# Reverse of SACD?

Started by June 24, 2004
```SACD uses 1-bit with a super-high sampling rate.

Could something similar be done using 1 Hz sampling with a super-wide
bit resolution?
```
```Curious wrote:

> SACD uses 1-bit with a super-high sampling rate.
>
> Could something similar be done using 1 Hz sampling with a super-wide
> bit resolution?

You can encode the entire contents of the Library of Congress on a stick
less than two inches long. Simply encode it all as 32-bit unicode,
concatenate all the codes. and place a binary point after the first bit.
That represents a number that is at most 1.111... with a zero certainly
somewhere. Cut a stick to that length, and there you have it, to carry
around, decode whenever you like, and have a wealth of information in

What's wrong with that scenario? The short answer is that like all other
schemes based on super-wide binary numbers, the theoretical resolution
exceeds what can be implemented in practice.

Jerry
--
Engineering is the art of making what you want from things you can get.
&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;

```
```On Fri, 25 Jun 2004 00:02:27 -0400, Jerry Avins <jya@ieee.org> wrote:

>Curious wrote:
>
>> SACD uses 1-bit with a super-high sampling rate.
>>
>> Could something similar be done using 1 Hz sampling with a super-wide
>> bit resolution?

The 1Hz sample rate causes problems with audio frequencies above 1/2
Hz.

Allan.
```
```
Curious wrote:

> SACD uses 1-bit with a super-high sampling rate.
>
> Could something similar be done using 1 Hz sampling with a super-wide
> bit resolution?

Yes, if you had a large enough table to contain all 1 second
sequences that meet a given SNR and bandwidth requirement
you could index into it and select the proper one with that
code you give it every second.  That's kinda big though, as
tables go, and your bit resolution would need to be log(2)
of the number of entries in it.

Bob
--

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

A. Einstein
```
```"Curious" <curious11112001@yahoo.com> wrote:
> SACD uses 1-bit with a super-high sampling rate.
>
> Could something similar be done using 1 Hz sampling with a super-wide
> bit resolution?

I think you'll also find that SACD is a little more complex than just
converting a signal into a single bit digital signal.  I imagine (without
much knowledge of it) that it uses a comparator and a sawtooth/triangular
wavefor to generate a PWM signal suited to the input waveform.
The PWM signal must be at least twice the input waveforms frequency (nyquist
theorem) and must actually be much greater to achieve some additional
processing gain from increased sample rate (engineering common sense).  This
"additional processing gain" allows the PWM output to be recognisably

You could implement a system with a very high bit resolution but very low
sampling rate, however all that allows you to do is very precisely represent
a very slowly changing signal.

Bevan

```
```Bevan Weiss wrote:

> "Curious" <curious11112001@yahoo.com> wrote:
>
>>SACD uses 1-bit with a super-high sampling rate.
>>
>>Could something similar be done using 1 Hz sampling with a super-wide
>>bit resolution?
>
>
> I think you'll also find that SACD is a little more complex than just
> converting a signal into a single bit digital signal.  I imagine (without
> much knowledge of it) that it uses a comparator and a sawtooth/triangular
> wavefor to generate a PWM signal suited to the input waveform.
> The PWM signal must be at least twice the input waveforms frequency (nyquist
> theorem) and must actually be much greater to achieve some additional
> processing gain from increased sample rate (engineering common sense).  This
> "additional processing gain" allows the PWM output to be recognisably
>
> You could implement a system with a very high bit resolution but very low
> sampling rate, however all that allows you to do is very precisely represent
> a very slowly changing signal.
>
>
> Bevan

At one time or another, we lose sight of Curious's obsession with
coding, as opposed to representing, signals. Suppose there were a huge
data base of digitized music available. Every performance of every piece
of music ever recorded and now in digital form. Suppose further that
each has a unique number. To play music, one does not need a number per
second, but a number per piece. Such a scheme doesn't violate the
Nyquist limit, bit it does give new meaning to the phrase, "Play that
number again."

Backing away from such a scheme, consider how a vocoder generates
speech. In fact, Curious should consider how a vocoder generates speech.
Then he might understand the true meanings of his questions.

A little learning is a dangerous thing; drink deep, or taste not the
Pierian spring: there shallow draughts intoxicate the brain, and
drinking largely sobers us again.  ..  Alexander Pope

Curious: Sober up!

Jerry
--
Engineering is the art of making what you want from things you can get.
&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;

