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Old 20th February 2013, 06:12 AM   #311
gk7 is offline gk7
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Quote:
Originally Posted by Robert F View Post
... individual timing of the bits within the cache ...
... timing of the cache itself ...
No, both things I have quoted do not exist. The "timing" occurs when sending
the bits out (via USB, SPDIF etc.) at a known and constant rate, there is no "individual" timing of samples stored within the file (no matter if itīs read from
harddisk, RAM or whatever).

Last edited by gk7; 20th February 2013 at 06:13 AM. Reason: corrected typos
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Old 20th February 2013, 06:28 AM   #312
sofaspud is offline sofaspud  United States
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Just FYI (or in case I'm wrong)..."cache" is just a smaller faster block of RAM. The "packets" would be bytes, nibbles, and words.
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Old 20th February 2013, 06:39 AM   #313
hochopeper is offline hochopeper  Australia
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He states something along the lines of masterclock ticking for a byte instead of for a bit, which afaik, is not the case.
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Old 20th February 2013, 06:58 AM   #314
qusp is offline qusp  Australia
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thats correct cache is a small piece of memory, it speaks of the action of accumulating information for 'later' in the short term.

Master clock is usually ticking 8->64 per bitclock cycle and 128-2048x FS (sample rate/word clock cycle)

but MCK is not part of the i2s standard, MCK is assumed to be on the convertor side, either on the USB->i2s convertor, or the local DAC clock, or its both the convertor and dac clock, with without some sort of division with logic parts. again this is running synchronously using its own clock at the receiving end, nothing to do with the incoming clock.

Last edited by qusp; 20th February 2013 at 07:19 AM.
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Old 20th February 2013, 07:25 AM   #315
qusp is offline qusp  Australia
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thus there may not even be audio clock timing for i2s in USB, there will be a separate USB data clock (usually 12MHz or something), but master clock (MCK) is not part of the i2s standard, it assumes a local clock and that is normally where the sample timing is imposed.

some dacs may have a PLL or reclocker, but the master clock does not need to be there to drive timing. sometimes SPDIF will recover an embedded clock, AES can have a separate Wordclock. thats very rare these days and easily avoided.

in all of that though, a buffer is simply where the data builds up in memory and spat out again in a burst, but again the clock on the USB bus is not imposing any timing on the DAC local master clock. the sample rate can be identified by the Wordclock (LRCK) or the bitclock and bitclock is preferred to sync to if any. but there is no room for a super-secret clock. mostly the USB receiver chip will have its own fifo buffer as well.

these are not places for evil to build up, quite the opposite....
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Old 20th February 2013, 08:21 AM   #316
gk7 is offline gk7
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I just read the article linked, besides highlights like "Impulse Discharge of Events in Atemporal Space"
itīs a lot of marketing BS made to sound "technical" and "knowledgeable".

The main claim made is the dicovery of a previously unknown (?) type of jitter:
"...the second type is jitter which we can predict, but have not been able to directly measure, called "packet jitter"."

The he continues to mix that up with the term "packet jitter" sometimes used in
in conjunction QoS (which is completely unrelated here).

Finally one can notice where the journey goes to:
"We are planning to offer "IDEAS for Audio", an internet-based service which will be available by subscription. One will be able to log on and reduce the jitter of his music library dramatically. Owners of music servers or even computer audio collections, may log on and run IDEAS on their music collection, with often astounding drops in jitter."

Iīm pretty sure this fantastically service canīt be cheap...
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Old 20th February 2013, 08:23 AM   #317
gk7 is offline gk7
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More highlights:

"ECC will raise jitter to intolerable levels."

"The idea behind memory playback was, in its most generic of definitions, that if we copy all of the bits to a piece of memory large enough to not fragment the music files, we'd have the time and accessibility to clear it of jitter."
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Old 20th February 2013, 12:32 PM   #318
marce is offline marce  United Kingdom
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I read it through!!!!! Audiophile based pseudo science to sell somthing for $17,950 that you could do with a $5,000 or less PC.
Fas42, thinking of playback and noise, when a PC plays back music from any source uit is not constantly accessing the data like on a CD, but will use burst mode to read the data into a cache, thus the activity of the computer will not be that different from one source to another. Hard drives can achieve read speeds of 50+mbs so the activity during a song playback may be a few seconds at the most.
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Old 20th February 2013, 05:45 PM   #319
Robert F is offline Robert F  New Zealand
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[QUOTE=gk7;3377780]I just read the article linked, besides highlights like "Impulse Discharge of Events in Atemporal Space"
itīs a lot of marketing BS made to sound "technical" and "knowledgeable".

Yes I thought that acronym in particular reeked...
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Old 20th February 2013, 06:10 PM   #320
Scott6113 is offline Scott6113  United States
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Atemporal Space? Buy that and I have some dehydrated water to sell you.
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