Stereo Tool
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Stereo Tool 5.02
https://www.forums.stereotool.com/viewtopic.php?t=2661		 Page 3 of 99
Author:  feeling [ Tue Aug 17, 2010 1:32 pm ]
Post subject:  Re: Stereo Tool 5.02
Maybe you can try with LAME 3.93.1 mp3 encoder, its the best encoder for streaming at 96 to 192k range. You can downloaded here. If you use eddcast (recomendded) You should see dsp_edcast_v3_1.cfg. Right-click this file, choose Open With, and click your way through until you can select Notepad. You need to change a few settings inside the file:
For 128kbps streaming:
LameCBRFlag=1
LameStrictISO=0
LameDisableReservior=0
LameQuality=0
LAMEPreset=12

For 192kbps streaming:
LameCBRFlag=1
LameStrictISO=0
LameDisableReservior=0
LameQuality=0
LAMEPreset=12
Try it with this settings and you can see that the overall quality is better and the overshoot reduce to minimal. The pre-emphasis recommended is 25us for 128k and 15us for 192k. ;)
Author:  Bojcha [ Tue Aug 17, 2010 2:17 pm ]
Post subject:  Re: Stereo Tool 5.02
Yes..
That's encoder and settings i use with EdCast
We must say that that is from JesseG tutorial and his optimized .dll and mp3 settings!

btw ..
this preemphasised output is for reducing overshots. Main overshots in mp3/aac encoding/decoding are from High frequencies..
At analyzer, levels for HFs are same with or w/o pre-ephasized output .. but on scope (waveform) is shown less.
In StereoTool case .. it placed before multiband, which i actyally found a good place, because multiband HF clippers are relaxed and less job for them.
In same tme i 'think' that highs are more "protected" from Bass sounds, so HF distortion caused by low tones should be less.
Author:  hvz [ Tue Aug 17, 2010 2:37 pm ]
Post subject:  Re: Stereo Tool 5.02
Ok, some more output data then! Based on 128 kbit MP3.

Slightly increasing the pre-emphasis does not really protect against every type of clipping, but it does protect loud 'S' sounds - which can sound really bad when clipping occurs.

Here are some frequency analyses:

Output level 100% (Post Amp = 1.00):
Image

Output level 90% (Post Amp = 0.90, -1 dB):
Image

Starting at 20 us, the pre-emphasis starts to have a noticeable effect on the 'S' sounds - so I would advice against using values higher than 20. That's with a Loudness setting of 3.60 (very high) - at lower Loudness settings the effect is much smaller (higher loudness setting = more RMS pressure = more difficult to handle; also more energy in the high frequencies (due to higher overall audio level) = bigger effect of the pre-emphasis).

In both images at 20 us the amount of clipping distortion (the lines shown above ~ 16 kHz) is greatly reduced. So I guess around 15-25 us (depending on encoding quality etc.) could be a good value.

At output level 90%, the number of clipped samples for the same 30 seconds of audio is:
OFF: 3500
0 us: 3300 (should have been the same... Probably just a slightly different portion of audio?)
10 us: 2300
20 us: 900
30 us: 300
40 us: 50
50 us: 20
So the big jump occurs between 10 and 20 us.

Clipping distortion above 18 kHz:
OFF: -63.8 dB
0 us: -64.0 dB
10 us: -66.8 dB
20 us: -73.2 dB
30 us: -81.0 dB
40 us: -90.0 dB
50 us: -91.5 dB
The biggest jump in absolute numbers (and I expect by far the biggest effect in audio quality) is between 10 and 20, but after 20 it keeps being reduced at a very high rate.
Author:  Bojcha [ Tue Aug 17, 2010 2:46 pm ]
Post subject:  Re: Stereo Tool 5.02
well good output :)

that's what i say erlier .. if is used .. best settings are 15-25 .. in StereoTool case depends on Loudness settings (overall output rms)

Maybe it;s good to reduse possible settings .. let's say .. 10-30 .. or simply 15-25 us
Author:  feeling [ Tue Aug 17, 2010 2:49 pm ]
Post subject:  Re: Stereo Tool 5.02
Low pass to 15khz helps too with the overshoots. In my aac plus v2.0 stream I have the LPF to 15khz and the output lowered -2db.
Author:  hvz [ Tue Aug 17, 2010 3:14 pm ]
Post subject:  Re: Stereo Tool 5.02
Quote:
Low pass to 15khz helps too with the overshoots. In my aac plus v2.0 stream I have the LPF to 15khz and the output lowered -2db.
That makes sense. You should set the lowpass filter at or below the lowpass frequency that the filter uses. AAC+ is especially difficult because it uses SBR, a mechanism to very efficiently encode high frequencies - but very efficiently also means very different from the original.

(By the way: Welcome on this forum!)
Author:  hvz [ Wed Aug 18, 2010 1:18 am ]
Post subject:  Re: Stereo Tool 5.02
- Changed default pre-emphasis to 15 us, maximum to 30 us
- All webradio presets now have this pre-emphasis turned on
- Divided default up/down speed of AGC by 4 (values suggested by Bojcha some time ago, this time corrected because he created them for 192 kHz what at the time behaved differently). Question: Isn't this too slow???

Winamp DSP plugin: http://www.stereotool.com/download/dsp_ ... A510-2.exe
Stand alone version: http://www.stereotool.com/download/ster ... A510-2.exe
VST version: http://www.stereotool.com/download/vst_ ... A510-2.dll
VST version (No SSE2): http://www.stereotool.com/download/vst_ ... A510-2.dll
Command line version: http://www.stereotool.com/download/ster ... A510-2.exe
Author:  hvz [ Wed Aug 18, 2010 1:47 am ]
Post subject:  Re: Stereo Tool 5.02
Idea for a new feature: Less strict limiting for web radio stations.

Rationale: For web radio stations, it's not really useful to limit the sound very strictly below a peak level, because the peaks change anyway during the MP3/AAC/... encoding.

In some cases (difficult sound) the very strict filtering DOES have a pretty big effect on audio quality.

So: For web radio, turn off the final filtering stage (that removes all the remaining peaks). "HARD LIMIT" should be turned off as well, but this idea also includes skipping the last stage of the "Loudness" filter.
Author:  Bojcha [ Wed Aug 18, 2010 1:56 am ]
Post subject:  Re: Stereo Tool 5.02
Quote:
- Divided default up/down speed of AGC by 4 (values suggested by Bojcha some time ago, this time corrected because he created them for 192 kHz what at the time behaved differently). Question: Isn't this too slow???
I never suggested that ?!
Quote:
1. AGC: Put whatever speed you think is ok, yes i made all on 192kHz but no problem for me to recalibrate that.
Author:  michi95 [ Wed Aug 18, 2010 6:37 am ]
Post subject:  Re: Stereo Tool 5.02
I guess this is a misunderstanding.

Hans has used values for AGC up/down speed, that Bojcha suggested some time ago (@ 192 KHz), but now Hans has used the necessary correction (divided by 4).

And this is was Hans has written.
Bojcha, please read it again !
Hans has not written, that you suggested the division by 4
(this was your misunderstanding).

I hope that it is not me, who has misunderstood both (Hans and Bojcha) :?: :)
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