Stereo Tool

Well you have clipping and clipping. I do agree that the Dutch stations sound tiring.
The French also use alot of clipping but alot less gain riding which makes it easier to listen to ... for an hour or so.
Btw: didn't know Leif lived in Holland now

This is really insane... They were using an emergency transmitter for one station, and now that one broke down as well...

i just discovered from where is coming, for me, that very anoying artifact when loud bass beat is played. I always thought that it was from Loudness filter. Nope, it's from Phase-Linear HPF !

So constatation that would be better to have same two phase-linear HPF is not good because that artifact will be just exactly double louder, and that's not good.

EDIT:
This is not over!
This special Artifact disappears when is used 1-band AGC (even without reduction) or AGC OFF.
Test File (play in loop)
http://www63.zippyshare.com/v/14583087/file.html
Turn on only 2-band AGC and Bandpass filter with HPF at 15/40Hz
Even first blocks of audio are better.

EDIT2:
Now, when is 1band AGC is ON and HPF ON, same artifact appears again when Loudness is ON.
Now when is Loudness ON too, when "deep bass disortion protection" is OFF, Artifact is almost gone.
Finaly, when now is MB ON Artifact appears again.

Hey Bojcha,

The issue here is that this artifact is caused by *all* filters combined. So you can have 2 filters that - separately - sound completely clean, but combined cause this artifact. Which, among others, makes it VERY hard to fix.

The highpass filter is one of the biggest contributors to this artifact - and making it steeper will make things worse. Loudness contributes as well, as does Multiband ('Prevent artifacts' was made to reduce it!), and Bass Boost. I'm a bit surprised though about what you're saying about the AGC if there's no reduction at all - that might point to a bug in a calculation somewhere...

I think I've posted a link to an explanation of what's going on a long time ago in a different thread... Actually it's not even that difficult to solve this issue, but it would cause a CPU load increment of a factor 4... Ow and that wouldn't completely fix it, to really solve it completely I would also have to double the latency.

Filters no need to do nothing, jut to stay ON and all this happens.

Strange
I mean..
AGC 1-Band + Phase Linear HPF 20Hz = No Artifact
AGC 2-Band + Phase Linear HPF 20Hz = Artifact
etc..

But it's true .. in all filter combinations HPF is ON when artifact appears

Really? So without that it's gone?! (Oh I think I know what you mean - it's not gone completely but far less noticeable. So basically HPF is the main culprit. Which in turn means that I have to look into the HPF a bit more - yet again...)

Yes...
Loudness filter does not have that artifact at ALL.. Only when in combination is with HPF and "Deep Bass Protect" ON

BETA077:
- Declipper: Improved handling of loud bass + soft highs (and a lot of other situations as well): For a block of samples ,if the reconstructed signal looks a lot like the original, chances are that there was no clipping in the first place. Depending on the amount of samples detected as clipped (only a few = declipping won't hurt anyway, and might remove some click sound; a whole lot = declipping will almost always introduce artifacts; loud bass present = declipping will work less well), I'm now checking if I expect the added artifacts to outweigh the expected clipping removal. If not, I cancel the declipping.

Winamp DSP plugin: http://www.stereotool.com/download/dsp_ ... 20-077.exe
Stand alone version: http://www.stereotool.com/download/ster ... 20-077.exe
VST version: http://www.stereotool.com/download/vst_ ... 20-077.dll
VST version (No SSE2): http://www.stereotool.com/download/vst_ ... 20-077.dll
Command line version: http://www.stereotool.com/download/ster ... 20-077.exe
Linux command line version: http://www.stereotool.com/download/ster ... ETA620-077 NOT AVAILABLE
Linux GUI version: http://www.stereotool.com/download/ster ... ETA620-077 NOT AVAILABLE

