Reply
 
Thread Tools Display Modes
  #1   Report Post  
Ric Oliva
 
Posts: n/a
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?


---
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


  #3   Report Post  
Denny F
 
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. 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   Report Post  
DJ
 
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   Report Post  
Arny Krueger
 
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   Report Post  
White Swan
 
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   Report Post  
Rick Powell
 
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   Report Post  
Jay - atldigi
 
Posts: n/a
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   Report Post  
Peter Gemmell
 
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   Report Post  
Bob Cain
 
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


  #11   Report Post  
Jay - atldigi
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article ,
wrote:

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 has it. Read his post and my post and you'll see that they are not
mutually exclusive.

White Sawn's satement seems to indicate that the extra bits are within
the same dynamic range, thereby giving you greater detail within that
range. You can't into the trap of viewing digital audio like it's
digital imagery. Unfortunately, 24 bits leaves the top 96db range of 16
bit alone, but lowers the noise floor and allows the recording of audio
events that are even smaller, at a lower level, i.e. below -96dB.

Rick understands that bit depth relates to amplitude and that DSP is
better with longer wordlengths. A small clarification is in order,
however. He seems to consider there to be extra headroom while
technically there is not, unless you change the zero reference. In other
words, increase the voltage that zero is referenced to. Nevermind
working at -10 or +4, you'll be using a new, nonstandard reference
voltage, and what about the analog electronics that probably can't
handle that voltage? You're asking for trouble for that reason and
several others (increasing the noise floor of the analog gear,
compatability, and more). Unless you want to do that, you really are
gaining what should be thought of as "footroom" more than headroom.

In practice some feel that you need to push a digital recording right up
to 0dB FS to "use all the bits". This really isn't as big an issue as
some would have you believe, as long as you use good gain stageing and
reasonable recording levels, especially with todays converters which
perform far better than much or the early crappy digital stuff. It
doesn't hurt to assumne that 24 bits gives you a little room to play
with, but unless you are recording a program with greater than average
dynamic range in a very quiet environment with excellent equipment and
minimal processing, you really aren't going to be able to take advantage
of those extra bits. Then again, they certainly don't hurt, and they
could help, so there's no reason not to. Still, it helps to understand
technically what's going on and when extra effort will pay off and when
if won't.

Some of these technical distinctions may not seem to matter much in
every day practice, but that's no reason to be uninformed. The lower
noise floor and extra dynamic range can really make a difference. Some
say it's "merely" dynamic range or "just" lower noise, like those things
are somehow unimportant and could hardly make a difference. It must be
something more esoteric that makes it sound better! Well, it's not.
Those things can be very important and it often does sound better. The
little details that were once buried below the noise floor may now be
audible, whether minute audio events or perhaps subtle overtones, and
the noise floor of the recording may be below your ability to hear it
anymore. That's not minced meat!

--
Jay Frigoletto
Mastersuite
Los Angeles
promastering.com
  #12   Report Post  
Arny Krueger
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Jay - atldigi" wrote in message


White Sawn's satement seems to indicate that the extra bits are within
the same dynamic range, thereby giving you greater detail within that
range. You can't into the trap of viewing digital audio like it's
digital imagery. Unfortunately, 24 bits leaves the top 96db range of
16 bit alone, but lowers the noise floor and allows the recording of
audio events that are even smaller, at a lower level, i.e. below
-96dB.


24 bits puts 16 extra levels between each pair of levels that exist with 16
bits. Thus, the resolution is increased at any level, not just the smallest
one.

The reduction of the noise floor due to 24 bits is a consequence of the
extra resolution 24 bit coding provides between any of the two levels in a
16 bit representation. The two go together hand-in-hand because the coding
is linear.

The idea that adding bits does not increase resolution is yet another
popular urban myth about digital. It's similar to the urban myth that analog
has resolution below the noise floor.

In an exactly linear system, whether digital or analog, the noise floor and
resolution are exactly the same. In a nominally linear (i.e., real-world)
system, whether digital or analog, the noise floor and resolution are
nominally the same.




  #13   Report Post  
Rick Powell
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

Jay - atldigi wrote in message ...

Rick understands that bit depth relates to amplitude and that DSP is
better with longer wordlengths. A small clarification is in order,
however. He seems to consider there to be extra headroom while
technically there is not, unless you change the zero reference. In other
words, increase the voltage that zero is referenced to. Nevermind
working at -10 or +4, you'll be using a new, nonstandard reference
voltage, and what about the analog electronics that probably can't
handle that voltage? You're asking for trouble for that reason and
several others (increasing the noise floor of the analog gear,
compatability, and more). Unless you want to do that, you really are
gaining what should be thought of as "footroom" more than headroom.

