focuses on one application: two-party network musical
performance over wide-area networks, following the interoperability
guidelines in Appendix C.7.2 of [RFC4695]. Underlying the
performances are RTP MIDI sessions over unicast UDP transport.
Resiliency is provided by the recovery journal system [RFC4695]. The
application also uses the RTP Control Protocol (RTCP, [RFC3550]).
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