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/************************************************************************** * * XVID MPEG-4 VIDEO CODEC * mpeg-4 quantization/dequantization * * This program is an implementation of a part of one or more MPEG-4 * Video tools as specified in ISO/IEC 14496-2 standard. Those intending * to use this software module in hardware or software products are * advised that its use may infringe existing patents or copyrights, and * any such use would be at such party's own risk. The original * developer of this software module and his/her company, and subsequent * editors and their companies, will have no liability for use of this * software or modifications or derivatives thereof. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * *************************************************************************/ /************************************************************************** * * History: * * 26.01.2002 fixed quant4_intra dcscalar signed/unsigned error * 20.01.2002 increased accuracy of >> divide * 26.12.2001 divide-by-multiplication optimization * 22.12.2001 [-127,127] clamping removed; minor tweaks * 19.11.2001 inital version <pross@cs.rmit.edu.au> * *************************************************************************/ #include "quant_mpeg4.h" #include "quant_matrix.h" // function pointers quant_intraFuncPtr quant4_intra; quant_intraFuncPtr dequant4_intra; dequant_interFuncPtr dequant4_inter; quant_interFuncPtr quant4_inter; #define DIV_DIV(A,B) ( (A) > 0 ? ((A)+((B)>>1))/(B) : ((A)-((B)>>1))/(B) ) #define SIGN(A) ((A)>0?1:-1) #define VM18P 3 #define VM18Q 4 // divide-by-multiply table // need 17 bit shift (16 causes slight errors when q > 19) #define SCALEBITS 17 #define FIX(X) ((1UL << SCALEBITS) / (X) + 1) static const uint32_t multipliers[32] = { 0, FIX(2), FIX(4), FIX(6), FIX(8), FIX(10), FIX(12), FIX(14), FIX(16), FIX(18), FIX(20), FIX(22), FIX(24), FIX(26), FIX(28), FIX(30), FIX(32), FIX(34), FIX(36), FIX(38), FIX(40), FIX(42), FIX(44), FIX(46), FIX(48), FIX(50), FIX(52), FIX(54), FIX(56), FIX(58), FIX(60), FIX(62) }; /* quantize intra-block // const int32_t quantd = DIV_DIV(VM18P*quant, VM18Q); // // level = DIV_DIV(16 * data[i], default_intra_matrix[i]); // coeff[i] = (level + quantd) / quant2; */ void quant4_intra_c(int16_t * coeff, const int16_t * data, const uint32_t quant, const uint32_t dcscalar) { const uint32_t quantd = ((VM18P * quant) + (VM18Q / 2)) / VM18Q; const uint32_t mult = multipliers[quant]; uint32_t i; int16_t *intra_matrix; intra_matrix = get_intra_matrix(); coeff[0] = DIV_DIV(data[0], (int32_t) dcscalar); for (i = 1; i < 64; i++) { if (data[i] < 0) { uint32_t level = -data[i]; level = ((level << 4) + (intra_matrix[i] >> 1)) / intra_matrix[i]; level = ((level + quantd) * mult) >> 17; coeff[i] = -(int16_t) level; } else if (data[i] > 0) { uint32_t level = data[i]; level = ((level << 4) + (intra_matrix[i] >> 1)) / intra_matrix[i]; level = ((level + quantd) * mult) >> 17; coeff[i] = level; } else { coeff[i] = 0; } } } /* dequantize intra-block & clamp to [-2048,2047] // data[i] = (coeff[i] * default_intra_matrix[i] * quant2) >> 4; */ void dequant4_intra_c(int16_t * data, const int16_t * coeff, const uint32_t quant, const uint32_t dcscalar) { uint32_t i; int16_t *intra_matrix; intra_matrix = get_intra_matrix(); data[0] = coeff[0] * dcscalar; if (data[0] < -2048) { data[0] = -2048; } else if (data[0] > 2047) { data[0] = 2047; } for (i = 1; i < 64; i++) { if (coeff[i] == 0) { data[i] = 0; } else if (coeff[i] < 0) { uint32_t level = -coeff[i]; level = (level * intra_matrix[i] * quant) >> 3; data[i] = (level <= 2048 ? -(int16_t) level : -2048); } else // if (coeff[i] > 0) { uint32_t level = coeff[i]; level = (level * intra_matrix[i] * quant) >> 3; data[i] = (level <= 2047 ? level : 2047); } } } /* quantize inter-block // level = DIV_DIV(16 * data[i], default_intra_matrix[i]); // coeff[i] = (level + quantd) / quant2; // sum += abs(level); */ uint32_t quant4_inter_c(int16_t * coeff, const int16_t * data, const uint32_t quant) { const uint32_t mult = multipliers[quant]; uint32_t sum = 0; uint32_t i; int16_t *inter_matrix; inter_matrix = get_inter_matrix(); for (i = 0; i < 64; i++) { if (data[i] < 0) { uint32_t level = -data[i]; level = ((level << 4) + (inter_matrix[i] >> 1)) / inter_matrix[i]; level = (level * mult) >> 17; sum += level; coeff[i] = -(int16_t) level; } else if (data[i] > 0) { uint32_t level = data[i]; level = ((level << 4) + (inter_matrix[i] >> 1)) / inter_matrix[i]; level = (level * mult) >> 17; sum += level; coeff[i] = level; } else { coeff[i] = 0; } } return sum; } /* dequantize inter-block & clamp to [-2048,2047] data = ((2 * coeff + SIGN(coeff)) * inter_matrix[i] * quant) / 16 */ void dequant4_inter_c(int16_t * data, const int16_t * coeff, const uint32_t quant) { uint32_t sum = 0; uint32_t i; int16_t *inter_matrix; inter_matrix = get_inter_matrix(); for (i = 0; i < 64; i++) { if (coeff[i] == 0) { data[i] = 0; } else if (coeff[i] < 0) { int32_t level = -coeff[i]; level = ((2 * level + 1) * inter_matrix[i] * quant) >> 4; data[i] = (level <= 2048 ? -level : -2048); } else // if (coeff[i] > 0) { uint32_t level = coeff[i]; level = ((2 * level + 1) * inter_matrix[i] * quant) >> 4; data[i] = (level <= 2047 ? level : 2047); } sum ^= data[i]; } // mismatch control if ((sum & 1) == 0) { data[63] ^= 1; } }
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