[vorbis] Re: An introduction to compressed audio with Vorbis

[fungus]

Graham Mitchell wrote:
>>That's not correct.  A single sample is not meaningful by itself; each
>>sample merely represents a voltage.  It's the *difference* between
>>samples that creates vibrations in a speaker, and therefore sound waves.
>>
> 

If you push the speaker cone half way out and leave it
there you won't hear aything. To produce an audible
sound you need to vibrate it.

> Thanks for the correction.  Even as I wrote it, I felt fairly sure that 
> -32,768 shouldn't represent silence.
> 

It doesn't....0 is silence, values can be measured from
-32768 (below the zero line) to +32767 (above the zero
line). Zero is in the middle.

<p> >>My explanation may leave a bit to be desired; and perhaps this is too
 >>technical/mathematical for your intended audience.  But the sentence I
 >>quoted is simply wrong. :-/
 >>
 >

If you look at the waveform in a sample editor like
Sound Forge then (assuming your sampler works correctly)
silence will be represented by a flat line with sample
values of zero. When a signal is present the sample
values will oscillate around the zero line and at
maximum volume will be in the range -32768 to +32767.

<p>
-- 
<\___/>
/ O O \
\_____/  FTB.

<p><p><p><p>--- >8 ----
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