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 Post subject: audible distortion
PostPosted: Mon Feb 04, 2013 9:37 am 

Joined: Sun Feb 03, 2013 2:39 pm
Posts: 334
In rare cases I get a red input level meter and audible distortion with the winamp plugin version (32-bit integer input), even using factory defaults (input level = 1x). Bypassing ST sounds fine. Why is that? What increases the volume of the input?


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 Post subject: Re: audible distortion
PostPosted: Mon Feb 04, 2013 3:05 pm 
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Joined: Mon Mar 17, 2008 1:40 am
Posts: 11213
The input really shows what comes in - it turns red ONLY if the input hits the peak level.... Could it be related to your other post (floats vs. ints), something like you're playing an MP3 and the values get cut off when they are converted from floats to ints? Which wouldn't occur as soon as you remove Stereo Tool from the chain?


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 Post subject: Re: audible distortion
PostPosted: Mon Feb 04, 2013 4:38 pm 

Joined: Sun Feb 03, 2013 2:39 pm
Posts: 334
The conversion to integers takes place before ST is entered, so it gets integers only. I don't understand how they can overflow with your tool being active but playing fine when pressing the bypass button or removing ST completely (still doing the int conversion for testing, of course). If the input is actually too loud (which could be possible) wouldn't I get distortions no matter what?
Just to clarify: if the peak level gets hit the input level meter turns red but sound shouldn't distort, right? Or is one of your many filters already intervening at this stage, maybe causing the problem here?
Btw: does ST work with floats internally, therefore converting input from ints to floats again and then vice versa on output?


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 Post subject: Re: audible distortion
PostPosted: Mon Feb 04, 2013 4:41 pm 
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Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4168
Done simple test with winamp and ST 7.03.
Two Sine tones 4kHz at 0.00dB one 32bit float and one 32bit non float. Both Stereo 44.1kHz samplerate.

Non-Float gives me red bars on input and float no.
Test Files

However, no distortions.

Edit: Lowering nonfloat file to -0.01dB removes red bar. So, not big deal.


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 Post subject: Re: audible distortion
PostPosted: Tue Feb 05, 2013 10:17 am 

Joined: Sun Feb 03, 2013 2:39 pm
Posts: 334
Thanks Bojcha. Your floats testfile works fine, the ints one does give distortions here.
My chain is: mpc-hc -> lav audio (mixing multichannel to stereo; always outputting 32-bit ints) -> ffdshow (just to allow for ST; no other processing at all) -> Stereo Tool -> reclock (resampler)
I also made my own 8-channel 24-bit ints 48kHz testfile. It plays fine when the lav audio mixing matrix is normalized (green level meter in ST) but distorts (red level meter in ST) when one uses 'clipping protection' instead which shouldn't overflow according to the author of lav filters.
Again all tests made with ST default settings (which means all processing off, right?) and audible distortions gone when pressing the bypass button.

EDIT: found out 2 things:
  • When setting lav audio to use 24-bit ints distortion is gone. The question is where's the problem: other software works fine with lav, only ST doesn't so far.
  • The first preset (constant volume, increased stereo) cannot be chosen in 7.03 (or it it just a title?)


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