Artifacts in unmixed audio

I have so far unmixed nine audio tracks, and in four of them there were loud noise artifacts in the unmixed version, always within the first or last few seconds of the file (where there is mostly audience noise and no music).

It’s possible to remove these using the eraser and other tools, but of course it would be nicer if these artifacts didn’t occur at all :slight_smile:

Before:

Unmixing using these settings:
image

After:

Zoomed in:

Should I send you the offending file by PM so you can check if this is reproducible?

Thanks,
Tim

Yes please ! Or you can also send it to contact [at] divideframe (dot) com. Up to you !

Did you get the file I sent to your e-mail address via WeTransfer (it was too big to be uploaded here)?

Thanks,
Tim

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I have more information about this problem, and more files to reproduce it with:

  1. These artifacts occur mostly during applause sections, but can appear at any time, it seems (see example below)
  2. The artifacts appear in two unmixed layers in inverted phase, so they cancel each other out when both layers are unedited and played together.

Here is an example:
The file Test SLP.wav contains a short clip with a bass solo from a jazz piano trio live recording. I have unmixed it using the Best Quality option and chosen the three instruments present (piano, bass, drums) to be unmixed:

The result is interesting:

  • There are some loud artifacts at 00:52 that can only be heard if either the piano layer or the unmixed layer is played.
  • The acoustic bass generally seems to confuse SLP quite a bit - large parts are placed in the unmixed layer and the piano layer, but this is a lot more obvious right after the artifacts.
  • Luckily, these spikes are easy to spot by choosing appropriate colors for the two affected layers, so I can “Cut Special” them into the other layer where they then cancel out.

But still it would of course be nice if those artifacts didn’t happen in the first place :slight_smile:

(using 10.0.40 Build 339)

But what create those noise spikes when the file is unmixed?

And is there a way to ensure that this doesn’t happen?

Interestingly, yesterday I had the exact same problem. I could take screenshots but they look the same as the ones above. (10.0.50 Build 343).

I have used SL on many old stereo recordings and this is the first time I have seen this - Any clues why?

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Same here. These artifacts are “cracks” across the whole frequency range. They can be as loud as +15.5 db in a file that originally doesn’t exeed -4 db. The last one that occured (see screenshot in Cubase) was about 50 ms long. This might be dangerous to speakers, headphones and ears.
In some cases they are phase-inverted on several layers (see screenshot in Cubase) so you don’t hear them as long as you do not mute a layer or start levelling them.
The problem is not repeatable. If I do a new demix of the same file the crack is usually gone - or has moved to another position :roll_eyes:
Of course you can get rid of it in several ways but it’s a bug anyway and I don’t want to spend my time with that …

And yes, it might be a problem with live recordings with audience because I’m working on that too. The example shown above appears very close to a stick click (count in for the band on a tom track while fading applause).

I have not noticed this problem unmixing multiple tracks (with applause) on a different PC (MS Surface Pro 9), so maybe it’s related to the AI processing device setting? On the affected PC, I’m using a NVIDIA GeForce GTX 1060. On the Surface, I’m using the CPU (GPU has less than 4GB RAM, so SL10 won’t let me use it).

Thanks for the advice. I’m using the CPU but I’ll give it a try on my notebook.