[Neil[_9_]]

On 3/6/2017 7:59 PM, Les Cargill wrote:
Neil wrote:
On 3/5/2017 4:41 PM, Neil wrote:
On 3/5/2017 11:28 AM, Les Cargill wrote:


Outside of pathological floating point cases ( most likely for filters
with some sort of feedback ), is there ever a good case for using 64
bit
math internal to DAW elements ( read: plugins ) rather than just 32
bit?

I'm not really seeing one. And for Intel processors, 32 bit has
possible performance advantages if you go with SSE math. SSE stuff
(very) roughly uses a 128 bit "register", in which fits four floats,
but only two doubles. So you get a hypothetical-but-not-really
2x speedup just from that for things like long complex multiplies.

Long vectors, being half the size, will also fit in cache better.

I see a breakdown along the lines of "if the plugin uses an FFT, keep
it in floats. If it's structured more like an IIR/FIR filter which
uses less internal data storage, 64 bit may or may not be any better,
depending on how small sample and internal values can be."

Greater bit depth for processing is not new. DAWs have been doing this
for decades, and yes, it makes an audible difference in the end results.
For example, CoolEdit Pro used 56 bit processing, and you can readily
hear is that there are fewer artifacts in things like trailing reverbs
and fade-outs than there are when using 32 bit processing. There was
little impact on the CPUs of the day, so I'd expect even less on modern
hardware. Still, I wouldn't care if there was some performance impact
because the end result is far superior.

Two corrections...
1) I meant to write "...and you can readily hear that..."
2) I was referring to floating point processing, which changes the
picture entirely.

So... my bad... never mind!



I hate when that happens!

No, I'm pretty skeptical that even reverb tails will be much different
in reality, at lest if proper dithering and what not is done. I know
that that sounds like - I had a Nanoverb.

The CoolEdit '96/2000 reverbs at least were just awful. Gor bless
'em, those reverbs were terrible. I never played with Pro, so maybe it
got better.

FWIW, I've set up some tests using the Waves IR plugin and some of the
big Samplicity impulses, and I can't get much if any difference. It's
the sort of thing that I am never quite sure I've done
correctly though.

In Pro, there were several reverb models, but I imagine that if one was
only using default settings of the simplest model the differences in
reverb tails would be slight. However, there were clearly audible
differences when tweaked, for instance when very long or
multi-directional reverb tails were used. Proper dithering is always a
prerequisite!

--
best regards,

Neil