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author | Justin Ruggles <justin.ruggles@gmail.com> | 2008-03-01 04:39:39 +0000 |
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committer | Justin Ruggles <justin.ruggles@gmail.com> | 2008-03-01 04:39:39 +0000 |
commit | a4de6dd2c17f96e434048c2350ae13ccd121805e (patch) | |
tree | bed6429f5bb6ad2004a26bbb05ce17a25991b781 /libavcodec | |
parent | 74e21d035292745be2128d0d00fe8aaeb0cdf1a8 (diff) | |
download | ffmpeg-streaming-a4de6dd2c17f96e434048c2350ae13ccd121805e.zip ffmpeg-streaming-a4de6dd2c17f96e434048c2350ae13ccd121805e.tar.gz |
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
Diffstat (limited to 'libavcodec')
-rw-r--r-- | libavcodec/ac3dec.c | 82 |
1 files changed, 37 insertions, 45 deletions
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c index 0ce75e7..6c725c4 100644 --- a/libavcodec/ac3dec.c +++ b/libavcodec/ac3dec.c @@ -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(AC3DecodeContext *s) 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(AC3DecodeContext *s) * 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(AC3DecodeContext *s, int ch_index, mant_group 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(AC3DecodeContext *s, int ch_index, mant_group 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(AC3DecodeContext *s, int ch_index, mant_group 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(AC3DecodeContext *s, int ch_index, mant_group 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(AC3DecodeContext *s) { 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(AC3DecodeContext *s) { 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(AC3DecodeContext *s) 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(AC3DecodeContext *s, int blk) 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(AC3DecodeContext *s, int blk) /* 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; } } |