125 lines
4.8 KiB
Common Lisp
125 lines
4.8 KiB
Common Lisp
$nyquist plug-in
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$version 1
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$type analyze
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$name (_ "Silence Finder")
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$manpage "Silence_Finder"
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$action (_ "Finding silence...")
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$author (_ "Alex S. Brown")
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$release 2.3.0
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$copyright (_ "Released under terms of the GNU General Public License version 2")
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;; by Alex S. Brown, PMP (http://www.alexsbrown.com)
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;;
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;; Adds point labels in areas of silence according to the specified
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;; level and duration of silence. If too many silences are detected,
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;; increase the silence level and duration; if too few are detected,
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;; reduce the level and duration."
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;; Released under terms of the GNU General Public License version 2:
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;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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;;
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;; For information about writing and modifying Nyquist plug-ins:
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;; https://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
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$control sil-lev (_ "Treat audio below this level as silence [ -dB]") real "" 26 0 100
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$control sil-dur (_ "Minimum duration of silence [seconds]") real "" 1.0 0.1 5.0
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$control labelbeforedur (_ "Label placement [seconds before silence ends]") real "" 0.3 0.0 1.0
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;Create a function to make the sum the two channels if they are stereo
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(defun mono-s (s-in) (if (arrayp s-in) (snd-add (aref s-in 0) (aref s-in 1))
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s-in))
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;Create a function to reduce the sample rate and prepare the signal for
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;analysis. RMS is good to monitor volume the way humans hear it, but is not
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;available in Audacity. Used a peak-calculating function instead.
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;NOTE: this is the place to add any processing to improve the quality of the
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;signal. Noise filters could improve the quality of matches for noisy signals.
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;PERFORMANCE vs. ACCURACY
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;Reducing the samples per second should improve the performance and decrease
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;the accuracy of the labels. Increasing the samples per second will do the
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;opposite. The more samples checked, the longer it takes. The more samples
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;checked, the more precisely the program can place the silence labels.
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;my-srate-ratio determines the number of samples in my-s. Set the number after (snd-srate s)
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;higher to increase the number of samples.
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(defun my-s (s-in)
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(setq my-srate-ratio (truncate (/ (snd-srate (mono-s s-in)) 100)))
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(snd-avg (mono-s s-in) my-srate-ratio my-srate-ratio OP-PEAK)
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)
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;Set the silence threshold level (convert it to a linear form)
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(setq thres (db-to-linear (* -1 sil-lev)))
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;Store the sample rate of the sound
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(setq s1-srate (snd-srate (my-s s)))
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;Initialize the variable that will hold the length of the sound.
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;Do not calculate it now with snd-length, because it would waste memory.
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;We will calculate it later.
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(setq s1-length 0)
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;Initialize the silence counter and the labels variable
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(setq sil-c 0)
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(setq l NIL)
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;Convert the silence duration in seconds to a length in samples
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(setq sil-length (* sil-dur s1-srate))
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;Define a function to add new items to the list of labels
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(defun add-label (l-time l-text)
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(setq l (cons (list l-time l-text) l))
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)
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;The main working part of the program, it counts
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;the number of sequential samples with volume under
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;the threshold. It adds to a list of markers ever time
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;there is a longer period of silence than the silence
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;duration amount.
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;It runs through a loop, adding to the list of markers (l)
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;each time it finds silence.
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(let (s1) ;Define s1 as a local variable to allow efficient memory use
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; Get the sample into s1, then free s to save memory
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(setq s1 (my-s s))
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(setq s nil)
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;Capture the result of this "do" loop, because we need the sountd's legnth
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;in samples.
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(setq s1-length
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;Keep repeating, incrementing the counter and getting another sample
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;each time through the loop.
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(do ((n 1 (+ n 1)) (v (snd-fetch s1) (setq v (snd-fetch s1))))
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;Exit when we run out of samples (v is nil) and return the number of
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;samples processed (n)
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((not v) n)
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;Start the execution part of the do loop
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;if found silence, increment the silence counter
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(if (< v thres) (setq sil-c (+ sil-c 1)))
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;If this sample is NOT silent and the previous samples were silent
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;then mark the passage.
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(if (and (> v thres) (> sil-c sil-length))
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;Mark the user-set number of seconds BEFORE this point to avoid clipping the start
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;of the material.
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; Should "S" be translated or become a control value?
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(add-label (- (/ n s1-srate) labelbeforedur) "S")
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)
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;If this sample is NOT silent, then reset the silence counter
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(if (> v thres)
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(setq sil-c 0)
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)
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)
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)
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)
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;Check for a long period of silence at the end
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;of the sample. If so, then mark it.
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(if (> sil-c sil-length)
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;If found, add a label
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;Label time is the time the silence began plus the silence duration target
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;amount. We calculate the time the silence began as the end-time minus the
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;final value of the silence counter
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(add-label (+ (/ (- s1-length sil-c) s1-srate) sil-dur) "S")
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)
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;If no silence markers were found, return a message
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(if (null l)
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(setq l (format nil (_ "No silences found. Try reducing the silence~%level and minimum silence duration.")))
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)
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l
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