[FFmpeg-devel] [PATCH] updated LGPL AC-3 decoder

[Michael Niedermayer]

Hi

On Fri, May 04, 2007 at 12:46:25AM -0400, Justin Ruggles wrote:
[...]
> 
> > 
> > [...]
> > 
> > 
> >>+static inline float
> >>+symmetric_dequant(int code, int levels)
> >>+{
> >>+    float m = (code - (levels >> 1)) << 1;
> >>+    return (m / levels);
> >>+}
> > 
> > 
> > as level is always a constant this could be simplified to
> > 
> > return (code - (levels >> 1)) * (2.0/levels);
> > 
> > gcc should here be able to change levels >> 1 and 2.0/levels to
> > constants
> 
> I almost get it...  Is it because the function is inlined and all the
> function calls use constants for levels that gcc will be smart enough to
> know to treat it this way?

yes


> 
> I can also create tables for the bap=3 and bap=5 dequantization so that
> this function will only need to be called during initialization.

that is a good idea too

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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