Ableton unwarped audio cuts not phase coherent?

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Royalston
Posts: 31
Joined: Sun Jan 29, 2012 6:09 am

Ableton unwarped audio cuts not phase coherent?

Post by Royalston » Fri Oct 26, 2018 1:31 am

Hi,
I was cutting a long sub kick drum in order to eq the first and second half of the drum hit differently...I never got as far as eq because I keep getting clicks in the middle of the drum hit where I don't think there should be...which makes wonder about ableton's audio accuracy. I don't think I'm being picky here - this is a fairly basic operation.

This is my test:
Get a long kick drum. Put it on an audio track. Make sure warping is off. auto fades are off.
Cut the drum hit somewhere in the middle, a fair bit after the transient so we are more in the sub region. Cut on a grid line to make it easy.
Move the second half onto a 2nd track, making sure its a aligned perfectly (ie. cut on the grid). Playback.

There's a click.

There shouldn't be a click. Should there?
There are no plugins on either channel.

fishmonkey
Posts: 4216
Joined: Wed Oct 24, 2007 4:50 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by fishmonkey » Fri Oct 26, 2018 3:17 am

i have reproduced this and it seems like it might be a bug.

what i've found is that if i cut a clip (i used the Kick Nice Clonk from the Live library) it will play without clicks when the two parts are on the same track, even if i introduce a gap between the two. If i move the second part to a different track, it introduces a click. it seems impossible to avoid this click.

however, i then tried consolidating the clips, and now the two pieces will play seamlessly, even when on different tracks. i also found that consolidating only the first clip made it possible for the clips to work together without clicks.

all this was done with warping and auto-fades off.
badbrainz wrote: I'm a drummer, so I'm already at an intellectual disadvantage here

Royalston
Posts: 31
Joined: Sun Jan 29, 2012 6:09 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by Royalston » Fri Oct 26, 2018 3:33 am

Weird! must be a bug.

If you resample the 2 track split version, it resamples with a huge glitch

TheCoil
Posts: 55
Joined: Tue Feb 28, 2012 6:12 pm

Re: Ableton unwarped audio cuts not phase coherent?

Post by TheCoil » Fri Oct 26, 2018 3:55 pm

Haha wonderful

Royalston
Posts: 31
Joined: Sun Jan 29, 2012 6:09 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by Royalston » Sat Oct 27, 2018 2:52 am

I've reported the bug...its a pretty basic thing to not be working.

pottering
Posts: 1072
Joined: Sat Dec 06, 2014 4:41 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by pottering » Sat Oct 27, 2018 5:46 am

Royalston wrote:Hi,
I was cutting a long sub kick drum in order to eq the first and second half of the drum hit differently...I never got as far as eq because I keep getting clicks in the middle of the drum hit where I don't think there should be...which makes wonder about ableton's audio accuracy. I don't think I'm being picky here - this is a fairly basic operation.

This is my test:
Get a long kick drum. Put it on an audio track. Make sure warping is off. auto fades are off.
Cut the drum hit somewhere in the middle, a fair bit after the transient so we are more in the sub region. Cut on a grid line to make it easy.
Move the second half onto a 2nd track, making sure its a aligned perfectly (ie. cut on the grid). Playback.

There's a click.

There shouldn't be a click. Should there?
There are no plugins on either channel.
You probably cut outside a zero-crossing point.

In that case, it SHOULD cause a click, it just what happens when a waveform is cut in the middle outside a zero crossing point, without any fades, that's just how digital audio works.

The fades are there exactly for removing clicks like these.

Check mistake #2 in this article:

https://ask.audio/articles/5-mistakes-t ... ting-audio
One of the first things taught to budding audio editors in engineering programs is that when two sections of audio are cut and pasted together, the waves need to be cut so there aren’t any waveform discontinuities—that means jumps in the visible line of the wave, as shown on the accompanying image. Jumps like this make the loudspeaker try to jump unnaturally quickly to follow the wave, and this results in an audible ‘click’, which can often stick out even in a bust mix and even when it’s relatively low in level.
So most editors use a slightly different approach—rather than restricting edits to zero-crossings, they utilize very short crossfades to smooth out any waveform discontinuities and the resulting clicks.

fishmonkey
Posts: 4216
Joined: Wed Oct 24, 2007 4:50 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by fishmonkey » Sat Oct 27, 2018 5:51 am

pottering wrote: You probably cut outside a zero-crossing point.

In that case, it SHOULD cause a click, it just what happens when a waveform is cut in the middle outside a zero crossing point, without any fades, that's just how digital audio works.

The fades are there exactly for removing clicks like these.

Check mistake #2 in this article:

https://ask.audio/articles/5-mistakes-t ... ting-audio
One of the first things taught to budding audio editors in engineering programs is that when two sections of audio are cut and pasted together, the waves need to be cut so there aren’t any waveform discontinuities—that means jumps in the visible line of the wave, as shown on the accompanying image. Jumps like this make the loudspeaker try to jump unnaturally quickly to follow the wave, and this results in an audible ‘click’, which can often stick out even in a bust mix and even when it’s relatively low in level.
So most editors use a slightly different approach—rather than restricting edits to zero-crossings, they utilize very short crossfades to smooth out any waveform discontinuities and the resulting clicks.
it's not a zero-crossing issue. we are talking about a waveform that has been chopped into two parts that match up exactly at the join. try the example i posted above...
badbrainz wrote: I'm a drummer, so I'm already at an intellectual disadvantage here

pottering
Posts: 1072
Joined: Sat Dec 06, 2014 4:41 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by pottering » Sat Oct 27, 2018 7:13 am

Cutting a waveform in two and putting one of the sliced parts in ANOTHER track is a zero-crossing issue.

