I completed a little research about how the speed
of Compactflash memory cards will affect nature
recording.=20
In summary: 12X or faster Compactflash cards will
work OK. 24X cards are optimal because they transfer
files to a PC at top speed using USB 1.1.
Compactflash memory cards come with a wide range
of speed ratings. Currently the fastest are rated
32x to 40x. X in this case =3D 150,000 bytes/second, so
a 40X card should be capable of write performance
close to 6MB/second. In actual practice, the observed
data rate is considerably lower.
For example, the popular 1GB Lexar 24X card is rated
at (150,000 x 24) =3D 3.6 MB/sec, but the actual
measured rate to write data is typically 1.2MB/second.
Is this data rate fast enough for sound recording?=20
If recording one channel:
Sampling.....Bytes/Second....capacity of 1GB card
16/44.1.........88,200.............3.1 hours
16/48............96,000............ 2.9 hours
24/48...........144,000........... 1.9 hours
Two channel recording uses twice the data rate. So
even stereo 24/48 would require only 288,000
Bytes per second, or roughly 0.3MB/second.
This data rate is easily met by the Lexar 24x CF card.
Less expensive 16X and 12X cards should also work OK.
Compactflash cards can read data quite a bit faster
than write it. The Lexar 24X 1GB card has been
measured reading data at up to 6MB/second. This is
useful when copying the contents of a Compactflash
card to your computer's hard disc.=20
At sustained throughput of 5MB/second (pretty much the
maximum that USB 1.1 can provide), it will take about 200
seconds (3.33 minutes) to copy the contents a 1GB
card from CompactFlash to your computer hard disc.
Using a USB 2.0, Firewire, or ATAPI compactflash reader
will copy the files somewhat more quickly.
--oryoki
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