TODO:
- Fix loading changed multiband frequencies
- Add buffer and filter for SCA output (SCA1 ok, SCA2 ok)
- Finish AGC improvement - make mono value configurable (replace checkbox by slider) 1 hour --> NO, not needed - anything else needed? -> NO
- Fix Punch
- Check what to do with new filters (such as bass AGC) - keep them, remove them, change them? --> KEEP
- Save new BASS_AGC setting in VST mode
- Loudness: Annoying cracking sound in bass. Slightly present in 5.00, worse in 6.00, maybe even worse in 6.10. Only when bass is too loud. Much worse than in Final Limiter (at same input level!) - so this clearly indicates a bug. Most likely cause: The filter that was added to remove bass artifacts....... - No, it's the louder bass. But it can be fixed by changing some settings. Default settings updated, and behavior for 'not Very strict' improved. Also Deep bass boost and Very deep bass protection are enabled for latency 512 now.
- Fix crash at program close
- Fix VST plugin version (does not run)
- Dynamically drop 'Allow louder highs, even if it causes vibrations' to 0 when bass filter suspects noticeable voice vibrations.
- Reduce Loudness CPU load
- Check and remove static variables
- Finish new de-essing filter (check what to do with the settings, remove at least some!)
- Convert Multiband input to MONO, then use arrays [2][4096] --> should give speedup. - FAILED
- Natural Dynamics: Fix or remove transient boost
- Natural Dynamics: Add expected + strength slider per band
- Finish declipping filter (clipping level detection + level reduction in dB). 1. Figure out why removal of unwanted frequencies causes flat lines at high quality setting with small overlap. This causes distortion, with this fixed repairs are MUCH better. 2. Fix MP3 correction, automatically scale down when this deteriorates the sound. --> TOP part fails!
- Declipping filter: Fix low latency behavior
- Always oversample clipping (configurable)
- Declipping filter: Change detection at lower input levels.
- "Test Right Channel" in "FM Transmitter Calibration" does not work since v6.10 (standalone) (bojcha)
- Declipper window close function - check! - Seems ok
- Scopes black background?
- Add AGC start level
- Declipping filter: Add comparting of sample history to make sure loud bursts are still detected properly (now, with 16 blocks of history, 65 samples are removed even when ignoring just 0.1%). I should also check the current block (probably with a margin of a factor 2).
- Declipping filter: Use reliability of tilt detection to determine movement speed; slowly move to default tilt (configurable!)
- Declipping filter: Far too many samples are marked as 'maybe/probably' clipped. Histogram not used or not cleared?
- Declipping filter: Optimize tilt detection for performance. SSE2 for maximum. And keep separate smaller histograms to determine the maximum (should perform much better).
- Declipping filter: Cleaned histogram must be mirrorred. After cleanup, mirror center is place where SIGMA above == SIGMA below! Only use on the lower end. Then run cleanup again! The result should contain approximately the same amount of data above and below. If not, that indicates incorrect detection.
- Declipping filter: Add a long term histogram, and use maximum of short term and long term start clipping level detection.
- Declipping filter: Check if 'No declipping when tilt cannot be determined' can safely be turned on.
- Declipping filter: Add setting and saving of new sliders (history size, percentage of highest samples to drop, tilt detection range start, end and precision)
- Declipping filter: Check why higher Quality settings causes cracking sounds. Answer: Rounding error, and too low filtering values to remove it.
- Move pre-emphasis to end of processing
- AGC: Separate 'Remove remaining peaks' settings for band 1 and 2
- Channels L/R swap in stand alone version when changing filtering/quality (eldoradofm)
- Declipping filter: Optimize peak matching for performance: Move determination to extra preprocessing step DONE; try to change if statements to min/max or something IMPOSSIBLE.
- Fix changing value of 'final limit' in Multiband when changing Loudness settings.
- Save bandpass filter order
- Save all new settings, also through VST interface
- Declipping filter: Change default values for Maximum distortion and Step size (see Bojcha's post)
- Try to improve reconstruction match (should remove artifacts for low bass + soft highs) ■ FAILED
