[linux-audio-user] Re: Recommendations for SPDIF/AESEBU (Bill Adair)

[Phil Mendelsohn]

>> Are you aware of the Shannon Nyquist Sampling Theorem:
>> >
>> >     http://en.wikipedia.org/wiki/Nyquist-Shannon_Sampling_Theorem
>> >
>> > Its corollary is that if you downsample and then upsample, the data
>> > destroyed during the downsampling can *never* be recreated.
>> >
>
>All right hi-fi is probably the wrong word for the end result but better
>sounding is the aim and allowing experimentation by hard drive audio users
>without spending silly money on cables, DAC flavours of the month etc.

Erik and Bill -- actually, there is some reason to consider upsampling, 
but only before further processing (usually filtering) is done.  The 
argument has to do with shifting noise artifacts generated during 
processing out of the audible band.  Andy Moorer wrote a paper on it 
about 10 years ago; don't have the citation handy, but Google his 
collected papers, or look at the AES (www.aes.org) publications (not 
free ).  :(

That said, it's probably one of those (many) things that don't really 
mean much unless you're in a carefully controlled listening environment, 
etc.  And it'll be lipstick on a pig if you have other problems in the 
recording.

Upsampling does not require a "convoluted" algorithm, either -- unless 
you're talking about polynomial interpolation of higher order or 
something, Bill.  Probably not worth the clock cycles.

Cheers,
Phil M



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