On Sun, 24 May 2020 at 04:32, Julius Smith <[email protected]> wrote:
Attached is my updated test and the plot it generates. At this point I > would go for "basic" with a reduced delay. > Yes, it seems to work best. When I use it, I have the attack time set to .002 seconds. I tested it recently with a song a 60 dB and the maximum peak recorded was 0.3823258089 dB when setting the limiting threshold at 0dB. The hold time in the usage example for the basic limiter is 0.1 seconds. I usually have that because I can have very low frequency components, so that hold time prevents distortions down to 5-Hz-signals, as it is the peak-to-peak period. If the input signal were high-passed at 20 Hz, the hold-time could be as low as .025 seconds without introducing distortion. Maybe even the release time could be improved. Should I still do a PR with Zölzer's limiter? Dario > On Sat, May 23, 2020 at 5:56 PM Dario Sanfilippo < > [email protected]> wrote: > >> >> Great, my pleasure. >> >> Here attached is also Zölzer's algorithm. I'll need to double-check and >> see if all is correct but it might be a good starting point. >> >> Dario >> >> >> On Sat, 23 May 2020 at 23:31, Julius Smith <[email protected]> >> wrote: >> >>> Cool, these are great to have for evaluation, learning, and variety of >>> choice, thanks! >>> >>> - Julius >>> >>> On Sat, May 23, 2020 at 2:24 PM Dario Sanfilippo < >>> [email protected]> wrote: >>> >>>> >>>> Thanks for testing, Julius. >>>> >>>> I'll see if I can get the limiter in Zölzers book in the next few days >>>> and I'll do another PR with that if I manage. >>>> >>>> I've also just added the stereo version of the other limiter: >>>> https://github.com/grame-cncm/faustlibraries/pull/37/commits/12763e053c7fb84371cfaa17bf89f2c9a1821418 >>>> . >>>> >>>> Dario >>>> >>>> >>>> On Sat, 23 May 2020 at 22:10, Julius Smith <[email protected]> >>>> wrote: >>>> >>>>> Since the delay for the input path is our "lookahead delay", setting >>>>> it to the attack time sounds ideal to me. >>>>> >>>>> On Sat, May 23, 2020 at 12:54 PM Julius Smith <[email protected]> >>>>> wrote: >>>>> >>>>>> I've been happy with limiter_1176_R4_mono, but I'll now compare it >>>>>> to limiter_basic_mono, by offering both with a checkbox to choose, and >>>>>> listen for the difference (see attached test program). >>>>>> My limiter needs are merely to turn hard-clipping into soft-clipping >>>>>> for voice and tonal instruments. >>>>>> >>>>>> I believe the "limiter slope" is the compression ratio to use above >>>>>> threshold (4 in the case of limiter_1176_R4_mono). >>>>>> >>>>>> >>>>>> >>>>>> On Sat, May 23, 2020 at 3:57 AM Dario Sanfilippo < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> >>>>>>> Hi, Julius. I understand. >>>>>>> >>>>>>> See this: >>>>>>> https://github.com/grame-cncm/faustlibraries/pull/37/commits/8f1bd1ba78ff4919637a9bfd9ec635225cfb4ba5 >>>>>>> . >>>>>>> >>>>>>> That's a basic lookahead limiter based on this post: >>>>>>> http://iem.at/~zmoelnig/publications/limiter/. >>>>>>> >>>>>>> This algorithm is even simpler: it just calculates the amplitude >>>>>>> profile using a peak-holder and it smooths out attack and release using, >>>>>>> respectively, a one-pole lowpass and a peak envelope. Those filters are >>>>>>> based on the e^(-2pi) time constant (Chamberlin's design for 1pole >>>>>>> filters). This time constant works in this case as the input delay is >>>>>>> set >>>>>>> by the attack of the system, so the amplitude profile to calculate the >>>>>>> scaling factor roughly reaches its maximum after the attack time. The >>>>>>> release time might be changed with some other constant, if more >>>>>>> appropriate. >>>>>>> >>>>>>> Personally, I'm satisfied with it but I also designed it for my >>>>>>> specific case, that is, stability in self-oscillating systems. I needed >>>>>>> a >>>>>>> cheap solution with low distortion; I'm not sure if this works well for >>>>>>> most applications. People are invited to test and comment. >>>>>>> >>>>>>> I had a look at Zölzer's limiter, pp 231 and 232, but I don't quite >>>>>>> understand what "the slope of the limiter" is. What do you think? >>>>>>> He also doesn't mention a specific delay for the input path but I'd >>>>>>> assume >>>>>>> that it is the same as the attack time. >>>>>>> >>>>>>> Dario >>>>>>> >>>>>>> >>>>>>> On Sat, 23 May 2020 at 01:38, Julius Smith <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> Hi Dario, >>>>>>>> >>>>>>>> Yes the current limiter is simply a compressor, using the usual >>>>>>>> (causal) amplitude follower, that applies a ratio of 4 starting >>>>>>>> halfway up >>>>>>>> (-6 dB). Please feel free to make us a new one that is nicer! >>>>>>>> >>>>>>>> Julius >>>>>>>> >>>>>>>> On Fri, May 22, 2020 at 11:19 AM Dario Sanfilippo < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>>> Hello, list. >>>>>>>>> >>>>>>>>> Am I missing something with co.limiter_1176_R4_mono? I see that >>>>>>>>> there is no lookahead mechanism inside and, if I test it with a song >>>>>>>>> at >>>>>>>>> +60dB, the output of the limiter is rather consistently at about 25 >>>>>>>>> dB. >>>>>>>>> >>>>>>>>> Best, >>>>>>>>> Dario >>>>>>>>> _______________________________________________ >>>>>>>>> Faudiostream-users mailing list >>>>>>>>> [email protected] >>>>>>>>> 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 >>>>> >>>> >>> >>> -- >>> "Anybody who knows all about nothing knows everything" -- Leonard >>> Susskind >>> >> > > -- > "Anybody who knows all about nothing knows everything" -- Leonard Susskind >
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