On Mon, 2004-08-30 at 16:56, Julian Rohrhuber wrote:
> osc has quite a good system for timing I think.
> It uses the NTP time server, to create time stamps according to the
> osc time format (64 bit, first 32bit is seconds since 1970, second 32
> is divisions of a second).
> You then simply schedule the packets ahead in time, so the maximum
> lag time is accounted for. This way you get very exact timing.
Yep but OSC doesn't really have a system for timing beyond being able to
specify that timestamp. I mean, OSC doesn't directly interact with NTP
beyond borrowing its timestamp format, does it?
http://www.cnmat.berkeley.edu/OpenSoundControl/OSC-spec.html
NTP is great for synchronising clocks before and during a live jam, but
the various systems also need to start at the same time and go at the
same speed. If one joins in while others are running then it needs to
be able to work out when to start, and when the speed is to change all
the systems need to know about it.
It would be great to work out a TOPLAP standard for time synch, a simple
one that is easy to implement. Does anyone feel like working something
out together? I don't mind taking my system apart and describing it in
detail if it would help, but bear in mind that while it works in
practice without drifting, it is fairly naive.
The time server is here:
http://cpan.org/authors/id/Y/YA/YAXU/perl-music-article/examples/tm-0.1.pl
and the client side stuff is here, in the spread_event_loop() routine:
http://cpan.org/authors/id/Y/YA/YAXU/perl-music-article/examples/feedback-0.1.pl
I'm using the 'spread' protocol and libraries to send timing information
around out of programmer's laziness, it would be better to use OSC for
this. When it comes to sending messages to SuperCollider, I'm using
timestamped OSC bundles, with a little bit of buffering as Julian
describes.
Or does an OSC based timing protocol already exist without me knowing
about it? How does SuperCollider deal with this? Klippav, how do you
keep SuperCollider and Max in synch?
alex
Received on Mon Aug 30 2004 - 17:15:55 BST