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16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain



 
 
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  #1  
Old November 15th 03, 03:50 PM
Ric Oliva
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

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?

Another question - if I'm recording a project to audio CD, is it better to
just record at 16/44 since that's what the CD will be anyway, and I can save
system resources? or should I do 24/48 and then dither it down, essentially
changing what I originally heard? I read in the ProTools book by Berklee
Press that its best to record on LE using 24/44 since you won't hear much
difference between the 48k and 44.1k. Any insights into this?


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  #3  
Old November 15th 03, 05:52 PM
Denny F
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Ric Oliva" > wrote in message
...
> 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?


The term bit "rate" does contribute to the confusion. I think bit "depth"
would be better.

The quick answer is sampling rate (rate makes sense here) is directly
related to frequency response. Bit depth is directly related to dynamic
range.

According to the theory, your sampling rate needs to be twice the highest
frequency you want to record. So theoretically, 44.1 gives you 22kHz
response, which is beyond human hearing. In practice, the actual top end
limit will be somewhat lower due to analog filtering required to keep the
clock noise out of the audio. But still, anything over 44.1 is probably
superfluous rather than "better."

Each sample has to reflect the amplitude of the signal at that sample. That
value is stored in a digital "word." We're talking about storing the value
in either a 16-bit or 24-bit word. The more bits, the better the
resolution, which in audio is refered to as "dynamic range."

> Another question - if I'm recording a project to audio CD, is it better to
> just record at 16/44 since that's what the CD will be anyway, and I can

save
> system resources? or should I do 24/48 and then dither it down,

essentially
> changing what I originally heard? I read in the ProTools book by Berklee
> Press that its best to record on LE using 24/44 since you won't hear much
> difference between the 48k and 44.1k. Any insights into this?


24/44.

While your finished product can sound just fine to the vast majority of ears
at 16-bit depth, 24 is still worthwhile for recording, applying effects
(transforms) and mastering. The reason is that the greater dynamic range of
the 24-bit depth manifests itself in a lower "noise floor." This extra
"room" at the bottom of your dynamic range is valuable because each time you
perform any kind of transform to your audio signal(s), you'll add a bit of
noise due to rounding errors. A greater bit depth makes these errors
smaller, and when you resample or dither your final, mastered recording to
16-bit, most of those rounding errors will hopefully live in those truncated
bits.

That's not to imply that you can't do a fair number of transforms on a
16-bit file without seriously degrading it. But there is at least a good
argument for using greater bit depths for recording/editing. Moreso than for
higher sampling rates, anyway.

--------------------------------------------------
Denny Fohringer
Itinerant guitarist
--------------------------------------------------
Lessons and music:
http://surf.to/dennyf
Bands:
http://bluepearlband.com http://doubletakeband.com
--------------------------------------------------


  #4  
Old November 15th 03, 06:22 PM
DJ
external usenet poster
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

What he said.

;-)


"Denny F" > wrote in message
...
> "Ric Oliva" > wrote in message
> ...
> > 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?

>
> The term bit "rate" does contribute to the confusion. I think bit "depth"
> would be better.
>
> The quick answer is sampling rate (rate makes sense here) is directly
> related to frequency response. Bit depth is directly related to dynamic
> range.
>
> According to the theory, your sampling rate needs to be twice the highest
> frequency you want to record. So theoretically, 44.1 gives you 22kHz
> response, which is beyond human hearing. In practice, the actual top end
> limit will be somewhat lower due to analog filtering required to keep the
> clock noise out of the audio. But still, anything over 44.1 is probably
> superfluous rather than "better."
>
> Each sample has to reflect the amplitude of the signal at that sample.

That
> value is stored in a digital "word." We're talking about storing the value
> in either a 16-bit or 24-bit word. The more bits, the better the
> resolution, which in audio is refered to as "dynamic range."
>
> > Another question - if I'm recording a project to audio CD, is it better

to
> > just record at 16/44 since that's what the CD will be anyway, and I can

> save
> > system resources? or should I do 24/48 and then dither it down,

> essentially
> > changing what I originally heard? I read in the ProTools book by

Berklee
> > Press that its best to record on LE using 24/44 since you won't hear

much
> > difference between the 48k and 44.1k. Any insights into this?

>
> 24/44.
>
> While your finished product can sound just fine to the vast majority of

ears
> at 16-bit depth, 24 is still worthwhile for recording, applying effects
> (transforms) and mastering. The reason is that the greater dynamic range

of
> the 24-bit depth manifests itself in a lower "noise floor." This extra
> "room" at the bottom of your dynamic range is valuable because each time

you
> perform any kind of transform to your audio signal(s), you'll add a bit of
> noise due to rounding errors. A greater bit depth makes these errors
> smaller, and when you resample or dither your final, mastered recording to
> 16-bit, most of those rounding errors will hopefully live in those

truncated
> bits.
>
> That's not to imply that you can't do a fair number of transforms on a
> 16-bit file without seriously degrading it. But there is at least a good
> argument for using greater bit depths for recording/editing. Moreso than

for
> higher sampling rates, anyway.
>
> --------------------------------------------------
> Denny Fohringer
> Itinerant guitarist
> --------------------------------------------------
> Lessons and music:
> http://surf.to/dennyf
> Bands:
> http://bluepearlband.com http://doubletakeband.com
> --------------------------------------------------
>
>



  #5  
Old November 15th 03, 07:03 PM
Arny Krueger
external usenet poster
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Ric Oliva" > wrote in message


> 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.


