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Audio being modified when it shouldn't be
https://forums.stereotool.com/viewtopic.php?t=1962		 Page 1 of 3
Author:  lukpac [ Sat Apr 24, 2010 12:24 am ]
Post subject:  Audio being modified when it shouldn't be
First off, the reason I'm using Stereo Tool is to undo CSG processing on '60s recordings. The only function I need (for that, anyway) is the Phase Angle slider - either -90 degrees or 90 degrees. I don't want anything else in the chain, and the resulting file should *only* be different with regards to that phase change, and only in the right channel. The left channel shouldn't be touched.

While experimenting with both the command line versions (3.55 and 4.22) and the Winamp plug-in versions (4.22 and 5 beta 2) I've noticed that even if I have everything off, the audio is still being modified. It shouldn't be. It should be an exact copy of what is fed in.

While playing with the Compare WAVs function in EAC, I've noticed the following:

- 3.55 and 4.22 give identical results on the command line
- 3.55/4.22 generate files that have some unchanged samples and some changed samples
- loading the settings into the 5b2 Winamp GUI generates files that are completely different from the original files
- turning Stereo Image *on* but keeping all of its settings off results in *different* changed samples from having it off

Everything *should* be transparent when not being used, no?

Here's my current settings file. "Extra phase shift" would normally be 0.5 for 90 degrees, but I have it set to 0 for testing transparency. Is there a setting I'm missing that is causing things to not be transparent when they should be?

