Re: 64bit v Intel Macs?
Re: 64bit v Intel Macs?
- Subject: Re: 64bit v Intel Macs?
- From: William Stewart <email@hidden>
- Date: Thu, 19 Jan 2006 14:53:33 -0800
Right - Here's some factoids to mull on.
64Bit - in general terms this means the available address space (size
of a pointer).
Currently a 32bit Mac OS X system, provides you a full 32 bit address
space (4gbyte) per application/process
Currently, a 32bit Win XP system provides you with a 31 bit address
space (2gbyte) per application/process
There is obviously more motivation for Windows apps to become 64 bit
due to this limit - in fact most of the motivation for audio apps is
really just to get that extra 2gbyte...
It is a mistake to associate 64bit sample sizes with 64bit addressing.
CoreAudio already support arbitrary sample sized data. We state that
32bit floats are the canonical format for linear PCM. This is
generally specified in the AudioStreamBasicDescription (ASBD) in
<CoreAudio/CoreAudioTypes.h> . This struct enables for a flexible
description of diverse formats from compressed VBR formats, to
differently packed and sized lpcm.
AudioUnits too use this struct to define the formats they use - so to
support 64bit samples would not require API changes, but rather
implementation and adoption. We've currently seen no need to support
this (AUs can of course use 64bit floats internally in any case), but
are always open to suggestions.
Bill
On 19/01/2006, at 1:33 PM, Richard Dobson wrote:
Evan Olcott wrote:
Though I'm not on the Apple team, it'd be pretty safe to say that
the 32-bit audio stream is what we'll be sticking with for a long
time. I don't think the benefits (if there are any, speed-wise) of
a 64-bit audio stream versus the potential dynamic range gain of
32-bit vs 64-bit (whose math escapes me currently) is probably not
worth the paradigm shift.
Out of interest, VST 2.4 has just been announced, complete with
64bit sample support (reflecting an initiative from Cakewalk, who
are making a forceful case for 64bit streams - I must admit to
being a little skeptical myself). However, my post was concerned
only with 32/64 architecture, not sample size.
Richard Dobson
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