What is the REAL latency?

[tmac]

Hi!

I often use JACK, and it typically reports e.g. a latency of 6ms. When I play guitar, letting the sound go through JACK and out of my computer speakers, I do notice the latency.

On the other hand, when playing through my real guitar amp, 6ms should correspond to sitting only around 2m away from my real guitar amp (since it has practically no internal latency), since the speed of sound is 340m/s.

But, I do not notice this latency when sitting 2m away from my guitar amp. This leads me to believe that the total latency when using my computer is larger than 6ms, since I notice it.

Has anyone actually split one signal, let one part through a computer with JACK, recorded both in the other end and compared the timing? And then compared the delay with the latency value reported by JACK?

I'm thinking about doing this just to find out...

[tmac]

Ok, I decided to do the measurements.

Reported latency from JACK: 6ms

Measured latency when configuring JACK to send the input signal straight to the output: 6ms

Measured latency when sending the signal through Rakarrack, using only a single parametric EQ plugin: 9ms

I also measured the latency in my Vox ToneLab ST guitar amp modelling unit: 2ms (tried both a clean and distorted sound). I use only amp modelling and speaker cabinet modelling. No extra effects.

I wonder how the Rakarrack latency increases as the number of plugins is increased. I usually use more than a parametric EQ...

I'm not sure if I notice the 6ms. I don't usually just route the signal directly from input to output.... I'll have to listen to that later. I'll have to think about why I'm not bothered by latency when sitting 5m from my amp After all. that is a latency of 15ms... Perhaps only because I don't hear the guitar strings at the same time?
Perhaps I would not notice either if I routed the computer signal into a big amp and speaker cabinet.

[DoosC]

Hello Tmac !

My understanding of the problem, is that you have Software Latency + Hardware Latency.

If you have a "regular" sound card, your hardware latency can be very bad because those sound cards are designed for music/sound playing. So the goal here is to avoid clicks and pops hence adding a big buffer to prevent that.
On the other end on professional sound cards the goal is to reduce latency to a minimum because you don't want it and you are more focused on recording than playing.

So you could have a 6ms on jack + a 60ms hardware latency (I don't know how bad it can be), that would be a huge 66ms latency.

I think that's where the main difference lies in your perception.

DoosC

[spm_gl]

Perhaps I would not notice either if I routed the computer signal into a big amp and speaker cabinet.

That would definitely make a difference. The louder the signal, the more the rooms reverb comes into play. Your room will probably have an RT60 of around 1-2s. So if you play loud, the room will smear the sound, and you won't notice the delay so much. Try playing softly at 5m distance, you should feel the delay then.

[autostatic]

tmac, try the jdelay (Jack_delay) program. It measures the hardware+software delay. And yes, every plugin and everything you route through another app (like Rakarrack) adds extra latency.

Best,

Jeremy

[tmac]

tmac, try the jdelay (Jack_delay) program. It measures the hardware+software delay. And yes, every plugin and everything you route through another app (like Rakarrack) adds extra latency.

Thanks! I will try jack_delay. And thanks DoosC and spm_gl for your answers.

Fortunately, I prefer a a basic guitar sound with no fancy effects. With a real amp I don't use any effects apart from a barely noticeable reverb if it is built into the amp. On the computer I only want to simulate that. Also, I will try to use get a more realistic "room-sound" in my computer modelling. Perhaps that is more important than I thought previously.

Regarding the "5m from the amp" thing I mentioned. I do notice a latency when I'm that far away but somehow it just doesn't bother me as much. Probably due to room-effects as mentioned. I do prefer to be close to the amp while playing, though.

[Capoeira]

we have to think when a low latency is really necessary......in fact only in a overdubbing situation.
So, if you don't here it, don't worrie about it

[raboof]

every plugin and everything you route through another app (like Rakarrack) adds extra latency.

With Jack, this is not necessarily true. As long as there are no loops in your connection graph the length of the audio path should not matter, except when the application itself adds some buffer of its own. Some of the Rakarrack effects probably do that.

when a low latency is really necessary......in fact only in a overdubbing situation

And when playing softsynths or applying 'live' effects to your playing...

[Capoeira]

when a low latency is really necessary......in fact only in a overdubbing situation

And when playing softsynths or applying 'live' effects to your playing...

OK, I included this in overdubbing but its correcter like this, you'r right