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
10000 -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 <kla...@posteo.de>
> 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
> >
> >
> > _______________________________________________
> > Faudiostream-users mailing list
> > Faudiostream-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/faudiostream-users
>
>
>
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