[Common]
Pre amplifier=1
Post amplifier=1
Extra loudness=0
Hard limit output=0
Process for low latency=0
Mode=Advanced
[Noise Gate]
Enabled=0
Difference=0
Noise level=0.800000012
[Singleband Compressor]
Enabled=0
Difference=0
Maximum volume=1.5
Maximum value=24576
Attack speed=0.00009
Decay speed=0.100000001
Above Top Limiter=0
[Pre Compressor]
Enabled=0
Difference=0
Delay enabled=0
Maximum volume - Band 1=68640
Maximum volume - Band 2=14230
Attack speed - Band 1=0
Attack speed - Band 2=0.000005001
Decay speed - Band 1=0.001414664
Decay speed - Band 2=0.000249943
[Multiband Compressor]
Enabled=0
Difference=0
Delay enabled=0
Very high quality enabled=0
Maximum volume - Band -1=5380
Maximum volume - Band 0=6260
Maximum volume - Band 1=6750
Maximum volume - Band 2=6940
Maximum volume - Band 3=6850
Maximum volume - Band 4=6310
Maximum volume - Band 5=5670
Maximum volume - Band 6=4990
Maximum volume - Band 7=3720
Maximum volume - Band 8=1560
Attack speeds linked=1
Attack speed - Band -1=0.000049975
Attack speed - Band 0=0.000049975
Attack speed - Band 1=0.000049975
Attack speed - Band 2=0.000049975
Attack speed - Band 3=0.000049975
Attack speed - Band 4=0.000049975
Attack speed - Band 5=0.000049975
Attack speed - Band 6=0.000049975
Attack speed - Band 7=0.000049975
Attack speed - Band 8=0.000049975
Decay speeds linked=1
Decay speed - Band -1=0.000399904
Decay speed - Band 0=0.000399904
Decay speed - Band 1=0.000399904
Decay speed - Band 2=0.000399904
Decay speed - Band 3=0.000399904
Decay speed - Band 4=0.000399904
Decay speed - Band 5=0.000399904
Decay speed - Band 6=0.000399904
Decay speed - Band 7=0.000399904
Decay speed - Band 8=0.000399904
Above Top Limiter=0
Clipping enabled=1
Postprocessing enabled=0
Relative clip position - Band -1=3
Relative clip position - Band 0=3
Relative clip position - Band 1=2.508771658
Relative clip position - Band 2=1.985074759
Relative clip position - Band 3=1.985074759
Relative clip position - Band 4=1.985074759
Relative clip position - Band 5=1.985074759
Relative clip position - Band 6=1.985074759
Relative clip position - Band 7=1.985074759
Relative clip position - Band 8=1.985074759
Final limiter value=1
Final limiter decay speed=0.000700178
Final limiter clipping=2.508771658
Equalizer enabled=0
Equalize before multiband-compression=1
Equalizer position - Band -1=1
Equalizer position - Band 0=1
Equalizer position - Band 1=1
Equalizer position - Band 2=1
Equalizer position - Band 3=1
Equalizer position - Band 4=1
Equalizer position - Band 5=1
Equalizer position - Band 6=1
Equalizer position - Band 7=1
Equalizer position - Band 8=1
[Stereo]
Enabled=1
Delay enabled=0
Difference=0
Center bass=0
AZIMUTH limit=0
AZIMUTH change speed=0
Image phase amplifier=1
Image phase amplifier maximum angle=180
Image phase amplifier maximum separation strength=100
Image width amplifier=1
Extra phase shift=0
Mono or stereo only=0
[Channel Delay]
Enabled=0
Left Delay=0
[Output Filter]
Enabled=0
Lowpass filter=15000
Highpass filter=20
[Final Limiter]
Enabled=0
Difference=0
Pre-amp=1
[FM Transmitter]
Enabled=0
Pre-emphasize=0
Pre-emphasis time=50
Output is pre-emphasized=0
Stereo encoder enabled=0
RDS encoder enabled=0
Pilot signal volume=9
RDS signal volume=4.5
FM overdrive volume=1
RDS PS text=2s:STEREO/2s:TOOL/<1=1.5s,2..-2=2t,-1=1.5s:WWW.STEREOTOOL.COM
RDS RadioText text=60s:Stereo Tool: Professional Audio Processing - http://www.stereotool.com/30s:Stereo Tool by Hans van Zutphen, 1999-2008 - http://www.stereotool.com
RDS PTY=0
RDS PI=65535
RDS Alternative frequency 1=0
RDS Alternative frequency 2=0
RDS Alternative frequency 3=0
RDS Alternative frequency 4=0
RDS Alternative frequency 5=0
RDS Alternative frequency 6=0
RDS Alternative frequency 7=0
RDS Alternative frequency 8=0
RDS Alternative frequency 9=0
RDS Alternative frequency 10=0
RDS Alternative frequency 11=0
RDS Alternative frequency 12=0
RDS Alternative frequency 13=0
RDS Alternative frequency 14=0
RDS Alternative frequency 15=0
RDS Alternative frequency 16=0
RDS Alternative frequency 17=0
RDS Alternative frequency 18=0
RDS Alternative frequency 19=0
RDS Alternative frequency 20=0
RDS Alternative frequency 21=0
RDS Alternative frequency 22=0
RDS Alternative frequency 23=0
RDS Alternative frequency 24=0
RDS Alternative frequency 25=0
RDS TP=0
RDS TA=0
RDS Music=1
RDS Artificial Head=0
RDS Compressed=1
RDS Dynamic PTY=0
RDS RadioText Enabled=1
RDS ClockTime Enabled=1
FM Transmitter Calibration Enabled=0
MPX Oversampling mode=Follow main Quality setting
FM Transmitter Calibration - Volume 20 Hz=1
FM Transmitter Calibration - Volume 40 Hz=1
FM Transmitter Calibration - Volume 80 Hz=1
FM Transmitter Calibration - Volume 160 Hz=1
FM Transmitter Calibration - Volume 320 Hz=1
FM Transmitter Calibration - Volume 640 Hz=1
FM Transmitter Calibration - Volume 1280 Hz=1
FM Transmitter Calibration - Volume 2560 Hz=1
FM Transmitter Calibration - Volume 5120 Hz=1
FM Transmitter Calibration - Volume 10240 Hz=1
FM Transmitter Calibration - Volume 19000 Hz=1
FM Transmitter Calibration - Volume 23000 Hz=1
FM Transmitter Calibration - Volume 28000 Hz=1
FM Transmitter Calibration - Volume 33000 Hz=1
FM Transmitter Calibration - Volume 38000 Hz=1
FM Transmitter Calibration - Volume 43000 Hz=1
FM Transmitter Calibration - Volume 48000 Hz=1
FM Transmitter Calibration - Volume 53000 Hz=1
FM Transmitter Calibration - Volume 57000 Hz=1
FM Transmitter Calibration - Phase shift 20 Hz=0
FM Transmitter Calibration - Phase shift 40 Hz=0
FM Transmitter Calibration - Phase shift 80 Hz=0
FM Transmitter Calibration - Phase shift 160 Hz=0
FM Transmitter Calibration - Phase shift 320 Hz=0
FM Transmitter Calibration - Phase shift 640 Hz=0
FM Transmitter Calibration - Phase shift 1280 Hz=0
FM Transmitter Calibration - Phase shift 2560 Hz=0
FM Transmitter Calibration - Phase shift 5120 Hz=0
FM Transmitter Calibration - Phase shift 10240 Hz=0
FM Transmitter Calibration - Phase shift 19000 Hz=0
FM Transmitter Calibration - Phase shift 23000 Hz=0
FM Transmitter Calibration - Phase shift 28000 Hz=0
FM Transmitter Calibration - Phase shift 33000 Hz=0
FM Transmitter Calibration - Phase shift 38000 Hz=0
FM Transmitter Calibration - Phase shift 43000 Hz=0
FM Transmitter Calibration - Phase shift 48000 Hz=0
FM Transmitter Calibration - Phase shift 53000 Hz=0
FM Transmitter Calibration - Phase shift 57000 Hz=0
[Direct soundcard access]
Enabled=0
Device ID=SigmaTel Audio
Volume=1
Buffer size=1
Send to Winamp=Nothing
ASIO Override channel 1=4
ASIO Override channel 2=5
[Low latency output]
Enabled=0
Device ID=
Volume=1
Buffer size=0.079999998
ASIO Override channel 1=2
ASIO Override channel 2=3
Author:  hvz [ Sat Apr 24, 2010 1:57 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Welcome lukpac,

