Fix Bug 2722 - Noise Gate fails on a one hour stereo selection
Also fixes bug 2733 - Noise Gate 'Level Reduction' has a minimum of -60 dB. Thanks to Roger for 'snd-oneshot' suggestion.
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@ -6,7 +6,7 @@ $manpage "Noise_Gate"
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$debugbutton false
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$preview enabled
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$author (_ "Steve Daulton")
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$release 3.0.0
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$release 3.0.1
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$copyright (_ "Released under terms of the GNU General Public License version 2 or later.")
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;; Released under terms of the GNU General Public License version 2 or later:
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;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html .
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@ -32,17 +32,16 @@ $control decay (_ "Decay (ms)") float "" 100 10 4000
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;; rather than a fixed level.
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;;
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;; To create the gain envelope:
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;; 1. Resample to around 1000 Hz (bug 2519).
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;; 2. If stereo track and stereo-link = 1, get the max of left and right.
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;; 3. TRIGGER hold when level > threshold.
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;; 1. If stereo track and stereo-link = 1, get the max of left and right.
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;; 2. Add 'hold' when level > threshold.
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;; This adds a high level signal for 'hold' seconds when the level
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;; falls below the threshold.
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;; 4. Nyquist GATE function to generate exponential rise and decay.
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;; 3. Nyquist GATE function to generate exponential rise and decay.
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;; Unlike analog noise gates, lookahead is used so that the gate
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;; begins to open before the signal rises above the threshold, so
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;; that when the threshold is reached, the gate is fully open.
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;; begins to open before the signal rises above the threshold.
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;; When the threshold is reached, the gate is fully open.
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;; This prevents the gate from clipping the beginning of words / sounds.
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;; 5. Scale level of envelope and offset so that we have unity gain above
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;; 4. Scale level of envelope and offset so that we have unity gain above
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;; threshold, and 'level-reduction' below the threshold.
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;; If silence-flag is set (= 1), gain below the threshold is zero.
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@ -52,11 +51,8 @@ $control decay (_ "Decay (ms)") float "" 100 10 4000
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(setf gate-freq (* 1000.0 gate-freq))
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(setf floor (db-to-linear level-reduction))
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(setf threshold (db-to-linear threshold))
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;; As envelope is resampled to ~1000 Hz, the rise time will always be ~1 ms
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;; longer than specified attack, so compensate here.
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(setf attack (/ attack 1000.0))
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(setf lookahead attack)
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(setf attack (+ attack 0.001))
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(setf decay (/ decay 1000.0))
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(setf hold (/ hold 1000.0))
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@ -110,8 +106,7 @@ Suggested Threshold Setting ~a dB.")
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(let ((peakL (peak (aref sig 0) test-len))
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(peakR (peak (aref sig 1) test-len)))
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(linear-to-db (max peakL peakR)))
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(let ((peak (peak sig test-len)))
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(linear-to-db peak))))
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(linear-to-db test-len)))
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;;; Utility functions
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@ -120,7 +115,7 @@ Suggested Threshold Setting ~a dB.")
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(round (+ num 0.5)))
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(defun roundn (num places)
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;; Round number to specified decimal places.
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;; Return number rounded to specified decimal places.
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(if (= places 0)
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(round num)
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(let* ((x (format NIL "~a" places))
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@ -139,78 +134,58 @@ Suggested Threshold Setting ~a dB.")
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;;; Gate Functions
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(defun noisegate (sig follower)
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;; Takes a sound and a peak follower envelope (a low sample rate sound) as arguments.
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;; Override Nyquist GATE function (from nyquist.lsp)
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;; The default version has minimum floor of -60dB, which is not low enough here.
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(defun gate (sound lookahead risetime falltime floor threshold
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&optional (source "GATE"))
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(let (s) ;; s becomes sound after collapsing to one channel
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(cond ((arrayp sound) ;; use s-max over all channels so that
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(setf s (aref sound 0)) ;; ANY channel opens the gate
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(dotimes (i (1- (length sound)))
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(setf s (s-max s (aref sound (1+ i))))))
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(t (setf s sound)))
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(setf s (snd-gate (seq (cue s)
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(stretch-abs 1.0 (s-rest lookahead)))
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lookahead risetime falltime floor threshold))
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(prog1 (snd-xform s (snd-srate s) (snd-t0 s)
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(+ (snd-t0 s) lookahead) MAX-STOP-TIME 1.0)
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(setf s nil) (setf sound nil))))
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(defun noisegate (sig follow)
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;; Takes a sound and a 'follow' sound as arguments.
