[chuck-users] syncing computers with OSC

[Ge Wang]

In one particular piece for PLOrk (and later SLOrk), TBA (orchestral live 
coding), we actually sent occasional global synch messages via OSC 
(similar in concept as the system clock synchronization Rob mentioned), 
which then informed a ChucK shred (on each machine) that kept track of a 
localized, synchronizable "now" (it moved at the same rate as 'now', but 
could be reset at will).

This is not "sample-accurate" across machines, but make things more 
"sample-precise" and subject to the initial global synch and eventual 
clock drifts.  It allowed us to more precisely synchronize to phase 
computed from time (e.g., via the localized "now") and to work more 
easily with certain types of near audio rate processes.  Once in a while, 
we would manually trigger a global synch to combat effects of clock 
drifts.

I am not sure how well this generalizes, but it perhaps presents another 
option to synchronization.

Ge!

On Tue, 27 Jan 2009, dan trueman wrote:

> well, we actually do a lot of synchronization over the network, and it 
> works amazingly well (with UDP). it's nowhere near sample accurate, but 
> it's musically powerfully accurate, and it's important to keep in mind 
> that "accuracy" in something like plork is not easy to define, since all 
> the sound sources (multichannel hemispheres) are spatially separate and 
> there is a lot going on with phase -- the speed of sound becomes a major 
> factor! if you are mixing multiple computers with a mixer, then i can 
> well imagine that network sync will be insufficient, but when the room 
> is doing the mixing, it is almost overly accurate; it feels un-natural 
> how well a large ensemble can sync this way (and it is!).
> 
> dt
> 
> On Jan 27, 2009, at 7:39 PM, kevin wrote:
>
>       nobody in plork or slork is synced, which is, in my opinion, one
>       of its stronger points. the music sounds more attached to the
>       performers and less attached to a computer, if that makes any
>       sense.
>
>       intra-computer sample-accurate syncing over a network is
>       difficult because neither TCP nor UDP are suited to such things.
>       TCP guarantees packet delivery by requiring a call-back
>       (sometimes called a handshake). if the sender does not receive a
>       call back, it assumes that the packet was dropped and then
>       resends info. this works for things like websites, where the
>       request is not time-sensitive.
>
>       UDP on the other hand, does NOT guarantee packet delivery, and
>       thus expects no call back. when packets get dropped over UDP,
>       the sender is not notified, so the sender will not resend. this
>       is better in situations like VoIP, where a single dropped packet
>       will not ruin the audio stream (sure, there'll be a noticeable
>       glitch). the idea is that if you're talking to someone, you'd
>       rather hear a glitch than hear that packet arrive 5 seconds
>       later.
>
>       without modification, neither are sufficient for real-time
>       synchronization.
>
>       and even if they are, wifi bandwidth will definitely get in your
>       way. i haven't looked at any numbers, but i'd intuitively guess
>       that wifi drops more packets than wired.
> 
> 
>
>       On Tue, Jan 27, 2009 at 4:15 PM, <james.hurlbut at utoronto.ca>
>       wrote:
>             I see. so none of the Plork pieces are dependant on
>             precise synchronization? I guess because I am coming
>             from a dance music background its more critical for
>             me that the music is running off a master clock. I
>             was thinking that Chucks strongly timed quirkiness
>             would enable me to send sample accurate osc messages
>             albeit at a very high speed cost. I suppose I can
>             try midi but was hoping for a wifi solution.
> 
> 
> Quoting dan trueman <dtrueman at princeton.edu>:
>
>       i don't think there is any way to get
>       sample-accurate sync via
>       conventional networking...
>
>       dt
>
>       On Jan 27, 2009, at 6:51 PM,
>       james.hurlbut at utoronto.ca wrote:
>
>             Hi, chuck newbie here. I am wondering
>             what the best way to get sample
>             accurate sync between two laptops. I
>             have tried using
>             http://music.princeton.edu/~dan/plork/autosocket_chuck.zip
>             but the two
>             computers receive the 16th beats at
>             slightly off times. I also have
>             tried sending an osc message every
>             sample or 100 samples but that
>             completely bogs down the machine. Is the
>             solution to have one machine do
>             all the audio and another just send
>             program changes? Thanks,
>
>             James
> 
> 
>
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