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post #1 of 21 Old 01-28-2013, 07:14 PM - Thread Starter
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I want to ask why is 24-bit considered to be better than 16-bit? CD's are now just starting to record at 24-bit but why? 16-bit gives a dynamic range of 96dB 24-bit gives you a dynamic range of 144dB but no engineer even would make something this dynamic hell no CD even used that wide of a dynamic range. Let me give you an example of how I record a song; I have the quietest noise recorded at -40dB and my loudest sound recorded at -1dB that's a dynamic range of 59dB. As you can see a dynamic range of 96dB is rare. So discuss why 24-bit is necessary.

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post #2 of 21 Old 01-28-2013, 07:31 PM
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CD's are now just starting to record at 24-bit but why?
Uh, no. CDs are 16 bit. Period. There are some recordings out there that are available in 24 bit. But they aren't on CDs.
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So discuss why 24-bit is necessary.
It isn't, in part for the reasons you give. But there's this whole audiophile mythology that grew up around the idea that there's something wrong with CDs. So anything that comes along that claims to be better automatically has credibility among the myth-believers.

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post #3 of 21 Old 01-28-2013, 07:52 PM
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Hi Kevin,
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Originally Posted by kbeam418 View Post

. . . So discuss why 24-bit is necessary.
As you and Mcnaris stated, 24-bit isn't necessary for the finished product, but might be necessary for mixing. If you have something recorded at 16-bits, and then turn it down 12db for the mix, then you had better have a few bits under those top 16 to catch the two bits you would otherwise loose. 16-bits in and 16-bits out is adequate, but more may be needed for the processing in between, to handle math overflow and underflow. That's why audio DSPs have at least 24-bits.
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post #4 of 21 Old 01-28-2013, 08:05 PM
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Originally Posted by kbeam418 View Post

I want to ask why is 24-bit considered to be better than 16-bit? CD's are now just starting to record at 24-bit but why? 16-bit gives a dynamic range of 96dB 24-bit gives you a dynamic range of 144dB but no engineer even would make something this dynamic hell no CD even used that wide of a dynamic range. Let me give you an example of how I record a song; I have the quietest noise recorded at -40dB and my loudest sound recorded at -1dB that's a dynamic range of 59dB. As you can see a dynamic range of 96dB is rare. So discuss why 24-bit is necessary.
You are measuring it wrong smile.gif. You have to use psychoacoustically correct measurements or you get the wrong dynamic range. I explain it all in my article on dynamic range here: http://www.madronadigital.com/Library/RoomDynamicRange.html

Net summary, 120 db is the channel we need for transparency for all content and all rooms.

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post #5 of 21 Old 01-28-2013, 08:16 PM - Thread Starter
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Originally Posted by MarkHotchkiss View Post

Hi Kevin,
As you and Mcnaris stated, 24-bit isn't necessary for the finished product, but might be necessary for mixing. If you have something recorded at 16-bits, and then turn it down 12db for the mix, then you had better have a few bits under those top 16 to catch the two bits you would otherwise loose. 16-bits in and 16-bits out is adequate, but more may be needed for the processing in between, to handle math overflow and underflow. That's why audio DSPs have at least 24-bits.
It defiantly is necessary for recording to have a minimum of 24 bits I actually use 32-bit floating for my mixes in pro tools.

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post #6 of 21 Old 01-28-2013, 08:18 PM - Thread Starter
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Originally Posted by mcnarus View Post

Uh, no. CDs are 16 bit. Period. There are some recordings out there that are available in 24 bit. But they aren't on CDs.
It isn't, in part for the reasons you give. But there's this whole audiophile mythology that grew up around the idea that there's something wrong with CDs. So anything that comes along that claims to be better automatically has credibility among the myth-believers.
So CD isn't 24-bit? There is something wrong with CD it's digital biggrin.gif I'm referring more to those people who say 24-bit is better.

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post #7 of 21 Old 01-28-2013, 08:33 PM - Thread Starter
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Originally Posted by amirm View Post

You are measuring it wrong smile.gif. You have to use psychoacoustically correct measurements or you get the wrong dynamic range. I explain it all in my article on dynamic range here: http://www.madronadigital.com/Library/RoomDynamicRange.html

Net summary, 120 db is the channel we need for transparency for all content and all rooms.
Good article.

