Calculating Latency

[tone4407]

Hey. When I'm using instrument plug-ins, I always check the latency before starting a beat. Its kind of a drag and very time consuming doing it everytime. So my question is this...

Will latency vary depending on CPU speed, or is it based soley upon the plugin itself?

Say I calculated latency for NI Battery and its 500ms. Will it be 500ms everytime? Or could it be 450ms one time because my CPU is lacking speed.

I figure if its the same amount of latency everytime, I can write the latency times down and I can get my project started quicker.

[manning1]

with respect there are no simplistic answers to this.
latency can depend on many factors. your pc itself...and how its configged.
the sound device and drivers your useing, the inner workings possibly of your host software and vst's/vsti's etc. and how the two interract at a technical level.
where folks often make a mistake is trying to load too many plug in instances on a poorly configged or underpowered pc.
the only solution is to run tests. you can mitigate problems by properly configuring the fastest pc you can afford and use the lowest latency sound device you can find , as well as use low latency plug ins.
plug in instruments can consume a lot of resources of a pc, and bring an underpowered one to its knees. especially with lots of instances.
because of their real time nature. what is your pc ?? config ??
i'll let you in on a little secret...my industry, the computer industry has been plagued for years with problems in running real time applications.
right thru the mainframe, minicomputer, and now the pc era.
i lost more than a few hairs debugging mainframe and mini systems.
basically the machines of each era were never powerfull enough to do everything the end users often wanted to do.
particularly related to high volumes of real time transactions.
try developing a real time banking system sometime with millions of transactions per hour. very very complex.
which is why atm's go down sometimes.
similarly with audio... lots of real time and time dependent processes occurring.
only recently at the pc level would i say the pc itself has reached sufficient processing capability to achieve the type of performance that users are demanding. and its only going to get better with the coming of multiple cores
in processors and new architectures.

[tone4407]

I'm in the process of finishing my new PC. It has an AMD Athlon 64 3800 processor running at 2ghz. Its a dual core processor as well. I'll have 2 gigs of RAM, upgradeable to 4 gigs. I feel that this setup should be sufficient for computer based sequencing.

Thanks for all the info!

[bradyvickers]

I'm not sure what kind of latency your talking about. But regardless it will always vary. Sometimes significantly so. Whereas the latency of an AD or DA is normally the same at all times (and most are around 2ms), the latency within your DAW will vary depending on CPU load, HDD seek times, Front Side Bus speeds, etc. If your refering to the latency when trying to monitor through a virtual instrument like NI Battery, this would be the latency of your DAW combined with the latency of the DA conversion to get to your ears. So to answer your question, finally , there is no consistent number you can "plugin" for the latency of your DAW.

[Geert van den Berg]

I disagree...

The latency is determined by the buffersizes that you set in your software and the D/A converter and offcourse if you're tracking also the A/D's come into play.

If you set the drivers for your audio interface to a lower buffer you get less latency but then your computers CPU needs to do more calculations in a shorter timespan thus you'll have a bigger cpu load and it will perform less stable.

The buffersize is not variable, so your latency is fixed. If your computer can't keep up, you just get CPU overload errors and your audio playback will s.t.u.t.t.e.r.

So back to the original question, the latency is always the same for Battery if you leave your drivers set at the same buffersize, if you make the buffer larger you'll get more latency. (if you go above a buffersize of 128 most people find the responsive of VI's too slow) and you need to keep working at the same sample rate, because this also affects the latency, higher sample rates have less latency (but again put more strain on your CPU).

[Methlab]

If you have a PC, why don't you use Nuendo? Latency won't really be an issue with PDC.

[theblue1]

Interesting how some PT users just seem to assume the whole world uses PT and often don't mention their platform even when it's extremely pertinent to their request for information or help.

But, in this case, of course... I guess we pretty well can guess that tone4407 is using PT LE since he does not appear to have full automatic plug compensation and PT LE is the last major DAW that has failed to adequately address that crucial requirement for modern recording.


Still... for those of us who choose NOT to live in the "company town" of PT, it can't help but be at least faintly amusing.

[Geert van den Berg]

Well even if he would use Nuendo/Cubase/Logic, delay compensation would not help him while recording the VI's, then you still have to lower your buffersizes. But on playback it's nice to be able to switch to a higher buffer on these compensated systems.

[theblue1]

Doh!

Good point, Geert!

I think I must CERTAINLY need more coffee...