[Trombone-l] iPod as audio recorder [Was: Advice onMinidiskRecorders]

[Jeff Albert]

On 10/19/06, Daniel Pliskin <daniel_pliskin at hotmail.com> wrote:
>
>
> >>All this talk about CD quality is a bit misleading.  In studio digital
> >>recording, tracks are recorded at considerably higher bit rates and at
> 24
> >>bits of resolution.  Doing so allows the engineer to have a little
> >>headroom,
> >>so that signals don't clip and compression isn't needed.
>
> >No, headroom is not a function of bit rate or sample  rate.  You can clip
> >24
> >bit 96 k just as easy as 16/44.1.  Bit rate and sample rate  only measure
> >the amount of information stored.
>
>
> Not true.
>
> If you're recording at 24 bits of resolution and your target resolution is
> 16 bits, you can set your VUs at 24 dB down, and have 24 dB of headroom
> and
> 24 dB to spare, before getting down to 16 bits of signal.   That's where
> your headroom comes from.


I hate to start/continue a Tim Richardson style  "discussion" here, but that
isn't right.  If you are recording at 24 bits, every sample is defined with
24 bits if information, as opposed to 16, or 20, or 8 for that matter.

I asked a friend who is the Technology Professor in the Loyola University
Music Industry Studies Program.  Here is his response:

Additional bits allow you to more accurately measure the signal. It doesn't
add head room. Imagine you're measuring the height of someone. Their height
doesn't change if you use yards, feet inches, etc. So someone who's 5'9"
tall would be measured as  2 yards, 6 feet, or 69 inches. In the first case,
you have 9" of quantization error. In the second, 3" and none in the last
case.

Changing resolution changes how accurate you are, which minimizes
quantization errors, which get perceived as noise. That's all it does.  You
could also think of it as increasing dynamic range. Each bit adds 6.02dB of
dynamic range.

Back to me:  Dynamic range being the incremental distance from zero to
clipping.  Clipping isn't any higher, there are just more gradations between
zero and there.

Lets say we are recording a decrescendo. If it was one bit, it would either
be on or off.  At 8 bits there is more information to record the volume
changes, and at 24 bits there is even more.  It can't handle more volume,
but it can distinguish more diffeent volumes.

Jeff


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