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post #8 of 21 Old 01-29-2013, 04:44 AM
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Originally Posted by kbeam418 View Post

So CD isn't 24-bit? There is something wrong with CD it's digital biggrin.gif I'm referring more to those people who say 24-bit is better.
The CD (Redbook) standard was set in 1980 at 16bit (44.1 sampling rate) and can't be changed. it is a standard.

Also each bit is = to 6dB of dynamic range. So 16bit x 6 gives you 96dB of dynamic range which is more than any environment you will experience (unless you have access to an anechoic chamber). 24bit x 6 is 144dB. There are other factors that can come into play like quantization errors.
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post #9 of 21 Old 01-29-2013, 05:59 AM
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Originally Posted by kbeam418 View Post

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Originally Posted by amirm View Post

You are measuring it wrong smile.gif. You have to use psychoacoustically correct measurements or you get the wrong dynamic range. I explain it all in my article on dynamic range here: http://www.madronadigital.com/Library/RoomDynamicRange.html

Net summary, 120 db is the channel we need for transparency for all content and all rooms.

Good article.

Actually, an overly enthusiastic article that defies common sense, was amended by later science, and failed to produce salable products when people tried to implement its ideas. It represents an unreachable goal.

First off, a 120 dB dynamic range is unsafe for humans if ever implemented. In an ideal world, the threshold of hearing is around 0 dB SPL, while any amount of listening at 120 dB will either permanently damage or temporarily deafen your ears. In the real world, rooms with acoustic noise levels of 25 dB SPL are difficult or impossible to implement in ordinary residential circumstances, Most rooms in a house come closer to 35 to 45 dB SPL range. But lets momentarily accept 25 dB SPL. 120 dB dynamic range implies that the louder passages play at 145 dB SPL. SPLs on this order are harmful or fatal when unprotected humans are exposed to them without ear protection and protective clothing.

Secondly, there is a widely-recognized international standard for audio evaluation known as ITU recommendation BS 1116-1 which represents later science and art than those few earlier papers favor. It basically mandates 100 dB dynamic range which is of course far less demanding and more realistic than 120 dB.

Thirdly we had three formats for recorded music that were designed to meet or approach the 120 dB standard being HDCD, DVD-A and SACD. All three were invested in heavily by large audio firms, large number of players embodying their technology were sold, many no doubt at a loss to their manufacturers. Large numbers of recorded releases with their logos on them were put into the marketplace. None were successful in the mainstream, and all three are in various stages of disappearing.

Finally, there just aren't any commercial musical recordings that actually have 120 dB dynamic range. Their media may support it but quite a bit gets lost when people actually try to record music. The widest dynamic range musical recording I've been able to find in about 20 years of searching has less than 90 dB dynamic range. If you set up some microphones in a typical concert hall in accordance with the best accepted standards, bring in about 100 musicians and record something they play, you end up with a recording with something like 65-70 dB dynamic range.
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post #10 of 21 Old 01-29-2013, 06:08 AM
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Originally Posted by kbeam418 View Post

I want to ask why is 24-bit considered to be better than 16-bit?

Depends what you mean by better. In theory 24 bits supports wider dynamic range than 16 bits. In theory a NASCAR Sprint Cup car is better than my daily driver because it will go at least 60% faster. What do I want to drive on a road trip or a run to the store?
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CD's are now just starting to record at 24-bit but why?

Not so. CDs themselves can never be more than 16 bit data. There is a very well-known and widely implemented standard that says so. Its called the "The Red Book"

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16-bit gives a dynamic range of 96dB 24-bit gives you a dynamic range of 144dB but no engineer even would make something this dynamic

Actually, no equipment that implements a full 24 bits is on the commercial market today. The best DACs and getting close. And if you try to make a regular recording with 24 bit dynamic range, it is as I show in another post I just added to this thread, mission impossible.
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hell no CD even used that wide of a dynamic range. Let me give you an example of how I record a song; I have the quietest noise recorded at -40dB and my loudest sound recorded at -1dB that's a dynamic range of 59dB. As you can see a dynamic range of 96dB is rare. So discuss why 24-bit is necessary.

