[PD-ot] how low (latency) can you go?

[IOhannes m zmoelnig]

hi.

Hans-Christoph Steiner wrote:
> 
>>
>> as always when it comes to latency and people tell numbers, i have to
>> ask my question: have you measured this? how? or was it just "putting a
>> number somewhere and assuming that it's the real latency"?
>> how much load do your settings allow?
> 
> Yes, its true, I am too lazy to do an actual measurement.  I am just
> talking about the buffer setting.  

thank you for this clarification.
i think it is important to have such things articulated correctly.
as soon as the word "latency" can be found on the web, i am pretty sure
that a lot of myth and rumour are involved.
people keep telling that they can go as low as 3ms in pd, which is
simply not possible.

> For what I do, I don't really need
> much lower.

this is fine for you.

> 
> And always, when talking about latency, I feel the need to point out the
> speed of sound: 340 m/s or .34 m/ms.  So if your speakers are 2m away
> from you, that's 6ms of latency.  You could spend days tweaking your
> machine to get 3ms less latency, or you could move 1m closer to your
> speakers.  Puts things into perspective...

this is correct.
but unfortunately perspectives can change. as a musician you might be
happy with one machine adding latency of 3ms.
however, it is common practice to stack several machines (synthesizers,
effect-hardware, PCs), all adding a small latency. if you have 3
machines, all with a perfectly low latency of 10ms, you get a resulting
latency of 30ms which might be intolerably low.

that is just music. as soon as you get into technical applications,
things get far worse (e.g. there might really be a need to get as low as
2ms).


so again: it is my concern to get clarity when people use the term
"latency".
i have done a lot of latency measurements over the last years; usually
the numbers i saw in various control panels (be it jack, pd, rme
hammerfall's settings,...) are not identical with the actual latency;
though the often (not always) directly related.


mf.asdr
IOhannes

PS: thanks to all of you for your explanations about latency; my remark
was really not about latency (what it is; what you need) but about what
we think when we hear the buzzword "latency".