Re: Technical Question (was Digital Talking Book Standard )

["Martin G. McCormick" <martin@dc.cis.okstate.edu>]

	Yes, I am a bit slow, but I am catching on.  I definitely
need to understand more about time scale shifting methods and how
to accomplish them without adding distortion.

	Each digit represents a moment in time and we can make
things appear to speed up or slow down by intelligently inserting
or deleting  information.

	If we do it on a sample by sample basis, we can make the
recording appear to speed up or slow down with the expected pitch
changes.  If we do it on a wave form by wave form basis, we can
appear to keep the same pitch, but speed up the tempo or, for
that matter, we can add extra wave forms and stretch out the
syllables or whatever and slow them down.

	The old pitch correcting devices like the one I presently
use to read magazines butcher the sound because they aren't smart
enough to make sure the next snippet of sound starts at the same
place on the wave form that the previous one ended so we get that
characteristic gravelly sound at high rates.  I usually run mine
at maximum throttle so it is pretty bad, but with headphones, I
can still understand it.

	Thanks to both of you for giving me some more food for
thought.  I may play some more with /dev/dsp and see what weird
sounds I can come up with.

Martin McCormick

Janina Sajka writes:
>Martin:
>
>It sounds like you're extrapolating from experience with analog systems 
>that achieve similar results. Fortunately, the science has become much 
>more sophisticated. I say that's fortunate because the results can be much 
>much better than those we've heard on analog tape decks.