WALTER
> > >What you are also saying is that a DAT recorded original transferred to
>> >CD is changed by the process. I would agree, everything we do changes
>> >the signal some. Even simple digital transfers are not 100% accurate.
> > >That's why there are error correction routines in the software.
DAN
> >Not so. Simple digital transfers (like CD or DAT into DAW, or
>>vice-versa) are normally perfect, that is, bit-for-bit identical
>>files are produced.
JOHN CAMPBELL
>The output signal from a DAW is usually dithered on conversion to
>16-bit with a digital transfer to CD or DAT or MD, and can also be
>dithered to, for example, 24-bit for DVD where the source is greater
>than 24-bit. This reduction of the wordlength means that the least
>significant bit is in fact changed. Just what implications this
>(among all the other processing tasks that may occur within the DAW)
>has for an audiofile that is then used to supposedly evaluate the
>effect of data compression at point of recording is the question I
>was raising in my previous post. If processing causes a change in a
>file, how do we know what effects can be ascribed to data
>compression? If these variables are omitted, by only comparing raw
>recordings with and without data compression, we might have some hope
>of enlightenment.
DAN
I didn't dither nothin'. I took a 16-bit file from a CD (bit-perfect
transfer), dubbed it digitally to an MD deck, returned the MD deck
output digitally to Pro Tools (now not the same data, but new data
that is supposed to sound the same), and made my blind comparison
sequence from that. No dither, no truncation, no gain changes,
everything in 16-bit. I don't think there is any more fair way to do
it. You get the untouched original recording, and a copy of the
recording that's been through ATRAC. If you can't hear the
difference, it's fair to say that with your ears on your system with
that type of material, ATRAC is transparent. Of course other
material, other playback systems may reveal something else. I'm
particularly interested in finding out if there are types of sounds
that trip up ATRAC.
-Dan Dugan
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