Reply by Geoff Wood April 1, 20042004-04-01
Curious wrote:
> Why is it whenever I record from one wave file - at an extremely low > volume - another wave file, I get noise? > > The process is completely digital. There is no analog, no D-A, and no > A-D. Why the #%!$@%!@# is their noise? > > Since this is not analog-to-digital, this is obviously *not* > quantization noise. Quantization noise only occur during A-D > conversion when the input volume and/or bit-resolution is inadequate.
"Record from one wav file to another " - what ? What's wrong with copy/paste ? geoff PS Dunno how you could be getting your noise, but considering you are attempting something a bit whacky in the first place (maybe), anything's possible.
Reply by Dave Platt March 29, 20042004-03-29
>>> SoundMAX >> >> You understand that this is a low-end on-motherboard consumer sound >> card, right? > >No doubt this is the ADI 1981 Soundmax, currently used for on-board sound on >a large number of motherboards. > >The basic doc for this chip can be found at >http://www.analog.com/UploadedFiles/Data_Sheets/35206112273846AD1981B_b.pdf >. > >Someone can correct me if I've overlooked something, but according to the >"Functional Block Diagram" , the chip has only a digital SP/DIF output, and >no discernable digital inputs. All other inputs and outputs are analog.
Sure looks that way to me. If I'm reading this correctly, the "record what I am playing back" signal path goes through the 20-bit sigma-delta DAC (and, possibly, through the signal-rate-conversion logic) and converted to analog. The analog signal flows through a gain-adjust and muting block, through an analog summing block, and is then fed back up to the record selector, through another gain-control block, and into the 16-bit sigma-delta ADC. I do not see a purely digital "record what I am actually hearing" data flow path. -- Dave Platt <dplatt@radagast.org> AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!
Reply by Arny Krueger March 29, 20042004-03-29
Arny Krueger wrote:
> Curious wrote: >> "Arny Krueger" <arnyk@hotpop.com> wrote in message >> news:<9-GdnRJuQZzBkPXdRVn-uw@comcast.com>... > >>> Name your sound card! > >> SoundMAX > > You understand that this is a low-end on-motherboard consumer sound > card, right?
No doubt this is the ADI 1981 Soundmax, currently used for on-board sound on a large number of motherboards. The basic doc for this chip can be found at http://www.analog.com/UploadedFiles/Data_Sheets/35206112273846AD1981B_b.pdf . Someone can correct me if I've overlooked something, but according to the "Functional Block Diagram" , the chip has only a digital SP/DIF output, and no discernable digital inputs. All other inputs and outputs are analog. According to page 3 the ADC dynamic range is 85 dB A weighted with nonlinear distortion down about 84 dB down, while DAC dynamic range is 85 dB with line output nonlinear distortion 85 dB down. This is really pretty good for a low-end on-board chip, but it is insufficient to guarantee anything like bit-perfect performance. All operations that involve copying computer data through this chip can be expected to be measurably degraded, with the loss of roughly the lowest two bits worth of resolution.
Reply by Arny Krueger March 29, 20042004-03-29
Curious wrote:
> "Arny Krueger" <arnyk@hotpop.com> wrote in message > news:<9-GdnRJuQZzBkPXdRVn-uw@comcast.com>...
>> Name your sound card!
> SoundMAX
You understand that this is a low-end on-motherboard consumer sound card, right?
Reply by Dick Pierce March 29, 20042004-03-29
curious11112001@yahoo.com (Curious) wrote in message news:<34a4f456.0403290055.2ca6aab3@posting.google.com>...
> chris@nospam.com wrote in message news:<iace60hkrbgkdfo2fvcmaqvdbuav91b7c8@4ax.com>... > > Please describe how you are doing this re-recording? > > Play wave file in Realone player and record using Wavelab at approx. > the same time. First click record in Wavelab and then click play on > Realone.
So, in other words, you don't know if it is routed back through the cound card or not.
> > If this is > > windows and you're playing the file and using a recorder, then you are > > actually doing a/d -> d/a. > > It all occurs within the computer itself. No cables needed. The only > thing "analog" is the end product, that is the signal the human ear > can perceive. Before the d-a, the information is purely digital. > > It is poor a-d (not d-a) conversion that results in quantization > noise.
NO IT IS NOT. It is ANY process, digital or analog, that results in requantization. You've been given several examples and explanations where even a pure digital process MUST result in quantization noise, and the means necessary to alleviate the problem.
> An analog signal too soft will have its values improperly > rounded. This will cause quantization noise.
So will ANY process that results in requantization. Do you understand that?
> I think - but don't know - that the noise I'm getting is due to random > amplification of any expected digital signal.
Nope.
> > Also check that you don't have other > > sources enables such as the line-in or mic inputs which will > > contribute. > > I mute all inputs other than the "wave in"
And, thus far, you have not been able to prove that the "wave in" recording is NOT routed by the relevant device drivers to the D/A converter of your sound card and routed right back in through the A/D conversion. No external cables are needed, the switching can be done right on the soundcard itself.
Reply by Jerry Avins March 29, 20042004-03-29
Curious wrote:

   ...

