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On 20/03/11 18:38, Jörn Nettingsmeier wrote:

quoted text
> On 03/20/2011 06:25 PM, andy baxter wrote:

>> Hi,

>>

>> I am thinking about a possible design for the second version of the

>> position sensing drum pad I have been working on, and I have a question

>> about latency. I am working around the assumption that 10ms latency is

>> about the worst it can get before people start to notice it in practice,

>> so I am thinking of building the pad in a way where the normal latency

>> is about 1ms, but it degrades to between 10-15 ms in the very worst case

>> (many simultaneous strikes and pressure variations across the pad).

>> Allowing this level of degradation would make it possible (I think) to

>> use an arduino rather than a faster processor, which would be nice.

>

> a drummer will get very grumpy indeed over latencies in the 10ms

> range. (i understand your use of the term to mean "time it takes for

> the sound to come out after the drummer has hit the pad").

>

Yes that's what I meant.
> you should aim for 2ms or less, which takes considerable effort and a

quoted text
> very good sound card.

>

> but if you can't do that, then by all means keep the latency constant.

> shifting latency will make the the drummer eat his sticks, or worse

> yet, direct random acts of violence against other people, possibly

> even you.

>

> just imagine you are playing a constant 16th note pattern at 120 bpm.

>

> one beat will be 0.125 seconds.

> say your second beat is delayed by 10ms ue to jittery time, and the

> next one is dead on again. the groove will appear to "swing" in weird

> ways. real swing would mean 0.167s, then 0.083s, so that's

> considerably more, but to keep a groove going, the drummer has to keep

> such times very accurately, and 10ms is a major earthquake to a

> flowing groove, especially since the drummer's physical feel and the

> acoustic result do not match when your software jitters.

> even when the following beats are all delayed by 10ms because your

> application scheduler has now entered its high-load steady state, the

> drummer will hear a drag, try to speed up to compensate, and oscillate

> around the correct time for a number of beats. this ruins the feel and

> i could imagine it could even cause physical harm due to dysfunctional

> use of muscles.

>

> but even when the latency is constant, drummers are used to get very

> sharp and distinct physical feedback when the stick rebounds from the

> drum head, and they are very close to the instrument. so they will

> usually be a lot less tolerant than electric guitarists (who are used

> to operate at 3 or 4 m distance from their amps or monitor speakers)

> or (extreme example) church organists, who can learn to deal with tens

> or even hundreds of milliseconds of latency (plus a dragging

> congregation choir on top) :-D

>

OK - thanks for pointing this out.

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