linuxaudio.org

--nextPart1994003.inRXKnruA3

Content-Type: Text/Plain;

  charset="iso-8859-1"

Content-Transfer-Encoding: quoted-printable
On Saturday 13 November 2010 18:51:17 Ralf Mardorf wrote:

quoted text
> On Sat, 2010-11-13 at 16:26 +0100, fons@kokkinizita.net wrote:

> > On Sat, Nov 13, 2010 at 02:57:44PM +0000, Folderol wrote:

> > > Paul Davis  wrote:

> > > > there's an awful lot of math for which a modern processor can compu=

te

quoted text
> > > > the answer faster than it can look it up. this is one such example

> > > > (as fons noted), but there are many others. this started changing

> > > > about 8 years ago, and its only gotten more true since then.

> > >=20

> > > Oh dear. I didn't realise I was so far out of date :(

> >=20

> > It's absolutely true.

> >=20

> > Note that the calculation I posted earlier runs entirely on

> > the FP processor, and two variables, q and d, will probably

> > only exist there and never be written to memory. If it takes

> > any time at all, the CPU can meanwhile do something else,

> > such as getting the pointers to the audio data it will need

> > later. Using a LUT will mean the CPU has to do all the work,

> > which includes getting the base pointer and calculating the

> > required offset(s).

> Just to ensure you aren't talking about different claims.

>=20

> Is math even faster, as e.g. 4 states for left, 1 for centre and 4

> states for right, provided e.g. by an array? Or are you thinking about

> nearly stepless panning?

Unless your memory runs (and is connected) at the same speed of the process=

or=20

(which afaik no platform has, even the first and second cache run at lower=

=20

speeds), simple math of only a limited number of operations is always faste=

r=20

then getting stuff from memory. Todays processors contain even more=20

optimizations for fast and parallelized math.

The trick Fons showed is about doing the pan calculations in simple math=20

instead of using trigonometry which would require complicated functions lik=

e=20

sin/cos to be called or tables from memory to be checked.
Have fun,
Arnold
--nextPart1994003.inRXKnruA3

Content-Type: application/pgp-signature; name=signature.asc

Content-Description: This is a digitally signed message part.
-----BEGIN PGP SIGNATURE-----

Version: GnuPG v1.4.10 (GNU/Linux)
iEYEABECAAYFAkze2TkACgkQuYLL1cDjHx1XTACcDsxTkAzXZ2LSZOhsTSXaLMF4

Q7kAniXgsncJDCsR9Fc1CHtAL35XhbV1

=5Sx0

-----END PGP SIGNATURE-----
--nextPart1994003.inRXKnruA3--