Phil Leigh;503281 Wrote: > Definitions are tricky... They seem to have become so of late.
Back in the Good Olde Days(tm), oversampling meant something very specific: the stuffing of extra samples into the data stream in order to move the aliasing artefacts to higher frequencies, so that the subsequent reconstruction filters have an easier job of removing them. It doesn't matter what sample values are added (different sample values will change the nature of the artefacts, but since we're going to be removing them that's unimportant). Therefore oversamplers typically just added zeros. Oversamplers always did so by a factor of 2 (ie. they oversample by 2x, 4x, 8x, 16x, etc). OTOH, my understanding is that upsamplers tend to "invent" extra data values. The marketing departments typically refer to this as a way of "smoothing out" the signal, which of course is BS since the reconstruction filter in all DACs does precisely that. And of course it's impossible to know whether the extra data is anything like what the original signal might have been before it was bandwidth limited, although pragmatically you could argue that interpolations might be a fair approximation. If you then retain this data all the way to the analogue output (ie. you don't then remove it with the reconstruction filter), it strikes me that what you end up with is the original in-band signal plus some additional high frequencies which may or may not bear some vague similarity to whatever original signal was present prior to A/D conversion. (Perhaps you can tell that I'm skeptical about the value of upsampling :-). -- cliveb Transporter -> ATC SCM100A ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=69145 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
