/** Maximum possible frame size when the specification limit is ignored */
#define AC3_MAX_FRAME_SIZE 21695
-/** table for grouping exponents */
-static uint8_t exp_ungroup_tab[128][3];
+/**
+ * table for ungrouping 3 values in 7 bits.
+ * used for exponents and bap=2 mantissas
+ */
+static uint8_t ungroup_3_in_7_bits_tab[128][3];
/** tables for ungrouping mantissas */
{
int i;
+ /* generate table for ungrouping 3 values in 7 bits
+ reference: Section 7.1.3 Exponent Decoding */
+ for(i=0; i<128; i++) {
+ ungroup_3_in_7_bits_tab[i][0] = i / 25;
+ ungroup_3_in_7_bits_tab[i][1] = (i % 25) / 5;
+ ungroup_3_in_7_bits_tab[i][2] = (i % 25) % 5;
+ }
+
/* generate grouped mantissa tables
reference: Section 7.3.5 Ungrouping of Mantissas */
for(i=0; i<32; i++) {
}
for(i=0; i<128; i++) {
/* bap=2 mantissas */
- b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
- b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
- b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
+ b2_mantissas[i][0] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][0], 5);
+ b2_mantissas[i][1] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][1], 5);
+ b2_mantissas[i][2] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][2], 5);
/* bap=4 mantissas */
b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
int v = (i >> 5) - ((i >> 7) << 3) - 5;
dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
}
-
- /* generate exponent tables
- reference: Section 7.1.3 Exponent Decoding */
- for(i=0; i<128; i++) {
- exp_ungroup_tab[i][0] = i / 25;
- exp_ungroup_tab[i][1] = (i % 25) / 5;
- exp_ungroup_tab[i][2] = (i % 25) % 5;
- }
}
group_size = exp_strategy + (exp_strategy == EXP_D45);
for(grp=0,i=0; grp<ngrps; grp++) {
expacc = get_bits(gbc, 7);
- dexp[i++] = exp_ungroup_tab[expacc][0];
- dexp[i++] = exp_ungroup_tab[expacc][1];
- dexp[i++] = exp_ungroup_tab[expacc][2];
+ dexp[i++] = ungroup_3_in_7_bits_tab[expacc][0];
+ dexp[i++] = ungroup_3_in_7_bits_tab[expacc][1];
+ dexp[i++] = ungroup_3_in_7_bits_tab[expacc][2];
}
/* convert to absolute exps and expand groups */