- Zeta Instrument Processor Interface
Zeta Instrument Processor Interface (ZIPI) was a research project initiated by
Zeta Instrumentsand UC Berkeley's CNMAT(Center for New Music and Audio Technologies). Introduced in 1994in a series of publications in Computer Music Journalfrom MIT Press, ZIPI was intended as the next-generation transport protocolfor digital musical instruments, designed with compliance to OSI model.
The draft working version of ZIPI was primarily aimed at addressing many limitations of
MIDI(Musical Instrument Digital Interface). Unlike MIDI which uses a peer-to-peer serial portconnection, ZIPI was designed to run over a star networkwith a hub in the center. This allowed for faster connection and disconnection, because there was no need to daisy-chainmultiple devices. Ethernet 10Base-Twas used at the physical layer, but the authors tried to distance themselves from physical implementation as much as possible.
There were proposals for
querying device capabilities, patch names and other system and patch parameters, as well as uploading and downloading samples into device memory.
ZIPI used completely new event system and complex note addressing scheme. At the heart of the new protocol was Music Parameter Description Language [http://www.cnmat.berkeley.edu/ZIPI/mpdl.html] seen as a direct replacement to MIDI events.
The main change was the addressing of devices. Instead of dealing with 16 channels each having one single bank/patch combination at a time, MPDL was designed to deal with up to 63 "Families" each capable of addressing 127 "Instruments" which could actually be combined from different physical devices. Each instrument was capable of playing 127 notes, just like in MIDI. This created a possible 1,016,127 of note addresses, and each of them could possibly have a different program associated with it (although the developers hinted that devices would impose some practical limit upon the number of simultaneously available programs). Each note could then be triggered, retriggered or released, with its pitch, loudness, pan position etc. changed in a series of note-specific messages. The events could be grouped, providing the possibility to change parameters of several notes, or even instruments, at once.
The unusual addressing method provided for implementing non-standard scenarios like MIDI guitar controller, where each of the six strings would be controlled independently. Also, the instant note-on capability was supposed to improve on deficiences of note detection (tracking) on lower strings in guitar MIDI systems - the note would begin sounding as a noise or some undefined low note, but once the logic has tracked the actual pitch , it would be sent by a follow-up message without retriggering the note.
Most events were direct carryovers from MIDI, although some were given more pronounceable names in order to avoid
ambiguity. The resolution of control message parameters could be any multiple of 8-bit, potentially extending 7-bit resolution typical of MIDI to 32 or more bits.
There were also some higher-level messages corresponding to advanced program parameters, such as
modulation, envelopes and 3D spatialization of voices.
Outcome of the project
Although ZIPI provided many outstanding new features, they did not line up well with existing MIDI-based implementations. Its complex note addressing scheme was the main factor in the lack of its adoption.
As no commercial devices were released supporting ZIPI, the introduction of the superior "
FireWire" (IEEE1394) standard and the sufficiency of MIDI for most applications soon led to the practical demise of the project. The [http://www.cnmat.berkeley.edu/ZIPI/ web site] that is home to the ZIPI project asserts that IEEE1394 "supersedes ZIPI in every respect," mainly because it doesn't require a hub and has simpler interface requirements for modern devices. IEEE 1394 is much faster than ZIPI, to be sure. IEEE1394 also includes an isolated power distribution scheme and hot plugging (devices may be added or removed more conveniently), both of which were not supported in ZIPI.
The developers continued on to work on
OpenSound Controlprotocol, currently supported in a wide variety of musical instruments, sensors and software [http://opensoundcontrol.org/osc-application-areas] .
* [http://www.cnmat.berkeley.edu/ZIPI/ CNMAT: ZIPI project]
* [http://mitpress.mit.edu/catalog/search/default.asp?qtype=t&query=ZIPI ZIPI publications in Computer Music Journal]
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