Stereo Tool

The highpass filter is getting better... Dunno if I'll be able to get it finished today, but at least it's moving in the right direction (it's still less good than for Overlap>0, it will probably stay less good)

Hi Hans,
Can i ask for next beta to be default blockoverlap=0 (or saveble).. so i can put it on transmitter and not to worry if something happen with pc after restart or so.
After that you can continue work at any time.

^C
re-building now


I think I managed to get the highpass filter to work correctly at latency 4096/frequency 30 Hz. It looks like I'm going to have to manually tweak all the latency/frequency combinations to get a good sound without too many artifacts...

But at 4096/30Hz it's working perfectly now.

Update should - as always - be ready in about an hour.

Update is available.

Stereo Tool now starts in Overlap=0 mode. This means that the singleband compressor/limiter does not work! Also, the output signal after Hard Limit can contain small spikes (upto about 1-2% above the maximum level) - not if FM output + FM Overdrive is enabled.

Highpass filter works much better now, but that's mainly the case in latency=4096 mode, when filtering at 30 Hz. At different latencies artifacts may occur. At different frequencies the filtering doesn't work too good. Will be fixed in a later version (I know how to fix it, but I still have to do it). Highpass filter CPU load is 50% lower than before in Overlap=0 mode (but on the total processing that won't make much of a difference).

great

New todo list: MOVED TO PAGE 35

TODO:
- Remove (small) remaining peaks in Final Limiter - they are a bit higher now due to the improved bass handling ■ OK
- Fix very bad Final Limiter quality in low latency settings. ■ OK, fixed. Equal to v4.22 now, but I think I have some more improvements that I can try...
- Beep sounds are not completely constant in volume when they come out - check why and try to solve it. ■ OK, was caused by Pre Limiter, also Highpass filter
- Fix Stereo Boost - I found that it's behaving very differently from what I expected, but I don't know why. ■ OK
- Bass protection in Overlap=0 mode is less good than in Overlap>0 mode. ■ Nearly fixed, todo: add a selection checkbox to choose whether you want best sound quality or no very low frequency sounds
- Fix Singleband compressor.
- Attempt to improve the highpass filter in Overlap=0 mode. ■ PARTIAL, works for 30 Hz phase linear at higher latency values (2048, 4096), there's now also a non-phase linear version for 20, 30 and 40 Hz that causes NO artifacts at all. Question: Should I ALSO offer the possibility to use v4.22 filtering? It's better at high freqs.
- Fix Hard Limit in Overlap>0 mode (completely destroys the sound at lower latencies at the moment)
- Attempt to reduce CPU load by simplifying processing (example: Can FAST4 be turned off when Final Limiter and Loudness are both on? That might even improve the sound quality...)
- Make CPU load configurable in Overlap=0 mode.
- Restore quality/latency display based on the new settings.
- Check the interface for settings that are no longer used (for example "Multiband HQ").
- Fix Stereo Boost meter (stops after few/many minutes/hours of work)
- Fix Stereo Boost meter (shows wrong levels, too low - sound is ok though)

Later:
- Add "Phase Rotator" usefull for microphone processing
- Add Pre-Emphasize for Normal Output (10,15,20,25us), useful for web streaming (?)
- "Do you really want to close ..." message in stand alone version
- Add "LINK" checkbox for "phase differences" in "Calibrate FM transmitter..." (20Hz-10240Hz), [someone call it TILT]

New version is online now. Not much changes though...

The Highpass filter is still problematic (in v4.22 it had less artifacts and filtered much stronger). I'm not yet sure if I can fix it.

It does now work at least reasonably well for most latency settings - 512 is still very problematic, higher latencies work with some artifacts. For best results, you might need to turn it off at lower latency settings. NOTE: To test, make sure you set the latency BEFORE turning the highpass filter on, or there are weird clicking sounds again (there's still something wrong with the highpass filter in Overlap=0 mode).

Note: I've now heard the problems with Hard Limit in latency 512 mode - it sounds pretty bad. Will check that later.

I think to be able to get a good highpass filter at low latency values, I'm going to need to drop phase linearity. I'll do some more tests tomorrow.


Edit: I think I've just found a filter that restores phase linearity with very little effect on the sound itself (I do hear some artifacts at latency 512/1024, but it's not THAT bad - and this 2nd filter can be turned off if it's not needed).

Will get back on this...


Edit #2: No, that only worked for simple tones, not for music... So I'll still have to drop phase linearity

Small update (BETA3A): There's now in the BANDPASS window a choice between 'phase linear' filtering (same as in previous versions) and 'non-phase linear' filtering, which gives much better filtering results, but - as the name says - does not maintain the phasing.

By default, the option 'auto' is chosen, which means that for Block Overlap > 0 phase linear filtering is used, and in Block Overlap = 0 for latencies 2048 and 4096 phase linear filtering is used, for 512 and 1024 non-phase linear filtering is used.

Notes:
- Non phase-linear filtering uses much less CPU power.
- Non-phase linear filtering currently only works for filtering at 20, 30 or 40 Hz (frequencies 16-44 should work, assuming 44.1 kHz input) - lower or higher frequencies currently cause the output to fall completely silent (!). I'll fix that later.


The next step I've planned is to fix the final limiter - I think I have a solution for both the bad quality in very low latency modes, and the small (1-2%) peaks that are still present in the current solution.



Edit: It seems that when using the NON-phase linear bass filter, I hear more bass - and that's still the case when Loudness is enabled. Actually it seems that this corresponds a lot to the bass punch filter that someone posted here some time ago...

So maybe I should make the non-phase-linear filter the default regardless of the latency setting...

Hi Hans,
I check Highpass and it's much better now for 4096 mode. Almost ideal!

I notice another strange thing with multiband EQ.
First "Before Multiband" is OFF, but if i change some EQ settings it affect the multiband. Easy to check this is by playing "white noise" thru ST.