DUGAN
> > What I've done to evaluate the effect of bit rate reduction is to
>> take a fine example of nature sound (a bit of a Gordon Hempton CD),
>> transfer it digitally to an MD, then transfer that back, again
>> digitally, to PCM.
>>
>> I can then do blind A/Bs between original and MD copy with my ABX
>> setup. No one has been able to distinguish the recordings yet. And I
>> can subtract the original and the encoded-decoded, resulting in a
>> difference file that is what the encoding took out. An interesting
>> experiment.
KNAPP
>I take it you managed to find a way around clock syc to get the
>difference file. When I tried this using the Portadisc via USB to my G4,
>I got a beat frequency in the difference file that basically made it
>useless. Did find out the two clocks differed by about 1 cycle every 2.7
>seconds or so.
My Pro Tools can be set to synch to the incoming digital signal.
>I should try it again using the Roland and see if the results are the same.
>
>Your experience is typical of what's found doing these tests carefully.
>The blind testing has worked out this way since ATRAC 4 came in.
>
>What I found when I did the version for the group using a analog
>transfer was that the difference file simply contained what appeared by
>sonogram to be a attenuated version of the original (or the MD copy).
>Which may explain the inability of people to distinguish. It removes the
>same thing it keeps. Which is what a good compression method is supposed
>to do.
What I hear in the difference file is not what you describe. It's
low-level, swishy and staticy sound.
-Dan Dugan
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