Hi Klaus,
Could the averaging time be too small? I'm worried about the line
Tg = 0.4; // 3 second window for 'short-term' measurement
The comment seems to indicate it should be "Tg = 3;", i.e., 3 seconds of
averaging instead of 0.4 s.
Below is an expansion of your test program that allows for more exploration.
Cheers,
Julius
import("stdfaust.lib");
freq = hslider("[0] Test Sine Frequency (Hz) [unit:Hz]",1000,30,16000,1);
level = hslider("[1] Test Sine Level (dBFS) [unit:dBFS]",-10,-80,0,0.1);
avg = hslider("[2] Averaging Time (s) [unit:sec]",3,0.01,10,0.1);
amp = 10^(level/20);
testSignal = amp * os.osc(freq);
process = testSignal <: _,_ : lk2 : vbargraph("[3] LUFS S",-40,0) : *(1e-7);
//Tg = 0.4; // 3 second window for 'short-term' measurement
Tg = avg;
zi = an.ms_envelope_rect(Tg); // mean square: average power = energy/Tg =
integral of squared signal / Tg
kfilter = fi.highpass(1, 60) : fi.high_shelf(4, 1800);
// 2-channel
lk2 = par(i,2,kfilter : zi) :> 10 * log10(max(ma.EPSILON)) : -(0.691);
On Tue, May 10, 2022 at 7:00 AM Klaus Scheuermann wrote:
> Hi Julius,
>
> this is, of course, the way to go.
>
> I did some test with a series of sines, each at -18lufs, and found these
> filter settings to be quite close (except for the 30Hz):
> kfilter = fi.highpass(1, 60) : fi.high_shelf(4, 1800);
>
> Hz lufs
> 30 -16.693
> 60 -18.111
> 80 -18.204
> 100 -18.211
> 130 -18.177
> 180 -18.133
> 250 -18.113
> 300 -18.099
> 400 -18.099
> 600 -18.169
> 1000 -18.405
> 2000 -18.241
> 3000 -17.894
> 4000 -17.784
> 6000 -17.503
> 8000 -18.083
> 1 -18.026
> 12000 -18.035
> 14000 -17.784
> 16000 -18.083
>
> What I don't quite understand is why the values read a little different,
> every time I do the test with same filter settings and same sines. (I am on
> faustide.grame.fr).
>
> For my application, this should work fine. Out of curiosity, why do I
> approximate the filters? So that it works on all samplerates?
>
> Full test code is this:
> import("stdfaust.lib");
>
> process = _,_ : lk2 : vbargraph("LUFS S",-40,0);
>
> Tg = 0.4; // 3 second window for 'short-term' measurement
> zi = an.ms_envelope_rect(Tg); // mean square: average power = energy/Tg =
> integral of squared signal / Tg
> kfilter = fi.highpass(1, 60) : fi.high_shelf(4, 1800);
>
>
> // 2-channel
> lk2 = par(i,2,kfilter : zi) :> 10 * log10(max(ma.EPSILON)) : -(0.691);
>
> Thanks!!
> Klaus
>
>
>
>
> On Sun, 2022-05-08 at 13:17 -0700, Julius Smith wrote:
>
> Hi Klaus,
>
> To go after this, it would be useful to measure the discrepancy for
> some number of sinusoidal frequencies across the audio band, with at
> least one example including both single-channel and multichannel
> input.
> Based on the filter approximations used, I would predict a measurable
> discrepancy around 1 kHz (guessed transition-frequency tuning), and
> very high frequencies (due to bilinear transform frequency-warping).
>
> The high-frequency discrepancy should go away with oversampling, even 2x.
>
> Glad to hear noise is looking good!
>
> - Julius
>
> On Sat, Jul 3, 2021 at 1:08 AM Klaus Scheuermann wrote:
>
>
> Hello everyone :)
>
> Would someone be up for helping me implement an LUFS loudness analyser
> in faust?
>
> Or has someone done it already?
>
> LUFS (aka LKFS) is becoming more and more the standard for loudness
> measurement in the audio industry. Youtube, Spotify and broadcast
> stations use the concept to normalize loudness. A very positive side
> effect is, that loudness-wars are basically over.
>
> I looked into it, but my programming skills clearly don't match
> the level for implementing this.
>
> Here is some resource about the topic:
>
> https://en.wikipedia.org/wiki/LKFS
>
> Specifications (in Annex 1):
>
> https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-3-201208-S!!PDF-E.pdf
>
> An implementation by 'klangfreund' in JUCE / C:
> https://github.com/klangfreund/LUFSMeter
>
> There is also a free LUFS Meter in JS / Reaper by Geraint Luff.
> (The code can be seen in reaper, but I don't know if I should paste it
> here.)
>
> Please let me know if you are up for it!
>
> Take care,
> Klaus
>
>
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