[FFmpeg-soc] AACSBR review: sbr_env_estimate

[Alex Converse]

Diego has been bugging me to do some review of the sbr code in the soc
svn so here we go...

> // Estimation of current envelope (14496-3 sp04 p218)
> static void sbr_env_estimate(float **e_curr, float ***x_high,
>                              SpectralBandReplication *sbr, SBRData *ch_data,
>                              int ch)
> {
>     int i, l, m;
>     int ilb = sbr->t_env[ch][l]     * 2 + ENVELOPE_ADJUSTMENT_OFFSET;
>     int iub = sbr->t_env[ch][l + 1] * 2 + ENVELOPE_ADJUSTMENT_OFFSET;

Danger Will Robinson, l is not yet defined.

>
>     if (sbr->bs_interpol_freq) {
>         for (l = 0; l < ch_data->bs_num_env[1]; l++) {
>             const int env_size = (sbr->t_env[ch][l + 1] - sbr->t_env[ch][l]) << 1;
>
>             for (m = 0; m < sbr->m; m++) {
>                 float sum = 0.0f;
>
>                 for (i = ilb; i < iub; i++) {
>                     sum += x_high[m + sbr->k[3]][i][0] * x_high[m + sbr->k[3]][i][0] +
>                            x_high[m + sbr->k[3]][i][1] * x_high[m + sbr->k[3]][i][1];
>                 }
>                 e_curr[l][m] = sum / env_size;
>             }
>         }
>     } else {
>         int k, p;
>
>         for (l = 0; l < ch_data->bs_num_env[1]; l++) {
>             const int env_size = (sbr->t_env[ch][l + 1] - sbr->t_env[ch][l]) << 1;
>             const uint16_t *table = ch_data->bs_freq_res[l + 1] ? sbr->f_tablehigh : sbr->f_tablelow;
>
>             for (p = 0; p < sbr->n[ch_data->bs_freq_res[l + 1]]; p++) {
>                 float sum = 0.0f;
>                 const int den = env_size * (table[p + 1] - table[p] + 1);
>
>                 for (k = table[p]; k < table[p + 1]; k++) {
>                     for (i = ilb; i < iub; i++) {
>                         sum += x_high[k][i][0] * x_high[k][i][0] +
>                                x_high[k][i][1] * x_high[k][i][1];
>                     }
>                     e_curr[l][k - sbr->k[3]] = sum / den;
>                 }
>             }
>         }
>     }
> }
>
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