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Old November 16th 03, 04:59 AM
Peter Gemmell
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

Jay - atldigi wrote:
> In article >, "Ric Oliva"
> > wrote:
>
>
>>Ok, so I understand that 44.1k is 44,100 samples per second and 48k is
>>48,000 samples per second. Obviously 48,000 is better. I'm not exactly
>>sure what bit rate is though? CDs are 16 bit, DVDs are 24. What exactly
>>does that mean though?

>
>
> http://www.promastering.com/pages/techtalk.html
>
> Article 1 and 2 deal with bit depth and dither, article 3 with sampling
> rates. Recording at wordlegths higher than 16 bit is helpful. In
> practice, 20 is almost always as good as 24 for recording since A to D
> converters don't have the dynamic range to capture 24 bits and the lower
> bits just contain the self noise of the box. For digital processing,
> however, you want to use longer wordlengths like 48 bit, or at the very
> least, 32 bit floating point.
>
> Most simply stated, wordlength (or bit depth) is dynamic range. Bit rate
> actually means something a little different, but we won't get into that
> right now as you obviously are asking about bit depth. For every bit you
> get about 6 dB (just over actually) of dynamic range. 16 bit CD has 96dB
> while 24 bit has 144. Extra bits do not add headroom; they add footroom.
> 0 dB FS (full scale) represents the same value in both 16 bit and 24 bit
> audio. The extra bits come into play at the bottom of the range. You are
> able to record smaller events - sounds at a lower level.
>
> In addition to dynamic range, it also means noise. in 16 bit, there is a
> noise floor of -96dB while 24 bit has a noise floor of -144 dB. 24 bit
> offers no additional accuracy in the top 96db of the dynamic range.
> Actually, an 8 bit recording is just as accurate as a 24 bit recording
> from 0dBFS to -48 dB. The -48 dB noise floor is quite obtrusive and the
> 8 bit recording certainly sounds worse, but those top 48 dB are just as
> accurate as a 24 bit recording. If you took a 24 bit file and added 96
> dB of noise, it would sound like an 8 bit file.
>
> Invariably any discussion of bit depths must eventually include dither.
> This, however, I'll leave to the tech talk articles I've pointed you to,
> or to a google search for the many posts that have appeared here in
> r.a.p. Be aware, however, that there are some common mistakes made
> quite often when discussing these subjects, so avoid the myths.
> Sometimes common sense tends to fail you until you understand how
> digital audio truly works, so some things that seem to make intuitive
> sense at first are actually technical rubbish.
>


So, what answer is correct? Whiteswan, Rick Powell, and Jay have given
three answers that sound good but are mutually exclusive. I've been at
this a few years and I still don't know what is right. Does 24 bit give
greater resolution than 16 bit or does it merely give a larger dynamic
range without a finer resolution?

Peter

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