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Page 40 ï~~Recent Developments of MidiShare Dominique Fober, St6phane Letz, Yann Orlarey GRAME Research Laboratory, 6 quai Jean Moulin, BP 1185, 69202 LYON Cedex 01, France Email: [fober,letz,orlarey] @rd.grame.fr Abstract MidiShare is a real-time multi-tasks musical operating system first presented at the ICMC 89. Based on a client/server model, MidiShare offers fast and accurate real-time performances, multi-platform support, powerful inter-application communications, while considerably simplifying the development of complex real-time musical applications. MidiShare has been used by our institution for internal developments for more than 7 years. It was awarded by the Apple Trophy 89 and the Paris-Cite 90 prize. Today, it is evolving, toward a distributed multi-platform environment. The poster session will present and demonstrate its recent developments: the MidiShare environment, the developer's kit and documentation, multi-platform development issues, libraries, Ethernet support, compatibility with other systems and third parties applications. 1. Introduction MidiShare is a real-time multi-tasks musical operating system originally developed for the Macintosh by Y. Orlarey and H. Lequay [Orlarey, Lequay, 1989] and recently ported on PC/Windows by D. Fober [Fober et al. 1995]. MidiShare has been designed in response to commonly met problems in the development of real-time musical applications. Particularly, standard operating systems on micro-computers don't take account of real-time memory management or critical resources sharing. Time management is often expensive and is generally not suitable for the complex real-time operations required by musical applications. Moreover inter-application communications, when they exist apart from side effects communication, don't take account of time and can't be used for real-time communication. MidiShare provides its client applications with the appropriate solutions and constitutes an efficient toolbox for the developers. 2. MidiShare environment 2.1 Data representation. MidiShare offers high level representation for musical data. Instead of using MIDI byte packets, it provides its client applications with fully structured events, time stamped with a millisecond resolution. These events include both the MIDI and the MIDIFile typologies. They also include various internal representations, from Notes (shortcut for a Key On and its associated Key Off) to tasks (client applications functions that need to be called at precise dates). Their semantic can be easily extended, they constitute the base of inter-application communications. To allocate, copy and dispose these events, MidiShare includes a real-time memory manager able to operate at interrupt level. 2.2 Time management MidiShare maintains the current date of the system with a Ims resolution and supports accurate and transparent SMPTE synchronization. It includes a scheduler in charge of delivering events at their falling dates to the communication manager. The scheduling algorithm [Orlarey, 1990] ensures a very low and constant time overhead per event, even when the scheduler is heavily loaded. Client applications needn't worry about time: they can schedule events in the future (including tasks, messages for itself or other applications), MidiShare ensures by means of its communication manager, that these events will be rendered at the right date, according to their semantic. 2.3 The communication The MidiShare communication manager routes the events received from the scheduler and from the input drivers to the client applications, the output drivers or the tasks manager, according to the events type and the connection set between applications. This connection set can be dynami - cally configured by the users. Inter-application communications are transparent for the developer but provide users with a simple and efficient way to freely assemble applications in a collaborative network. Fober et al. 40 ICMC Proceedings 1996
Page 41 ï~~2.4 Real-time tasks management MidiShare offers several mechanisms to control the real-time behavior of an application. Function calls can be scheduled in the future and are automatically achieved by MidiShare at interrupt level as soon as the specified date is due. Incoming MidiShare events as well as global context changes (new clients starting a session, modifications of the connections between applications, SMPTE synchronization changes, etc.) can be processed in real-time by user defined "alarms". figure 1: MidiShare internal structure overview 3. Recent Developments 3.1 Ethernet support MidiShare communication scheme has been extented to real-time communication over Ethernet [Fober, 1994] in order to enlarge interapplications collaboration to inter-stations collaboration. Our implementation respects the traditional services of the network while allowing at least 25 stations to transmit a full MIDI data flow. Users can see the remote stations like any other MidiShare applications and can include them within their communication scheme using the same way and the same tools. 3.2 OpenShare Since MidiShare first version, several other musical operating systems appeared (and sometimes disappeared). On the Macintosh, the main ones are Apple Midi Manager [Apple Computer Inc., 1990] and Opcode OMS [Opcode, 1993]. Open Share has been developed to allow applications from these different systems to run simultaneously on the same machine and to collaborate using the MidiShare inter-application communication manager. Via Open Share, Midi Manager and OMS applications can also benefit of the Ethernet support. 3.3 Internet Several new developments are related to Internet: Â~ msNetPlayer, a MidiShare based MIDIfile player Plug-in for Netscape 2.0. Â~ a set of MidiShare-JAVA classes for Macintosh and PC/Windows platforms. Â~ an extension of MidiShare inter-application communications over TCP/IP. 3.4 Third parties applications Various MidiShare compatible applications are provided by third parties developers. Among them: " Inter-Actors, by TimeTech, an innovative software for controlling MIDI devices. ICMC Proceedings 1996 41 Fober et al.
