1 /****************************************************************************** 2 * 3 * Copyright (C) 2015 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ***************************************************************************** 18 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore 19 */ 20 21 /** 22 ******************************************************************************* 23 * @file 24 * ih264e_globals.h 25 * 26 * @brief 27 * Contains declarations of global variables for H264 encoder 28 * 29 * @author 30 * Ittiam 31 * 32 * @remarks 33 * 34 ******************************************************************************* 35 */ 36 37 #ifndef IH264E_GLOBALS_H_ 38 #define IH264E_GLOBALS_H_ 39 40 41 /*****************************************************************************/ 42 /* Extern global declarations */ 43 /*****************************************************************************/ 44 45 /** 46 ****************************************************************************** 47 * @brief Computes the lamda for varying quantizer scales that would be used to 48 * compute the RD cost while deciding on the MB modes. 49 * input : qp 50 * output : lambda 51 * @remarks lambda = 0.85 * pow(2, (qp - 12)/3), when SSD is used as metric 52 * for computing distortion (Bit rate estimation for cost function of H.264/ 53 * AVC by Mohd Golam Sarwer et. al.) If the use of distortion metric is SAD 54 * rather than SSD in the stage of encoding, consider sqrt(lambda) simply to 55 * adjust lambda for the lack of squaring operation in the error computation 56 * (from rate distortion optimization for video compression by sullivan). 57 ****************************************************************************** 58 */ 59 extern const UWORD16 gu2_qp_lambda[52]; 60 61 /** 62 ****************************************************************************** 63 * @brief Computes the lamda for varying quantizer scales that would be used to 64 * compute the RD cost while deciding on the MB modes. 65 * input : qp 66 * output : lambda 67 * @remarks lambda = pow(2, (qp - 12)/6). When Lagrangian multiplier is disabled 68 * the same constant is used across mode decision and mv decisions. 69 ****************************************************************************** 70 */ 71 extern const UWORD8 gu1_qp0[52]; 72 73 /** 74 ****************************************************************************** 75 * @brief unsigned exp. goulumb codelengths to assign cost to a coefficient of 76 * mb types. 77 * input : Integer 78 * output : codelength 79 * @remarks Refer sec. 9-1 in h264 specification 80 ****************************************************************************** 81 */ 82 extern const UWORD8 u1_uev_codelength[32]; 83 84 /** 85 ****************************************************************************** 86 * @brief Look up table to assign cost to a coefficient of a residual block 87 * basing on its surrounding coefficients 88 * input : Numbers of T1's 89 * output : coeff_cost 90 * @remarks Refer Section 2.3 Elimination of single coefficients in inter 91 * macroblocks in document JVT-O079 92 ****************************************************************************** 93 */ 94 extern const UWORD8 gu1_coeff_cost[6]; 95 96 /** 97 ****************************************************************************** 98 * @brief Indices map to raster scan for luma 4x4 block 99 * input : scan index 100 * output : scan location 101 * @remarks The scan order assumes the stride to access the next row is 16 102 ****************************************************************************** 103 */ 104 extern const UWORD8 gu1_luma_scan_order[16]; 105 106 /** 107 ****************************************************************************** 108 * @brief Indices map to raster scan for chroma AC block 109 * input : scan index 110 * output : scan location 111 * @remarks The scan order assumes the stride to access the next row is 32 112 ****************************************************************************** 113 */ 114 extern const UWORD8 gu1_chroma_scan_order[15]; 115 116 /** 117 ****************************************************************************** 118 * @brief Indices map to raster scan for luma 4x4 dc block 119 * input : scan index 120 * output : scan location 121 * @remarks The scan order assumes the stride to access the next row is 16 122 ****************************************************************************** 123 */ 124 extern const UWORD8 gu1_luma_scan_order_dc[16]; 125 126 /** 127 ****************************************************************************** 128 * @brief Indices map to raster scan for chroma 2x2 dc block 129 * input : scan index 130 * output : scan location 131 * @remarks The scan order assumes the stride to access the next row is 16 132 ****************************************************************************** 133 */ 134 extern const UWORD8 gu1_chroma_scan_order_dc[4]; 135 136 137 /** 138 ****************************************************************************** 139 * @brief choice of motion vectors to be used during mv prediction 140 * input : formatted reference idx comparison metric 141 * output : mv prediction has to be median or a simple straight forward selec 142 * tion from neighbors. 143 * @remarks If only one of the candidate blocks has a reference frame equal to 144 the current block then use the same block as the final predictor. A simple 145 look up table to assist this mv prediction condition 146 ****************************************************************************** 147 */ 148 extern const WORD8 gi1_mv_pred_condition[8]; 149 150 151 /** 152 ****************************************************************************** 153 * @brief maps the h264 quantizer to the mpeg2 quantizer scale 154 * input : h264 qp 155 * output : eqvivalent mpeg 2 qp 156 * @remarks mpeg2qscale = 2 ^ [((h264qp - 12) / 6) + 1] 157 ****************************************************************************** 158 */ 159 extern const UWORD8 gau1_h264_to_mpeg2_qmap[H264_QP_ELEM]; 160 161 /** 162 ****************************************************************************** 163 * @brief maps the mpeg2 quantizer to the h264 quantizer scale 164 * input : mpeg2 qp 165 * output : eqvivalent h264q p 166 * @remarks MPEG-2 dequantization: (2*QFij + k)*Wij*qscale/32 167 * k = 0 (for intra) k = sign(QFij) 168 * H.264 dequantization: (QFij*R(QP%6,i,j))>>(6 - QP/6) 169 * 170 * Excluding the portion of R(QP%6,i,j) that is due to 171 * the DCT scale factors, the 6 entries after dividing by 64 (2^6) 172 * correspond to dequant values of 173 * 2.5, 2.8125, 3.125, 3.5625, 3.9375, 4.4375. 174 * (a=0.5 b=sqrt(2/5) - refer to JVT-B038.doc) 175 * 176 * Assuming that h264Qp=12 corresponds to MPEG2 qscale of 2 177 * (the actual mapping seems to be to MPEG2 qscale of 2.5), 178 * and the fact that the effective h264 quantizer changes by 179 * a factor of 2 for every 6 steps, the following mapping is 180 * obtained: 181 * h264qp = 6*(log2(mpeg2qscale/2)) + 12. 182 * 183 * Note that the quant matrix entry assumed for the above 184 * equality is 16. Hence when the mpeg2 quant matrix entries 185 * are all 16, this lookup can be used as is (which is the 186 * default inter quant matrix in mpeg-2). 187 ****************************************************************************** 188 */ 189 extern const UWORD8 gau1_mpeg2_to_h264_qmap[MPEG2_QP_ELEM]; 190 191 192 #endif /* IH264E_GLOBALS_H_ */ 193