- Declipper: Fix loud bass with soft higher frequencies issue. Do something with loudest frequency vs. peak level - if it cannot fit (Madonna, Metallica) there must be clipping, otherwise there might not be. On top of this I should somehow try to preserve deformed bass sounds (if they are not hard clipped). Maybe this will work: Find loudest frequency, if it's very low. Than assume that it's clipped at the maximum restoration level (?); generate a new tone (using lowpass filter) of the same frequency and clip that at some margin below the maximum peak level. Then filter the input signal based on the FFT of the clipped signal. Finally analyze this new signal; if it is indeed clipped the filtered output will resemble a clipped waveform (visible in sample histogram; no tilt issues!) instead of a sine wave. Use the output of this as input to determine how strict the clipping detection for the input waveform should be (eg. based on normal or sinusoid signals). This is all way too difficult and it just won't work. Here's the real solution: Detect if a loud bass sound is present, if so make sure that symmetrical clipping detection is used, possibly with automatic 'maybe clipped' level adjustment. This should only slightly affect Metallica (which still sounds very reasonable with symmetrical enabled), but has a big effect on DBN - Jack is Back (which is far less affected with symmetrical enabled; auto likely/maybe adjustment based on symmetrical should help even more). Using veil solution now
- Move veil processing to detilted signal
- Switch to symmetrical detection if very loud very low frequencies are present NO, not needed anymore because artifacts are fixed using another mechanism
- Finish blind interface WAITING FOR FEEDBACK TODO: TEST: Only display this window when needed.
- RDS issue reported here: viewtopic.php?f=15&t=3703&p=11524#p11524 partially solved
- Save veil settings and 'not reconstruct if like original' (STS + VST)
- If the reconstructed samples are close to the original samples, and there are a lot of 'clipped' samples OR there are very loud low frequencies present, don't declip. Solved, but should use a slider to set the sensitivity. Also increase the effect of bass and reduce overall level.
- Fix veil and detilting display (in declipper window; separate windows for separate channels; no change in DrawWave code needed!)
- Longer history for maximum level?
- Non phase linear highpass filter: Make steeper
- Update presets? (BASS_AGC etc.) 1 day
- Remove Natural Dynamics
- Change version number 1 hour
- Release 1 hour
- Add lowpass filter for stereo signal (will cause a lot of extra latency!) - it might be possible to avoid this latency using a Hilbert transform
- Add smarter clipping detection. Maybe something much simpler suffices: Current clipping detection with threshold + flat line detection
- Declipping filter: Automatically override the 3 clipping level sliders if the clipping level is detected very clearly (clear thin spike in sample value histogram). - NONSENSE, this is already done by the histogram function. But it can be made a BIT better - I think - by automatically LOWERING the 'always clipped' slider if a lot of data is present at the highest few bins (but care is needed for DBN - Jack is Back like tracks)
- Declipping filter: Create a new histogram after declipping, clean up and subtract from original.
- Change stand alone version to 32 bits.
- Optimization: Reduce CPU usage when input is silence.
- Natural Dynamics: Attempt to reduce number of bands by 2 (memory + cpu DIV 2), using bands with sloppy slopes (no interaction between bands -> memory usage DIV 2, out-of-cache reads gone, hopefull final filter gone too -> CPU DIV 2 again).
- Natural Dynamics: Voices, especially in chorus, still sound weird.
- Natural Dynamics: Smooth out different bands more to reduce low-bitrate-MP3-like sounds.
- Natural Dynamics: Optimize situation with no interaction between bands for performance.
- Natural Dynamics: Save settings in VST version

Hello Boys ,
I was found a guy that reports a buffer underrun ( buffer is empty in 15-20 seconds ) and program stops for a bit and again when buffer is full continue to work .
I confirm this - and happens when Natural Dynamics is ON
Other features ON - MB , AGC , Loudness(volume) , Hard Limit , Bandpass filter And FM panel ..... Soundcard is 192Khz capable .
and most important is that the "Use multiple cores for processing ..." is also ON

My CPU is at 50-51 % ( Athlon II X2 240e )
What is wrong in this case ?

With declipper this is not happen , only with Natural Dynamics .
excuse me I forgot the OS : Windows XP PRO SP2 , Beta77 Stand alone

That CPU cannot handle NaturalDynamics it just uses too much CPU.
No metter that you not see 100% usage. ST works just like that with Athlons (AMDs).

ST and Athlons.. not good idea.