>> from my point of view, preserving the transmitted events scheduling with a >maximum accuracy is important as this scheduling is part of the musical >information itself. However, except considering that the protocol is >intented to run on a fast local dedicated network, the transport latency >will introduce an important time distortion. Therefore, a mecanism to >compensate for the latency variation seems to me to be necessary. > >RTP timestamps are used for this.
Sure, it may be used for this but it isn't: MIDI events are played at reception time. In MWPP for example, the timestamp is only used to determine wether a packet is too late or not. > >> Another point is the efficient use of the transmitted packets: sending one >packet for each event is probably not the best solution. In this case and >due to the underlying protocols overhead, the useful information part of a >packet may become less than 10% of the packet size. Moreover, hardware >layers such as Ethernet for example, often require a minimum packet size to >operate correctly. > >I think a protocol for realtime MIDI over UDP will always have significant >protocol overhead, I >don't see this as a problem however. Considering a 44 bytes overhead (IP + UDP) + the 4 DMIDI header bytes intended to address a specific node and device, sending a full MIDI data flow (about 1000 3-bytes events per second) requires nearly 400 kbs when the MIDI rate is 31.25 kbs. It's not a problem as long as the corresponding bandwith is available to you. But if you plan to address different devices on the same node (for example using a multiport interface), you should be able to provide each device with an equivalent full MIDI data flow and then the problem seriously increases with the number of devices. --df ---------------------------------------------- Dominique Fober <[EMAIL PROTECTED]> ---------------------------------------------- GRAME - Centre National de Creation Musicale - 9 rue du Garet 69001 Lyon France tel:+33 (0)4 720 737 06 fax:+33 (0)4 720 737 01 http://www.grame.fr