```
```"Bevan Weiss" <kaizen__@NOSPAMhotmail.com> wrote in message news:<iUWCc.3931\$LT3.154181@news.xtra.co.nz>...
> "Curious" <curious11112001@yahoo.com> wrote:
> > SACD uses 1-bit with a super-high sampling rate.
> >
> > Could something similar be done using 1 Hz sampling with a super-wide
> > bit resolution?
>
> I think you'll also find that SACD is a little more complex than just
> converting a signal into a single bit digital signal.  I imagine (without
> much knowledge of it) that it uses a comparator and a sawtooth/triangular
> wavefor to generate a PWM signal suited to the input waveform.
> The PWM signal must be at least twice the input waveforms frequency (nyquist
> theorem) and must actually be much greater to achieve some additional
> processing gain from increased sample rate (engineering common sense).  This
> "additional processing gain" allows the PWM output to be recognisably
> You could implement a system with a very high bit resolution but very low
> sampling rate, however all that allows you to do is very precisely represent
> a very slowly changing signal.
>
>
> Bevan

Pulse Width Modulation is used for SACD because there is only 1-bit of
represenatation of the amplitude. Could the "reverse" use Pulse Height
Modulation to acheive similar results?
```
```Curious wrote:
>>"Curious" <curious11112001@yahoo.com> wrote:
>>
>>>SACD uses 1-bit with a super-high sampling rate.
>>>
>>>Could something similar be done using 1 Hz sampling with a super-wide
>>>bit resolution?
>
> Pulse Width Modulation is used for SACD because there is only 1-bit of
> represenatation of the amplitude. Could the "reverse" use Pulse Height
> Modulation to acheive similar results?

SACD doesn't use pulse-width modulation.  It uses noise-shaped
sigma-delta modulation.  Totally different, more subtle animal.

referred to as "sampling", the precursor to PCM quantization.  As
Allan has pointed out, 1Hz sampling limits you to only being able
to reproduce frequencies lower than 0.5Hz.  Good for geological
surveys, perhaps, but not audio.

On the other hand, if you meant a 1Hz encoded symbol rate,
independent of the signal sampling rate, then yes, you can do
that, but all that you would gain is inconvenience and memory
consumption.  It's meaningless.  Think of an audio CD as a
(1/3600)Hz (or so) data-rate representation of a stereo album.

--
Andrew
```
```Curious wrote:

> "Bevan Weiss" <kaizen__@NOSPAMhotmail.com> wrote in message news:<iUWCc.3931\$LT3.154181@news.xtra.co.nz>...
>
>>"Curious" <curious11112001@yahoo.com> wrote:
>>
>>>SACD uses 1-bit with a super-high sampling rate.
>>>
>>>Could something similar be done using 1 Hz sampling with a super-wide
>>>bit resolution?
>>
>>I think you'll also find that SACD is a little more complex than just
>>converting a signal into a single bit digital signal.  I imagine (without
>>much knowledge of it) that it uses a comparator and a sawtooth/triangular
>>wavefor to generate a PWM signal suited to the input waveform.
>>The PWM signal must be at least twice the input waveforms frequency (nyquist
>>theorem) and must actually be much greater to achieve some additional
>>processing gain from increased sample rate (engineering common sense).  This
>>"additional processing gain" allows the PWM output to be recognisably
>>You could implement a system with a very high bit resolution but very low
>>sampling rate, however all that allows you to do is very precisely represent
>>a very slowly changing signal.
>>
>>
>>Bevan
>
>
> Pulse Width Modulation is used for SACD because there is only 1-bit of
> represenatation of the amplitude. Could the "reverse" use Pulse Height
> Modulation to acheive similar results?

Sure. That's analog, but harder to implement than other analog
strategies.

Jerry
--
Engineering is the art of making what you want from things you can get.
&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;

```