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22 | "use strict";
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23 |
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24 | Object.defineProperty(exports, "__esModule", {
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25 | value: true
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26 | });
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27 | exports.ArithmeticDecoder = void 0;
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28 | const QeTable = [{
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29 | qe: 0x5601,
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30 | nmps: 1,
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31 | nlps: 1,
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32 | switchFlag: 1
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33 | }, {
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34 | qe: 0x3401,
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35 | nmps: 2,
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36 | nlps: 6,
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37 | switchFlag: 0
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38 | }, {
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39 | qe: 0x1801,
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40 | nmps: 3,
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41 | nlps: 9,
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42 | switchFlag: 0
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43 | }, {
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44 | qe: 0x0ac1,
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45 | nmps: 4,
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46 | nlps: 12,
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47 | switchFlag: 0
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48 | }, {
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49 | qe: 0x0521,
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50 | nmps: 5,
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51 | nlps: 29,
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52 | switchFlag: 0
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53 | }, {
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54 | qe: 0x0221,
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55 | nmps: 38,
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56 | nlps: 33,
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57 | switchFlag: 0
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58 | }, {
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59 | qe: 0x5601,
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60 | nmps: 7,
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61 | nlps: 6,
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62 | switchFlag: 1
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63 | }, {
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64 | qe: 0x5401,
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65 | nmps: 8,
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66 | nlps: 14,
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67 | switchFlag: 0
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68 | }, {
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69 | qe: 0x4801,
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70 | nmps: 9,
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71 | nlps: 14,
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72 | switchFlag: 0
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73 | }, {
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74 | qe: 0x3801,
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75 | nmps: 10,
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76 | nlps: 14,
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77 | switchFlag: 0
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78 | }, {
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79 | qe: 0x3001,
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80 | nmps: 11,
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81 | nlps: 17,
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82 | switchFlag: 0
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83 | }, {
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84 | qe: 0x2401,
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85 | nmps: 12,
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86 | nlps: 18,
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87 | switchFlag: 0
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88 | }, {
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89 | qe: 0x1c01,
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90 | nmps: 13,
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91 | nlps: 20,
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92 | switchFlag: 0
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93 | }, {
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94 | qe: 0x1601,
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95 | nmps: 29,
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96 | nlps: 21,
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97 | switchFlag: 0
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98 | }, {
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99 | qe: 0x5601,
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100 | nmps: 15,
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101 | nlps: 14,
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102 | switchFlag: 1
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103 | }, {
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104 | qe: 0x5401,
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105 | nmps: 16,
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106 | nlps: 14,
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107 | switchFlag: 0
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108 | }, {
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109 | qe: 0x5101,
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110 | nmps: 17,
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111 | nlps: 15,
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112 | switchFlag: 0
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113 | }, {
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114 | qe: 0x4801,
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115 | nmps: 18,
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116 | nlps: 16,
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117 | switchFlag: 0
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118 | }, {
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119 | qe: 0x3801,
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120 | nmps: 19,
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121 | nlps: 17,
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122 | switchFlag: 0
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123 | }, {
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124 | qe: 0x3401,
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125 | nmps: 20,
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126 | nlps: 18,
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127 | switchFlag: 0
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128 | }, {
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129 | qe: 0x3001,
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130 | nmps: 21,
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131 | nlps: 19,
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132 | switchFlag: 0
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133 | }, {
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134 | qe: 0x2801,
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135 | nmps: 22,
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136 | nlps: 19,
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137 | switchFlag: 0
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138 | }, {
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139 | qe: 0x2401,
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140 | nmps: 23,
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141 | nlps: 20,
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142 | switchFlag: 0
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143 | }, {
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144 | qe: 0x2201,
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145 | nmps: 24,
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146 | nlps: 21,
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147 | switchFlag: 0
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148 | }, {
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149 | qe: 0x1c01,
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150 | nmps: 25,
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151 | nlps: 22,
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152 | switchFlag: 0
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153 | }, {
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154 | qe: 0x1801,
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155 | nmps: 26,
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156 | nlps: 23,
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157 | switchFlag: 0
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158 | }, {
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159 | qe: 0x1601,
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160 | nmps: 27,
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161 | nlps: 24,
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162 | switchFlag: 0
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163 | }, {
