Hmmm, '!' means "block the signal", but attach should save the bargraph
from being optimized away as a result. Maybe I misremembered the argument
order to attach? While it's very simple in concept, it can be confusing in
practice.
I chose not to have a gate at all, but you can grab one from
misceffects.lib if you like. Low volume should not give -infinity, that's
a bug, but zero should, and zero should become MIN as I mentioned so
-infinity should never happen.
Cheers,
Julius
On Mon, Jul 5, 2021 at 10:39 AM Klaus Scheuermann <kla...@posteo.de> wrote:
> Cheers Julius,
>
>
>
> At least I understood the 'attach' primitive now ;) Thanks.
>
>
>
> This does not show any meter here...
> process(x,y) = x,y <: (_,_), attach(x, (Lk2 : vbargraph("LUFS",-90,0)))
> : _,_,!;
>
> But this does for some reason (although the output is 3-channel then):
> process(x,y) = x,y <: (_,_), attach(x, (Lk2 : vbargraph("LUFS",-90,0)))
> : _,_,_;
>
> What does the '!' do?
>
>
>
> I still don't quite get the gating topic. In my understanding, the meter
> should hold the current value if the input signal drops below a
> threshold. In your version, the meter drops to -infinity when very low
> volume content is played.
>
> Which part of your code does the gating?
>
> Many thanks,
> Klaus
>
>
>
> On 05.07.21 18:06, Julius Smith wrote:
> > Hi Klaus,
> >
> > Yes, I agree the filters are close enough. I bet that the shelf is
> > exactly correct if we determined the exact transition frequency, and
> > that the Butterworth highpass is close enough to the Bessel-or-whatever
> > that is inexplicably not specified as a filter type, leaving it
> > sample-rate dependent. I would bet large odds that the differences
> > cannot be reliably detected in listening tests.
> >
> > Yes, I just looked again, and there are "gating blocks" defined, each Tg
> > = 0.4 sec long, so that only ungated blocks are averaged to form a
> > longer term level-estimate. What I wrote gives a "sliding gating
> > block", which can be lowpass filtered further, and/or gated, etc.
> > Instead of a gate, I would simply replace 0 by ma.EPSILON so that the
> > log always works (good for avoiding denormals as well).
> >
> > I believe stereo is supposed to be handled like this:
> >
> > Lk2 = _,0,_,0,0 : Lk5;
> > process(x,y) = Lk2(x,y);
> >
> > or
> >
> > Lk2 = Lk(0),Lk(2) :> 10 * log10 : -(0.691);
> >
> > but since the center channel is processed identically to left and right,
> > your solution also works.
> >
> > Bypassing is normal Faust, e.g.,
> >
> > process(x,y) = x,y <: (_,_), attach(x, (Lk2 : vbargraph("LUFS",-90,0)))
> > : _,_,!;
> >
> > Cheers,
> > Julius
> >
> >
> > On Mon, Jul 5, 2021 at 1:56 AM Klaus Scheuermann <kla...@posteo.de
> > <mailto:kla...@posteo.de>> wrote:
> >
> >
> > > I can never resist these things! Faust makes it too enjoyable :-)
> >
> > Glad you can't ;)
> >
> > I understood you approximate the filters with standard faust filters.
> > That is probably close enough for me :)
> >
> > I also get the part with the sliding window envelope. If I wanted to
> > make the meter follow slowlier, I would just widen the window with
> Tg.
> >
> > The 'gating' part I don't understand for lack of mathematical
> knowledge,
> > but I suppose it is meant differently. When the input signal falls
> below
> > the gate threshold, the meter should stay at the current value, not
> drop
> > to -infinity, right? This is so 'silent' parts are not taken into
> > account.
> >
> > If I wanted to make a stereo version it would be something like
> > this, right?
> >
> > Lk2 = par(i,2, Lk(i)) :> 10 * log10 : -(0.691);
> > process = _,_ : Lk2 : vbargraph("LUFS",-90,0);
> >
> > Probably very easy, but how do I attach this to a stereo signal
> (passing
> > through the stereo signal)?
> >
> > Thanks again!
> > Klaus
> >
> >
> >
> > >
> > > 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
> > <mailto:kla...@posteo.de>
> > > <mailto:kla...@posteo.de <mailto: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
> > <https://en.wikipedia.org/wiki/LKFS>
> > <https://en.wikipedia.org/wiki/LKFS
> > <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
> > <
> https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-3-201208-S!!PDF-E.pdf
> >
> > >
> > <
> https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-3-201208-S!!PDF-E.pdf
> > <
> 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
> > <https://github.com/klangfreund/LUFSMeter>
> > > <https://github.com/klangfreund/LUFSMeter
> > <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
> > <mailto:Faudiostream-users@lists.sourceforge.net>
> > > <mailto:Faudiostream-users@lists.sourceforge.net
> > <mailto:Faudiostream-users@lists.sourceforge.net>>
> > >
> > https://lists.sourceforge.net/lists/listinfo/faudiostream-users
> > <https://lists.sourceforge.net/lists/listinfo/faudiostream-users>
> > >
> > <https://lists.sourceforge.net/lists/listinfo/faudiostream-users
> > <https://lists.sourceforge.net/lists/listinfo/faudiostream-users>>
> > >
> > >
> > >
> > > --
> > > "Anybody who knows all about nothing knows everything" -- Leonard
> > Susskind
> >
> >
> >
> > --
> > "Anybody who knows all about nothing knows everything" -- Leonard
> Susskind
>
--
"Anybody who knows all about nothing knows everything" -- Leonard Susskind
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