Evert just conducted another test (many thanks to him for doing
that). This time he used the original full-bandwidth test file at a
sample rate of 44.1 kHz (no resampling at all), recorded it
digitally onto his KENNWOOD DM3020 MD recorder (that device has a
fixed sample rate of 44.1 kHz) and played it back via SPDIF. The
spectrogram created from this sound file still shows some dramatic
artifacts:
http://www.avisoft.de/compression/compressed441MD.gif
So I guess, that this is the normal behavior of ATRAC 4.5.
The low-pass filtered test file which were recorded and played back
in the same way as the above example is still acceptable:
http://www.avisoft.de/compression/compression.htm.
If I interpret these results correctly (and if no other faults were
involved), then ATRAC 4.5 (like MP3) would do a good job as long as
no major high-frequency energy is present in a recording. In more
extreme situations as the more demanding full-bandwidth test signal,
ATRAC 4.5 will reach its limitations and will clearly lose against
MP3.
Regards,
Raimund
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