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



 
 
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  #11  
Old November 16th 03, 10:15 AM
Jay - atldigi
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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
Ads
  #12  
Old November 16th 03, 11:39 AM
Arny Krueger
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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  
Old November 16th 03, 12:52 PM
Mike Rivers
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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
  #14  
Old November 16th 03, 01:35 PM
Tommi
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain


"Arny Krueger" > wrote in message
...
> "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.



So, if you're recording, say, someone's vocals at both 16 and 24 bits, and
the peaks are at -6dB to 0dB FS, does the 24 bit recording represent more
accurately the signal in that region than the 16-bit version?


  #15  
Old November 16th 03, 02:24 PM
Arny Krueger
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Tommi" > wrote in message

> "Arny Krueger" > wrote in message
> ...
>> "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.


> So, if you're recording, say, someone's vocals at both 16 and 24
> bits, and the peaks are at -6dB to 0dB FS, does the 24 bit recording
> represent more accurately the signal in that region than the 16-bit
> version?


The 24 bit recording has the capability to represent the signal much more
accurately in *any* range from zero to max, than the 16 bit recording.


  #16  
Old November 16th 03, 03:13 PM
Mike Rivers
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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
  #17  
Old November 16th 03, 04:20 PM
Carey Carlan
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Tommi" > wrote in
:

> So, if you're recording, say, someone's vocals at both 16 and 24 bits,
> and the peaks are at -6dB to 0dB FS, does the 24 bit recording
> represent more accurately the signal in that region than the 16-bit
> version?


The extra 8 bits give you 48 db more dynamic range between EVERY sample.
Between sample value = 0 and sample value = 1 they give you an extra 48 db
on the bottom end.

On the loud end, 16 bit max value is 32767 (0x7FFF), second value is 32766
(0x7FFE). That equates to 24 bit values 8388352 (0x7FFF00) and 8388096
(0x7FFE00), a difference of 256 values, the equivalent of 48 dB dynamic
range.
  #18  
Old November 16th 03, 05:16 PM
White Swan
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

Arny and I obviously agree about the resolution issue. I believe Arny
is cvorrect, but I make no claim to infallibility, so I'm very
interested in the opposing points of view as well.

Having no tech expertise, I'm going more on intuitve logic. Let's use
reductio ad absurdum (or whatever it's called!). Let's take a 1 bit
system. Now we have only two volume values: full volume, and full
silence. using the 6dB per bit formula, we have values of 0dB and 6
dB. (I'm not using full scale dB, obviously, for this purpose). Now
let's assume a 2 bit system. Now we have inserted two intermediate
steps between the on and off. And we've also increased the dynamic
range by 6 dB. This would give us values of 0db, 4 dB, 8 dB, and 12
dB. (For the sake of argument, let's assume a linear system in terms
of dB values. For all I know, it might not be.)

So what has happened? Yes, we have increased out dynamic range by 6 dB
between the loudest and softest signals the system can represent. But
we have increased the resolution throughout the system: from a 6dB
increment to a 4 dB increment.

Continuing to a 3 bit system: dynamic range is 18 dB. Values are 0dB,
2.25 dB, 4.5 dB, etc. to 18 dB. Wth each additional bit the dynamic
range is increasing, but ALSO the resolution is increasing everywhere
in the system.

Now, my logic may well be flawed, so I'm most interested in finding
out where the flaw is. This is a great way to learn, and i thank
everyone who is teaching me!
  #20  
Old November 16th 03, 07:13 PM
Arny Krueger
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Arny Krueger" > wrote in message

> "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.


Correction: 24 bits puts 256 (!!) additional levels between every pair of
levels that exist with 16 bits.


 




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