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aacPlus CODEC Pre-Processing...
https://forums.stereotool.com/viewtopic.php?f=8&t=305
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Author:  SuperH [ Fri Dec 12, 2008 11:35 pm ]
Post subject:  Re: aacPlus CODEC Pre-Processing...

The "slushiness" I am referencing is CODEC related. The processing scheme that I've been working on -- using your DSP -- is trying to reduce the slushiness that is inherent to low bitrate HE-AAC (aacPlus).

I don't know how old you are, or what your career ambitions are, but in my opinion, there is room for a fourth major player in the audio processing arena.

We have Orban, Omnia, and Neural Audio now (and countless other little "guys"). There's room for an HVZ! Seriously, we need equipment from people who LISTEN to music!

The fact that you've designed a software application "plug-in" that is comparable -- and better in many areas, than audio equipment that costs several thousands of dollars (often tens of) blows my mind.

Keep up the good work!

:-D

Author:  SuperH [ Mon Jan 05, 2009 4:08 pm ]
Post subject:  Re: aacPlus CODEC Pre-Processing...

Hey... wanted to give an update.

I changed the way I'm processing audio completely. This seems to do a better job with handling the artifacts.

http://superh.dyndns.org:8000/listen.pls

CODEC: aacPlus V2/Parametric Stereo/40kbps/44.1kHz

As always, feedback is awesome.

HVZ: Your software is amazing!

Update: I found I was able to drop the bitrate to 40kbps without sacrificing substantial quality. :)

Author:  SuperH [ Sun Feb 08, 2009 7:20 pm ]
Post subject:  Re: aacPlus CODEC Pre-Processing...

So... go ahead and give'er a listen! ;)

The idea is to optimize aacPlus at low bitrates, so the top two links are the important ones:
http://superh.dyndns.org:8000/listen.m3u 40kbps aacPlus V2 (Parametric Stereo) 44.1kHz
http://superh.dyndns.org:8000/test.m3u 32kbps aacPlus V1 (Stereo) 44.1kHz

Here is 128kbps MP3 for reference:
http://superh.dyndns.org:8000/high.m3u 128kbps MP3 (Stereo) 44.1kHz

I think I attacked most of the annoying artifacts without coloring the audio too much. It's always a work in progress, but I'm extremely content with this.

