[Ffmpeg-devel] ac3enc.c modifications

Rich Felker dalias
Fri May 20 01:21:18 CEST 2005

On Fri, May 20, 2005 at 12:56:07AM +0200, M?ns Rullg?rd wrote:
> Rich Felker <dalias at aerifal.cx> writes:
> > On Thu, May 19, 2005 at 09:53:33PM +0200, Michael Niedermayer wrote:
> >> both float and int should be supported, there are people with cpus
> >> where float IS faster then int
> >
> > This is only possible if the cpu has a horribly botched integer
> > implementation.
> Or a damn good floating point unit.  Have you ever used an IBM Power
> or Digital Alpha CPU?  A 300 MHz IBM Power3 (Power5 is the latest) I
> ran some tests on beat a 1 GHz Pentium3 at floating point math, as did
> a 500 MHz Alpha a few generations older than the P3.

but will a 300 mhz ibm power3 using floats beat a 1ghz athlon using
integers? i think not!

> > However I have no objection to supporting both if it can be done
> > without bloat or slowdown for the integer case, but i'm seriously
> > doubtful that float is ever faster than a well-optimized integer
> > implementation, especially when the final output will be integers.
> Dividing by a variable on Alpha is sometimes faster to do in floating
> point.

yes, usually faster. this is not a usual operation, and if it's really
important you can find faster ways to approximate it with integer


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