What determines the delay compensation of a plugin?

[camshash]

Sorry if this is the wrong place for this question,

What determines the delay compensation for a plug in/track?

Is it the host computers performance, or is it a predetermined number that the plug in tells pro tools what its delay is?

For the same exact plugin would you experience a lower delay comp on a more powerful computer versus a less powerful computer?

thanks!

[Darryl Ramm]

It has nothing to do with CPU performance, audio latency is happening many orders of magnitude slower than CPUs work at. Latency is caused by the internal plugin algorithm, if the plugin is deliberately delaying all or part of the signal (e.g. to perform look ahead for a limiter), if it’s doing frequency up conversion, etc. it will have latency from doing that. The latency varies at different sample rates. The plugin knows what that latency is, the set of latency vs sample rate data is hard coded into the plugin by the developer and Pro Tools queries the plugin to get that data. Yes there are very occasional mistakes.

CPU performance and overall systems optimization determines how large a session with how many plugins you can run but not any of the plugin latency numbers themselves. The moment Pro Tools gets close to being unable to keep up with keeping everything running with sample accurate time alignment it deliberately crashes itself with an AAE CPU error.

[Darryl Ramm]

And depending on what you mean by track latency, the IO buffer or disk playback buffer also add latency at input and output. As do latencies in the analog to digital and digital to analog conversions, and some additional latency interfacing to device drivers. All of which Pro Tools takes care of automatically. (you get that without enabling "delay compensation").

DSP based HDX (and older TDM) systems using HDX (or TDM) plugins don't utilize an IO buffer, except when converting back to use native plugins and back again to the DSP based mixer. HDX (or TDM) plugins are not guaranteed zero latency, any that perform look ahead or up conversion etc. will add latency. Especially true of mastering bus/limiting plugins with deliberate high look-ahead.

[nsureit]

Darryl,

These are great explanations. Easy for us less technical folks to understand. Thank you.

[nednednerb]

Yes thank you! Good to grok.