[FFmpeg-cvslog] r12284 - trunk/libavcodec/ac3dec.c
jbr
subversion
Sat Mar 1 05:39:39 CET 2008
Author: jbr
Date: Sat Mar 1 05:39:39 2008
New Revision: 12284
Log:
Use 24-bit fixed-point transform coefficients until just before MDCT. This
gives 7% faster decoding on average.
Modified:
trunk/libavcodec/ac3dec.c
Modified: trunk/libavcodec/ac3dec.c
==============================================================================
--- trunk/libavcodec/ac3dec.c (original)
+++ trunk/libavcodec/ac3dec.c Sat Mar 1 05:39:39 2008
@@ -45,22 +45,16 @@
*/
static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
-/**
- * table for exponent to scale_factor mapping
- * scale_factors[i] = 2 ^ -i
- */
-static float scale_factors[25];
-
/** table for grouping exponents */
static uint8_t exp_ungroup_tab[128][3];
/** tables for ungrouping mantissas */
-static float b1_mantissas[32][3];
-static float b2_mantissas[128][3];
-static float b3_mantissas[8];
-static float b4_mantissas[128][2];
-static float b5_mantissas[16];
+static int b1_mantissas[32][3];
+static int b2_mantissas[128][3];
+static int b3_mantissas[8];
+static int b4_mantissas[128][2];
+static int b5_mantissas[16];
/**
* Quantization table: levels for symmetric. bits for asymmetric.
@@ -161,7 +155,7 @@ typedef struct {
int surround_mix_level; ///< Surround mix level index
float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
float dynamic_range[2]; ///< dynamic range
- float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
+ int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
int num_cpl_bands; ///< number of coupling bands
int num_cpl_subbands; ///< number of coupling sub bands
int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin
@@ -174,6 +168,7 @@ typedef struct {
int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
+ int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
/* For IMDCT. */
@@ -201,10 +196,10 @@ typedef struct {
* reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
* Tables 7.19 to 7.23
*/
-static inline float
+static inline int
symmetric_dequant(int code, int levels)
{
- return (code - (levels >> 1)) * (2.0f / levels);
+ return ((code - (levels >> 1)) << 24) / levels;
}
/*
@@ -250,11 +245,6 @@ static void ac3_tables_init(void)
dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
}
- /* generate scale factors for exponents and asymmetrical dequantization
- reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
- for (i = 0; i < 25; i++)
- scale_factors[i] = pow(2.0, -i);
-
/* generate exponent tables
reference: Section 7.1.3 Exponent Decoding */
for(i=0; i<128; i++) {
@@ -461,9 +451,9 @@ static void uncouple_channels(AC3DecodeC
for(j=0; j<12; j++) {
for(ch=1; ch<=s->fbw_channels; ch++) {
if(s->channel_in_cpl[ch]) {
- s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
+ s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
if (ch == 2 && s->phase_flags[bnd])
- s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i];
+ s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
}
}
i++;
@@ -476,9 +466,9 @@ static void uncouple_channels(AC3DecodeC
* Grouped mantissas for 3-level 5-level and 11-level quantization
*/
typedef struct {
- float b1_mant[3];
- float b2_mant[3];
- float b4_mant[2];
+ int b1_mant[3];
+ int b2_mant[3];
+ int b4_mant[2];
int b1ptr;
int b2ptr;
int b4ptr;
@@ -494,11 +484,11 @@ static int get_transform_coeffs_ch(AC3De
int i, gcode, tbap, start, end;
uint8_t *exps;
uint8_t *bap;
- float *coeffs;
+ int *coeffs;
exps = s->dexps[ch_index];
bap = s->bap[ch_index];
- coeffs = s->transform_coeffs[ch_index];
+ coeffs = s->fixed_coeffs[ch_index];
start = s->start_freq[ch_index];
end = s->end_freq[ch_index];
@@ -506,7 +496,7 @@ static int get_transform_coeffs_ch(AC3De
tbap = bap[i];
switch (tbap) {
case 0:
- coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
+ coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
break;
case 1:
@@ -549,12 +539,14 @@ static int get_transform_coeffs_ch(AC3De
coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
break;
- default:
+ default: {
/* asymmetric dequantization */
- coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
+ int qlevel = quantization_tab[tbap];
+ coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
break;
+ }
}
- coeffs[i] *= scale_factors[exps[i]];
+ coeffs[i] >>= exps[i];
}
return 0;
@@ -567,12 +559,12 @@ static int get_transform_coeffs_ch(AC3De
static void remove_dithering(AC3DecodeContext *s) {
int ch, i;
int end=0;
- float *coeffs;
+ int *coeffs;
uint8_t *bap;
for(ch=1; ch<=s->fbw_channels; ch++) {
if(!s->dither_flag[ch]) {
- coeffs = s->transform_coeffs[ch];
+ coeffs = s->fixed_coeffs[ch];
bap = s->bap[ch];
if(s->channel_in_cpl[ch])
end = s->start_freq[CPL_CH];
@@ -580,13 +572,13 @@ static void remove_dithering(AC3DecodeCo
end = s->end_freq[ch];
for(i=0; i<end; i++) {
if(!bap[i])
- coeffs[i] = 0.0f;
+ coeffs[i] = 0;
}
if(s->channel_in_cpl[ch]) {
bap = s->bap[CPL_CH];
for(; i<s->end_freq[CPL_CH]; i++) {
if(!bap[i])
- coeffs[i] = 0.0f;
+ coeffs[i] = 0;
}
}
}
@@ -643,7 +635,7 @@ static void do_rematrixing(AC3DecodeCont
{
int bnd, i;
int end, bndend;
- float tmp0, tmp1;
+ int tmp0, tmp1;
end = FFMIN(s->end_freq[1], s->end_freq[2]);
@@ -651,10 +643,10 @@ static void do_rematrixing(AC3DecodeCont
if(s->rematrixing_flags[bnd]) {
bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
- tmp0 = s->transform_coeffs[1][i];
- tmp1 = s->transform_coeffs[2][i];
- s->transform_coeffs[1][i] = tmp0 + tmp1;
- s->transform_coeffs[2][i] = tmp0 - tmp1;
+ tmp0 = s->fixed_coeffs[1][i];
+ tmp1 = s->fixed_coeffs[2][i];
+ s->fixed_coeffs[1][i] = tmp0 + tmp1;
+ s->fixed_coeffs[2][i] = tmp0 - tmp1;
}
}
}
@@ -851,10 +843,10 @@ static int ac3_parse_audio_block(AC3Deco
cpl_coord_exp = get_bits(gbc, 4);
cpl_coord_mant = get_bits(gbc, 4);
if (cpl_coord_exp == 15)
- s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f;
+ s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
else
- s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
- s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
+ s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
+ s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
}
}
}
@@ -1037,14 +1029,14 @@ static int ac3_parse_audio_block(AC3Deco
/* apply scaling to coefficients (headroom, dynrng) */
for(ch=1; ch<=s->channels; ch++) {
- float gain = 2.0f * s->mul_bias;
+ float gain = s->mul_bias / 4194304.0f;
if(s->channel_mode == AC3_CHMODE_DUALMONO) {
gain *= s->dynamic_range[ch-1];
} else {
gain *= s->dynamic_range[0];
}
- for(i=0; i<s->end_freq[ch]; i++) {
- s->transform_coeffs[ch][i] *= gain;
+ for(i=0; i<256; i++) {
+ s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
}
}
More information about the ffmpeg-cvslog
mailing list