From ac7c48b4dee99d4c772f133d70d8d1b38262fcd2 Mon Sep 17 00:00:00 2001
From: Author Name <david@rowetel.com>
Date: Fri, 7 Jul 2023 12:20:59 +0930
Subject: shallow zip-file copy from codec2 e9d726bf20

---
 octave/plot_specgram.m | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 octave/plot_specgram.m

(limited to 'octave/plot_specgram.m')

diff --git a/octave/plot_specgram.m b/octave/plot_specgram.m
new file mode 100644
index 0000000..7b9e3a6
--- /dev/null
+++ b/octave/plot_specgram.m
@@ -0,0 +1,22 @@
+% plot_specgram.m
+% David Rowe May 2017
+%
+% As the name suggests.....
+
+function S = plot_specgram(x, Fs=8000, fmin, fmax)
+  
+  step = fix(20*Fs/1000);     # one spectral slice every 5 ms
+  window = fix(160*Fs/1000);  # 40 ms data window
+  fftn = 2^nextpow2(window);  # next highest power of 2
+  [S, f, t] = specgram(x, fftn, Fs, window, window-step);
+  S = abs(S(2:fftn/2,:));     # magnitude in range 0<f<=Fs/2 Hz.
+  S = S/max(S(:));            # normalize magnitude so that max is 0 dB.
+  S = max(S, 10^(-20/10));    # clip below -20 dB.
+  S = min(S, 10^(-3/10));     # clip above -3 dB.
+  imagesc (t, f, log(S));     # display in log scale
+  set (gca, "ydir", "normal"); # put the 'y' direction in the correct direction
+  if nargin > 2
+    axis([0 max(t) fmin fmax])
+  end
+  xlabel('Time (s)'); ylabel('Freq (Hz)');
+endfunction
-- 
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