In practice some feel that you need to push a digital recording right up
to 0dB FS to "use all the bits". This really isn't as big an issue as
some would have you believe, as long as you use good gain stageing and
reasonable recording levels, especially with todays converters which
perform far better than much or the early crappy digital stuff. It
doesn't hurt to assumne that 24 bits gives you a little room to play
with, but unless you are recording a program with greater than average
dynamic range in a very quiet environment with excellent equipment and
minimal processing, you really aren't going to be able to take advantage
of those extra bits. Then again, they certainly don't hurt, and they
could help, so there's no reason not to. Still, it helps to understand
technically what's going on and when extra effort will pay off and when
if won't.


Jay, I'm not suggesting changing the zero reference. Correct the
following if I'm wrong, but as a mastering engineer, you would rather
take in a 2-track digital mix that peaked at -2db than one that peaks
at 0 dbfs and has a few "flat tops". Using a 24 bit format to record
or mix down to allows less artifacts towards the noise floor, given 2
"identical" sources (one recorded at 16 bit and one at 24 bit) peaking
at, say, -2db. And reduces the need (perceived or real) to "slam" the
recording all the way to 0 dbfs to take "full advantage" of the bit
depth.

If this is "footroom' instead of "headroom", isn't it still a margin
nonetheless?

RP
  #14   Report Post  
Mike Rivers
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain


In article writes:

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?


All of the above. Dynamic range and resolution are inseparable, even
in the analog world. In the digital world it's easier to see both.

With more bits, the actual value recorded for each sample is
potentially more accurate, hence better resolution. The greater the
resolution, the more likely that you'll be able to tell that two
adjacent samples along a time-varying waveform actually have different
values. I say "potentially" since as has been pointed out already,
once you get much beyond 20 bits, the amplitude of the noise in the
input or output parts of the system (the A/D or D/A converters) is
greater than one bit's worth of change, so the last couple of bits
really don't contribute anything to accuracy. They only allow you to
record the low level system noise with reasonable accuracy. So that's
your limit to dynamic range.

The reason why it's important to allow for longer word lengths in
signal processing (including mixing) is that those are purely
mathematical, and theoretically noise-free processes. Since you aren't
adding noise, you can take advantage of the resolution of the longer
word length so that when you ultimately shorten it to accommodate the
output circuitry or final delivery medium, all the numbers to the
resolution of that final word length will be accurate.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
  #15   Report Post  
Mike Rivers
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain


In article writes:

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.


Obviously, but do you understand why, and why it might not be better
sometimes?

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 actually the length of the digital word that represents the
voltage of each sample. The more bits, the greater the resolution, and
the greater the potential for accuracy. Of course the actual accuracy
is a function of how good the analog-to-digital and digital-to-analog
converters that use that digital word is.

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?


You'll save some disk space. As to whether it's better, it depends on
what you're going to do between making the recording and making the
CD.

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?


I believe that most people won't. Every mathematical process that you
avoid (like changing the sample rate) means there's less chance to
change the sound. But as a beginner, your auditory perception isn't
likely to be acute enough to make these judgements yourself by
listening, so you might as well take someone's word for it.


--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo


  #16   Report Post  
Justin Ulysses Morse
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

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?

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?



The minimum necessary sample rate and bit depth is determined by the
sounds you want to reproduce.

The dynamic range (basically signal-to-noise ratio) of your material
determines the minimum necessary bit depth. In practice, you will
never record a source with a dynamic range greater than can be
represented in 16 bits.

The bandwidth (frequency range) determines the necessary sample rate.
The sample rate is required only to be more than double the highest
frequency you want to reproduce. In practice, almost nobody owns
reproduction equipment that is useful beyond 20kHz.

So in theory you can record at 44.1/16 and your digital audio will hold
all of the audio data necessary to reproduce anything you can put into
and pull out of any equipment.

The need for greater data rates comes when you plan to manipulate the
recording one or more times between the record and reproduce moments.
If you are going to re-sample your data (through sample rate conversion
or a D/A-A/D process), then you might benefit from an increased sample
rate. More importantly, if you plan to manipulate the VALUES of those
existing samples (by DSP processes such as gain changes, EQ, or
anything else), then you might benefit from an increased bit depth.