EDIT: In your preset, you have Phase Rotation (new in version 5.00) enabled, which completely changes the waveform. If you turn it off, the difference is at -90 dB (compared in CoolEdit), which means a sample value difference of at most -1 or +1.

(I've kept my old answer below, this might clear up where the +1/-1 difference comes from, and what the difference between GUI and command line versions is).

How did you check for changes? Possible causes for changes are:
- Delay may cause audio to be pushed forward in time. The command line versions correct this, the Winamp/VST versions don't (they add silence at the start).
- Small rounding errors may occur. If the input value is 30000, the output value might be something like 29999 or 30001. Stereo Tool also uses 'dithering' to add some random noise (at the last bit) which may also cause a +/- 1 change in sample value. For most processing steps (including rotating 90 degrees) this should actually make the sound more natural - although it is useless for the left channel in this situation.
Author:  lukpac [ Sat Apr 24, 2010 2:03 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Quote:
Welcome lukpac,

How did you check for changes? Possible causes for changes are:
- Delay may cause audio to be pushed forward in time. The command line versions correct this, the Winamp/VST versions don't (they add silence at the start).
- Small rounding errors may occur. If the input value is 30000, the output value might be something like 29999 or 30001. Stereo Tool also uses 'dithering' to add some random noise (at the last bit) which may also cause a +/- 1 change in sample value. For most processing steps (including rotating 90 degrees) this should actually make the sound more natural - although it is useless for the left channel in this situation.

My guess based on what you're writing:
- Difference between command line and plugin versions is the time shift
- Some samples are identical, some aren't: I'm guessing that this is caused by rounding errors, so the difference should be really really small. If it's not really small, something is wrong.
Like I said, I've been using the Compare WAVs function in EAC. That spits out a list of locations in a file that are different, and/or if one file is longer than the other. It does not, however, indicate exactly how the 2 files are different. The time shift in the plugin version should be accounted for in EAC, although I haven't closely investigated.