You have pointed out some facts that are hard to refute with any great margin. Many people have done experiments where they were able to reduce the resolution of so-called high resolution recordings down to 16 bits to see if there was any audible loss. No audible losses were found.

I routinely make live recordings of choirs and bands. I've made thousands in dozens of venues in the past 12 years. I am able to make recordings with 65-70 dB dynamic range in certain but not all auditoriums. HVAC noise is the usual limit to what I get.
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post #11 of 21 Old 01-29-2013, 01:30 PM
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Originally Posted by MarkHotchkiss View Post

If you have something recorded at 16-bits, and then turn it down 12db for the mix, then you had better have a few bits under those top 16 to catch the two bits you would otherwise loose.

Just to clarify, modern audio software doesn't work that way. 16-bit files (or any files) are loaded into RAM, then converted to 32-bit floating point for all subsequent manipulation. You can have a 16-bit file, reduce the volume by 100 dB, apply EQ or whatever, then raise it back up by 100 dB and it will still sound fine. The quote below is from my Audio Expert book.

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Bit Depth

Although 16 bits offers a sufficiently low noise level for almost any audio recording task, many people use 24 bits because, again, they believe the additional bits offer superior fidelity. Some programs can even record audio data as 32-bit floating point numbers. But the number of bits used for digital audio doesn't affect fidelity other than establishing the noise floor. The frequency response is not improved, nor is distortion reduced. Claims that recording at 24 bits is cleaner or yields more resolution than 16 bits are simply wrong, other than a potentially lower noise floor. I say potentially lower because the background acoustic noise of a microphone in a room is usually 30 to 40 dB louder than the inherent noise floor of 16-bit audio.

To my way of thinking, the main reason to use 24 bits is because it lets you be less careful when setting record levels. The only time I record at 24 bits is for orchestra concerts or other live events. When recording outside of a controlled studio environment, it's better to leave plenty of headroom now rather than be sorry later. In those situations, it's good practice to set your record levels so the peaks never exceed -20 dBFS. Then if something louder comes along, it will be captured cleanly.

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post #12 of 21 Old 01-29-2013, 01:57 PM - Thread Starter
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Actually, an overly enthusiastic article that defies common sense, was amended by later science, and failed to produce salable products when people tried to implement its ideas. It represents an unreachable goal.

First off, a 120 dB dynamic range is unsafe for humans if ever implemented. In an ideal world, the threshold of hearing is around 0 dB SPL, while any amount of listening at 120 dB will either permanently damage or temporarily deafen your ears. In the real world, rooms with acoustic noise levels of 25 dB SPL are difficult or impossible to implement in ordinary residential circumstances, Most rooms in a house come closer to 35 to 45 dB SPL range. But lets momentarily accept 25 dB SPL. 120 dB dynamic range implies that the louder passages play at 145 dB SPL. SPLs on this order are harmful or fatal when unprotected humans are exposed to them without ear protection and protective clothing.

Secondly, there is a widely-recognized international standard for audio evaluation known as ITU recommendation BS 1116-1 which represents later science and art than those few earlier papers favor. It basically mandates 100 dB dynamic range which is of course far less demanding and more realistic than 120 dB.

Thirdly we had three formats for recorded music that were designed to meet or approach the 120 dB standard being HDCD, DVD-A and SACD. All three were invested in heavily by large audio firms, large number of players embodying their technology were sold, many no doubt at a loss to their manufacturers. Large numbers of recorded releases with their logos on them were put into the marketplace. None were successful in the mainstream, and all three are in various stages of disappearing.

Finally, there just aren't any commercial musical recordings that actually have 120 dB dynamic range. Their media may support it but quite a bit gets lost when people actually try to record music. The widest dynamic range musical recording I've been able to find in about 20 years of searching has less than 90 dB dynamic range. If you set up some microphones in a typical concert hall in accordance with the best accepted standards, bring in about 100 musicians and record something they play, you end up with a recording with something like 65-70 dB dynamic range.
I totally agree with you. The most dynamic range I have recorded at was 60dB.