Both of these considerations serve to push the limitations of the
quantization processes beyond our ability to detect them. The idea is
that stacking these processes can compound their inherent errors and
eventually make them audible. Even this precaution represents a
judicious level of overkill in almost all cases, but data storage is
getting cheap so it doesn't hurt.

In summary: If you're recording live to 2-track and won't be doing any
processing at all, then 44.1/16 is more than adequate. If you will be
doing any processing, then start with 24 bits. If you will be doing
any resampling, then start with 96k. Whatever rate you choose for your
initial recording, you should maintain that rate until the final stage
of processing.
  #17   Report Post  
Jon Davis
 
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.


Correct. The more samples of a waveform you can gather, the easier it is to
reproduce it.

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, but rather bit depth.

MP3 files and other audio file formats are often saved in a format
determined by "bit rate", so as to determine the number of bits per actual
chunk of time--hence, an HTTP download of an MP3 file can be streamed with
highest quality possible if the bit rate is predetermined.

Bit depth, however, is the vertical sampling resolution of an audio sample.
As you know, 44kHz sample rate is the number of samples per second. On a
horizontal waveform drawing, this is the horizontal resolution (think screen
resolution on your monitor, 640x480 vs. 1024x768). Bit depth is the number
of bits of information per sample, or the vertical resolution.

For example, in an 8-bit sample bit depth, a waveform's amplitude in a
particular sample can be in any of 256 possible positions (2*8 = 256).
Obviously, that's a very small number of possibilities. So a 16-bit sample
bit depth the resolution is much higher: 65536.

Bit rate is determined by the two resolutions combined. Theoretically, an
MP3 file saved with a 64kbps bit rate means that the file must be downloaded
from the Internet at a rate of at least 64 kilobits per second in order for
it to be streamed through the MP3 player without hiccupping.

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?


In general, with audio it is better to sample at high depth and resolution
and then downgrade afterwards than it is to stay true to the final output.


Jon


  #18   Report Post  
dan lavry
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In general, with audio it is better to sample at high depth and resolution
and then downgrade afterwards than it is to stay true to the final output.

Jon


I followed all the postings, and there are a lot of fine comments out
there. I guess I'll add my 2 bits:

First, going back to some of the earlier dither comments: The concept
of digital dither was covered pretty well - word length reduction. I
would probably magnify the fact that reduction with no dither causes 2
bad things. The first is harmonic distortions, the second is noise
modulation. Think for a second of a tiny sine wave, less than 1
quantization peak to peak, residing between 2 quantization levels. It
yields nothing. That is and incorect result. Now shift it so it
"seats" on a quantization level, going over and under and over and
under... by only one bit. That gives you a 1 bit amolitude square
wave... This is not a good signal either... This is just a starting
point to think about. Again you can see pictures on
www.lavryengineering.com (under suport, "Do you need 20 Bits" artical.

But I was more interested in analog dither. Years ago, I was
experimenting with in. Some of it was around Nyquist frequencies, some
was "subtuctive dither" (remove much in the digital domain what you
injected in the analog domain). Why analog dither? Well, nothing
happens if you feed a signal into a circuit and it does not cvause
some digital transitions... Say your circuit generates a different
code every 1 millivolt, but the signal is small and is always between
5.1 and 5.7mV... No action. So you need to "force it" to go over and
under some threshold (transition) levels. So we add noise. It does get
pretty complicated in a hurry. First knee jerk reaction is to add all
the noise in high frequncey. It is not that simple, because after
truncation, a lot of the high frequncey reapears in the audio range.

But you "have to do somthing"- add some random noise, thus trade off
some noise (dynamic range). For word reduction it is done to fix the
distortions and noise modulation problems. On the analog side, it was
about "getting anything to move" (and more than that). So the question
beacme, was is the best tradeoff? Least energy added for fixing the
problem? That was when triangle dither (2 least significant bits peak
to peak) solution came about.

But than there was a period where analog dither died (at least for
me). The quantization levels got so close to each other, that the
circuit noise was way bigger than I wished for. Take say a 10V range
and try for 20 bits - 10uV steps
(10 microvolts). Getting the signal in there with such low noie (10 uV
peak to peak) is not a walk in the park... You "call" the noise "too
much dither" and move farward...

But than analog dither came back - BIG TIMES! It started with 1 bit
(like DSD) and is now an everyday thing wth the newer multibit ADC's.
Those have just very few bits, thus the quantization levels are very
far apart. No longer in the microvolts, but in the volts (or near it).
This are all noise shaping converters. You feed back a filtered
quantized output and subtuct from the input.. This will take too long
to explain, but such a raw structure will have all sorts of problems
thus it requires dither, and often very large amplitude. The dither
randomness tend to "break up" what would otherwise be consistant
repetative patterns (called limit cycles), not exactly what you want
in the audio...