I guess my concern is that dithering is happening even when no processing is occurring, be it when nothing is turned on or in the case of the left channel for the phase rotation.

I'm assuming you should be able to replicate the issue, but I could send small example files if necessary.
Author:  hvz [ Sat Apr 24, 2010 2:13 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Hi Lukpac, you're reading too fast :-) - I just re-read your initial post and edited my response.

Most of the difference comes from the Phase Rotation filter, which can be turned off in the Loudness/Limiting window.

What remains are occasional spikes of +1 or -1, basically rounding errors. I'll see if I can get rid of those (I see they are all in the same direction and happen very infrequently, maybe reducing the dithering strength suffices to get rid of them completely.)
Author:  lukpac [ Sat Apr 24, 2010 2:20 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Quote:
Hi Lukpac, you're reading too fast :-) - I just re-read your initial post and edited my response.

Most of the difference comes from the Phase Rotation filter, which can be turned off in the Loudness/Limiting window.
I'm not seeing that option in the settings I posted. Nor should it be there if it was introduced in version 5 - those settings were created with an earlier version (3.55 I believe). Also, every section is disabled (Enabled=0) except for Stereo, so I wouldn't expect any other settings to make a difference, beyond what's under Common.
Author:  hvz [ Sat Apr 24, 2010 2:43 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Quote:
I'm not seeing that option in the settings I posted. Nor should it be there if it was introduced in version 5 - those settings were created with an earlier version (3.55 I believe). Also, every section is disabled (Enabled=0) except for Stereo, so I wouldn't expect any other settings to make a difference, beyond what's under Common.
It's new in version 5.00, and - as has been the case for other new filters that were added later - it's turned on in the default settings that you get after installing Stereo Tool for the first time. For the majority of cases, turning it on greatly improves the sound quality - in your case it doesn't (in your case it has no or almost no effect on the sound that comes out, but the waveform looks completely different).

I'll see if I can find a way to detect that you're upgrading from an earlier version and not using any filters for which Phase Rotation improves the sound - and in that case keep it turned off. (I've just added this to the TODO list for version 5.00).
Author:  lukpac [ Sat Apr 24, 2010 2:50 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Quote:
It's new in version 5.00, and - as has been the case for other new filters that were added later - it's turned on in the default settings that you get after installing Stereo Tool for the first time. For the majority of cases, turning it on greatly improves the sound quality - in your case it doesn't (in your case it has no or almost no effect on the sound that comes out, but the waveform looks completely different).

I'll see if I can find a way to detect that you're upgrading from an earlier version and not using any filters for which Phase Rotation improves the sound - and in that case keep it turned off. (I've just added this to the TODO list for version 5.00).
Duly noted, although like I said, I tried both 3.55 and 4.22 via the command line.

Thanks for the help. It isn't a huge deal, but I'd like to reduce the amount of processing as much as possible.
Author:  hvz [ Sat Apr 24, 2010 3:04 am ]
Post subject:  Re: Audio being modified when it shouldn't be
I've now reduced the amount of dithering by 1%, for audio that has not been changed the output is now exactly identical to the input!

This change will be available in the next BETA that I'll post (dunno when yet).
Author:  lukpac [ Sat Apr 24, 2010 3:05 am ]
Post subject:  Re: Audio being modified when it shouldn't be
Quote:
I've now reduced the amount of dithering by 1%, for audio that has not been changed the output is now exactly identical to the input!

This change will be available in the next BETA that I'll post (dunno when yet).
Cool, sounds good.
Author:  hvz [ Sat Apr 24, 2010 1:08 pm ]
Post subject:  Re: Audio being modified when it shouldn't be
I just noticed that my answer about Phase Rotation was wrong. If I press RESET before I load your preset it's turned off, otherwise it's turned on. Apparently the "RESET" was missing when you load an STS file, which causes strange (unwanted) behavior if you're loading older version STS files. I've now added it; will also be available in the next version.
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