What do I not understand???????????

  • Thread starter Thread starter VTgreen81
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regebro said:
Pulse modulation is a way of making D/A conversion. Essentially, what you do is generate high frequency pulses, loads of them if you want a high value, few of them if you want a low value. Then you slap a filter on it to remove the high frequency contents, and you got yourself an audio signal. :)
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This much I understood, but how do the pulses correct the errors between the actual analog wave and the representation supplied by the LSB (least significant bit)? I know there's averaging involved but where to get the numbers to average?
 
VTgreen81 said:
This much I understood, but how do the pulses correct the errors between the actual analog wave and the representation supplied by the LSB (least significant bit)? I know there's averaging involved but where to get the numbers to average?
Click to expand...

They do? That's news to me.
 
upon further review

Let's see if I'm getting closer:

PWM doesn't change the wave mathmatically but converts the error to white noise by randomizing the error.

So is the purpose of dither noise basically to "fill up the buckets"?
 
I first discovered that the Aardvark Q10 doesn't support 24 bit depth. I'm a bit confused because CPA9 allows me to select both the audio driver depth and the file depth. I don't understand how the file depth can be 24 bit when it's recorded through a 16 bit audio driver...

Anyways, I went on to record bits of a song in both 44.1 kHz and 96 kHz. There was no noticeable difference to me. Now, I understand this difference may be subtle and indetectable either to my amateur ears or through my amateur equipment. But if that's the case, do I really need to be worrying about this?

Peter
 
Re: upon further review

VTgreen81 said:
PWM doesn't change the wave mathmatically but converts the error to white noise by randomizing the error.
Click to expand...

You are talking about something else that I am. I don't have any clue about this.
 
homerecor said:
....What happens if you draw a dot-to-dot picture using only a dozen dots or so? You have a very rough, “barely recognizable” picture. If you add more dots then the picture becomes a little clearer. Add still more dots and it takes on greater detail. Add tens of thousands of dots, or perhaps millions, and it can approach photo quality.

...A similar thing is happening with audio sample rates. A low rate of say 44.1 KHz is barely adequate to be recognizable at the highest frequencies.
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Except this analogy should be avoided as being very misleading.
The alt version is that any and all frequencies within the sample frequency's bandwidth is represented just fine. And any overtones that are not are by definition outside the bandwidth.
i.e.; if you're concerned about capturing frequencies beyond 22 kz, then record at the higher rates.
Something along those lines..:p
Wayne
 
My understanding of dithering is that it reintroduces a little noise, using some randomising algorithm.


I record at 16/44.1. I've tried higher bit depths and all but my software can't handle it. It really is time for an upgrade
 
Dithering does that yes. I've never heard of using pulse modulation to do dithering.
 
Incidentally, I just bought that book. Now I have only to learn how to read.
 
Thanks for the link Tex, looks to be a lot of knowledge in those pages.
 
Now I think I got it!!!

I must of dozed off for a minute (night class) when we changed topics from PCM to dither and thought the two were more closeley related.

dither adds to the signal, filling up the "bucket", correcting to some extent the quantization error,

PCM :
bits move at a constant rate
In the data stream of 1's and 0's, ie, 1110010001111100
basically PCM measures how long voltage is on or off determining how many consecutive 1's or 0's are in the stream. Way oversimplified, of course.
 
Another way to think of digital is that it is a stream of numbers trying to approximate an analog signal. An analog signal is curvy, but digital is squared and boxy.

The greater the number of square pegs, the better they fit in a round hole.

Yup. CD is a compromise between quality and storage. You get 73 minutes because that's about all of Beethoven's 9th.
 
All this data stream jargin is a real buzz kill. I need a re-touch.





Moo. We are cattle

and the new MBA's (young profit minded people in the manufacturing industry) have herded us to piss land.

Or maybe I'm just a vintage snob.
 
VTgreen81 said:
Now I think I got it!!!

I must of dozed off for a minute (night class) when we changed topics from PCM to dither and thought the two were more closeley related.

dither adds to the signal, filling up the "bucket", correcting to some extent the quantization error,

PCM :
bits move at a constant rate
In the data stream of 1's and 0's, ie, 1110010001111100
basically PCM measures how long voltage is on or off determining how many consecutive 1's or 0's are in the stream. Way oversimplified, of course.
Click to expand...

Good, that's what I thought. I was getting worried there. :)
 
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