Digital Audio Question

[merz]

Ok, maybe you will laugh at this question, but it is a question
i can't seem to get my head around it, no matter how muchPohlmann i read.
Let's say that you are doing a recording and you want to record
it in 24-bits, but you also want to have a 16-bit version.Is it better to:
1-Just record in 24-bits and then later convert (re-quantize) in
software to 16-bit
2-record 24-bits and 16-bits at the same time using 2 machines.
My concern is that when you record an analog signal it gets
sampled and quantized and that the 16-bit version will have been
quantized twice (though sampled once).
For example: doing a recording at 48kHz SF, which is destined
for CD is not good because it has to be downsampled to 44.1kHZ
SF and the you have to worry about the quality of the filters
and the resampling algorithm. It is always best to just go
ahead and record at 441.kHz. Saves you a heck of a lot of time
and disk space too! But of course that is the situation with
the Sampling frequency. I never thought about the bit width
problem because only now have we had the chance to use 24-bits.
Does the fact that it is being quantized two times matter? Or do
you end up with exactly the same final quantization error as if
you had done the recording in 16-bits to begin with?
I imagine it is the same, but...Anyone?


cheers,
kevin parks

[Lee Blaske]

I'd say record in 24 bits in the sample rate of your choice, and then convert to 16 bits. If you're not changing the sample rate, you're not re-quantizing. You're simply lopping off the bottom 8 bits and dithering. You do have some options as far as dithering goes (Waves, etc.).

If you're making a CD using MLCD, you could simply use 24 bit files in MLCD and let MLCD do the dithering for you (with two different noise shaping options).

I, for one, would definitely not be running two daw set-ups to record a 24 bit and a 16 bit version. Life's too short!

BTW, before you get too bent out of shape with this exercise, you might want to prepare files in several ways, then blinfold yourself and have a trusted friend play them to see if you can tell the difference. The "Tweak Head" sample rate conversion in PT doesn't sound bad at all (not that you'd want to record 48k if a 44.1 CD was your goal).

Lee Blaske

[merz]

Hmm.... Good suggestions. Thanks for reply.


cheers,
kevin parks

[Tom Pollock]

I would also be concerned about the hardware you're using to record. I have a DA-38, which records at 16 bits, but the A/D's sound great. An older ADAT probably wouldn't do as nice a job, in which case you'd be better off dithering down a 24 bit session.