Stereo Tool

Hi Hans,
I tested new version with new slider.
First, other tones except bass are definitely clearer.

About bass.
The new limiter do the job but i have feeling that the bass is not so natural anymore if i use slider lower then 70-80%
It manifesta not like distortion but like it's out of tune.

And, i think the FM output (after encode) is Higher then "Normal output".
When i make preset (on my pc) with normal output (with loudness e.g. x2.60) and transfer preset to transmitter pc and load into ST, then i have distortion and i must lower loudness.
This is not only with this last version.. same is with default v4.10.

edit:
i'll remind you again on one bug i present 2-3 months ago.
"Final Limiter Meter" is not working good. (IN MAIN WINDOW). In "Limiting and Loudness" Window works normaly.
Same is with stantalone version and Winamp plugin.

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control point
control point2

I may have a solution for the "unnatural bass" problem.

I went back to the original problem: Very loud bass sounds cause distortion, and due to that it's not possible to feed the Loudness filter with very loud bass peaks. So the bass needs to be set at a lower level to get a good quality sound.

I have now changed the range of the limiter max value - you can now set it to values up to 200% instead of 100%. 100% means that before the Final Limiter and Loudness filter, the bass level is limited to 100% of the maximum possible output amplitude. So at 200% the bass is still twice as loud as the maximum output level can be, and Loudness needs to handle it.

So now the order is changed to the opposite of what it was before: Instead of limiting the loudness to a low enough level immediately, the new method limits the very loud peaks and then relies on the old Loudness filter to handle the remaining peaks.


How to use it:
Default values are now: Max frequency: 125 Hz, Max Level: 140% (!). You can set "Allow louder lows" to values between 1250 and 2500 without getting a lot of distortion (about equal to that of the original 4.10 version, but you'll get more lows).

I have also changed the way the new slider works, it's now basically a bass boost filter for very low (up to about 70 Hz) frequencies. It still causes the same type of distortion, but as it turns out, for very low frequencies this is not very disturbing - and it DOES increase the very deep bass level by about 1 dB. (The default value is set to 100%, should probably be 0%...)


The advantage of this method:
- New limiter now limits at 140%, so nowhere near the 70-80% you were talking about. It still removes very loud peaks (note: I've tested that at a Loudness value of 4 (!), you should probably set the limit a bit lower for lower Loudness values).
- The sound is basically the sound of the original 4.10 version, without the distortion caused by very loud peaks. So increasing the bass level using the equalizer is possible now. Also, the "allow louder lows" slider can be set higher, which immediately leads to more lows. (Having said that, there are slightly less lows than in the original 4.10 version if this slider is set to 0.)


Updated version:
http://www.stereotool.com/download/dsp_ ... 00perc.dll
http://www.stereotool.com/download/radio_tool_SA.exe


Note: The default values that I mentioned in this post were just some numbers that I thought might sound fine, I haven't yet fine-tuned them. It's past 4AM here, so I really need to end it for today...

Actually, that makes sense.

In the FM output, I upsample the audio to 176.4 or 192 kHz. Doing so reveals a lot of peaks that are invisible before the upsampling is done. Those peaks need to be removed also, and there's a 2nd limiter (which is very similar to the Loudness filter) placed there to remove these new peaks, which are often over 10% of the amplitude of the total volume due to the fact that there are a lot of high frequencies in the signal - as it is pre-emphasized.

So basically you can see this as an extra 10% Loudness.

Unfortunately, I cannot run the entire Loudness filter at this sampling rate because that would quadruple the CPU usage of the Loudness filter - which is already the most CPU intensive filter of Stereo Tool. Instead, I'm using a simplified Loudness filter for the final filtering. (The normal Loudness filter must be able to handle sustained levels of more than 4 times the maximum level, and this simple filter only needs to be able to handle peaks of about 10-20% above the maximum level.)

It gets even worse: If you use the "FM Overdrive" functionality, the total MPX signal is upsampled another 4 times to 705600 or 768000 Hz to reveal new peaks again which are then limited by just quickly increasing and decreasing the volume. This ensures that there are no peaks left in the MPX signal that leaves the sound card.


If you DON'T enable any of the MPX functions and don't use 120 kHz or higher output sampling rate, I'm skipping the extra filtering for performance reasons. So it might indeed sound slightly better if you're using normal output instead of FM output.

i will just say SUPER !
This brand new version is totaly different story!

I did just 20 min tests .. and if you ask me .. this is great progress.
not just Bass overall sound is less distorted.

I hear some missed BASS beat sometimes when high "higs" and "mids" comes, but that is very rare.

Congrats!

/// i wonder what other thinks about this new version.

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control point
control point2

Great!
That should be easy to solve, right now I'm lowering (limiting) the bass level if there's a very loud bass, the highs remain intact. Then Loudness reduces the bass even further to make room for the much louder highs.

So I think I should lower the highs too if I filter out a lot of bass.
Me too

Sounds nice Hans! Nice lowlows and the balance between high and low is better then the original 4.10. The overall sound is more pleasant to listen to. It should be nice if the CPU load gets a little bit lower but that should be the trade-off I guess. Great work Hans.

I thought I had a solution for this, but it turns out that at times it causes very bad distortion. So for now I think I'll just leave it the way it is...
Yup, but I think I can reduce it a bit when the 3rd slider is set to 0. That will be part of the finishing touch of the new version.

Ok, here's a small update:

Winamp version: http://www.stereotool.com/download/dsp_ ... urable.dll
Stand alone version: http://www.stereotool.com/download/radio_tool_SA.exe

In this version, loud highs should have less effects on the deep bass. If there's a lot of high frequency content, the bass limiter limiting level is increased a bit, so the bass level that goes into the Loudness filter is a bit higher.

I have added 2 new sliders:
- "Raise clip level if highs get above" - set this to 100% to start raising the clip level if it gets higher than the bass clip level (by default 140%).
- "Dynamic clip level max boost" - the maximum increment of the clip level. A higher values means that a bass that is "pushed down" by loud highs will be louder, but potentially suffer from distortion.

Note: The new blue bar at the bottom displays the clip level. If it moves a lot, you should increase the "Raise clip level..." slider to avoid bass distortion - basically this slider should ONLY move up at moments where the bass sound would otherwise be reduced too much.

OOPS!

I just realized that the effect of the above update is very small. Because I'm filtering the lows in 2 steps, and I'm only increasing the level at the first step... It's getting too late now, I'll create a fix tomorrow. The current version may have a bit less "bass suppression", but tomorrow's version should have a lot less.

Now it works properly.

Winamp version: http://www.stereotool.com/download/dsp_ ... ynamic.dll [link fixed]
Stand alone version: http://www.stereotool.com/download/radio_tool_SA.exe

Just for clarity: This version fixes the "bass is pushed down too much by highs" problem, at the cost of possibly introducing some distortion.

The "Raise clip level if highs get above" slider is no longer relative to the "Filter below this..." slider: Basically it means that if the highs are above (the default value) 150% of the maximum level, more lows will be allowed. If you see the blue output bar at the bottom of the screen move when there's no problem with pushed down lows, increase the value of this slider.

The "Dynamic clip level max boost" slider determines how far the bass level clipping may be raised. Keep this low to reduce the amount of extra distortion that may be introduced. If the blue bar is completely filled, the maximum level is reached.