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In Reply to: OK John posted by Eric LeRouge on April 29, 2003 at 06:44:26:
And yet, the SBM direct process does indeed do a 5x, followed by a 2x oversample to generate enough data points to have a 192K datastream.There is (IMO) no point to 2x oversampling a 96K PCM datastream to get to the 192K datastream.
As far as a final value.... As I understand it, it's merely a summation of 1s (+2v) and 0s(-2v) divided by the number of samples.
nsamples == 147
1 samples == 100
0 samples == 47Aggregate voltage == 200 -94 or 106.
Divide aggregate voltage by number of samples (106 / 147) which is approximately .72 which gets encoded as a signed 22-bit value, then dithered out to 24 bits.
I know how the basics of the process works, I just don't think it's a sound idea above 48kHz fs. I can't prove it either ;-)
Regards,
Follow Ups:
JohnYour knowledge of DSD is far greater than mine.
The increased I/O processing added for that extra x2 step is enormous. There must be a good reason why there is an oversampling of x5 and x2 instead of x2 on the final 96k result, probably to prevent interpolation as much as possible.
The more I think about it, the more I find it intriguing.. 192k is the only rate where things do not translate smoothly with that method.As for the rest, I hope someone can challenge your post better than me. I'm out of my league at this point. : )
(Damn, where's Frank?)
Best
You don't get more information from dsd by oversampling it five times.
The oversampling is done to make things easier on the math applied.
Nope, I'm talking about having sufficient data to make the reduction meaningful.
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