From 9a7a71ed4c8a593e4b946d8a4ac16ce71306248f Mon Sep 17 00:00:00 2001 From: Justin Ruggles Date: Sun, 17 May 2009 06:53:24 +0000 Subject: eac3dec: use 16-bit pre-mantissas instead of 24-bit in AHT decoding. it is simpler and also fixes a bug in GAQ dequantization. Originally committed as revision 18860 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/eac3dec.c | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) (limited to 'libavcodec/eac3dec.c') diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c index 8af729dc22..f78c50b987 100644 --- a/libavcodec/eac3dec.c +++ b/libavcodec/eac3dec.c @@ -66,18 +66,18 @@ typedef enum { #define EAC3_SR_CODE_REDUCED 3 -/** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */ -#define COEFF_0 10273905LL +/** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<15)) */ +#define COEFF_0 40132 -/** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */ -#define COEFF_1 11863283LL +/** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<15)) = lrint(M_SQRT2*(1<<15)) */ +#define COEFF_1 46341 -/** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */ -#define COEFF_2 3070444LL +/** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<15)) */ +#define COEFF_2 11994 /** * Calculate 6-point IDCT of the pre-mantissas. - * All calculations are 24-bit fixed-point. + * All calculations are 16-bit fixed-point. */ static void idct6(int pre_mant[6]) { @@ -86,9 +86,9 @@ static void idct6(int pre_mant[6]) odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5]; - even2 = ( pre_mant[2] * COEFF_0) >> 23; - tmp = ( pre_mant[4] * COEFF_1) >> 23; - odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23; + even2 = ( pre_mant[2] * COEFF_0) >> 15; + tmp = ( pre_mant[4] * COEFF_1) >> 15; + odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 15; even0 = pre_mant[0] + (tmp >> 1); even1 = pre_mant[0] - tmp; @@ -155,13 +155,13 @@ void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch) if (!hebap) { /* zero-mantissa dithering */ for (blk = 0; blk < 6; blk++) { - s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000; + s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFF) - 0x4000; } } else if (hebap < 8) { /* Vector Quantization */ int v = get_bits(gbc, bits); for (blk = 0; blk < 6; blk++) { - s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk] << 8; + s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk]; } } else { /* Gain Adaptive Quantization */ @@ -175,22 +175,24 @@ void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch) for (blk = 0; blk < 6; blk++) { int mant = get_sbits(gbc, gbits); - if (mant == -(1 << (gbits-1))) { + if (log_gain > 0 && mant == -(1 << (gbits-1))) { /* large mantissa */ int b; - mant = get_sbits(gbc, bits-2+log_gain) << (26-log_gain-bits); + int mbits = bits - (2 - log_gain); + mant = get_sbits(gbc, mbits); + mant <<= (15 - (mbits - 1)); /* remap mantissa value to correct for asymmetric quantization */ if (mant >= 0) - b = 32768 >> (log_gain+8); + b = 32768 >> log_gain; else b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1]; - mant += (ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (mant>>8) + b) >> 7; + mant += ((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * mant) >> 15) + b; } else { /* small mantissa, no GAQ, or Gk=1 */ - mant <<= 24 - bits; + mant <<= 15 - (bits-1); if (!log_gain) { /* remap mantissa value for no GAQ or Gk=1 */ - mant += (ff_eac3_gaq_remap_1[hebap-8] * (mant>>8)) >> 7; + mant += (ff_eac3_gaq_remap_1[hebap-8] * mant) >> 15; } } s->pre_mantissa[ch][bin][blk] = mant; -- cgit v1.2.3