*/
/**
- * @file libavcodec/ac3.c
+ * @file
* Common code between the AC-3 encoder and decoder.
*/
/**
* Starting frequency coefficient bin for each critical band.
*/
-static const uint8_t band_start_tab[51] = {
+static const uint8_t band_start_tab[AC3_CRITICAL_BANDS+1] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 26, 27, 28, 31,
};
/**
- * Maps each frequency coefficient bin to the critical band that contains it.
+ * Map each frequency coefficient bin to the critical band that contains it.
*/
static const uint8_t bin_to_band_tab[253] = {
0,
int v = psd[bin++];
int band_end = FFMIN(band_start_tab[band+1], end);
for (; bin < band_end; bin++) {
+ int max = FFMAX(v, psd[bin]);
/* logadd */
- int adr = FFMIN(FFABS(v - psd[bin]) >> 1, 255);
- v = FFMAX(v, psd[bin]) + ff_ac3_log_add_tab[adr];
+ int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
+ v = max + ff_ac3_log_add_tab[adr];
}
band_psd[band++] = v;
} while (end > band_start_tab[band]);
uint8_t *dba_lengths, uint8_t *dba_values,
int16_t *mask)
{
- int16_t excite[50]; /* excitation */
+ int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */
int band;
int band_start, band_end, begin, end1;
int lowcomp, fastleak, slowleak;
band = 0;
for (seg = 0; seg < dba_nsegs; seg++) {
band += dba_offsets[seg];
- if (band >= 50 || dba_lengths[seg] > 50-band)
+ if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band)
return -1;
if (dba_values[seg] >= 4) {
delta = (dba_values[seg] - 3) << 7;
int snr_offset, int floor,
const uint8_t *bap_tab, uint8_t *bap)
{
- int i, j, k, end1, v, address;
+ int bin, band;
/* special case, if snr offset is -960, set all bap's to zero */
if (snr_offset == -960) {
- memset(bap, 0, 256);
+ memset(bap, 0, AC3_MAX_COEFS);
return;
}
- i = start;
- j = bin_to_band_tab[start];
+ bin = start;
+ band = bin_to_band_tab[start];
do {
- v = (FFMAX(mask[j] - snr_offset - floor, 0) & 0x1FE0) + floor;
- end1 = FFMIN(band_start_tab[j] + ff_ac3_critical_band_size_tab[j], end);
- for (k = i; k < end1; k++) {
- address = av_clip((psd[i] - v) >> 5, 0, 63);
- bap[i] = bap_tab[address];
- i++;
+ int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor;
+ int band_end = FFMIN(band_start_tab[band+1], end);
+ for (; bin < band_end; bin++) {
+ int address = av_clip((psd[bin] - m) >> 5, 0, 63);
+ bap[bin] = bap_tab[address];
}
- } while (end > band_start_tab[j++]);
+ } while (end > band_start_tab[band++]);
}
/* AC-3 bit allocation. The algorithm is the one described in the AC-3
uint8_t *dba_offsets, uint8_t *dba_lengths,
uint8_t *dba_values)
{
- int16_t psd[256]; /* scaled exponents */
- int16_t band_psd[50]; /* interpolated exponents */
- int16_t mask[50]; /* masking value */
+ int16_t psd[AC3_MAX_COEFS]; /* scaled exponents */
+ int16_t band_psd[AC3_CRITICAL_BANDS]; /* interpolated exponents */
+ int16_t mask[AC3_CRITICAL_BANDS]; /* masking value */
ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd);
}
/**
- * Initializes some tables.
+ * Initialize some tables.
* note: This function must remain thread safe because it is called by the
* AVParser init code.
*/
#if !CONFIG_HARDCODED_TABLES
/* compute bndtab and masktab from bandsz */
int bin = 0, band;
- for (band = 0; band < 50; band++) {
+ for (band = 0; band < AC3_CRITICAL_BANDS; band++) {
int band_end = bin + ff_ac3_critical_band_size_tab[band];
band_start_tab[band] = bin;
while (bin < band_end)
bin_to_band_tab[bin++] = band;
}
- band_start_tab[50] = bin;
+ band_start_tab[AC3_CRITICAL_BANDS] = bin;
#endif /* !CONFIG_HARDCODED_TABLES */
}