> It is poor a-d (not d-a) conversion that results in quantization > noise. An analog signal too soft will have its values improperly > rounded. This will cause quantization noise.
Not so. Imagine that you record a single sinewave (16 bit words) with peak amplitude $7FFF and $-7FFF. There is some round-off error, but not enough to keep it from sounding pretty good. Now reduce the volume by 6 dB (divide all amplitudes by 2). The maxima will be $3FFF and $-3FFF. Whoa! We started with 16 bits, and now we only have 15! To get back to the original number, we can always just double, right? Wrong! Try it, and you'll see that there are only even numbers in the file. Since you know ahead of time that the LSB is zero, that's still only 15 bits worth of information. Call it quantization error, call it truncation error, call it whatever you like. Once you discard information by lowering the volume, you can't get the information back. ... 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;
Reply by Curious March 29, 20042004-03-29
"Arny Krueger" <arnyk@hotpop.com> wrote in message news:<9-GdnRJuQZzBkPXdRVn-uw@comcast.com>...

> Name your sound card!
SoundMAX
Reply by Arny Krueger March 29, 20042004-03-29
Curious wrote:

> It all occurs within the computer itself.
Sure, because the data is being re-quantized.
> No cables needed. The only thing "analog" is the end product, that is the
signal the human ear
> can perceive. Before the d-a, the information is purely digital.
Not a problem, because the data is being re-quantized.
> It is poor a-d (not d-a) conversion that results in quantization > noise.
As others have pointed out, there are many kinds of processing in the digital domain that cause loss of SNR. Usually the processing is of sufficient quality for noise to not be a problem. However, this is not guaranteed.
> An analog signal too soft will have its values improperly > rounded. This will cause quantization noise.
The same thing can happen with digital domain level changing (even slight!), equalization, compression, a host of things.
> I think - but don't know - that the noise I'm getting is due to random > amplification of any expected digital signal. This is a lot like a PCM > radio receiver "trying its best" to catch and amplify a signal in an > area: > > 1. With extremely poor reception > > AND > > 2. Pervaded with EMI, RFI, magnetic, and other inteferences
Name your sound card!
> The PCM receiver expects a digital signal and not an analog one. Any > surrounding "PCM-like" radio waves at the receiver's frequency will > cause disruption. > >> Also check that you don't have other >> sources enables such as the line-in or mic inputs which will >> contribute.
> I mute all inputs other than the "wave in"
Just guessing, but your sound card is a SoundBlaster, right?
Reply by Arny Krueger March 29, 20042004-03-29
Curious wrote:
> Why is it whenever I record from one wave file - at an extremely low > volume - another wave file, I get noise? > > The process is completely digital. There is no analog, no D-A, and no > A-D. Why the #%!$@%!@# is their noise?
Because the copying is not bit-perfect.
> Since this is not analog-to-digital, this is obviously *not* > quantization noise.
Bad assumption. If your sound card resamples data, which many such as those sold by Creative Labs do, then there is requantization, albeit entirely in the digital domain.
> Quantization noise only occur during A-D conversion when the input volume
and/or bit-resolution is inadequate. Wrong. Quantization noise is a consequence of quantization. Audio can be requantized in the digital domain. It can happen without any A-D conversion, or loss of volume. However you are right about one thing - the noise is audible because the bit resolution is inadequate.
Reply by Don Hills March 29, 20042004-03-29
In article <34a4f456.0403290055.2ca6aab3@posting.google.com>,
curious11112001@yahoo.com (Curious) wrote:
> >It all occurs within the computer itself. No cables needed. The only >thing "analog" is the end product, that is the signal the human ear >can perceive. Before the d-a, the information is purely digital.
Most sound cards with which I am familiar do "wave to wave" using the D/A and A/D convertors. The output of the D/A is also an input to the mixer, which drives the A/D. So your noise is likely to be digital hash picked up by the analog wiring on the sound card.
>I mute all inputs other than the "wave in"
That implies that the mixer has an input fed from the D/A, so it's further evidence that your card is actually doing D/A - A/D. -- Don Hills (dmhills at attglobaldotnet) Wellington, New Zealand "I don't use Linux. I prefer to use an OS supported by a large multi- national vendor, with a good office suite, excellent network/internet software and decent hardware support."