From d903249930d2f7240efa37894e7e7a5c341b14a9 Mon Sep 17 00:00:00 2001
From: Connor Olding <cloningdonor@gmail.com>
Date: Wed, 21 Feb 2018 04:04:24 -0800
Subject: [PATCH] update 40

---
 README.md       | 45 ++++++++++++++++++++++++++++++++++-----------
 lib/cepstrum.py |  8 ++------
 2 files changed, 36 insertions(+), 17 deletions(-)

diff --git a/README.md b/README.md
index 800cdfb..813e5f9 100644
--- a/README.md
+++ b/README.md
@@ -4,31 +4,51 @@ it's a bunch of half-baked python code that's kinda handy.
 
 don't expect commits, docs, or comments to be any verbose.
 
+feel free to modify and adapt the [autoupdate](autoupdate)
+shell script for your own repos like this!
+
 ## the stuff
 
 * a basic BS.1770-3 normalization implementation
 — [bs.py](/lib/bs.py)
 
-* biquad butterworth/chebyshev filters [(via DSPFilters)][dspf]
+* biquad butterworth/chebyshev filters
+  [(via DSPFilters)][dspf]
 — [nsf.py](/lib/nsf.py)
 
-* bilinear transformation: s-plane to z-plane
+* modified bilinear transformation: s-plane to z-plane
 — [planes.py](/lib/planes.py)
 
 * various functions for biquad filters
-— [bq.py](/lib/bq.py) [\_\_init\_\_.py](/lib/__init__.py)
+— [bq.py](/lib/bq.py)
 
-* some functions for state-variable filters [(via Raph Levien)][svf]
+* some functions for state-variable filters
+  [(via Raph Levien)][svf]
 — [svf.py](/lib/svf.py)
 
-* sine sweeps, and the Optimized Aoshima's Time-Stretched Pulse [(via here)][sweeps]
+* sine sweeps, and the Optimized Aoshima's Time-Stretched Pulse
+  [(via here)][sweeps]
 — [sweeps.py](/lib/sweeps.py)
 
-* a lot of stuff for magnitude plotting like tilting and smoothing
-— [fft.py](/lib/fft.py) [smoothfft.py](/lib/smoothfft.py) [\_\_init\_\_.py](/lib/__init__.py)
+* basic [cepstrum][cep] utilities like minimum-phase reconstruction
+  [(via Julius Smith)][jos3]
+— [cepstrum.py](/lib/cepstrum.py)
 
-* rough experiments with psychoacoustic equalization ("neon pink" and other crap)
-— [data.py](/lib/data.py) [\_\_init\_\_.py](/lib/__init__.py)
+* utilities for magnitude plotting, including tilting and smoothing
+— [fft.py](/lib/fft.py) [smoothfft.py](/lib/smoothfft.py) [mag.py](/lib/mag.py)
+
+* a couple hard-coded polyphase halfband IIRs for nonlinear-phase resampling
+  or approximating hilbert transforms
+  (read more: [Olli Niemitalo][olli])
+— [piir.py](/lib/piir.py)
+
+* a dozen windowing functions and utility functions for constructing them
+— [windowing.py](/lib/windowing.py)
+
+* ad-hoc experiments with psychoacoustic equalization
+  ("neon pink" and other crap before i realized
+   "grey noise" was the term i was looking for)
+— [data.py](/lib/data.py)
 
 * miscellaneous matplotlib stuff
 — [plot.py](/lib/plot.py)
@@ -36,9 +56,12 @@ don't expect commits, docs, or comments to be any verbose.
 * miscellaneous utility functions
 — [util.py](/lib/util.py) [wav.py](/lib/wav.py)
 
-[dspf]: https://github.com/vinniefalco/DSPFilters/
+[dspf]: //github.com/vinniefalco/DSPFilters/
+[svf]: http://nbviewer.jupyter.org/github/google/music-synthesizer-for-android/blob/master/lab/Second%20order%20sections%20in%20matrix%20form.ipynb
 [sweeps]: http://www.sound.sie.dendai.ac.jp/dsp/e-21.html
-[svf]: http://nbviewer.ipython.org/urls/music-synthesizer-for-android.googlecode.com/git/lab/Second%20order%20sections%20in%20matrix%20form.ipynb
+[cep]: //en.wikipedia.org/wiki/Cepstrum
+[jos3]: //ccrma.stanford.edu/~jos/fp/
+[olli]: http://yehar.com/blog/?p=368
 
 all wrapped up in a inconveniently named "lib" module!
 
diff --git a/lib/cepstrum.py b/lib/cepstrum.py
index 54eb129..359f09b 100644
--- a/lib/cepstrum.py
+++ b/lib/cepstrum.py
@@ -42,15 +42,11 @@ def fold(r):
     return rw
 
 
-def minphase(s, pad=True, os=False):
+def minphase(s, pad=True):
     # via https://ccrma.stanford.edu/~jos/fp/Matlab_listing_mps_m.html
-    # TODO: actual oversampling
+    # TODO: oversampling
     if pad:
         s = pad2(s)
-    if os:
-        s = np.r_[s, np.zeros(len(s))]
     cepstrum = np.fft.ifft(np.log(clipdb(np.fft.fft(s), -100)))
     signal = np.real(np.fft.ifft(np.exp(np.fft.fft(fold(cepstrum)))))
-    if os:
-        signal = signal[:len(signal)//2]
     return signal