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post #13 of 21 Old 01-29-2013, 02:48 PM
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Originally Posted by MarkHotchkiss View Post

Hi Kevin,
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Originally Posted by kbeam418 View Post

. . . So discuss why 24-bit is necessary.
If you have something recorded at 16-bits, and then turn it down 12db for the mix, then you had better have a few bits under those top 16 to catch the two bits you would otherwise loose.

It may seem that way, but when you include reality, things are far better than that for 16 bit mixing.

If you have a typical good live recording, as both myself and other recordists have pointed out, the environmental noise floor is say, 66 dB down, or about 5 bits above the 16 bit noise floor.

When you turn it down by 12 dB or 4 bits, the environmental noise floor is still about one (1) bit above the 16 bit digital noise floor.

Furthermore, due to the favorable effects of dither any low level sounds that are below the environmental noise floor are not cut off by the close proximity to the digital noise floor, because sounds that are well below the digital noise floor can be recorded and played back and remain audible.
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post #14 of 21 Old 01-29-2013, 03:09 PM
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I totally agree with you. The most dynamic range I have recorded at was 60dB.
That would be the wrong measurement too smile.gif. As with the noise floor of the room, you need to look at the spectrum of the recorded content's noise floor, and then apply the math to covert the noise to equiv tone value. Once there, you can then compute what the dynamic range is for the frequencies where the ear is most sensitive. Your SPL meter or whatever you used doesn't do any of this analysis and hence produces vastly incorrect values. This is why we call them "dumb meters." smile.gif

While typing this, let me remark on the ITU BS.1116 comment. The ITU recommendations is for setting a set of standards for testing audio impairments. It is not a document that sets out the standard for reproduction fidelity. Here is what it says about dynamic range anyway:

"7.2.2.6 Dynamic range
The maximum operating sound level which the loudspeaker can produce for a time period of at least 10 min without thermal or mechanical damage and without overload circuits being activated, measured with a programme simulating noise signal (according to International Electrotechnical Commission (IEC) Publication 268-1c), should be:

L eff max > 108 dB"


So not sure where the 100 db reference came from and at any rate, 100 is > CD anyway.

As for going deaf, that is a function of both level and duration. And at any rate, if I am worried about going deaf, I can turn the volume down. I don't need someone to dumb down the dynamic range on my behalf smile.gif.

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post #15 of 21 Old 01-29-2013, 03:36 PM
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Hi Ethan,
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Originally Posted by Ethan Winer View Post

Just to clarify, modern audio software doesn't work that way.
Yes, you are right. However, just to clarify, I was not thinking about computer software, but DSP firmware.

Floating-point in DSPs are relatively new, starting with the recent chips from ADI. We DSP programmers have been stuck using fixed-point for the past 20 years, so when I say ". . . If you have something recorded at 16-bits, and then turn it down 12db for the mix, then you had better have a few bits under those top 16 to catch the two bits you would otherwise loose", that is exactly how my firmware is written.
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post #16 of 21 Old 01-29-2013, 03:41 PM
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Hi Arny,
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Originally Posted by arnyk View Post

It may seem that way, but when you include reality . . .

If you have a typical good live recording, as both myself and other recordists have pointed out, the environmental noise floor is say, 66 dB down, or about 5 bits above the 16 bit noise floor.

When you turn it down by 12 dB or 4 bits, the environmental noise floor is still about one (1) bit above the 16 bit digital noise floor.
Yes, I grant you that.

My problem is that I don't live in reality. smile.gif I live in the surreal world of DSP firmware, where nothing is considered noise.
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post #17 of 21 Old 01-29-2013, 06:32 PM - Thread Starter
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Originally Posted by Ethan Winer View Post

Just to clarify, modern audio software doesn't work that way. 16-bit files (or any files) are loaded into RAM, then converted to 32-bit floating point for all subsequent manipulation. You can have a 16-bit file, reduce the volume by 100 dB, apply EQ or whatever, then raise it back up by 100 dB and it will still sound fine. The quote below is from my Audio Expert book.