Regarding the comments on dynamic range and bits. Yes it was well
said, and about 6dB per bit is right. So 24 bits is about 144dB, and
we can all realize it is also a bit of crock. My AD122 MKII has the
largest dynamic range (127dB unweighted) so it is 21+ bits. My first
generation AD122 had 122dB (20 bits) and I called it a 20 bit
converter. Than all those 100-110dB devices apeared on the market with
"24 bits" on the panel and the sales guys insisted that I call mine a
24 bits. The bits are there, but the last few just bounce around
mindlesly - no realtion to the audio.

I have a cheap circuit for andom number generation. If I add 100 bits
of noie at the thend (least significant bits) will it be a 124 bits
machine? Lets go for it

I could probably design a 24 bit AD, and it will be an unbelivable
energy hog. Remember that we are on a log scale. The differance
between 20 and 24 is not "just 4 more". It is a factor of 16 more.
Sort of like a 6 earthquake vs an 8 earthquake. Big differance.

Do you need 24 bits AD? Probably not, short of some of the headroom
comments. What is the best Mic preamp out there? Say -130dBu? How much
gain is it set for? Say I use 30dB gain, than the noise floor is at
-100dBu and a peak to peak siganl out of the preampp is 24Bu driving
an AD. So we have 100+24=124dB
dynamic range. My AD122 MKII gives you 3dB margin. But say you need
40dB mic pre gain. Now you can use the 114dB dynamic range device... I
am not a recording engineer, but I think that 127dB is already only
for close mics that put out serious signal followed by a great mic
pre...

While I rather have folks specify dynamic range (not bits), the 24 bit
number is pretty good in the sense that it is a multiple of 8 bits
(thus 3 bytes). It is a good number for computers and hardware
(multiple of 8). I just wish 24 bits did not get used by industry
salesman as measure of quality.

Last comment for now: Whatever I said regarding 24 bits and what is
needed is ONLY for AD's and DA's. Let me call them CONVERSION BITS.
There are other type of bits. Let me call them PROCESSING BITS. If 24
conversion bits may be an overkill, 24 processing bits is way too
little. Folks need to realize it. A guy comes with some digital EQ and
tells you that it has 56 bits, or 32 floating point DSP, and he does
have a point to make. Just do not later go and look for a 56 bits
AD... Different issue.

I think it was already explained, but here we go: Say I want to
avarage 50 cent (money) and 51 cent. It is 50.5 cents. I can only deal
with cents so we either call it 50 or 51. We have 1/2 cent inacuracy.
In a bianry wold, I lost a bit of acuracy. So lets agree to have a new
coin - 1/2 cent. Now we avarage 50, 50 and 51. It yields 50.3333333...
Well ae can call it 50 or 50.5.... The general statment is that when
you add more and more computations, you reduce more and more of the
accuracy. So yes, we typicaly need a lot of computational bits.

To all, pardon me if soem of the above is a repeat of what you said, I
tried to fill some gaps, and probably covered things that needed no
help. I am new to audio NG.

BR
Dan Lavry
  #20   Report Post  
Mike Rivers
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain


In article writes:

My first
generation AD122 had 122dB (20 bits) and I called it a 20 bit
converter. Than all those 100-110dB devices apeared on the market with
"24 bits" on the panel and the sales guys insisted that I call mine a
24 bits. The bits are there, but the last few just bounce around
mindlesly - no realtion to the audio.


You're doing better than most, if not all. However, the term that we
throw around with reckless abandon is "24-bit" and not "24 bits of
resolution." Nobody said that those lowest order bits had to actually
carry information, they just have to be there so that a 24-bit
receiver will recognize the format.

I suspect that this may have been started by the A/D converter chip
manufacturers who wanted to produce chips with a 24-bit data word.
What goes in isn't their problem, it's the problem of the person
designing the application around the chip.

Do you need 24 bits AD? Probably not, short of some of the headroom
comments. What is the best Mic preamp out there? Say -130dBu? How much
gain is it set for? Say I use 30dB gain, than the noise floor is at
-100dBu and a peak to peak siganl out of the preampp is 24Bu driving
an AD. So we have 100+24=124dB
dynamic range. My AD122 MKII gives you 3dB margin. But say you need
40dB mic pre gain. Now you can use the 114dB dynamic range device...