The waveform doesn't continue from one track to another track, doesn't matter if the split slices in the 2 tracks are aligned.

And it does click with a gap between the 2 slices (and no fades), even in the same track.

You must have gotten lucky and split close to a zero-crossing point in your test, if you split closer to the top or bottom of a waveform you will hear the clicks with a gap between the slices, even in the same track.

Also, if you split a Clip in two (outside a zero-crossing point) without fades and select the 2nd slice, the playback will start right in the beginning of the 2nd slice with a click (maybe that's what you are all listening), because it is starting from zero to non-zero sample point instantly, but if looping (or starting playback elsewhere) it will stop clicking. It clicks only in that first moment where the sample value goes instantly from zero to non-zero.

fishmonkey
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Joined: Wed Oct 24, 2007 4:50 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by fishmonkey » Sat Oct 27, 2018 7:27 am

pottering wrote:Cutting a waveform in two and putting one of the sliced parts in ANOTHER track is a zero-crossing issue.

The waveform doesn't continue from one track to another track, doesn't matter if the split slices in the 2 tracks are aligned.

And it does click with a gap between the 2 slices (and no fades), even in the same track.

You must have gotten lucky and split close to a zero-crossing point in your test, if you split closer to the top or bottom of a waveform you will hear the clicks with a gap between the slices, even in the same track.

Also, if you split a Clip in two (outside a zero-crossing point) without fades and select the 2nd slice, the playback will start right in the beginning of the 2nd slice with a click (maybe that's what you are all listening), because it is starting from zero to non-zero sample point instantly, but if looping (or starting playback elsewhere) it will stop clicking. It clicks only in that first moment where the sample value goes instantly from zero to non-zero.
nope. a zero-crossing issue becomes audible when there is a sharp discontinuity in the signals that a speaker driver is being asked to reproduce.

a join between two clips should not cause a zero crossing issue if the waveforms on each side of the join match up, no matter where you make the cut. this should be true regardless of whether the clips are on the same or different tracks.

whether or not you get a click with a gap will of course depend on the waveform, where the cut in the waveform is, and on how big the gap is.

further testing suggests that Live is definitely not sample-accurate when moving clips between tracks, even when snapping to the grid.
badbrainz wrote: I'm a drummer, so I'm already at an intellectual disadvantage here

Royalston
Posts: 31
Joined: Sun Jan 29, 2012 6:09 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by Royalston » Sat Oct 27, 2018 8:36 am

pottering -
This isn't a zero crossing issue. Try this same test in any audio (other) editor and there won't be a click. The phase of the chopped waveform should line up and recreate the original waveform perfectly. There is no time gap between the two waveforms (if there was, yes, there would be a click)

What bothers me is that this is such a fundamental thing - I'm not talking phase alignment with PDC involved or return tracks or anything....this is basic audio editing. If Ableton is not getting something this simple right, I can't imagine how the phase is shifting across 50+ tracks with plugins, groups and groups within groups...

pottering
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Re: Ableton unwarped audio cuts not phase coherent?

Post by pottering » Sat Oct 27, 2018 9:05 am

OK, I see what you both mean, it should sum.

But the rest of the split Clips in separate tracks will still null with a 3rd track with a copy of the original un-split Clip (it is only in the split second in the cut where there are clicks), so there is no problem with moving the Clips between tracks or with phase coherence.

fishmonkey
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Joined: Wed Oct 24, 2007 4:50 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by fishmonkey » Sat Oct 27, 2018 9:10 am

pottering wrote:OK, I see what you both mean, it should sum.

But the rest of the split Clips in separate tracks will still null with a 3rd track with a copy of the original un-split Clip (it is only in the split second in the cut where there are clicks), so there is no problem with moving the Clips between tracks or with phase coherence.
in my tests the phase is not necessarily preserved when moving clips between tracks when snapping to the grid. and the clicks are worse when the clips are on separate tracks. even when zooming right in and nudging by tiny increments the clicks are worse using separate tracks.
badbrainz wrote: I'm a drummer, so I'm already at an intellectual disadvantage here

pottering
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Joined: Sat Dec 06, 2014 4:41 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by pottering » Sat Oct 27, 2018 9:23 am

Here, except for the clicks right in the cuts, the audio before and after the cuts nulls perfectly here.

And if they are in the same track there isn't any clicks at all, they null perfectly with the original.

fishmonkey
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Joined: Wed Oct 24, 2007 4:50 am

Re: Ableton unwarped audio cuts not phase coherent?

Post by fishmonkey » Sat Oct 27, 2018 9:32 am

ah, the phase got messed up when i moved the clip back to it's original track as i was zoomed in too far to snap to the grid.
badbrainz wrote: I'm a drummer, so I'm already at an intellectual disadvantage here

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