Hello,Last week I sent out an email to the list about a synchronization protocol I was working on with Perry and Dan for PLOrk. I thought I'd share the current product and invite you all to check it out, try it out, and give me feedback if you'd like. All relevant materials can be found at:
The protocol that was rather successful in testing is the Time-Tagged OSC (TOSC) and the source code for all that code is in the appropriately named folder. Apologies for the lack of comments in the source code for the new classes I wrote. The sample client and server programs I wrote have some comments which pretty much covers the main differences from OSC to TOSC. In the final report pdf file, the TOSC section will outline what's going on in general so that's worth checking out. You can also check out a demo that compares a controlled recording/TOSC test/OSC test in the Demo.tar file (it plays in Audacity).
I'll be continuing to work on this project next year for my senior thesis. There are a number of things I already want to fix/work on, but recommendations/suggestions are, again, very welcomed!
1. Code everything into the ChucK source code. Everything is written in ChucK right now so it can be made more efficient by coding directly into the source.
2. Improve the NTP protocols. My algorithms to synchronize clocks/calculate good time-to-open offsets are very, very, very crude and can certainly be improved on. Better NTP = better synchronization.
3. Netclock - Making TOSC interoperable with Netclock would be useful, as Kassen mentioned in an earlier email.
Thanks!
Best,
Mark
On Apr 29, 2009, at 1:30 PM, Kassen wrote:
Mark,
That seems quite similar in approach to this;
http://netclock.slab.org/wiki/index.php/FAQI'd like to invite you to have a look at that and perhaps join the
mailinglist on it. If these two could be made inter-operable it could
be used to sync ChucK to a range of other open source music and
graphics systems.
Yours,
Kas.
2009/4/29 Mark Cerqueira <mcerquei@princeton.edu>:
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 <signal.automatique@gmail.com>
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 <dtrueman@princeton.edu>
wrote:
On Apr 29, 2009, at 11:36 AM, Tom Lieber wrote:
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.
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