Stereo Tool

BETA078:
- Declipper: Small changes in the handling of loud bass sounds (actually only a configuration change - it is now slightly more likely that declipping still occurs when loud bass is present)
- Declipper: Replaced checkbox from previous version with a slider (Best declipping / artifact reduction), at value 1.00 the behavior should be very close to that of BETA077. At value 0 it's equal to BETA077 with the checkbox switched off. There's also a 'More' checkbox, if you check this declipping will ALWAYS be turned off if it results in a flatter waveform (ie. with less texture) than the original.
- Declipper: Added waveform displays in the configuration window so you can now see the result of detilting and veil settings.
- REMOVED NATURAL DYNAMICS. It didn't work too wel yet (too many artifacts), and the CPU load is insanely high, and I didn't want to wait with releasing version 6.20 until I've fixed this filter. So for now it's gone...
(Actually it's still usable, but you'll need to configure it via the STS file).

Winamp DSP plugin: http://www.stereotool.com/download/dsp_ ... 20-078.exe
Stand alone version: http://www.stereotool.com/download/ster ... 20-078.exe
VST version: http://www.stereotool.com/download/vst_ ... 20-078.dll
VST version (No SSE2): http://www.stereotool.com/download/vst_ ... 20-078.dll
Command line version: http://www.stereotool.com/download/ster ... 20-078.exe
Linux command line version: http://www.stereotool.com/download/ster ... ETA620-078 NOT AVAILABLE
Linux GUI version: http://www.stereotool.com/download/ster ... ETA620-078 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
- Fix veil and detilting display (in declipper window; separate windows for separate channels; no change in DrawWave code needed!)
- Fix declipper display cleanup
- 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. Also add texture based filtering, and use a slider to set the sensitivity. Also increase the effect of bass and reduce overall level.
- Save veil settings and 'not reconstruct if like original' (STS + VST)
- 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
- Remove Natural Dynamics Partially done, does the crash come from here?
- Longer history for maximum level?
- Update presets? (BASS_AGC etc.) 1 day
- 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.
- Non phase linear highpass filter: Make steeper
- 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

I'm still messing with Veil settings, but I've already found I need it to be at least this low during some songs, in order to maintain the added clarity of declipping.

On most songs where it made the difference, more than that didn't make a difference, but less definitely did.

[edit]
posted before the above update
[/edit]

The veil display might help with configuring it - so far I could get good declipping with the veil margin set to about 90% IF the elasticity is set high enough. If you find exceptions to this, please let me know...

Are these defaults not high enough?

A simple question :

Using the latest betas, does the declipper work when high pass filter is on NON LINEAR mode ?

Should be in linear mode for best declipping resaults maiby but also works on non linear ?



( finnaly, after 2 years...i discovered that the problem was NOT the low bass frequencies for DDS and analogue exciters high instability !
( even by pushing the high pass filter at 80 hz (!!!!) the instability phenomenon was still there, ,, so , in my case the problem WAS NOT the bass frequencies ! the problem was HIGH FREQUENCIES ( overclipped?! high frequencies) ! ,
i am still testing
maiby it's time for a ..lowpass filter for stereo signal

Are you using the analogue output of the soundcard to feed the transmitter?

Nice display.
- But there's a problem with clearing the screen. Some part in the middle is left when turning off SHOW TILT+VEIL.
- Another problem with SHOW INPUT and SHOW BIG OUTPUT on, the output is actually SMALLER then with the normal SHOW OUTPUT.

They are for the tracks that I tested. But so is the 90% margin...

I noticed. Will add it to todo list.

Should not make any difference. The declipper is placed BEFORE *any* other filter.
Hm, that's still odd. You can record the Stereo Tool output and oversample it as much as you want - won't get any peaks. I think you'll need to use the "FM Calibration" filter... You can do a reasonably reliably check by sending audio on one channel and silence on the other, and then checking if you receive silence on that channel (say, at least around -30 or -40 dB). If not the audio doesn't reach the FM receiver as it was sent out by Stereo Tool - and that can be caused by anthing that's in between...