On Mon, 2005-10-17 at 17:34 +0200, Maarten de Boer wrote: > Very interesting reads. Thanks! > > > > Here's some papers specifically geared toward DSP processors that > > support the use of fixed point: > > > > Superior Audio Requires Fixed-Point DSP > > http://www.rane.com/note153.html
what a lame author! he writes near the end: "This is not to say that floating-point DSPs will never have their day in achieving superior audio -- it's just not today. What will it take? Here are some pretty nasty "ifs" necessary for floating-point to overtake fixed-point: if it is a 56-bit floating-point processor (i.e., 48-bit mantissa plus 8-bit exponent) or 32-bit with double-precision (requiring a large accumulator), if the parts run at the same speed as the equivalent fixed-point part, if they use the same power, and if they cost the same, then the choice is made." this was written in 2002, when any FP unit worth mentioning in this context could operate in double or single precision mode. double precision mode vastly exceeds the requirements he mentions here, although i will concede that they may use more power (miniscule amounts in the overall scheme of things). the fact that most audio apps today use single precision FP (32 bit) has as much to do with performance and laziness by authors as with anything else. the technology is there to do 80 bit FP if people want to use it, and some do (Ron Kuper at Cakewalk just did a presentation at AES on Sonar's new 64 bit mode which uses double precision FP IIUC). --p
