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1 #include "StdAfx.h"
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2
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3 #include "mp3_utils.h"
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4 #include "bitreader_helper.h"
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5
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6 using namespace bitreader_helper;
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7
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8 static unsigned extract_header_bits(const t_uint8 p_header[4],unsigned p_base,unsigned p_bits)
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9 {
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10 PFC_ASSERT(p_base+p_bits<=32);
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11 return (unsigned) extract_bits(p_header,p_base,p_bits);
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12 }
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13
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14 namespace {
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15
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16 class header_parser
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17 {
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18 public:
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19 header_parser(const t_uint8 p_header[4]) : m_bitptr(0)
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20 {
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21 memcpy(m_header,p_header,4);
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22 }
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23 unsigned read(unsigned p_bits)
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24 {
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25 unsigned ret = extract_header_bits(m_header,m_bitptr,p_bits);
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26 m_bitptr += p_bits;
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27 return ret;
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28 }
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29 private:
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30 t_uint8 m_header[4];
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31 unsigned m_bitptr;
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32 };
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33 }
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34
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35 typedef t_uint16 uint16;
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36
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37 static const uint16 bitrate_table_l1v1[16] = { 0, 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448, 0};
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38 static const uint16 bitrate_table_l2v1[16] = { 0, 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384, 0};
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39 static const uint16 bitrate_table_l3v1[16] = { 0, 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320, 0};
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40 static const uint16 bitrate_table_l1v2[16] = { 0, 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256, 0};
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41 static const uint16 bitrate_table_l23v2[16] = { 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160, 0};
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42 static const uint16 sample_rate_table[] = {11025,12000,8000};
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43
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44 unsigned mp3_utils::QueryMPEGFrameSize(const t_uint8 p_header[4])
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45 {
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46 TMPEGFrameInfo info;
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47 if (!ParseMPEGFrameHeader(info,p_header)) return 0;
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48 return info.m_bytes;
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49 }
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50
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51 bool mp3_utils::ParseMPEGFrameHeader(TMPEGFrameInfo & p_info,const t_uint8 p_header[4])
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52 {
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53 enum {MPEG_LAYER_1 = 3, MPEG_LAYER_2 = 2, MPEG_LAYER_3 = 1};
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54 enum {_MPEG_1 = 3, _MPEG_2 = 2, _MPEG_25 = 0};
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55
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56 header_parser parser(p_header);
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57 if (parser.read(11) != 0x7FF) return false;
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58 unsigned mpeg_version = parser.read(2);
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59 unsigned layer = parser.read(2);
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60 unsigned protection = parser.read(1);
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61 unsigned bitrate_index = parser.read(4);
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62 unsigned sample_rate_index = parser.read(2);
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63 if (sample_rate_index == 3) return false;//reserved
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64 unsigned paddingbit = parser.read(1);
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65 int paddingdelta = 0;
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66 parser.read(1);//private
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67 unsigned channel_mode = parser.read(2);
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68 unsigned channel_mode_ext = parser.read(2);//channel_mode_extension
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69 parser.read(1);//copyright
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70 parser.read(1);//original
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71 parser.read(2);//emphasis
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72
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73 unsigned bitrate = 0,sample_rate = 0;
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74
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75 switch(layer)
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76 {
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77 default:
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78 return false;
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79 case MPEG_LAYER_3:
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80 paddingdelta = paddingbit ? 1 : 0;
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81
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82 p_info.m_layer = 3;
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83 switch(mpeg_version)
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84 {
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85 case _MPEG_1:
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86 p_info.m_duration = 1152;
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87 bitrate = bitrate_table_l3v1[bitrate_index];
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88 break;
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89 case _MPEG_2:
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90 case _MPEG_25:
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91 p_info.m_duration = 576;
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92 bitrate = bitrate_table_l23v2[bitrate_index];
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93 break;
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94 default:
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95 return false;
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96 }
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97
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98 break;
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99 case MPEG_LAYER_2:
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100 paddingdelta = paddingbit ? 1 : 0;
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101 p_info.m_duration = 1152;
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102 p_info.m_layer = 2;
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103 switch(mpeg_version)
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104 {
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105 case _MPEG_1:
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106 bitrate = bitrate_table_l2v1[bitrate_index];
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107 break;
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108 case _MPEG_2:
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109 case _MPEG_25:
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110 bitrate = bitrate_table_l23v2[bitrate_index];
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111 break;
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112 default:
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113 return false;
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114 }
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115 break;
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116 case MPEG_LAYER_1:
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117 paddingdelta = paddingbit ? 4 : 0;
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118 p_info.m_duration = 384;
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119 p_info.m_layer = 1;
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120 switch(mpeg_version)
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121 {
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122 case _MPEG_1:
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123 bitrate = bitrate_table_l1v1[bitrate_index];
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124 break;
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125 case _MPEG_2:
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126 case _MPEG_25:
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127 bitrate = bitrate_table_l1v2[bitrate_index];
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128 break;
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129 default:
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130 return false;
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131 }
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132 break;
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133 }
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134 if (bitrate == 0) return false;
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135
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136 sample_rate = sample_rate_table[sample_rate_index];
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137 if (sample_rate == 0) return false;
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138 switch(mpeg_version)
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139 {
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140 case _MPEG_1:
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141 sample_rate *= 4;
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142 p_info.m_mpegversion = MPEG_1;
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143 break;
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144 case _MPEG_2:
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145 sample_rate *= 2;
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146 p_info.m_mpegversion = MPEG_2;
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147 break;
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148 case _MPEG_25:
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149 p_info.m_mpegversion = MPEG_25;
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150 break;
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151 }
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152
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153 switch(channel_mode)
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154 {
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155 case 0:
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156 case 1:
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157 case 2:
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158 p_info.m_channels = 2;
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159 break;
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160 case 3:
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161 p_info.m_channels = 1;
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162 break;
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163 }
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164
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165
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166 p_info.m_channel_mode = channel_mode;
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167 p_info.m_channel_mode_ext = channel_mode_ext;
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168
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169 p_info.m_sample_rate = sample_rate;
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170 p_info.m_sample_rate_idx = sample_rate_index;
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171
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172 p_info.m_bitrate = bitrate;
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173 p_info.m_bitrate_idx = bitrate_index;
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174
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175 p_info.m_bytes = ( bitrate /*kbps*/ * (1000/8) /* kbps-to-bytes*/ * p_info.m_duration /*samples-per-frame*/ ) / sample_rate + paddingdelta;
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176
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177 if (p_info.m_layer == 1) p_info.m_bytes &= ~3;
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178
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179 p_info.m_crc = protection == 0;
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180
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181 return true;
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182 }
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183
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184 unsigned mp3header::get_samples_per_frame()
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185 {
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186 mp3_utils::TMPEGFrameInfo fr;
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187 if (!decode(fr)) return 0;
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188 return fr.m_duration;
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189 }
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190
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191 bool mp3_utils::IsSameStream(TMPEGFrameInfo const & p_frame1,TMPEGFrameInfo const & p_frame2) {
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192 return
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193 // FFmpeg writes VBR headers with null channel mode...