Page 42 ï~~right ou 0 "". mRate 22 1 / mI t. 5 "- Wmx ix 77 i Speed Â~05000 IT,,,,,+!; stereo 0 n~ormal levels 0 figure 2 Inter-Actors " Symbolic Composer, by Peter Stone (http://www.xs4all.nl/-psto/), a Common Lisp object-oriented music composition language. Â~ Phonogramme, by Vincent Lesbros (http://www. univ-paris8.fr/--gaiv/about - phono. html) a program to create, transform or compose sounds based on time/frequency representations. " Dmix, by Daniel Oppenheim (ftp://ftpccrma.stanford.edu/pub/dmix/), a state of the art environment for music composition and performance based on ParcPlace Smalltalk VisualWorks 2.5. 4. The developer's kit The MidiShare developer's kit is freely available on the Internet via our ftp server: ftp://ftp.grame.fr/pub/MidiShare, or via the MidiShare web page: http://www.grame.fr/ english/MidiShare.html. It includes a full programmer documentation, a C tutorial and full source code of several applications. Interested developers can also subscribe to the MidiShare mailing list to be periodically informed. 4.1 Multi-plateform support MidiShare currently runs on Macintosh, Windows (from 3.1 to Windows 95) and Atari. The API is the same on the three platforms and source code can be easily ported between them. Interface files exists for several languages: * C, Common Lisp, Pascal, SmallTalk for the Macintosh; * C, Delphi, Common Lisp for Windows; * Lattice C, Turbo C and Mark Williams C for the Atari. Several of them come from users contributions. Inline help is available for the MPW environment on the Macintosh. 4.2 Additional libraries Two additional libraries are also provides: a MIDI files management library and a Player library. The MIDI files library is intended to read and write MIDI format files and to convert them into MidiShare events sequences. The Player library is intended to facilitate the development of a complete multi-tracks MidiShare sequencer: each Player is a MidiShare application, can manage up to 256 tracks, supports three different synchronization modes, transparent events chase and loop markers. The MIDI files library is compatible with all the supported platforms. The Player library is provi - ded for the Macintosh and for Windows. 5. Acknowledgments The authors would like to thanks all the persons who contributes to MidiShare by providing interface files and applications. Olivier Carbonnel, Mark Bilton, Vassyli Lygeros, Michel Rousset, Gil Muller, Nicolas Roux have directly contributed to the kernel development. Colin Whyles and Lorien Dunn offered to support the Atari version on the Falcon. Thanks also to J.P. Smets, Georges Bloch, Laurent Veliscek, Olivier Delerue, Thierry Carron whose help has been very useful. References [Apple Computer Inc., 1990] MIDI Management tools 2.0. Apple Programmers Developers Association. [Fober, 1994] Fober D. Real time, musical data flow on Ethernet and MidiShare software architecture. Proceedings of the ICMC, 1994, ICMA, San Francisco. [Fober, Letz, Orlarey 1995] MidiShare, un systeme d'exploitation musical pour la communication et la collaboration - Proceedings of the Journ6es d'Informatique Musicale JIM95, Paris [Grame, 1990] MidiShare Developer Documentation. Grame 1990, Lyon [Opcode, 1993] DougWyatt, Opcode MIDI System, Application and Driver Interface, Opcode Systems, Inc., 1993 [Orlarey, 1990] Orlarey Y. An Efficient Scheduling Algorithm for Real-Ti me Musical Systems. Proceedings of the 1CMC, 1990, ICMA, San Francisco. [Orlarey, Lequay, 1989] Orlarey Y., Lequay H. MidiShare:a Real Time multi-tasks software module for Midi applications. Proceedings of the ICMC, 1989, ICMA, San Francisco. Fober et al. 42 ICMC Proceedings 1996