[CM] snd config, help

Bill Schottstaedt bil@ccrma.Stanford.EDU
Mon, 20 Nov 2006 11:25:06 -0800

> 1. to visually see or other way detect clipping (or identify 
> lossy coding) 

Here's a function that looks for clipping:

(define* (channel-clipped? :optional snd chn)
  (let ((last-y 0.0))
     (lambda (y)
       (let ((result (and (>= (abs y) 0.9999)
                          (>= (abs last-y) 0.9999))))
         (set! last-y y)
     0 #f snd chn)))

On the mpeg filtering -- I haven't paid much attention to that
business, so I don't know exactly what to look for, but presumably
you could take a spectrum and look for the mpeg signature.

> 2. do "Hard Limiting" (I don't know how to do it in snd) 

I don't know what "hard limiting" means.

> 4. Identify digital silence in audio 

I usually use some form of moving-average for this -- map-silence
in extsnd.html for example.