tremor (libivorbis) on mips

[jscottkasten at yahoo.com]

--- On Fri, 4/23/10, Reinhard Tartler <siretart at tauware.de> wrote:

> From: Reinhard Tartler <siretart at tauware.de>

> (CEST), Thorsten Hirsch wrote:
>
> > decoding ogg on my mips based nas device is slower
> than real-time, so
> > it's not really usable here.
> > I've already done some research on this and I think
> the reason is that
> > the mips cpu has no fpu, so floating point
> calculations are really
> > slow. Unfortunately libogg is based on floating point
> calculations.
> > But there's also an integer based version of libogg:
> tremor (or is it
> > called libivorbis?). It's also available in ffmpeg
> (there's a
> > configure parameter "--enable-tremor" or something
> like that)
> >
> > And here's my question to you: is it possible to use
> tremor-enabled
> > packages on mips instead of the normal ones? Can you
> provide something
> > like a ffmpeg (libavcodec) package on mips that
> depends on libivorbis
> > instead of libvorbis?
>
> If the debian-mips porters confirm that there are FPU
> enabled mips
> machines, or they are at least pretty uncommon, then I
> think we should
> add this switch for mips only. CC'ing debian-mips for their
> feedback on
> this.

Here's the deal.  The mips port covers desktop mips systems such as SGI's and embedded mips devices such as PDA's.  Desktop mips chips have decent floating point units, while embedded mips chips traditionally have not.  Traditionally, the desktop mips have usually run big endian, and the embedded have usually been little endian.  (I did say "usually".)  The mips port has been divided into separate mips and mipsel builds.  Thus you may be able to accomplish such a change without offending too many people by targeting mipsel for either the fast integer library, or possibly using -msoft-float as a general build-option for the media libaries.  (The -msoft-float flag causes gcc to emit emulation code in the binary itself, thus avoiding the costly overhead of the kernel emulation for the missing FPU.)

The newer embedded mips chips sometimes do have traditional FPU, or more likely some flavor of SIMD.  I'm not aware for general, widespread support for the mips SIMD that is out there yet, but it may happen thanks to the wide spread demand for embedded multi-media devices.

Cheers,

-S-