Re: [chuck-users] other ways to live-code with time

I've spent this semester doing some independent work with Perry and Dan on how to get good network synchronization for PLOrk so that we don't need a conductor and can focus on doing other things. I implemented a Time-Tagged OSC protocol similar to the stuff Adrian Freed does. Essentially the protocol first synchronizes everyone's clock via a protocol that is based on the Network Time Protocol (NTP). On the PLOrk network, one machine runs as a NTP Server and all others run as NTP Clients - NTP Clients calculate the offset of their VM time to the server VM time, as well as keeping track of the round-trip time of packets sent to synchronize to account for that in the offset. Once the clocks are synchronized, packets sent over the network include the current time (which should be synchronized pretty closely if the above protocol works) and a time-to-execute offset. When someone receives the packet they add the current time plus the time-to-execute offset and schedule the packet to be opened only at that time. The NTP-like synchronization protocol I described above also keeps track of all RTTs and broadcasts to everyone what a good time-to-execute field is (i.e. make sure we give enough time for the packet to travel over the network). If all works well, everyone should open the packet at the same time. Not sure how successful this implementation will be...I'm testing it tomorrow during PLOrk rehearsal! If anyone's interested in seeing the code/my write-up I can pass around a copy once I *crosses fingers* complete it and hand it in on Monday. Best, Mark Tom Lieber wrote:

On Wed, Apr 29, 2009 at 12:28 PM, Kassen wrote:

Yeah, a wireless network. And for whatever reason (AirPort updates, OS X updates, variation in laptop hardware), timing issues got worse from the previous year. Actually, I don't know how this was solved in the end, because I think things had improved by the end (or maybe we stopped relying on the network so much and I didn't notice)...

On Wed, Apr 29, 2009 at 12:27 PM, Daniel Trueman wrote:

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On Apr 29, 2009, at 11:36 AM, Tom Lieber wrote:

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A lot of rehearsal time in PLOrk this past semester was dedicated to synchronizing the performers because we lacked good network synchronization.

i've come to view this as a feature, not a bug... ;--}

I chose my words carefully! There's no way I can view getting everybody to practice being in sync as a bad thing, but having the option of good network synchronization means we can make pieces where players can give their full attention to something else, like making patterns in beepsh.