[PD] multi-pc synchrony

[Hans-Christoph Steiner]

With NTP and no tricks, you can get 1-2ms of accuracy, if you buy a  
external clock sync device, you can get 10 microseconds.  I don't have  
a specific software package in mind, its more a technique.

.hc

On Oct 10, 2009, at 5:03 AM, Brian FG Katz wrote:

> Dear Mans-Christian,
>
> This is an interesting idea. I first pose a question, to see if it is
> suitable for the problem as I understand it. First, you assume that  
> the CPU
> clocks of all machines are synchronized at a sub-sample level. Now,  
> if you
> send a message for an event to occur at t0+20msec, how precise is this
> timing executed? Can it execute the function in mid-buffer?
>
> Thanks for your help.
>
> -Brian
>
> ---
> Brian FG Katz, Ph.D
> Audio & Acoustique
> LIMSI-CNRS
> BP 133
> F91403 Orsay
> France
> tel. (+33) 01 69 85 81 55
> fax. (+33) 01.69.85.80.88
> e-mail Brian.Katz at limsi.fr
> web_theme: http://www.limsi.fr/Scientifique/aa/thmsonesp/
> web_group: http://www.limsi.fr/Scientifique/aa/
>
>
> -----Message d'origine-----
> De : Hans-Christoph Steiner [mailto:hans at at.or.at]
> Envoyé : jeudi 8 octobre 2009 19:16
> À : Brian FG Katz
> Cc : pd-list at iem.at
> Objet : Re: [PD] multi-pc synchrony
>
>
> If you use some kind of time-tagging, which some implementations of
> OSC support, then you add add a bit of latency to the whole system and
> use that to reduce the inter-machine latency.  The basic idea is that
> each message has a time tag that marks when that message should take
> effect.  Then you put that time tag 20ms in the future when you send
> it, every machine should have it within 20ms, and then they'll all
> execute the message at the same time.
>
> .hc
>
> On Oct 8, 2009, at 6:27 AM, Brian FG Katz wrote:
>
>> Dear PD-ers,
>>
>> We are working on an installation with 4 machines running PD to feed
>> 157
>> loudspeakers. We are interested in reducing latency to a minimum
>> between
>> channels, and especially between machines. The inter-channel latency
>> in less
>> than a sample, so all is fine there. For inter-machine latency, we
>> arrive at
>> differences on the order of 10msec, close to our minimum audio-
>> buffer length
>> of 11msec. Any small audio-buffer and we get audio artifacts.
>>
>> We are using a word clock synchronizer (Nanosyncs HD; Rosendahl),
>> but I
>> don't think that does latency synchronization.
>>
>> My question, is there another means to improve inter-machine latency
>> performance other than reducing the audio-buffer?
>>
>> -Brian
>> ---
>> Brian FG Katz, Ph.D
>> Audio & Acoustique
>> LIMSI-CNRS
>> BP 133
>> F91403 Orsay
>> France
>> tel. (+33) 01 69 85 81 55
>> fax. (+33) 01.69.85.80.88
>> e-mail Brian.Katz at limsi.fr
>> web_theme: http://www.limsi.fr/Scientifique/aa/thmsonesp/
>> web_group: http://www.limsi.fr/Scientifique/aa/
>>
>>
>>
>>
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>
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