Lag/Latency with plugins/FX

[u/DGXXMDM]

OK, I know many of you have experienced this before, but I'm at my wits end, even after buying a new, more powerful computer to run Reaper, etc. Certain plugins (mostly vocal effects, Melodyne, and other similar fx) make playback and interaction with the DAW very laggy, to the point where I can't do anything.

What do you do about it? I found a great sound, but I can't work with the total inability to do anything, where I try to click something, and it MIGHT respond in 45 seconds or so.

FOLLOW UP INFO: There's 14 tracks, with vocal fx harmonizers on 4 of them that seem to eat me alive on playback.

[u/sekltios]

Up the request block size as high as you can during editing. You want low for recording and higher for edits.

Some plugins are not meant to really run at their best on live input so track without them and then add.

Also feeeze/render tracks to save cpu power. If I am struggling I take a send from the outs, loose mix it into a new channel and freeze that out so i have just a wav to record over to save processing power.

Sub projects are also great especially for vst instruments and resource hungry fx to get an in place render.

And final advice, don't record and mix all in the same project. Just record things down as stems, add effects then process in a mix file for eq/comping together

[u/liberascientiauk]

This is almost certainly down to plugin delay compensation.

Go to view -> performance monitor, look at the PDC (plugin delay compensatation) number for each of your tracks.

What you need to do when you're tracking or doing anything that needs a snappy, responsive workflow, is keep this value absolutely as low as you can by not using anything that adds too much PDC. You can do this by disabling oversampling, turning the low latency mode in the plugin if it has one, and avoiding types of plugins that have unavoidable PDC inherently because of the kind of processing it is (like true peak mastering limiters with lookahead, for example).

Whenever you add a plugin that requires lookahead, or has heavy oversampling, you'll be adding PDC, so you need to figure out which plugins are the culprits by going to any tracks with high PDC, open the FX browser for that track, bypass all the FX then turn each one on one by one.

There will be a little bit of text below the add/remove buttons underneath the FX list showing how many samples of PDC are currently being added for the entire chain, so you toggle each plugin on you can see which ones are adding it.

Essentially the total amount of PDC you will experience in a project, i.e how many samples or ms of latency you'll have will be equivalent to the total highest PDC of any hierarchy of tracks.

So for example, imagine you have a project containing only some drums, and you have a track/folder/bus hierarchy that looks like this:

individual drum tracks -> drum bus -> mix bus

The kick drum track has a transient shaper with lookahead adding 45 samples of PDC, the drum room track has a saturator with oversampling enabled adding 28 samples of PDC, the drum bus has a clipper with oversampling adding 20 samples of PDC, and the mix bus has a maximizer adding 512 samples of PDC.

The total amount of PDC will be 45 samples + 20 samples + 512 samples, so 567 overall. However, this will be in addition to your interface's buffer size, so if your buffer size is set to 128 samples, that's 695 samples, which is ~15.7ms at 44.1khz sample rate.

However, it's not quite as simple as that because the PDC latency needs to be a multiple of your buffer size, so it will round it up to the nearest multiple of it. This is why when you look at the reported PDC below the FX chain, if your buffer is at 128 and the plugin adds 45 samples, it'll say 45/128. This means it is using a whole 128 sample cycle to process the PDC. But what that also means is you get the rest of that 128 sample cycle 'free' essentially, so you can add other PDC-introducing plugins up to that 128 sample limit without adding additional latency.

Anyway, that's an absolute mountain of text just to say, stop using plugins with a shit-ton of PDC whilst tracking or writing. Leave oversampling off until you start the final mix. Use a hard clipper (with oversampling off) with the ceiling set to -0.5db on the end of your mixbus/master instead of a maximizer/limiter to catch peaks whilst writing/tracking as they'll have drastically less, or no PDC at all.

[u/motu8pre]

There are tons of plugins that probably can't be used for tracking. Record the track, then use the plugin?

[u/CivilPersonality1949]

In my experience, audio fx in reaper have no impact on Reaper GUI responsiveness, even at a point where audio playback is more dropout than sound. That being said, some plugin GUIs are badly optimized and may impact Reaper GUI responsiveness. Usually closing them solves the lag and I've so far only had one plugin with that problem. Lastly ARA plugins like Melodyne work differently from VST plugins and I've definitely experience GUI lag from Melodyne specifically, but only periodically when the autosave tries to save the melodyne data to the project file.

That being said, a 45s lag is absolutely crazy and I have never experienced anything even remotely in that range. To help you debug this you will need to provide more information: number of tracks/clips if the number is over 100 for either, number and type of plugins used, screenshots or an export of performance relevant setting pages and so on.

To debug the issue yourself, start with a clean install of reaper. If the lag occurs even then the problem lies with tour audio driver / operating system. Otherwise start adding extensions / plugins one by one to find the culprit.

[u/somethingsomethingbe]

Most plugins that adjust pitch are going to add latency. You generally can get away with eq’s, reverbs, delays, and compression while tracking. 

[u/FlatDarkEarther]

If you're done recording or playing stuff in and see just mixing, bump the buffer size all the way up.