hi. i have a question regarding resampling. i have a 48khz digital
signal that i need to convert to 44.1khz. i have two ways at my
disposal to do this: (1) using the hardware sample rate converter in
my edirol ua-5 audio hardware interface; (2) sending 48khz into my
computer and using Logic Pro to do the conversion in software.

i can't tell the difference in sound quality between the two. but i
know that this type of conversion can be noticeably distructive. i am
curious if any experts can help me understand what salient differences
there are, if any, between hardware and software conversion. i
remember hearing somewhere that in hardware, it's almost like a d/a
and a/d back-to-back to make the conversion.

thanks for any info. replies with math are ok.

david

David Petrou wrote:

hi. i have a question regarding resampling. i have a 48khz digital
signal that i need to convert to 44.1khz. i have two ways at my
disposal to do this: (1) using the hardware sample rate converter in
my edirol ua-5 audio hardware interface; (2) sending 48khz into my
computer and using Logic Pro to do the conversion in software.

i can't tell the difference in sound quality between the two. but i
know that this type of conversion can be noticeably distructive. i am
curious if any experts can help me understand what salient differences
there are, if any, between hardware and software conversion. i
remember hearing somewhere that in hardware, it's almost like a d/a
and a/d back-to-back to make the conversion.

It's all software. It's just that on "hardware" the
software runs on a DSP. You get more options with host
based software and can archive it at its original rate if
you might want to take later advantage of better
implementations than currently exist.

Modern PC's are quite a bit faster than the DSP's in
inexpensive interfaces so you will probably get better
results there if a generalization is possible.

The most highly rated current implementation among DSP folks
is something called SRC for "Secret Rabbit Code". It uses a
long sinc interpolation method which keeps it from being the
swiftest despite its name but no DSP based converter is
going to touch it for accuracy. I'm not sure if it exists
as a plugin for DAW's but you can Google to see.

OTOH, source rate conversion is not that difficult to do
well even with moderate power DSP's in terms of any audible
effect so whether it is worth the time and effort to seek
better solutions than you have in hardware is equivocal and
you probably should rely on your ears.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein