[Pdmtl] [PD] 24 bit causing distortion
matju at artengine.ca
Fri Aug 12 00:28:41 EDT 2005
On Thu, 11 Aug 2005, Robin Millette wrote:
> > but as i've said before, my ears are only 16bit anyway...so it's not
> > big deal for me.
> You should care about that extra byte if you're mixing a lot of tracks
> and need more headroom.
In PureData, all mixing is done using 32-bit floats, which are like
24-bit integers, plus adaptive resolution, so that the effective number
of bits stays 24 no matter what's the dB. So that's a lot more headroom
than anything you can get with 24-bit integers. That kind of resolution is
mostly only useful during processing.
The 24-bit integers would only be for recording to .wav.
Honestly I don't really know what's the fuss about 24-bit recordings.
Maybe because some company got pushed into higher-end equipment than what
was ever desired, so they created the desire and thus the market. Each bit
of resolution requires 6 more dB of S/N ratio in order to not get masked
by the hiss. Multiply that by just 16 and try to find me a soundcard with
a S/N ratio of 2^16 = 65536 = 96.3 dB (!!!).
And then fetch me an ear with 96.3 dB of S/N.
BTW, one can cheat by recording at a very, very quiet level, and then
playing that real loud. This allows your salesman and/or brother-in-law to
effectively disable the top bits of your 16-bit range, making the 24-bit
recording of the same thing sound so much better.
I must add that if you mix a lot of tracks together then the result still
has to go through the same file, soundcard, loudspeakers, room and ears
than before, and if there are 8 simultaneous sounds playing in the same
frequency band with equal loudness then they compete for the available
amplitude range in a way that each of them needs 3 _less_ bits in their
The float stuff of Pd is more useful than that because Pd's DSP is used
for more than just sound: e.g. it is also used for indexing into recorded
sounds, and that needs a lot more resolution (and, in fact, many would say
float32 is not enough for that purpose).
(did i write anything inaccurate here?)
Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju
Freelance Digital Arts Engineer, Montréal QC Canada
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