Use 24-bit fixed-point transform coefficients until just before MDCT. This
gives 7% faster decoding on average. Originally committed as revision 12284 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles
parent
74e21d0352
commit
a4de6dd2c1
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@ -45,22 +45,16 @@
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*/
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static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
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/**
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* table for exponent to scale_factor mapping
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* scale_factors[i] = 2 ^ -i
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*/
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static float scale_factors[25];
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/** table for grouping exponents */
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static uint8_t exp_ungroup_tab[128][3];
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/** tables for ungrouping mantissas */
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static float b1_mantissas[32][3];
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static float b2_mantissas[128][3];
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static float b3_mantissas[8];
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static float b4_mantissas[128][2];
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static float b5_mantissas[16];
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static int b1_mantissas[32][3];
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static int b2_mantissas[128][3];
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static int b3_mantissas[8];
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static int b4_mantissas[128][2];
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static int b5_mantissas[16];
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/**
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* Quantization table: levels for symmetric. bits for asymmetric.
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@ -161,7 +155,7 @@ typedef struct {
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int surround_mix_level; ///< Surround mix level index
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float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
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float dynamic_range[2]; ///< dynamic range
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float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
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int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
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int num_cpl_bands; ///< number of coupling bands
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int num_cpl_subbands; ///< number of coupling sub bands
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int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin
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@ -174,6 +168,7 @@ typedef struct {
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int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
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int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
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int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
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DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
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/* For IMDCT. */
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@ -201,10 +196,10 @@ typedef struct {
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* reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
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* Tables 7.19 to 7.23
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*/
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static inline float
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static inline int
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symmetric_dequant(int code, int levels)
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{
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return (code - (levels >> 1)) * (2.0f / levels);
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return ((code - (levels >> 1)) << 24) / levels;
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}
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/*
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@ -250,11 +245,6 @@ static void ac3_tables_init(void)
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dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
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}
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/* generate scale factors for exponents and asymmetrical dequantization
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reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
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for (i = 0; i < 25; i++)
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scale_factors[i] = pow(2.0, -i);
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/* generate exponent tables
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reference: Section 7.1.3 Exponent Decoding */
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for(i=0; i<128; i++) {
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@ -461,9 +451,9 @@ static void uncouple_channels(AC3DecodeContext *s)
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for(j=0; j<12; j++) {
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for(ch=1; ch<=s->fbw_channels; ch++) {
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if(s->channel_in_cpl[ch]) {
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s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
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s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
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if (ch == 2 && s->phase_flags[bnd])
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s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i];
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s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
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}
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}
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i++;
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@ -476,9 +466,9 @@ static void uncouple_channels(AC3DecodeContext *s)
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* Grouped mantissas for 3-level 5-level and 11-level quantization
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*/
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typedef struct {
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float b1_mant[3];
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float b2_mant[3];
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float b4_mant[2];
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int b1_mant[3];
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int b2_mant[3];
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int b4_mant[2];
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int b1ptr;
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int b2ptr;
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int b4ptr;
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@ -494,11 +484,11 @@ static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_group
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int i, gcode, tbap, start, end;
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uint8_t *exps;
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uint8_t *bap;
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float *coeffs;
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int *coeffs;
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exps = s->dexps[ch_index];
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bap = s->bap[ch_index];
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coeffs = s->transform_coeffs[ch_index];
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coeffs = s->fixed_coeffs[ch_index];
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start = s->start_freq[ch_index];
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end = s->end_freq[ch_index];
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@ -506,7 +496,7 @@ static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_group
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tbap = bap[i];
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switch (tbap) {
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case 0:
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coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
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coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
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break;
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case 1:
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@ -549,12 +539,14 @@ static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_group
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coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
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break;
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default:
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default: {
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/* asymmetric dequantization */
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coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
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int qlevel = quantization_tab[tbap];
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coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
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break;
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}
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}
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coeffs[i] *= scale_factors[exps[i]];
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coeffs[i] >>= exps[i];
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}
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return 0;
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@ -567,12 +559,12 @@ static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_group
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static void remove_dithering(AC3DecodeContext *s) {
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int ch, i;
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int end=0;
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float *coeffs;
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int *coeffs;
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uint8_t *bap;
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for(ch=1; ch<=s->fbw_channels; ch++) {
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if(!s->dither_flag[ch]) {
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coeffs = s->transform_coeffs[ch];
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coeffs = s->fixed_coeffs[ch];
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bap = s->bap[ch];
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if(s->channel_in_cpl[ch])
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end = s->start_freq[CPL_CH];
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@ -580,13 +572,13 @@ static void remove_dithering(AC3DecodeContext *s) {
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end = s->end_freq[ch];
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for(i=0; i<end; i++) {
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if(!bap[i])
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coeffs[i] = 0.0f;
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coeffs[i] = 0;
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}
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if(s->channel_in_cpl[ch]) {
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bap = s->bap[CPL_CH];
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for(; i<s->end_freq[CPL_CH]; i++) {
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if(!bap[i])
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coeffs[i] = 0.0f;
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coeffs[i] = 0;
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}
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}
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}
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@ -643,7 +635,7 @@ static void do_rematrixing(AC3DecodeContext *s)
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{
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int bnd, i;
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int end, bndend;
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float tmp0, tmp1;
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int tmp0, tmp1;
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end = FFMIN(s->end_freq[1], s->end_freq[2]);
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@ -651,10 +643,10 @@ static void do_rematrixing(AC3DecodeContext *s)
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if(s->rematrixing_flags[bnd]) {
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bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
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for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
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tmp0 = s->transform_coeffs[1][i];
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tmp1 = s->transform_coeffs[2][i];
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s->transform_coeffs[1][i] = tmp0 + tmp1;
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s->transform_coeffs[2][i] = tmp0 - tmp1;
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tmp0 = s->fixed_coeffs[1][i];
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tmp1 = s->fixed_coeffs[2][i];
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s->fixed_coeffs[1][i] = tmp0 + tmp1;
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s->fixed_coeffs[2][i] = tmp0 - tmp1;
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}
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}
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}
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@ -851,10 +843,10 @@ static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
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cpl_coord_exp = get_bits(gbc, 4);
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cpl_coord_mant = get_bits(gbc, 4);
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if (cpl_coord_exp == 15)
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s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f;
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s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
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else
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s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
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s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
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s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
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s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
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}
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}
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}
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@ -1037,14 +1029,14 @@ static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
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/* apply scaling to coefficients (headroom, dynrng) */
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for(ch=1; ch<=s->channels; ch++) {
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float gain = 2.0f * s->mul_bias;
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float gain = s->mul_bias / 4194304.0f;
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if(s->channel_mode == AC3_CHMODE_DUALMONO) {
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gain *= s->dynamic_range[ch-1];
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} else {
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gain *= s->dynamic_range[0];
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}
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for(i=0; i<s->end_freq[ch]; i++) {
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s->transform_coeffs[ch][i] *= gain;
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for(i=0; i<256; i++) {
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s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
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}
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}
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