Audacity3.0.2 compressor error

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tac2
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Audacity3.0.2 compressor error

Post by tac2 » Wed Apr 21, 2021 3:22 pm

An internal error if the beginning of the sound is a negative time was improved.
However, if the beginning of the sound is a negative time, the compressor will move the truck time shift even if I have locked the track sync.
macOS Catalina.

waxcylinder
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Re: Audacity3.0.2 compressor error

Post by waxcylinder » Wed Apr 21, 2021 3:51 pm

tac2 wrote:
Wed Apr 21, 2021 3:22 pm
An internal error if the beginning of the sound is a negative time was improved.
Thanks for confirming
tac2 wrote:
Wed Apr 21, 2021 3:22 pm
However, if the beginning of the sound is a negative time, the compressor will move the truck time shift even if I have locked the track sync.
macOS Catalina.
I can't replicate this on my Macbook Pro under 11.2.3 Big Sur with Audacity 3.0.2

Peter.
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tac2
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Re: Audacity3.0.2 compressor error

Post by tac2 » Thu Apr 22, 2021 2:47 pm

I have reconfirmed this phenomenon on iMac 27-inch 2020 macOS 10.15.7, Mac mini Late 2012 macOS 10.14.6 and iMac 27-inchi Late 2013.

steve
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Re: Audacity3.0.2 compressor error

Post by steve » Thu Apr 22, 2021 2:50 pm

tac2 wrote:
Wed Apr 21, 2021 3:22 pm
the compressor will move the truck time shift
What does that mean?
Perhaps a couple of screen shots may help to show what you mean.
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tac2
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Re: Audacity3.0.2 compressor error

Post by tac2 » Fri Apr 23, 2021 4:42 am

When I apply the compressor to the upper track, the time shifts in the positive direction.
Attachments
Audacity302CompressorError.jpg
Audacity302CompressorError.jpg (125.48 KiB) Viewed 174 times

steve
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Re: Audacity3.0.2 compressor error

Post by steve » Fri Apr 23, 2021 9:18 am

I can't reproduce that on Linux.

Is this the compressor that you are using? https://manual.audacityteam.org/man/compressor.html

Does it still happen if you turn off "Sync Lock"?
Does it still happen if you "Reset configuration" ("Tools" menu)?

If it does still happen, what settings are you using in the compressor effect?
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waxcylinder
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Re: Audacity3.0.2 compressor error

Post by waxcylinder » Fri Apr 23, 2021 11:38 am

I can reproduce the problem now on W10 - having seen tac2's last image post (thanks for that tac2). I manage to repeat it with some simpler steps:

1) Generate 30 second chirp
2) select from 0-10 seconds
3) Silence that selection with Ctrl+L
4) Ctrl+A to select all
5) Effect>Compressor
01 Compreesor no negative time.png
01 Compreesor no negative time.png (32.81 KiB) Viewed 159 times


6) Undo to remove the compression
7) Drag track leftwards with Timeshift tool so 9 seconds are in negative time
8) Ctrl+A to select all
9) Effect>Compressor
02 Compressor 9secs negative time.png
02 Compressor 9secs negative time.png (35.29 KiB) Viewed 159 times
Note carefully that the waveform is now only 11 seconds log and the 20 it should be



10) drag waveform right with Timeshift tool so that all the audio is in positive time sating at T=0
03 Compressor fault.png
03 Compressor fault.png (35.03 KiB) Viewed 159 times
It looks to me as though
a) the waveform has been pushed rightwards by the 9 seconds with 9 seconds silence added
b) the waveform has bee truncated on the right by 9 seconds

This could be serious for a user who (for whatever reason) has a large amount of audio in negative time and applies compression to the whole track - as they will lose track data from the far end and that may bot be immediately visible or apparent to them.



The workaround is to
11)use click&drag (or the Selection Toolbar) to select just the portion in positive time ( and NOT Ctrl+A)
12) Effect>Compressor
04 Compressor no selection in negative time.png
04 Compressor no selection in negative time.png (36.49 KiB) Viewed 159 times



Note too that when you have a selection in negative time - the start Time in the Timer toolbar gives no helpful information
05 Compressor issue - unhelpful Start time.png
05 Compressor issue - unhelpful Start time.png (44.93 KiB) Viewed 159 times
But this is a different issue




I tried this with several other effects and this does not affect them in the same way.

I plan to log this , but first I will need to test this on my Big Sur Macbook.

@Steve: can you please retest on Linux with these steps to reproduce.
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steve
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Re: Audacity3.0.2 compressor error

Post by steve » Fri Apr 23, 2021 11:51 am

waxcylinder wrote:
Fri Apr 23, 2021 11:38 am
9) Effect>Compressor

Image
This is what I get at that step:

Trackpanel000.png
Trackpanel000.png (10.6 KiB) Viewed 152 times
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waxcylinder
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Re: Audacity3.0.2 compressor error

Post by waxcylinder » Fri Apr 23, 2021 11:54 am

I get the same results on My Big Sur macOS 11.2.3 Macbook Pro

I'll be logging this later today.

Peter.
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steve
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Re: Audacity3.0.2 compressor error

Post by steve » Fri Apr 23, 2021 11:57 am

waxcylinder wrote:
Fri Apr 23, 2021 11:38 am
Note too that when you have a selection in negative time - the start Time in the Timer toolbar gives no helpful information
That is to be expected because time widgets only support positive values. It's the result of the (frankly, rather dumb) idea that supporting negative time regions was a good thing, when actually it opens a big can of worms. I don't see this to be a "bug", but rather a consequence of a series of bad design decisions.
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