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;; Returns the gated audio.
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(let ((gain (/ (- 1 (* silence-flag floor)))) ; silence-flag is 0 or 1.
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(env (get-env follower)))
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(env (get-env follow)))
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(if (> gate-freq 20)
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(let* ((high (highpass8 sig gate-freq))
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(low (lowpass8 sig (* 0.91 gate-freq)))) ;magic number 0.91 improves crossover.
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(sim (mult high gain env) low))
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(mult sig gain env))))
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(defun get-env (follow)
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;; Return gate's envelope
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(let* ((gate-env (gate follow lookahead attack decay floor threshold))
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(gate-env (clip gate-env 1.0))) ;gain must not exceed unity.
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(diff gate-env (* silence-flag floor))))
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(defun gate (sound lookahead risetime falltime floor threshold)
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;; This replaces Nyquist's GATE function. See bug 2519
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;; Note: this does NOT perform the actual gating, it just generates an exponential
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;; rise and decay for our "gain envelope".
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(setf sound (snd-gate (seq (cue sound) (stretch-abs 1.0 (s-rest lookahead)))
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lookahead risetime falltime floor threshold))
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(snd-xform sound (snd-srate sound) (snd-t0 sound)
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(+ (snd-t0 sound) lookahead) MAX-STOP-TIME 1.0))
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(defun peak-follower (sig) ;;FOLLOW
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(defun peak-follower (sig)
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;; Return signal that gate will follow.
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;; Reduce sample rate to around 1000 Hz to allow
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;; longer tracks to be processed (bug 2519).
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(let ((step (round (/ *sound-srate* 1000))))
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(setf sig (multichan-expand #'snd-avg sig step step op-peak))
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(when (and (arrayp sig)(= stereo-link 0))
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(setf sig (s-max (aref sig 0) (aref sig 1))))
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; SND-AVG looks for peak in next 'step', so shift envelope one sample earlier.
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(setf sig (multichan-expand #'trim-first-sample sig))
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(if (> hold 0)
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(multichan-expand #'add-hold sig)
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sig)))
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(defun trim-first-sample (sig)
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;; Remove the first sample from sig.
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(let ((t0 (/ (snd-srate sig))))
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(extract-abs t0 MAX-STOP-TIME (cue sig))))
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(defun add-hold (sig)
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;; Extend 'above threshold peaks' by 'hold' seconds.
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;; TRIGGER acts when transitioning from less than or equal to zero to greater than zero,
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;; which is not ideal, but it's a lot faster than looping through samples with Lisp.
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;; We therefore need to invert the signal and offset vertically so that a fall across threshold
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;; becomes a rise above zero.
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(setf sig (mult -1 (diff sig threshold)))
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(let ((holding (trigger sig (cue (hold sig hold)))))
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(setf sig (sum threshold (mult -1 sig)))
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(sum sig holding)))
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(defun hold (sig dur)
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;; generate 'hold' sound.
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(control-srate-abs (snd-srate sig)
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(stretch-abs 1.0 (const 1.0 dur))))
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(setf sig (multichan-expand #'snd-abs sig))
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(when (and (arrayp sig)(= stereo-link 0))
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(setf sig (s-max (aref sig 0) (aref sig 1))))
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(if (> hold 0)
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(multichan-expand #'snd-oneshot sig threshold hold)
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sig))
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(defun process ()
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(error-check)
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;; 'peak-follower' may return a sound or array of sounds.
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;; For stereo tracks, 'peak-follower' may return a sound
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;; or array of sounds, so pass it to 'noisegate' rather than
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;; calculating in 'noisegate'.
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(multichan-expand #' noisegate *track* (peak-follower *track*)))
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;; Run program
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(case mode
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(0 (catch 'err (process)))
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