[vorbis] Re: An introduction to compressed audio with Vorbis
meditvr at teleline.es
Fri Feb 8 01:11:35 PST 2002
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.
/ O O \
<p><p><p><p>--- >8 ----
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