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194 /* p_frame1.m_channel_mode == p_frame2.m_channel_mode && */
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195 p_frame1.m_sample_rate == p_frame2.m_sample_rate &&
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196 p_frame1.m_layer == p_frame2.m_layer &&
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197 p_frame1.m_mpegversion == p_frame2.m_mpegversion;
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198 }
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199
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200
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201
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202 bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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203 if (frameSize < info.m_bytes) return false; //FAIL, incomplete data
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204 if (!info.m_crc) return true; //nothing to check, frame appears valid
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205 return ExtractFrameCRC(frameData, frameSize, info) == CalculateFrameCRC(frameData, frameSize, info);
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206 }
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207
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208 static t_uint32 CRC_update(unsigned value, t_uint32 crc)
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209 {
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210 enum { CRC16_POLYNOMIAL = 0x8005 };
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211 unsigned i;
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212 value <<= 8;
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213 for (i = 0; i < 8; i++) {
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214 value <<= 1;
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215 crc <<= 1;
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216 if (((crc ^ value) & 0x10000)) crc ^= CRC16_POLYNOMIAL;
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217 }
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218 return crc;
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219 }
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220
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221
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222 void mp3_utils::RecalculateFrameCRC(t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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223 PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );
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224
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225 const t_uint16 crc = CalculateFrameCRC(frameData, frameSize, info);
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226 frameData[4] = (t_uint8)(crc >> 8);
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227 frameData[5] = (t_uint8)(crc & 0xFF);
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228 }
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229
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230 static t_uint16 grabFrameCRC(const t_uint8 * frameData, t_size sideInfoLen) {
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231 t_uint32 crc = 0xffff;
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232 crc = CRC_update(frameData[2], crc);
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233 crc = CRC_update(frameData[3], crc);
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234 for (t_size i = 6; i < sideInfoLen; i++) {
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235 crc = CRC_update(frameData[i], crc);
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236 }
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237
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238 return (t_uint32) (crc & 0xFFFF);
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239 }
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240
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241 t_uint16 mp3_utils::ExtractFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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242 PFC_ASSERT(frameSize >= info.m_bytes && info.m_crc); (void)info; (void)frameSize;
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243
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244 return ((t_uint16)frameData[4] << 8) | (t_uint16)frameData[5];
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245
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246 }
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247 t_uint16 mp3_utils::CalculateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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248 PFC_ASSERT(frameSize >= info.m_bytes && info.m_crc); (void)frameSize;
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249
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250 t_size sideInfoLen = 0;
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251 if (info.m_mpegversion == MPEG_1)
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252 sideInfoLen = (info.m_channels == 1) ? 4 + 17 : 4 + 32;
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253 else
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254 sideInfoLen = (info.m_channels == 1) ? 4 + 9 : 4 + 17;
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255
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256 //CRC
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257 sideInfoLen += 2;
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258
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259 PFC_ASSERT( sideInfoLen <= frameSize );
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260
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261 return grabFrameCRC(frameData, sideInfoLen);
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262 }
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263
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264
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265 bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize) {
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266 if (frameSize < 4) return false; //FAIL, not a valid frame
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267 TMPEGFrameInfo info;
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268 if (!ParseMPEGFrameHeader(info, frameData)) return false; //FAIL, not a valid frame
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269 return ValidateFrameCRC(frameData, frameSize, info);
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270 }
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271
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272
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273 bool mp3_utils::ParseMPEGFrameHeader(TMPEGFrameInfo & p_info, const void * bytes, size_t bytesAvail) {
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274 if (bytesAvail < 4) return false; //FAIL, not a valid frame
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275 return ParseMPEGFrameHeader(p_info, reinterpret_cast<const t_uint8*>(bytes));
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276 }
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277
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278 bool mp3_utils::IsValidMPEGFrameHeader(const void* fourbytes) {
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279 TMPEGFrameInfo info = {};
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280 return ParseMPEGFrameHeader(info, fourbytes, 4);
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281 }
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