On Sat, 14 Nov 2009 09:34:15 -0500 Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Sat, Nov 14, 2009 at 8:04 AM, Karl Hammar <karl@xxxxxxxxxxx> wrote: > > > So what is the consensus among the applications, is it e.g. "/mixer/1/ > > volume", "/mixer/a/vol", or what? > > To the best of my knowledge, there is no consensus about the format of > any significant messages sent via OSC. There is no standard way to > generate specific behaviour in an unknown OSC receiver, whether it is > volume control, note generation, or anything else. All the uses of OSC > that I am aware of involve a set of messages specified by the sender > (in the case of, say, the Lemur or Monome control surfaces, or the > Mrmr iPhone app) or by the receiver (in the case of, say, Ardour or > Reaktor). Well it's been wet and windy all day today, so instead of going out I did some more reading :) With this lack of standardisation is there any point in going for OSC with it's quite significant overhead? Netjack also seems to have quite a high overhead, and no specific mechanism for RT syncing audio. It seems that the UDP protocol is already the preferred protocol for a number of streaming media apps (1) for the same reasons as I mooted earlier. Low packet overhead, virtually any packet size, chuck it out as fast as the transport layer can cope with. Maximum packet size for Ethernet is 1500 bytes, but I suggest we really don't want to get anywhere near that big if we are to keep latency down. Off the top of my head, a 'full' frame would hold about 15mS of 1 channel 48kHz 16bit. The downside is no congestion control, so if the network gets congested you will lose packets rather than have them stack up in a (probably high latency) buffer. With just one card talking to the computer I don't think packet loss is a significant problem. With enough bandwidth, I would suggest a simple round-robin system whereby every slave listens continously, but only sends when told to by the master. On the hardware side, that Atmel development kit (2) looks very interesting as a proving ground as it already has both the network and the 48kHz DAC parts built in. For rough testing it could be used to lock a pair of ADCs. TLC4545ID looks like a good (cheap) possibility here. (1) http://www-net.cs.umass.edu/kurose/transport/UDP.html (2) http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4102 -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
