Importing 44.1khz files in Cubase SX with 48/96khz sampler..

Archived from groups: rec.audio.pro,rec.audio.tech (More info?)

In article <40A3CDD2.928B14BE@in.group>, Mike <please.reply@in.group> wrote:

>If you upsample a 44.1khz wav file to 48khz or 96khz, what happens to
>that file? Is (audible) white noise added or something? What happens to
>a file when it is being upsampled (explained in simple wording please)?!

Basically, the upsampling software/hardware will compute the values
for the new samples, based on the old ones. The mathematics of this
are nontrivial... but you can think of it as the software (or
hardware) mathematically reconstructing what the original waveform
would have looked like in between the existing samples, and then
sampling this reconstructed waveform at the new rate.

The quality of this resampling process can and does vary - the more
mathematical horsepower you're willing to throw at it, the better the
accuracy of the resampled signal.

Whenever you perform this sort of sample-rate conversion, or perform
similar sorts of calculations, a small amount of error creeps into
the process. This "quantization" error occurs because it's usually
impossible to represent the results of the calculations exactly, in
the limited precision (e.g. 16 bits) of the number system being
used... some amount of numerical precision from each calculation is
lost when the data values are truncated to 16 bits. If you simply
round off the numbers to 16 bits, the quantization errors can result
in audible distortion (especially audible during low-level passages).

In order to prevent this quantization-related distortion, it is usual
(and necessary) to add a small amount of random noise (white noise or
similar) to the calculated data _before_ it is truncated to 16 bits.
This has the effect of removing the distortion, while raising the
noise floor of the signal very slightly.

If you're using a good resampling system, the resampled signal should
be almost indistinguishable from the original, even with very careful
listening. Low-quality resampling systems can introduce objectionable
distortion.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!