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Thanks for your note Chris, I'll add it to the ATRAC Problems page and
also forward it to the MD mailing list. I wonder if you've tried
playing the problem discs back in a different machine? One person
commented in http://www.minidisc.org/atrac_breakdown.html that the
Sharp problem seemed to be in the playback path. -Rick
ChrisO <[EMAIL PROTECTED]> writes:
>Hi..
>
>I don't have any rigidly-controlled and repeatable examples of how to bust
>the ATRAC compression algorithm, but I do have some experience with
>portable MD equipment creating the *exact* type of waveform distortion that
>is illustrated in the example graphic
>http://www.amulation.co.uk/minidisc/atrac_trouble/badwav.jpg.
>
>I was recording a folk-rock band at a club using a Sony MZ-R50 and a pair
>of AT cardiod mikes. My levels were set fairly conservatively (I may have
>gone over once or twice during a 90 minute performance), and neither the
>recorder or the mikes were disturbed during the show, except to move the
>deck once to change discs.
>
>When I played the discs back in my car on the way to my hotel after the
>show, I was disturbed to find that the recording was peppered with very
>prominent clicks. I later digitized the show onto my computer. When I
>looked at these clicks in my sound editor, I found the exact distortion
>pattern pictured in the image referenced above *hundreds* (if not more)
>times throughout the recording.
>
>This distortion pattern was found in both of the discs I used that night (2
>different brands), occurred roughly equally in both stereo channels (but
>never in both channels at the same time), and was loosely correlated with
>the sound of a loud kick drum. (I say "loosely" as the distortion was
>often introduced when the kick drum was struck, but it also happened at
>very quiet times when the drummer wasn't even behind his kit!) After
>playing with the errors in my sound editor for a while, I realized that
>this distortion was basically an inversion of the sample values that
>*should* have been recorded, with the exception of the "ramp" samples at
>the extreme edges of the click where a sample or three were recorded
>between the proper sample value and the inverse of the proper sample value.
>
>Of course, it was not truly an inversion (which would have been *easy* to
>fix in my editor...) --- the sections of the signal which appeared inverted
>exhibited the same "wobbly" pattern that is shown in the example graphic
>instead of a clean inverse of the curve that would have been there if this
>were a true inverse of the signal.
>
>I used the same equipment a few nights later without further incident.
>
>I'd absolutely *love* to find out what caused this to occur. But I think
>that is somewhat of a tall order at this point. So please accept this as
>anecdotal information. Feel free to redistribute this in any way you deem
>appropriate so that someone who maybe knows more about MD or ATRAC than I
>might be able to gain an understanding of how this situation can happen.
>
>Best Regards <<>> ChrisO
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