[dvd-discuss] High resolution audio recording

[John Schulien <schulien(at)speakeasy.net>]

 > 24 bit quantization permits a 144dB dynamic range (vs 96)
 > which corresponds to a pin drop to the level of pain and damage. If one
 > believes in digital signal processing the the Nyquist rate, then there is
 > nothing to be gained by using 192 vs 48ksps except that 192ksps permits a
 > maximum frequency of 96kHz which is well beyond the range of human hearing,
 > possibly to the  level of sensation but might possibly be useful for 
enthusists
 > working to provide the  audiophile experience for canines or bats....

Audio engineers love 24 bit quantization and 192 KHz recording because it
makes their job a whole lot easier.

When recording a track on a 16 bit recorder that will eventually be 
released on
CD, the engineer is faced with a decision:  how much headroom to leave, meaning
how much below the absolute maximum does he or she set the recording levels.

If the engineer leaves a lot of headroom -- sets the recording levels so 
that the
signal peaks at, for instance, -6 dB, then the recording will sound 
noticeably duller
than if the recording levels were set so that the signal were to peak at 0 dB.

On the other hand, if the engineer carefully watches/rides the levels and 
tries
to record as hot a signal as possible, then he or she is going to get the best
possible sounding 16 bit recording, BUT there is the danger that at some point
the musicians will dig in and play a little louder.  This will either cause 
the digital
signal to clip, resulting in a particularly brutal form of  distortion that 
can be best
described as sounding like a digital chainsaw, or will cause a 
compressor/limiter
to kick in, producing an audible artifact.

A lot of this has to do with the experience and technical skill of the 
musicians.
Musicians inexperienced at the recording process tend to play louder when they
get excited, and tend to turn themselves up so they can hear themselves better.
Seasoned studio professionals know not to do this, and make life easier for the
engineer.

By using a 24 bit recorder, the engineer gets way, way more headroom and gets
the best of both worlds.  The engineer can set the recording levels for, 
say -6dB.
This way there is no way that the musicians are going to clip the signal, AND
each track is recorded with well over 16 bits of resolution.

Then, once the master recording is made, the engineer can go into the mixing
studio, mix the recording at 24 bits, then resample the completed master 
down to
16 bits, fully utilizing the CD dynamic range, but without the 
safety/resolution
compromise of 16 bit mastering.

Similarly, a high sampling rate allows for more accurate digital signal 
processing
of high-frequency signals.  Say you want to apply a filter to a drum track 
that includes
symbols crashes or snare hits.  Many digital signal processing algorithms will
introduce artifacts when applied to signals approaching the Nyquist limit.
Sampling way, way beyond the human hearing range improves the performance
of signal processing algorithms when applied to such high frequency signals.
Once the recording is fully signal-processed at 192KHz, it can be downsampled
to 44.1KHz and the resulting recording will sound better than if it had 
been signal
processed at 44.1KHz in the first place.

These are good reasons for recording engineers to use high resolution
equipment, and this is why the equipment is manufactured and used, and why it
is taking over the professional recording field.  These are not good 
reasons for
having such equipment in a home stereo.

Which isn't to claim that high resolution audio can't sound better on a high
end stereo.  It very well might.  My point is that high resolution audio offers
huge, tangible benefits to recording engineers, and at the best, subtle 
benefits
to the home listener.

I suppose a good analogy would be race car technology.  A professional race
car driver can certainly benefit from a top of the line, ultra-high power 
engine.
Ordinary drivers on the other hand don't need to the ability to accelerate 
from
zero to 200 miles per hour in a few seconds, leaving a quarter mile of burned
rubber behind them. The automakers will certainly be happy to sell you such
an engine if you like, at a high price, but  you'll have to come up with 
your own
justifications for putting such an engine in a street car, and it they 
certainly won't
be the same reasons that a professional race car driver would have for putting
such an engine in a race car.