Inconsistent latency --> automatic track shift woes

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Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by gpk » Sun Nov 26, 2017 8:15 pm

Hi, I flagged up a problem I was having a while back...
http://forum.audacityteam.org/viewtopic.php?f=47&t=65943&start=10#p235015

At the time I thought it might be down to old versions of OS X or Audacity I was using so I didn't pursue the problem further back then.

But it's still there :?

Am running MacOS 10.12.6, Audacity 2.2.0
Using the built in audio i.e. laptop speaker and microphone, just to do really simply multitrack stuff.

My track shift setting in preferences is set to -377 (which seems quite a lot to me). Sometimes this figure works, but not always. Makes multitracking a bit of a pain. Have I missed anything obvious?

TIA!
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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by kozikowski » Sun Nov 26, 2017 9:48 pm

laptop speaker and microphone

You can't overdub with the built-in speakers and microphone. You can totally do that with the built-in microphone and headphones plugged in the side.

Were you using the speaker? I would expect echoes and sound management problems if you are. Do you have bad sound that appears as if it's latency shifting?

As a side issue, make sure there's nothing else running on the machine, shut down the WiFi. Shut down the Mac, wait a bit and start. The new machines don't chong any more, right?

Make sure you have enough hard drive space.

Go > Computer > Control Click Macintosh HD (or whatever you called it) > Get INFO.

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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by gpk » Sun Nov 26, 2017 9:59 pm

Thanks, yes I meant to say it's a Macbook pro 2012 2.3Ghz Intel core i7 which has 4 dual core CPUs, 250GB free HD space (SSD), so there should be plenty of oomph there.

Though TBH if I'm going to have to shut down wifi etc. in order to use Audacity then I might decide to try something else... but maybe you were suggesting for testing purposes.... :geek:
I mean it used to work fine on my old 2002 Dell XP laptop without having to mother it too much

Yes I was just testing using built-in speakers. To see how the latency thing was.

Do you have bad sound that appears as if it's latency shifting?
Not quite sure what you mean?

Thanks again...
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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by kozikowski » Sun Nov 26, 2017 11:20 pm

but maybe you were suggesting for testing purposes

Maybe. I have too many times when my laptop fans kicked in for no good reason and Go > Utilities > Activity Monitor told me "web page content" was taking up 125% of system resources and most of the memory. Apparently I can have a fist-fight between two companies about who's going to sell my personal data and to whom.

Audacity is a 32-bit app, not 64 and not multi-processor compliant. It doesn't take much to leave it bleeding by the side of the road.

You seem to be skittish about turning off WiFi. What are you running and are any of them audio services? Audacity doesn't Play Well With Others. That's one of the reasons it's not recommended to record Skype or Games.

Does the latency ever change within one single performance? That's very serious.

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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by gpk » Mon Nov 27, 2017 12:31 am

Yes I too know all to well that Google Chrome mission to take over the computer.....

The only things I generally run are web browsers, word processor, email and the like.... but sometimes itunes (not that it's usually doing anything) and others. Will see what happens after a reboot then. I don't have a problem turning wifi off, just a bit of resistance if Audacity was regularly going to need what seemed to me like it might be excessive molly-coddling. But for testing then yes I agree a clean sheet is needed.

Strange if no one else is experiencing this problem though.
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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by kozikowski » Mon Nov 27, 2017 1:15 am

Strange if no one else is experiencing this problem though.

Yes. It's not a hair-on-fire problem if only you have the problem on only your machine.
if Audacity was regularly going to need ... molly-coddling.

But we won't know until we solve it. If it makes absolutely no difference at all, then that wasn't it.

I should ask the magnitude of the problem. No home machine is ever going to hit it down to the digital sample (1/44100). Audacity is a musical editor not a scientific instrument.

I'm moved to ask how you set the Recording Latency.


Side Issue: Macs do have microphone processing. Best turned off for music.

Apple > System Preferences > Sound > Input > Microphone: [_]Use Ambient Noise Reduction (de-select)

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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by steve » Mon Nov 27, 2017 10:28 am

gpk wrote:My track shift setting in preferences is set to -377 (which seems quite a lot to me). Sometimes this figure works, but not always.

What is the "Preferences > Devices > Latency : Buffer Length"?
Try changing that value in steps of say 20 ms, both down to 0, and up to 200 ms. Don't worry about whether the latency correction (the track shift) is 'correct' during this testing - what you are looking for is consistent results. The default buffer is 100. Can you get consistent results with a larger or smaller buffer?

(Mac's are a bit weird in this respect and sometimes work better with a smaller buffer).

If you find a buffer size that gives consistent results, use that and set the track shift as described here: http://manual.audacityteam.org/man/latency_test.html

Note that any changes to the sound set-up is likely to change the amount of latency, so it's important to set up latency correction using the exact same audio set-up as you will be using when recording. If you change the set up in any way, you may need to repeat the latency correction procedure.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by gpk » Mon Nov 27, 2017 11:19 pm

@koz: magnitude of the problem: track shift is currently set to -377ms. Sometimes that works, sometimes it's 200ms off (roughly) or more.

I set the latency using the air between the mic and the speakers as a rough and ready loopback cable.

Ambient Noise Reduction was already turned off :)

Am still mystified - can't imagine what is causing the problem - my setup seems pretty ordinary to me, but obviously isn't.

@steve: buffer length currently 100. I assume that's the default - when I installed Audacity 2.2 yesterday I cleared out all the old prefs and plugins (AFAIK)

Will see if I can find a loopback cable to set the latency and do the other steps suggested. It will probably be some time before I get round to all of that, and actually get a coherent set of results, but I will post back in due course.

Thanks for all the suggestions. :-D
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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by kozikowski » Tue Nov 28, 2017 2:06 am

OK, so you produce a click track and play that back in overdubbing. Laptop Speakers and Internal Microphone.

You inspect both tracks, measure the difference between the two sets of clicks and add that correction to what's already in latency correction.

Do another recording. Then play the composite to make sure everything is OK.

Image

OK, so far? When does it fail? Do you need to have an extended time between alignment and performance for it to be off? Or you just never get there?

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Re: Inconsistent latency --> automatic track shift woes

Permanent link to this post Posted by kozikowski » Tue Nov 28, 2017 2:14 am

The default click track has three identical clicks and one counter click. What's that, a fox-trot?

Is it possible you're aligning to the wrong clicks? Oddly, it's better to sneak up on proper alignment rather than hit it first time out. That lets you listen to the one that's almost right and hear that you're aligning to the right clicks.

TICK-TICK took-took took-took took-took TICK-TICK....

Aligning to the wrong ticks could give you corrections that far off.

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