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AIFF 'bug' (and Sound Forge) - continued BHQ: Just
to clarify then...it is a bug when Sound Forge says
the .aif attributes are at 44.082 instead of
44.1? GH: (note:
Cliff's explanation is right on. Below is the error
in more depth, however unnecessary) It's
an ASR-X bug. The ASR-X writes funny stuff in those
fields, but the end result is that the ASR-X plays
back and samples ONLY at 44.1 kHz, nothing more,
nothing less. BHQ: It
seems like it is more than that cuz the waveform
does change after resampling...and if the wav is
already 44.1, Sound Forge doesn't do anything when
you resample... GH A
waveform by itself does not have a sample rate,
technically. It's just data. However, if you know
at what rate the file was sampled AND SAVED at,
then if you played it back at that same rate, the
pitch should be the same. That
is what commonly is supposed to happen. On your PC,
if you sampled at 44.1 kHz, you will come up with a
.aif file that has 44.1 in the sample rate field in
the header of the file. If you choose to sample at
some other rate, that rate will appear in header.
The purpose of that is so that the "player-back" of
the sample can know (if it wants to) what rate to
play it back at "unity pitch". OK -
for example, if I took a Kurzweil, and sampled at
36.5K, and saved that sample as a .wav file, it
will have 36.5K written in the sample header field
- because the Kurzweil is doing it's job right.
Let's say I load it into Sound Forge, and try to
play it back. Sound Forge complains that my sound
card doesn't support that sample rate - because
Sound Forge read the field, and yes - most every
sound card doesn't play back 36.5. So you have to
go to the Process-Resample page in Sound Forge.
"Resample" is bad terminology, because the default
setting in Sound Forge is New Sample rate=44.1, and
the "Set the sample rate only - do not resample"
field is checked - so the default behavior is NOT
to "resample", but to simply rewrite the sample
rate field, so Sound Forge can at least sound the
sample through your computers sound card. The pitch
WILL be higher, because you are playing it back at
a higher sample rate. The data IS NOT changed;
however, it you resampled, the sample rate would be
different, rewritten, and the data will be changed
AND the pitch will be the same - because resampling
will process the sample to change the
pitch. Regarding
the ASR-X - the ASR-X does not do it's job right
because the information in the sample rate field is
wrong, so when you deal with the AIFF in Sound
Forge, you are dealing with skewed information.
Simply "resampling" without changing the data in
Sound Forge makes the sample play back out of your
sound card, AND makes it play back EXACTLY how it
was sampled, which is the solution. And
it's sad to think that this bug will NEVER be
fixed. Too bad.
There
were some additional, compelling posts in this
thread - particularly Shifty's adventures in
hacking the OS v2.67 EPROM from the original ASR-X
wherein he determines the suspect data being
written. Read the whole thread beginning
here. |
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