[Ffmpeg-devel] Fixed point arithmetic RealAudio G2 (cook) decoder

Benjamin Larsson banan
Wed Mar 7 18:04:41 CET 2007

Ian Braithwaite skrev:
> Hi,
> I've modified ffmpeg's cook decoder to operate with fixed point.
> I have an ARM based box I'm using as an audio media player, so now
> it can stream radio from the BBC, too.
> Regarding speed, the fixed point version runs about half the speed
> of floating point on my Athlon. On the ARM, it runs about 25 times
> faster than (soft) floating point, good enough for real time (25% load).
> (I've used C's integer multiplication, I've not looked into assembler
>  optimisations for specific CPU's.)
> As regards quality, I've compared the fixed and floating point outputs
> on a 46s sample. 95% of the output values are identical, the rest
> differ by +-1.
> Is there any interest in taking this code back into ffmpeg? I can
> see in the archives that fixed point comes up occasionally, but it
> doesn't seem to attract much attention.
> regards,
> Ian
Please send it, I'm interested.

Benjamin Larsson

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