[FFmpeg-devel] [PATCH] ALS decoder
Justin Ruggles
justin.ruggles
Sun Aug 23 19:56:45 CEST 2009
Thilo Borgmann wrote:
> Revision 6 attached.
>
> +/** Converts PARCOR coefficient k to direct filter coefficient.
> + */
> +static void parcor_to_lpc(unsigned int k, int64_t *par, int64_t *cof)
> +{
> + int i;
> +
> + for (i = 0; i < (k+1) >> 1; i++) {
> + int32_t tmp1, tmp2;
> +
> + tmp1 = cof[ i ] + ((par[k] * cof[k - i - 1] + (1 << 19)) >> 20);
> + tmp2 = cof[k - i - 1] + ((par[k] * cof[ i ] + (1 << 19)) >> 20);
> + cof[k - i - 1] = tmp2;
> + cof[ i ] = tmp1;
> + }
> +
> + cof[k] = par[k];
> +}
> +
You can use 32-bit for the PARCOR and LPC coefficients like is done in
the specification. You just have to make sure the multiplication is 64-bit.
Also, your declarations can be inline with the code.
int32_t tmp1 = ...
int32_t tmp2 = ...
-Justin
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