Re: 16-Bit Stereo PCM Standard?

> Hi, Patrick,
>
> In 16-bit PCM, you typically use signed 16-bit
> values, so you can think of it this way:  a value of 0 means the speaker's
> cone is centered, or at "rest", a value of -32768 means the speaker's cone
> is pushed into the cabinet as far as it can go, and a value of 32767 means
> it is pushed out of the cabinet as far as it can go.
>

Ah that is indeed a good way of putting it. But the confusion however
still stands. I might not have stated it clearly, but I'm curious
about three things:

1) What is the _scale_ by which the [-32768, 32767] get converted to
  sound. E.g. as you said, using 32767 would mean the speakers cone
  pushes out as far as it can go, and 0 means it's not pushed out at
  all, but then does the value (32767 / 2) mean that it's pushed out
  half way? That would be a linear scale. Or is the scale something
  else?

2) It is slowly making sense to me that there can't be a requirement
  that says anything along the lines of "PCM value 16,383 yields
  decibel value 120db"? The user can always change the speaker volume
  and foil your attempts to produce any particular decibel
  values. However, this leaves me baffled as to what part of the
  [-32768, 32767] range a sound file ought to use. Should every sound
  file use all of the range? This leads into question #3:

3) How does sound get captured from a microphone? Do you get 16-bit
  PCM input as well? But if you do get something like 16-bit PCM data
  from a microphone then there _must_ be some mapping going on from
  "decibels -> 16-bit PCM", since the microphone really can be
  guaranteed to capture exact decibel levels (even if the speakers
  aren't guaranteed to output exact decibel levels). Additionally,
  is there some maximum decibel level that a mic can usually capture?
  Might that get mapped to something like the 32767 PCM value?

Apologies in advance if any of these questions seem strange, my head
is still spinning :-)

-Patrick
_______________________________________________
Openal mailing list
[email protected]
http://opensource.creative.com/mailman/listinfo/openal