[FFmpeg-devel] Review request - ra288.{c,h} ra144.{c,h}

[Michael Niedermayer]

On Tue, Jul 29, 2008 at 08:20:45PM +0200, Vitor Sessak wrote:
> Hi,
> 
> Those four files never passed a review. I've just finished cleaning them 
> up, so if anyone wants to review them (Michael already said he will), 
> now is time.

heres 288

[...]
> static void decode(RA288Context *ractx, float gain, int cb_coef)
> {
>     int i, j;
>     double sumsum;
>     float sum, buffer[5];
> 
>     memmove(ractx->sp_block + 5, ractx->sp_block, 36*sizeof(*ractx->sp_block));
> 
>     for (i=4; i >= 0; i--)
>         ractx->sp_block[i] = -scalar_product_float(ractx->sp_block + i + 1,
>                                              ractx->sp_lpc, 36);
> 
>     /* block 46 of G.728 spec */
>     sum = 32. - scalar_product_float(ractx->gain_lpc, ractx->gain_block, 10);
> 
>     /* block 47 of G.728 spec */
>     sum = av_clipf(sum, 0, 60);
> 
>     /* block 48 of G.728 spec */
>     sumsum = exp(sum * 0.1151292546497) * gain; /* pow(10.0,sum/20)*gain */
> 
>     for (i=0; i < 5; i++)
>         buffer[i] = codetable[cb_coef][i] * sumsum;
> 
>     sum = scalar_product_float(buffer, buffer, 5) / 5;
> 
>     sum = FFMAX(sum, 1);
> 
>     /* shift and store */
>     memmove(ractx->gain_block, ractx->gain_block - 1,
>             10 * sizeof(*ractx->gain_block));
> 
>     *ractx->gain_block = 10 * log10(sum) - 32;
> 

>     for (i=1; i < 5; i++)
>         for (j=i-1; j >= 0; j--)
>             buffer[i] -= ractx->sp_lpc[i-j-1] * buffer[j];

duplicate of scalar_product_float() if half of the arrays wherent stored
in right to left order


> 
>     /* output */
>     for (i=0; i < 5; i++)
>         ractx->sp_block[4-i] =
>             av_clipf(ractx->sp_block[4-i] + buffer[i], -4095, 4095);

i think some of the arrays can be fliped 0..N wise which would clear up
things a little


> }
> 

> /**
>  * Converts autocorrelation coefficients to LPC coefficients using the
>  * Levinson-Durbin algorithm. See blocks 37 and 50 of the G.728 specification.
>  *
>  * @return 0 if success, -1 if fail
>  */
> static int eval_lpc_coeffs(const float *in, float *tgt, int n)
> {
>     int i, j;
>     double f0, f1, f2;
> 
>     if (in[n] == 0)
>         return -1;
> 
>     if ((f0 = *in) <= 0)
>         return -1;
> 
>     in--; // To avoid a -1 subtraction in the inner loop
> 
>     for (i=1; i <= n; i++) {
>         f1 = in[i+1];
> 
>         for (j=0; j < i - 1; j++)
>             f1 += in[i-j]*tgt[j];
> 
>         tgt[i-1] = f2 = -f1/f0;
>         for (j=0; j < i >> 1; j++) {
>             float temp = tgt[j] + tgt[i-j-2]*f2;
>             tgt[i-j-2] += tgt[j]*f2;
>             tgt[j] = temp;
>         }
>         if ((f0 += f1*f2) < 0)
>             return -1;
>     }
> 
>     return 0;
> }

duplicate of compute_lpc_coefs() ?


> 
> static void prodsum(float *tgt, const float *src, int len, int n)
> {
>     for (; n >= 0; n--)
>         tgt[n] = scalar_product_float(src, src - n, len);
> 
> }

i think convolution() is  a better name


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

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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