Hi Klaus, I can never resist these things! Faust makes it too enjoyable :-)
I made a pass, but there is a small scaling error. I think it can be fixed by reducing boostFreqHz until the sine_test is nailed. The highpass is close (and not a source of the scale error), but I'm using Butterworth instead of whatever they used. I glossed over the discussion of "gating" in the spec, and may have missed something important there, but I simply tried to make a sliding rectangular window, instead of 75% overlap, etc. If useful, let me know and I'll propose it for analyzers.lib! Cheers, Julius import("stdfaust.lib"); // Highpass: // At 48 kHz, this is the right highpass filter (maybe a Bessel or Thiran filter?): A48kHz = ( /* 1.0, */ -1.99004745483398, 0.99007225036621); B48kHz = (1.0, -2.0, 1.0); highpass48kHz = fi.iir(B48kHz,A48kHz); highpass = fi.highpass(2, 40); // Butterworth highpass: roll-off is a little too sharp // High Shelf: boostDB = 4; boostFreqHz = 1430; // a little too high - they should give us this! highshelf = fi.high_shelf(boostDB, boostFreqHz); // Looks very close, but 1 kHz gain has to be nailed kfilter = highshelf : highpass; // Power sum: Tg = 0.4; // spec calls for 75% overlap of successive rectangular windows - we're overlapping MUCH more (sliding window) zi = an.ms_envelope_rect(Tg); // mean square: average power = energy/Tg = integral of squared signal / Tg // Gain vector Gv = (GL,GR,GC,GLs,GRs): N = 5; Gv = (1, 1, 1, 1.41, 1.41); // left GL(-30deg), right GR (30), center GC(0), left surround GLs(-110), right surr. GRs(110) G(i) = *(ba.take(i+1,Gv)); Lk(i) = kfilter : zi : G(i); // one channel, before summing and before taking dB and offsetting LkDB(i) = Lk(i) : 10 * log10 : -(0.691); // Use this for a mono input signal // Five-channel surround input: Lk5 = par(i,5,Lk(i)) :> 10 * log10 : -(0.691); // sine_test = os.oscrs(1000); // should give –3.01 LKFS, with GL=GR=GC=1 (0dB) and GLs=GRs=1.41 (~1.5 dB) sine_test = os.osc(1000); process = sine_test : LkDB(0); // should read -3.01 LKFS - high-shelf gain at 1 kHz is critical // process = 0,sine_test,0,0,0 : Lk5; // should read -3.01 LKFS for left, center, and right // Highpass test: process = 1-1' <: highpass, highpass48kHz; // fft in Octave // High shelf test: process = 1-1' : highshelf; // fft in Octave 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 > -- "Anybody who knows all about nothing knows everything" -- Leonard Susskind
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