Audio is very dynamic, yet normalized. I hate how much I have to manipulate the stereo image to kill so many artifacts. That's not as true as I'd like it.
Code:
[Common]
Pre amplifier=5
Post amplifier=0.75
Extra loudness=1
Hard limit output=1
Process for low latency=1
Mode=Advanced
[Noise Gate]
Enabled=1
Difference=0
Noise level=2.200000048
[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=1
Difference=0
Delay enabled=0
Maximum volume - Band 1=40010
Maximum volume - Band 2=5500
Attack speed - Band 1=0.000002059
Attack speed - Band 2=0.000002059
Decay speed - Band 1=0.0004578
Decay speed - Band 2=0.0004578
[Multiband Compressor]
Enabled=1
Difference=0
Delay enabled=0
Very high quality enabled=1
Maximum volume - Band -1=4410
Maximum volume - Band 0=4070.000244141
Maximum volume - Band 1=4400
Maximum volume - Band 2=3100
Maximum volume - Band 3=3250
Maximum volume - Band 4=5650
Maximum volume - Band 5=3550
Maximum volume - Band 6=2700
Maximum volume - Band 7=3100
Maximum volume - Band 8=3950
Attack speeds linked=1
Attack speed - Band -1=0.000027837
Attack speed - Band 0=0.000027837
Attack speed - Band 1=0.000027837
Attack speed - Band 2=0.000027837
Attack speed - Band 3=0.000027837
Attack speed - Band 4=0.000027837
Attack speed - Band 5=0.000027837
Attack speed - Band 6=0.000027837
Attack speed - Band 7=0.000027837
Attack speed - Band 8=0.000027837
Decay speeds linked=1
Decay speed - Band -1=0.002081846
Decay speed - Band 0=0.002081846
Decay speed - Band 1=0.002081846
Decay speed - Band 2=0.002081846
Decay speed - Band 3=0.002081846
Decay speed - Band 4=0.002081846
Decay speed - Band 5=0.002081846
Decay speed - Band 6=0.002081846
Decay speed - Band 7=0.002081846
Decay speed - Band 8=0.002081846
Above Top Limiter=1
Clipping enabled=1
Postprocessing enabled=1
Relative clip position - Band -1=2.508771658
Relative clip position - Band 0=2.508771658
Relative clip position - Band 1=2.508771658
Relative clip position - Band 2=1.857142687
Relative clip position - Band 3=1.857142687
Relative clip position - Band 4=1.352941036
Relative clip position - Band 5=1
Relative clip position - Band 6=0.801801801
Relative clip position - Band 7=0.709401608
Relative clip position - Band 8=0.801801801
Final limiter value=0.5
Final limiter decay speed=0.000239358
Final limiter clipping=0.307189584
Equalizer enabled=1
Equalize before multiband-compression=0
Equalizer position - Band -1=1.702702761
Equalizer position - Band 0=1.702702761
Equalizer position - Band 1=1.352941036
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=1
AZIMUTH limit=75.61000061
AZIMUTH change speed=0.300000012
Image phase amplifier=1.600000024
Image phase amplifier maximum angle=90
Image phase amplifier maximum separation strength=75.169998169
Image width amplifier=0.75
Extra phase shift=0
Mono or stereo only=-1
[Channel Delay]
Enabled=0
Left Delay=0
[Output Filter]
Enabled=1
Lowpass filter=16500
Highpass filter=20
[Final Pre-Limiter]
Enabled=1
Difference=0
Pre-amp=1.230895996
Response time=0.025
[Final Limiter]
Enabled=1
Difference=0
Pre-amp=1.595456004
Response time=0.0125
[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 - www.stereotool.com/30s:Stereo Tool by Hans van Zutphen, 1999-2008 - 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=Microsoft Sound Mapper
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 [ Mon Feb 09, 2009 11:37 pm ]
Post subject:  Re: aacPlus CODEC Pre-Processing...

Impressive, not bad at all considering the low bitrate!

I have 3 minor tips:
1. I think the noise gate is set a bit too agressive. (Of course, it could be that this helps the encoder, in which case you should leave it as it is)
2. I noticed that you have "Low latency" processing enabled - if you need it, great, but if you don't, turning it off will (slightly) improve the sound quality. Although I doubt that the difference will be noticeable.
3. About the Stereo filtering: The "Limit" (90 degrees) slider causes artifacts. My own experience is that I'm getting better results with Limit set to 180 degrees, and "max phase" at 30-40 %. Again, this may be different when using very low bitrate encoding. I'll see if I can improve this in a future version (but I've tried it before and I didn't manage to).

Author:  SuperH [ Tue Feb 10, 2009 2:57 am ]
Post subject:  Re: aacPlus CODEC Pre-Processing...

Thanks!

I forgot about the Low Latency setting. :oops:

I was using it to better analyze the effects. The noise processing too -- :oops: -- I removed a bunch of noisy (hissy) tracks, and forgot to back that off a bit. I'm trying to use that to make the change in multiband levels not noticeable. You know -- the hiss sound that changes with the multiband.

I started with the width set at 180 degrees, but I was losing a lot of information with that setting -- it's the fault of the CODEC. Notably, the cowbell in Funkytown by Lipps Inc and the guitars in Radar Love by Golden Earring would completely disappear.

aacPlus is a fun CODEC if you want to make your encoder do some funky stuff, that's for sure.

I'll keep working on it. Thanks for the feedback! :)

Tweaked on processing.

http://superh.dyndns.org:8000/listen.pls

Switched CODEC: aacPlus/Parametric Stereo/40kbps/44.1kHz

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