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post #18 of 21 Old 01-29-2013, 06:48 PM - Thread Starter
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Originally Posted by amirm View Post

That would be the wrong measurement too smile.gif. As with the noise floor of the room, you need to look at the spectrum of the recorded content's noise floor, and then apply the math to covert the noise to equiv tone value. Once there, you can then compute what the dynamic range is for the frequencies where the ear is most sensitive. Your SPL meter or whatever you used doesn't do any of this analysis and hence produces vastly incorrect values. This is why we call them "dumb meters." smile.gif

While typing this, let me remark on the ITU BS.1116 comment. The ITU recommendations is for setting a set of standards for testing audio impairments. It is not a document that sets out the standard for reproduction fidelity. Here is what it says about dynamic range anyway:

"7.2.2.6 Dynamic range
The maximum operating sound level which the loudspeaker can produce for a time period of at least 10 min without thermal or mechanical damage and without overload circuits being activated, measured with a programme simulating noise signal (according to International Electrotechnical Commission (IEC) Publication 268-1c), should be:

L eff max > 108 dB"


So not sure where the 100 db reference came from and at any rate, 100 is > CD anyway.

As for going deaf, that is a function of both level and duration. And at any rate, if I am worried about going deaf, I can turn the volume down. I don't need someone to dumb down the dynamic range on my behalf smile.gif.
I base my dynamic range on whatever is the lowest sound whather than noise floor, the noise floor in pro tools is very low (probably in the -90dB range) which nobody records at in fact I cut anything below -70. If your going to base dynamic range on noise than there are going to be completely different levels some people have cheap stereos which have a horrible noise floor, while some are listening to a system that cost 20,00$ I don't think that is true dynamic range. I very rarely use compression when I record a mix, dynamic range is the amount of decibels between the quietest sound in a track and the loudest decibel in a track.

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post #19 of 21 Old 01-30-2013, 05:32 AM
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Originally Posted by amirm View Post

Quote:
Originally Posted by kbeam418 View Post

I totally agree with you. The most dynamic range I have recorded at was 60dB.
That would be the wrong measurement too smile.gif.

Is this an unfounded assertion, merely overstated or what?
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As with the noise floor of the room, you need to look at the spectrum of the recorded content's noise floor, and then apply the math to covert the noise to equiv tone value. Once there, you can then compute what the dynamic range is for the frequencies where the ear is most sensitive. Your SPL meter or whatever you used doesn't do any of this analysis and hence produces vastly incorrect values. This is why we call them "dumb meters." smile.gif

To make this claim credible, we'd need a worked out solution. Without real world application, the above claims are just hypothetical mathematical hand waving.
Quote:
While typing this, let me remark on the ITU BS.1116 comment. The ITU recommendations is for setting a set of standards for testing audio impairments. It is not a document that sets out the standard for reproduction fidelity.

So we are to believe that reproduction quality has nothing to do with audio impairments?

This has to be one of the more incredible and unbelievable claims I've heard yet from this source!

If we perchance use our brains, simple logic tells us that reproduction fidelity and audio impairments are the two sides of the same sound quality coin. If there are few impairments then reproduction fidelity is high and if there are many impairments then reproduction fidelity is low. Please don't be distracted by such obvious and illogical double talk!

Executive summary: more unsupported claims and double talk with no apparent goal or benefit.
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post #20 of 21 Old 01-30-2013, 05:37 AM
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Originally Posted by MarkHotchkiss View Post

Hi Arny,
Quote:
Originally Posted by arnyk View Post

It may seem that way, but when you include reality . . .

If you have a typical good live recording, as both myself and other recordists have pointed out, the environmental noise floor is say, 66 dB down, or about 5 bits above the 16 bit noise floor.

When you turn it down by 12 dB or 4 bits, the environmental noise floor is still about one (1) bit above the 16 bit digital noise floor.
Yes, I grant you that.

My problem is that I don't live in reality. smile.gif I live in the surreal world of DSP firmware, where nothing is considered noise.

In the mathematical world of DSPs added precision comes as easily as adding some more silicon or stuffing more gates onto the same silicon.

When I are recording, performance limits are set by influences such as building design and construction that are actually cast in cement and completely out of my control.

I get all that! ;-)
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post #21 of 21 Old 01-30-2013, 12:25 PM
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We DSP programmers have been stuck using fixed-point for the past 20 years

Ah, okay, gotcha.

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