1/* ------------------------------------------------------------------ 2 * Copyright (C) 1998-2009 PacketVideo 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 13 * express or implied. 14 * See the License for the specific language governing permissions 15 * and limitations under the License. 16 * ------------------------------------------------------------------- 17 */ 18/* 19------------------------------------------------------------------------------ 20 21 PacketVideo Corp. 22 MP3 Decoder Library 23 24 Filename: pvmp3_alias_reduction.cpp 25 26 Date: 09/21/2007 27 28------------------------------------------------------------------------------ 29 REVISION HISTORY 30 31 32 Description: 33 34------------------------------------------------------------------------------ 35 INPUT AND OUTPUT DEFINITIONS 36 37Input 38 int32 *input_buffer, Ptr to fequency lines of current channel 39 struct gr_info_s *gr_info, structure with granuke information for the 40 input 41 mp3Header *info mp3 header information 42 43------------------------------------------------------------------------------ 44 FUNCTION DESCRIPTION 45 46 Alias Reduction 47 48 49 50 Alias reduction before processing by the IMDCT 51 52 Csi + 53 >---------0---------0--------> 54 \ / - 55 Cai \ / 56 \ / 57 \ / 58 \ 59 / \ 60 Cai / \ 61 / \ + 62 >--------0---------0----------> 63 Csi + 64 65 Aliasing Butterfly 66 Alias reduction is not applied to short blocks 67 68------------------------------------------------------------------------------ 69 REQUIREMENTS 70 71 72------------------------------------------------------------------------------ 73 REFERENCES 74 75 [1] ISO MPEG Audio Subgroup Software Simulation Group (1996) 76 ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension 77 78------------------------------------------------------------------------------ 79 PSEUDO-CODE 80 1 ci 81 csi = ---------------- csi = ---------------- 82 sqrt( 1 + (ci^2)) sqrt( 1 + (ci^2)) 83 84 85 ci = -0.6, -0.535, -0.33, -0.185, -0.095, -0.041, -0.0142, -0.0037 86 87 ------------------------------------------------------------------------------ 88*/ 89 90 91/*---------------------------------------------------------------------------- 92; INCLUDES 93----------------------------------------------------------------------------*/ 94 95#include "pvmp3_alias_reduction.h" 96#include "pv_mp3dec_fxd_op.h" 97 98 99/*---------------------------------------------------------------------------- 100; MACROS 101; Define module specific macros here 102----------------------------------------------------------------------------*/ 103 104 105/*---------------------------------------------------------------------------- 106; DEFINES 107; Include all pre-processor statements here. Include conditional 108; compile variables also. 109----------------------------------------------------------------------------*/ 110#define NUM_BUTTERFLIES 8 111 112#define Q31_fmt(a) (int32(double(0x7FFFFFFF)*a)) 113 114/*---------------------------------------------------------------------------- 115; LOCAL FUNCTION DEFINITIONS 116; Function Prototype declaration 117----------------------------------------------------------------------------*/ 118 119/*---------------------------------------------------------------------------- 120; LOCAL STORE/BUFFER/POINTER DEFINITIONS 121; Variable declaration - defined here and used outside this module 122----------------------------------------------------------------------------*/ 123const int32 c_signal [ NUM_BUTTERFLIES ] = 124{ 125 126 Q31_fmt(0.85749292571254f), Q31_fmt(0.88174199731771f), 127 Q31_fmt(0.94962864910273f), Q31_fmt(0.98331459249179f), 128 Q31_fmt(0.99551781606759f), Q31_fmt(0.99916055817815f), 129 Q31_fmt(0.99989919524445f), Q31_fmt(0.99999315507028f) 130 131}; 132 133 134const int32 c_alias [ NUM_BUTTERFLIES ] = 135{ 136 137 Q31_fmt(-0.51449575542753f), Q31_fmt(-0.47173196856497f), 138 Q31_fmt(-0.31337745420390f), Q31_fmt(-0.18191319961098f), 139 Q31_fmt(-0.09457419252642f), Q31_fmt(-0.04096558288530f), 140 Q31_fmt(-0.01419856857247f), Q31_fmt(-0.00369997467376f) 141}; 142 143/*---------------------------------------------------------------------------- 144; EXTERNAL FUNCTION REFERENCES 145; Declare functions defined elsewhere and referenced in this module 146----------------------------------------------------------------------------*/ 147 148/*---------------------------------------------------------------------------- 149; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES 150; Declare variables used in this module but defined elsewhere 151----------------------------------------------------------------------------*/ 152 153/*---------------------------------------------------------------------------- 154; FUNCTION CODE 155----------------------------------------------------------------------------*/ 156 157void pvmp3_alias_reduction(int32 *input_buffer, /* Ptr to spec values of current channel */ 158 granuleInfo *gr_info, 159 int32 *used_freq_lines, 160 mp3Header *info) 161{ 162 int32 *ptr1; 163 int32 *ptr2; 164 int32 *ptr3; 165 int32 *ptr4; 166 const int32 *ptr_csi; 167 const int32 *ptr_csa; 168 int32 sblim; 169 170 int32 i, j; 171 172 *used_freq_lines = fxp_mul32_Q32(*used_freq_lines << 16, (int32)(0x7FFFFFFF / (float)18 - 1.0f)) >> 15; 173 174 175 if (gr_info->window_switching_flag && gr_info->block_type == 2) 176 { 177 if (gr_info->mixed_block_flag) 178 { 179 sblim = ((info->version_x == MPEG_2_5) && (info->sampling_frequency == 2)) ? 3 : 1; 180 } 181 else 182 { 183 return; /* illegal parameter */ 184 } 185 } 186 else 187 { 188 sblim = *used_freq_lines + 1; 189 190 if (sblim > SUBBANDS_NUMBER - 1) 191 { 192 sblim = SUBBANDS_NUMBER - 1; /* default */ 193 } 194 195 } 196 197 198 ptr3 = &input_buffer[17]; 199 ptr4 = &input_buffer[18]; 200 ptr_csi = c_signal; 201 ptr_csa = c_alias; 202 203 /* NUM_BUTTERFLIES (=8) butterflies between each pair of sub-bands*/ 204 205 for (i = NUM_BUTTERFLIES >> 1; i != 0; i--) 206 { 207 int32 csi1 = *ptr_csi++; 208 int32 csi2 = *ptr_csi++; 209 int32 csa1 = *ptr_csa++; 210 int32 csa2 = *ptr_csa++; 211 212 ptr1 = ptr3; 213 ptr3 -= 2; 214 ptr2 = ptr4; 215 ptr4 += 2; 216 217 /* 218 * "sblim" alias-reduction operations between each 219 * pair of sub-bands 220 */ 221 222 for (j = sblim >> 1; j != 0; j--) 223 { 224 int32 y = *ptr2; 225 int32 x = *ptr1 << 1; 226 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); 227 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); 228 y = *ptr2; 229 x = *ptr1 << 1; 230 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); 231 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); 232 ptr1 += 19; 233 ptr2 += 17; 234 y = *ptr2; 235 x = *ptr1 << 1; 236 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); 237 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); 238 y = *ptr2; 239 x = *ptr1 << 1; 240 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); 241 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); 242 ptr1 += 19; 243 ptr2 += 17; 244 245 } 246 247 if (sblim & 1) 248 { 249 int32 x = *ptr1 << 1; 250 int32 y = *ptr2; 251 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); 252 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); 253 254 x = *ptr1 << 1; 255 y = *ptr2; 256 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); 257 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); 258 } 259 } 260 261} 262