[BC] dueling algorithms and audio quality

[Acuff, Marty]

On Thursday, October 01, 2009 13:28 Dana Puopolo wrote:

> Actually you are only partially right, Chip, because
> eventually digital HAS to become part of the analog 
> domain-and that's frequently where mucho quality is lost.
> ..
> 
> Just keep it linear and digital is OK.
> 
> --chip

This would only be true if either the A-to-D or D-to-A converters are cheesy, OR if the digital transport path ISN'T linear.  

What chip says is true, perhaps a bit oversimplified.

It's important to differentiate between linear and non-linear digital audio.  

Linear digital is the PCM WAV that you get from a direct rip of a CD.  Linear is not "compressed" (i.e. bit-rate reduced). In a properly designed digital system there is a bit-for-bit data transfer. It is a transparent system.  But there's a price tag: the bit rate is very high.  

Too high for some STLs.  

For STL systems that cannot pass the high bit rate of linear digital audio, they use "compression" (i.e. bit-rate reduction). Many of the bit-rate reduction algorithms are lossy, permanently removing audio data.  Others are "lossless" algorithms.  

My point is this: loss of quality DOES NOT occur because of a linear digital audio transport system; the loss of quality usually occurs because of bit-rate reduction, or improper configuration of the transport system, or (God forbid) a crappy A/D or D/A conversion. 

Cheesy converters have no business being used in a broadcast facility.  

Sometimes out of necessity, bit-rate reduction is unavoidable.

But please, don't shoot the messenger ;-)

	-- Marty

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