Why is this obvious?

> I'm not
> exactly sure what bit rate is though? CDs are 16 bit, DVDs are 24.
> What exactly does that mean though?


That's not bit rate. It's sample size.

> Another question - if I'm recording a project to audio CD, is it
> better to just record at 16/44 since that's what the CD will be
> anyway, and I can save system resources?


If you are going to do very much processing, it is wise to record with 24
bit samples to preserve dynamic range as you process the tracks. After
you've mixed the channels you are going to distribute, dither them down to
16 bits.

> or should I do 24/48 and then dither it down, essentially changing what I

originally heard?

Dithering down is a fast operation with most software. A proper job of
downsampling can involve quite a bit of processing time. If you're going to
throw away all audio > 22.05 KHz in the end, why bother ever recording it?

> I read in the ProTools book by Berklee Press that its best to record on
> LE using 24/44 since you won't hear much difference between the 48k
> and 44.1k. Any insights into this?


Yes, I just made a post entitled "Why 24/96 sampling isn't necessarily
better-sounding than 24/44 sampling" that addresses this question.

You can also investigate this issue yourself by downloading and listening to
files of the same musical sounds recorded in various sample formats, from
http://www.pcabx.com/technical/sample_rates/index.htm .




  #6  
Old November 15th 03, 08:14 PM
White Swan
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

If sample rate is viewed as resolution over time (horizontal axis),
bit rate is resolution of the amplitude (vertical axis). Each bit
doubles the resolution, or in other words, the smallest increment of
volume possible is hlaved with each additional bit.

The difference between 16 bits and 24 bits is 2 to eighth power, or
256. That means between each volume increment in a 16 bit recording
there are 256 intermediate steps added in a 24 bit recording. This
means that volume changes can be portrayed far more accurately and
smoothly. Also, when you manuipulate tracks with faders and plug-ins,
you are essentially doing mathematical operations, so with much higher
resolution the rounding errors are minimized. In practice, the result
is increased dynamic range, better stereo imaging, smoother less
grainy fades and reverb tails, and less worry about having to track
"hot". There is no reason not to track atr 24 bits if you can. The
only disadvantage is each sound file will be 150% bigger.

The difference between recording at 44.1 and 48k, on the other hand,
is pretty tiny. Many people (myself included) record at 44.1 so that
you don't have to worry about doing a sample rate conversion somewhere
down the line (to a 44.1 CD) which may do more harm than whatever tiny
gain you are getting from the slightly higher sample rate. If you are
concerned with using a higher sample rate, 88.2 seems to make more
sense. If you are going to do all your mixing on an analog board,
however, then you might as well use 48k.
  #7  
Old November 15th 03, 08:26 PM
Rick Powell
external usenet poster
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Ric Oliva" > wrote in message m>...
> 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?
>
> Another question - if I'm recording a project to audio CD, is it better to
> just record at 16/44 since that's what the CD will be anyway, and I can save
> system resources? or should I do 24/48 and then dither it down, essentially
> changing what I originally heard? I read in the ProTools book by Berklee
> Press that its best to record on LE using 24/44 since you won't hear much
> difference between the 48k and 44.1k. Any insights into this?
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.541 / Virus Database: 335 - Release Date: 11/14/2003


Basically speaking, the bit resolution determines the ability to
describe the amplitude of a signal. Having 24 bits available gives
you a safety cushion in digital recording, among other things. The
same input signal that you are slamming to 0 dbfs in 16 bit format
(not a good thing because of the possibility of "overs") can be
recorded in 24 bit format with the same or better resolution while
staying well below the red. In a MIX article years ago, Stephen St.
Croix stated that, sound improvement-wise, he'd rather have 17 bits
vs. 16 instead of 96 kHz sampling rate vs. 48 kHz, if he had to make a
choice.

Most pro's would rather work in the higher resolutions until the
absolute last bounce or mix to 16/44.1. This is partly because, with
digital processing (EQ, compression, etc.), the extra headroom yields
real sonic benefits when recording, editing, etc. There are some that
prefer to keep everything in 44.1 all the way through to avoid sample
rate conversion at the end, but there is almost universal use of
higher bit resolutions whenever possible.

RP
  #8  
Old November 15th 03, 10:13 PM
Jay - atldigi
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

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.

--
Jay Frigoletto
Mastersuite
Los Angeles
promastering.com
  #9  
Old November 16th 03, 04:59 AM
Peter Gemmell
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Posts: n/a
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

  #10  
Old November 16th 03, 05:39 AM
Bob Cain
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain



Peter Gemmell wrote:
>
> 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?


The way that finer resolution manifests is as a larger
signal to noise ratio. The noise is due to quantization and
the wider the sample, the lower the noise is relative to the
maximum representable signal. The noise is an approximately
random error of +-1/2 the value of the low order bit. It is
inescapable. It is intimately related to the dynamic range
because it determines how small the signal can be before it
loses signifigance relative to that error noise limit. The
ratio of how large a signal that can be represented to how
small a signal can be represented is the dynamic range.

In practice, I don't think that yet any front end to a 24
bit ADC is itself nearly as quiet as that quantization noise
so that you will see specifications, if they are honest,
that are signifigantly lower than the theoretical 144 dB SNR
that can be achieved with 24 bits.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
 




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