Re: How to remove buffering silence from wav files

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Nigel Henry:

Big problem for dialup users since BBC stopped realmedia streams.

Listening to BBC radio on dialup is now hopeless as both the BBC's iplayer
(flash), and wm streams need all the dialup bandwidth plus more (48kbps), so
what I'm doing is recording the programmes, and hope to remove the silent
buffering sections after which I can listen to them in the normal manner.

Removing the silent bits manually, in mhwaveedit for example is going to take
forever, so the question is, does anyone know of anything that would
accomplish this automatically?  I can think of 2 options as below, but how to
accomplish them.

1: Some way of doing these recordings where the recording device will pause
for the buffering silences, then continue when the speech starts again.
Obviously it wouldn't want to stop for speech pauses, but these are not
completely silent as are the buffering silences. I'm using qarecord at the
moment for the recordings.

2: Some program to run the recorded wav files through, which would remove the
buffering silence sections.


If you load your file into Snd, it should work to paste the following lines into the terminal Snd was started from:

(let loop ((x 0)
           (x0 -1))
  (let ((y (sample x)))
    (cond ((and (= x0 -1)
                (= y 0))
           (loop (1+ x)
                 x))
          ((and (not (= x0 -1))
                (not (= y 0))
                (> (- x x0) 32))
           (display "deleting")(display x0)(display " -> ")(display x)(newline)
           (let loop ((ch 0))
             (cond ((< ch (channels))
                    (delete-samples x0 (- x x0) (selected-sound) ch)
                    (loop (1+ ch)))))
           (loop x0 -1))
          ((and (not (= x0 -1))
                (not (= y 0)))
           (loop (1+ x) -1))
          ((< x (frames))
           (loop (1+ x) x0)))))


You might want to adjust the number 32 (minimum number of zero-frames to yield a deletion), but I think 32 should work fine.

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