3rd party plugins reporting "0 latency" cause phasing with looper

[orbita]

Hi,
I've been doing some tests with the Ableton Loopers to record from other tracks in my set. (In Live 10).

I place a looper on several tracks and record from other tracks, then I record from one looper to another.

If I use any Ableton Audio Plugins that are 0 latency on the tracks I can record from one channel to another and it sounds fine.

Once I start introducing 3rd party plugins, even those that report 0 sample latency, I start to experience phasing issues when playing both the source and looped recording simultaneously. Why is this? Is there a default 1 or 2 samples latency added to 3rd party plugins that is not added to internal ones?

[Angstrom]

Are these plugins in parallel chains filters, or EQs?

Common Filters like EQs often rotate phase. They aren't latent like a compressor with a 5 ms lookahead, but they will rotate phase by the duration of a wavelength , which is unequal. Low frequencies are long durations and hugh frequencies are short. That will produce a notch filter effect as its summed to the source.

Not a bug, just physics..

[orbita]

Everything I've tried.
- Endless Smile
- WOW
- bx_opto
- all 0 latency psp plugins
- Replika
- Side Widener
- Transient Master
- and others.

I found another weird thing - If I recorded into a looper from another track - it sounded fine. Then I added one of these 0 latency plugins after the looper. Still sounds fine. Then I stopped the looper and recorded again with the plugin there. Then it starts phasing. So, if the plugin is on the track before I record it sounds ok, but if I record after the plugin is added it starts to phase!

Ableton's own plugins don't appear to suffer from this, at least the not 0 latency ones.

Also seems to happen if I turn Latency compensation off - I thought it was the compensation that might be moving the loopers back and forward in time slightly.

[orbita]

oh and I should say it doesn't matter if the plugin is on or off, just being present causes it.

[orbita]

To replicate

Create 2 channels, set input of each to the other channel.

Add loopers to each channel, set to record 1 bar, turn monitoring in the looper to never and set to play after record.

Add a 0 latency plugin after both loopers and disable it.

Add a 1 bar clip to track 1 and play it.

Turn on monitoring on track 2 and enable recording on the looper.

Now you should have 2 versions of the clip playing in sync nicely.

Now turn on monitoring on track 1 and enable recording on the looper.

You should get phasing.

Recording again on looper2 brings them inline again.

Recording on 1 causes phasing, recording on 2 seems to correct the phasing.

Do the same thing without the plugins and you don't get phasing at all.

Removing the plugin once phasing is occurring doesn't stop it.

[orbita]

Also realised this happens without looper - just recording from one track to another and back.

[Angstrom]

Try> Options menu.
uncheck "reduced latency when monitoring".
In short: that option makes any armed or monitored track ignore the latency calculations of other sibling tracks. It's so you can play-through with the shortest latency. But it comes a cost of sync between siblings. More information in the manual.

[orbita]

I don't have that ticked. I tried all combinations of the latency controls.

[orbita]

Seems like "Echo", "LFO" and max4live plugins also cause phasing in the example above.