I've just stirred up a discussion over on the Pro-Audio mailing list
about a related subject. How does someone who thinks that the
difference between a line level and mic level input is the kind of
connector used compare a the gain and noise performance of a preamp
which has only a digital output (integrated A/D converter with no
user-adjustable calibration) with a straight analog preamp and an A/D
converter of unknown input sensitivity for full scale (needless to say
and also unknown noise performance)? You can compare volts out to
volts in and get gain, or volts out for no volts in and get dB of
quiescent noise. But how do you relate volts in to dBFS on your DAW's
meter or headroom indicator? It's a different ball game, but trying ot
explain that you have to think differently about these things requires
more learning than some people (who buy by looking at spec sheets)
want to bother with.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo


  #21   Report Post  
dan lavry
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

(Mike Rivers) wrote in message

You're doing better than most, if not all. However, the term that we
throw around with reckless abandon is "24-bit" and not "24 bits of
resolution." Nobody said that those lowest order bits had to actually
carry information, they just have to be there so that a 24-bit
receiver will recognize the format.


Well, perhapse you are correct for most cases. I will try and explain
my angle. I am not a recording or mastering engineer. I am an
equipment designer and manufacturer, so it does make a differance to
me when someone says: You sell 24 bits, your competition does too.
Both are 24 bits, and you cost more. It is the same thing with that
192Khz crock. I actualy did lose a big sale because I did not want to
join the "king has no cloth" parade and do 192KHz.

I do not know the precentage of folks that would be influenced by such
nonsense. But there are some out there that would buy a 192KHz 24Bits
machine that has over 1 ns jitter, 103dB dynamic range, bad
distortion, 10 msec recovary from clipping (overdrive)... and not take
the time to look at a 96KHz, 20 bits 110dB range low distortions, 20ps
jitter, 2usec recovary... for about the same price. After all, one
machine does 192/24. The other is only 96/20

As far as I know, digital recivers can handel various data length up
to 24 bits just fine. They assume "a bunch of trailing zeros" so a 16
bits with 8 trailing zeros look like a 24 bit. Yes, there is the
coding in the information side (declaring sample rate, bit,
emphasis...) and I do belive it defaults to 24 bits. It is not wise to
assume it. Most companies do not pay too much attention to the
information bits, certainly not on the DA side.

I've just stirred up a discussion over on the Pro-Audio mailing list
about a related subject. How does someone who thinks that the
difference between a line level and mic level input is the kind of
connector used compare a the gain and noise performance of a preamp
which has only a digital output (integrated A/D converter with no
user-adjustable calibration) with a straight analog preamp and an A/D
converter of unknown input sensitivity for full scale (needless to say
and also unknown noise performance)? You can compare volts out to
volts in and get gain, or volts out for no volts in and get dB of
quiescent noise. But how do you relate volts in to dBFS on your DAW's
meter or headroom indicator? It's a different ball game, but trying ot
explain that you have to think differently about these things requires
more learning than some people (who buy by looking at spec sheets)
want to bother with.


Good luck. I understand what you are saying. When you make mic pre,
you must specify analog in and analog out. You make an AD, you must
specify AD... and so on. For an oveall system one needs to incluse the
mic as well. Going for a high end system, one can disable the mic
pickup and still account for the mic noise by replacing the mic with a
noise equivalent physical resistor. One can measure the whole system,
or take the various parts and figure it out. But yes, once passed the
AD, you have to look at the digital outcome. I use FFT's and digital
distortion meters...

I tend to be blessed with customers that know what they are doing,
both in terms of gear and the musical ear and artistic tast. So I
should not complain too much. But often, the big time customers can
plain a simple do what it takes by using the best gear money can buy.
That is one way to go, if you have deep pockets, like the movie
industry. But there are a lot of folks that can not go up against the
stops on everything. At that point, it is wise to look for the
performance bottlenack and improve things one at a time... That is
when that knowladge can come handy...

BR

Dan L
Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Explain me this Schizoid Man Audio Opinions 6 April 11th 04 12:43 AM
TS/TRS balanced/unbalanced can someone explain TheKeith General 6 March 4th 04 07:56 PM
Can you explain this 50Hz hum?? me Pro Audio 18 October 28th 03 09:46 PM
Reverb & EQ and "damping" etc .. please explain .. Daniel Pro Audio 3 October 13th 03 09:09 AM


All times are GMT +1. The time now is 07:12 PM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"