Distorted sound in Mulab

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There is something definitely wrong with the Mulab audio processing. I don't know whether it´s a matter of M9 or whether its already wrong with M8. I'm just trying M9 v21 on Mac and have some weird audio issues. After working some times with a few plugins ( internal and vst´s) suddenly the sound gets distorted and the cpu indicator in Mulab goes above 100%, although nothing is playing. From this moment on every sound is distorted. The system cpu is quite low. I have to restart the project to fix this issue. It could be a matter of special vst´s, but I tried a lot of them and have the same issue. So, I don't think that is a special plugin which causes this issue.
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Now I have tried a similar project with the same plugin combination in M8 and haven´t this issue. So, it seems to be a problem of M9.

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Does the issue also happen when you disable multi-core processing?
Disable multi-core processing = Audio Setup -> Num Audio Processor Threads = 1

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Yes, the number of threads is =1.
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Does the issue also happen when purely using internal sounds & effects thus no VSTs at all?

You wrote "I have to restart the project to fix this".
What do you mean with this: Reload the project? Or restart MuLab?

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wibem1 wrote: Sun Feb 06, 2022 5:55 pm Yes, the number of threads is =1.
Are you using exactly the same audio setup in M8 and M9?
Thus also using that same audio device?

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Does the issue also happen when using the Mac built-in audio output?

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In the meantime I found out that I can get similar distortions with M8 too. So, it seems not to be a matter of M9, although it seems a bit different, when the distortions appear. They are kind of randomly. My audio output goes through a USB interface. But with the internal audio output there are distortions too. For the case of using only internal plugins and effects, I haven´t got the distortions until now. But I haven´t really tested it .
The distortions disappear, when I reload the project or restart the program.
I must say, that I get similar distortions in other cases, which I reported in another thread.
When I have a project open for a long time or go into sleep mode , I often get distortions too. But its not predictable.

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wibem1 wrote: Sun Feb 06, 2022 7:48 pm For the case of using only internal plugins and effects, I haven´t got the distortions until now. But I haven´t really tested it .
It's essential to test that. Please make a copy of the project that causes the issue, replace every VST synth by an internal synth and each VST effect by an internal effect. It doesn't have to sound perfect at all, it's just a test. Then save that test project as a separate file. Quit MuLab. Relaunch MuLab and open that test project and try to repeat that distorted sound issue. Can you repeat it? If yes then make sure to keep that test project for possible next tests.
wibem1 wrote: Sun Feb 06, 2022 7:48 pm When I have a project open for a long time or go into sleep mode , I often get distortions too. But its not predictable.
1) What do you call "a long time" ?

2) Note that keeping MuLab open in sleep mode is not a supported case as it's too much system dependent. On some systems it may be ok, on others it may cause issues. Could also depend on the audio driver. If you notice that there are issues when keeping MuLab open while you put your computer to sleep, then first quit MuLab before your computer goes into sleep.

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Hey wibem, when I had only a 2-core cpu on my old Mac I got distortion when some plugins exceeded its limited processing ability (see cpu meter). Some plugins are cpu-intensive, patches with effects require more cpu, and multiple instances or rapid sequencing even more. You may be trying new things in M9 that require more cpu than you have.
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Thanks for your answers.
Jo, I will try to test it with only internal plugins.
Michael, it can of course happen due to my cpu limitation, but it seems for me at least not logically. I don't have very cpu intensive plugins in that project (at least 3 vst's and one internal) and the system cpu meter doesn't show any overload of the cpu. It's just the internal cpu meter, which gets crazy. How is that possible? And why is this happening not from the beginning of the playback, but after a while? I can play around with the critical project for a while without any overload and after a while the issues begin, that the sound gets distorted and the internal cpu meter jumps to a high value and stays there until I restart or reload the project. Why?
Why does Mulab behave this way that it has an overload, even if the playback stops? I would expect that the overload ends, when the playback stops. This is a behavior which I know from other daws.
Another question is about the audio buffer, which is normally an important thing to prevent an overload. In other daws I can increase the audio buffer and the problems are often solved. In Mulab I found a setting for the audio buffer in the general settings and I set it to the very high value 2048. But that doesn't seem to help. In fact a high value should be reflected in the cpu usage, but I can't observe it in Mulab. Is there another setting in Mulab to reduce the cpu usage?

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Hey wibem, my main point is to consider the plugin and how you are using it. For example some plugin patches with long release times will steadily increase cpu if you have a sequence of short notes, because the releases overlap.

Do a science experiment: change one variable at a time.
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wibem1 wrote: Mon Feb 07, 2022 4:51 am Why does Mulab behave this way that it has an overload, even if the playback stops? I would expect that the overload ends, when the playback stops. This is a behavior which I know from other daws.
There are plugins which might cause this kind of behaviour, which can be easily overlooked. For example I noticed with a project that the longer I left it open the larger the file size would become if I saved it. This happened regardless of whether playback was engaged or not. It took a while, stripping back tracks, plugins etc. to locate the cause. It turned out to be Youlean Loudness Meter, which continues to record playback data as long as the track is activated, irrespective of playback. This would also cause instability if computer was left in sleep mode.
The point is you will need to test your project to destruction this way, and the cause does not even have to be related to a sound generator plugin.

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wibem1 wrote: Mon Feb 07, 2022 4:51 am Jo, I will try to test it with only internal plugins.
It's essential to test that. Please make a copy of the project that causes the issue, replace every VST synth by an internal synth and each VST effect by an internal effect. It doesn't have to sound perfect at all, it's just a test. Then save that test project as a separate file. Quit MuLab. Relaunch MuLab and open that test project and try to repeat that distorted sound issue. Can you repeat it? If yes then make sure to keep that test project for possible next tests.

Sorry for repeating this, but it really is essential to test this if we want to proceed the analysis of this issue.

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