[FFmpeg-devel] [PATCH] Common ACELP code & G.729 [2/7] - pitch lag decoding

[Michael Niedermayer]

On Fri, Jun 27, 2008 at 06:30:00AM +0700, Vladimir Voroshilov wrote:
> 2008/6/27 Michael Niedermayer <michaelni at gmx.at>:
> > On Fri, Jun 27, 2008 at 12:00:01AM +0700, Vladimir Voroshilov wrote:
> 
> [...]
> 
> >> +
> >> +    for(i=0; i<ma_pred_order; i++)
> >> +        energy += quant_energy[i] * ma_prediction_coeff[i];
> >> +
> >> +    innov_energy = sum_of_squares(fc_v, subframe_size, 0, 0);
> >> +#ifdef G729_BITEXACT
> >
> >> +    energy +=  MULL(ff_log2(innov_energy), -24660) << 10;
> >
> > s/24660/6165/
> > and i wonder if a normal * would do with the correctly simplified constant?
> 
> Breaks bitexactness.

you mean (x*2)>>1 != x then you have a overflow in your code

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is not what we do, but why we do it that matters.
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