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Old 10-01-2019, 04:19 AM   #1
Mage
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Default [5.983] Snap + Loop is inaccurate

1. Open a new project.
2. I used 138 BPM. Maybe it matters, please do the same.
3. Set the grid to 1/16th
4. Create a new track with an instrument
5. Draw a midi item. One bar length will do. Put a lot of notes in it.
6. Render the midi item to audio
7. On the new track with the audio item, slice the audio item to 1/4th long by clicking on a grid line, slice, clicking on the 4th line on the right and slice again
8. Remove the rest of the audio item. Keep only the 1/4th part of it
9. Glue it
10. Loop it to 289.1. At 138 BPM, this should be about 8:20.
11. Zoom on one of the grid lines at 289.1

You’ll see that the loop marks will be shifted. The audio will be shifted by about 1.9 ms compared to the grid lines (and compared to the beginning of the track)

It doesn’t seem much but considering that in a normal track, anything you would want to loop that long could be a drum, bass, or percussions, it makes the loop feature useless for this purpose. Yet it’s usually how one wants to start creating an EDM track.

I checked it in other DAWs.

In Ableton Live, it will be accurate, although, you can loop the audio only if the warp is turned on.

In Logic Pro X, I think the slice is already buggy. I gave up and wondered how people could use it.

In Cubase, there is the shared copy. I don’t know Cubase well. I think it’s like looping. (The default "loop" will place individual copies but the shared copies behave like a single item, I think). In my test, the audio was not shifted. At 289.1 at maximum zoom, the wave had the same position compared to the grid as it had at 1.1.

In Reaper, if you don’t use the loop but you duplicate or copy-paste it, then it will be correct, except for you will have a thousand copies of the item.

https://imgur.com/a/E5ADfaj
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Old 10-02-2019, 05:46 AM   #2
mawi
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i can confirm. the audio loop does not stay exactly on the grid. a midi loop stays exactly on the grid.

https://www.dropbox.com/s/sj361l3s4t...43437.png?dl=0

Last edited by mawi; 10-02-2019 at 05:56 AM.
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Old 10-02-2019, 08:59 PM   #3
Dstruct
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Check

"Snap to project sample rate" in Snap settings
"Force projet tempo ... to occur on whole samples" in project settings


Another workaround: use the "Loop section of item source" function to "fix" it.
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Old 10-05-2019, 01:59 AM   #4
Mage
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Quote:
Originally Posted by Dstruct View Post
Check

"Snap to project sample rate" in Snap settings
"Force projet tempo ... to occur on whole samples" in project settings


Another workaround: use the "Loop section of item source" function to "fix" it.
The snap to project sample rate didn’t help. I could see no difference.

The force project tempo helped. At least at first glance, it seemed to eliminate the issue. I compared the position of the wave at maximum zoom. It seemed identical at 1.1 and 289.1

I wonder why it isn’t the default setting (turned on). Does it have any disadvantages?
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Old 10-05-2019, 05:40 AM   #5
Dstruct
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Quote:
Originally Posted by Mage View Post
I wonder why it isn’t the default setting (turned on).
Agreed, should be on by default.


Quote:
Originally Posted by Mage View Post
Does it have any disadvantages?
Some values for Project tempo are not possible with that (140 BPM at 48 kHz for example will be 140.003 BPM).
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Old 10-05-2019, 02:11 PM   #6
Mage
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Quote:
Originally Posted by Dstruct View Post
Agreed, should be on by default.

Some values for Project tempo are not possible with that (140 BPM at 48 kHz for example will be 140.003 BPM).
Interesting. I don’t know anything about how it works. If I had to guess, I would start with:

60.0 * 48000 / (140.003 * 128)
=> 160.71084191053052

60.0 * 48000 / (140.000 * 128)
=> 160.71428571428572

None of them is an integer. The idea was that 1/128th is the smallest grid setting, one minute has 60 * 48k samples, and 140 BPM should have 140 * 128 measures (maybe it has another name).

Then:
60.0 * 48000 / (160.000 * 128)
=> 140.625

I would think 140.625 BPM would fit.

But it’s indeed 140.003, or 136.003, or 138.003, etc.

48000 * 0.003
=> 144.0

That’s 9 * 16 or 4 * 36 or 12 * 12.

Yeah, it only shows I have no idea how it works.

Anyway, I don’t want to make a 140.003 BPM song. I guess I will just duplicate the audio items. Samplers are also inaccurate in any DAW I tried. I guess the reason is the same.
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Old 10-05-2019, 02:19 PM   #7
Dstruct
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Like I said:

Another workaround: use the "Loop section of item source" function to "fix" it (this one is subsample accurate).
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