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164 | qe: 0x1401,
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165 | nmps: 28,
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166 | nlps: 25,
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167 | switchFlag: 0
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168 | }, {
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169 | qe: 0x1201,
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170 | nmps: 29,
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171 | nlps: 26,
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172 | switchFlag: 0
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173 | }, {
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174 | qe: 0x1101,
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175 | nmps: 30,
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176 | nlps: 27,
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177 | switchFlag: 0
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178 | }, {
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179 | qe: 0x0ac1,
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180 | nmps: 31,
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181 | nlps: 28,
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182 | switchFlag: 0
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183 | }, {
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184 | qe: 0x09c1,
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185 | nmps: 32,
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186 | nlps: 29,
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187 | switchFlag: 0
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188 | }, {
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189 | qe: 0x08a1,
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190 | nmps: 33,
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191 | nlps: 30,
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192 | switchFlag: 0
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193 | }, {
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194 | qe: 0x0521,
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195 | nmps: 34,
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196 | nlps: 31,
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197 | switchFlag: 0
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198 | }, {
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199 | qe: 0x0441,
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200 | nmps: 35,
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201 | nlps: 32,
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202 | switchFlag: 0
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203 | }, {
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204 | qe: 0x02a1,
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205 | nmps: 36,
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206 | nlps: 33,
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207 | switchFlag: 0
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208 | }, {
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209 | qe: 0x0221,
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210 | nmps: 37,
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211 | nlps: 34,
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212 | switchFlag: 0
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213 | }, {
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214 | qe: 0x0141,
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215 | nmps: 38,
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216 | nlps: 35,
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217 | switchFlag: 0
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218 | }, {
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219 | qe: 0x0111,
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220 | nmps: 39,
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221 | nlps: 36,
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222 | switchFlag: 0
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223 | }, {
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224 | qe: 0x0085,
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225 | nmps: 40,
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226 | nlps: 37,
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227 | switchFlag: 0
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228 | }, {
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229 | qe: 0x0049,
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230 | nmps: 41,
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231 | nlps: 38,
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232 | switchFlag: 0
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233 | }, {
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234 | qe: 0x0025,
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235 | nmps: 42,
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236 | nlps: 39,
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237 | switchFlag: 0
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238 | }, {
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239 | qe: 0x0015,
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240 | nmps: 43,
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241 | nlps: 40,
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242 | switchFlag: 0
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243 | }, {
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244 | qe: 0x0009,
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245 | nmps: 44,
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246 | nlps: 41,
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247 | switchFlag: 0
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248 | }, {
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249 | qe: 0x0005,
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250 | nmps: 45,
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251 | nlps: 42,
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252 | switchFlag: 0
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253 | }, {
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254 | qe: 0x0001,
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255 | nmps: 45,
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256 | nlps: 43,
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257 | switchFlag: 0
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258 | }, {
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259 | qe: 0x5601,
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260 | nmps: 46,
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261 | nlps: 46,
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262 | switchFlag: 0
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263 | }];
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264 |
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265 | class ArithmeticDecoder {
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266 | constructor(data, start, end) {
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267 | this.data = data;
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268 | this.bp = start;
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269 | this.dataEnd = end;
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270 | this.chigh = data[start];
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271 | this.clow = 0;
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272 | this.byteIn();
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273 | this.chigh = this.chigh << 7 & 0xffff | this.clow >> 9 & 0x7f;
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274 | this.clow = this.clow << 7 & 0xffff;
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275 | this.ct -= 7;
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276 | this.a = 0x8000;
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277 | }
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278 |
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279 | byteIn() {
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280 | const data = this.data;
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281 | let bp = this.bp;
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282 |
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283 | if (data[bp] === 0xff) {
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284 | if (data[bp + 1] > 0x8f) {
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285 | this.clow += 0xff00;
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286 | this.ct = 8;
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287 | } else {
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288 | bp++;
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289 | this.clow += data[bp] << 9;
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290 | this.ct = 7;
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291 | this.bp = bp;
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292 | }
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293 | } else {
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294 | bp++;
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295 | this.clow += bp < this.dataEnd ? data[bp] << 8 : 0xff00;
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296 | this.ct = 8;
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297 | this.bp = bp;
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298 | }
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299 |
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300 | if (this.clow > 0xffff) {
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301 | this.chigh += this.clow >> 16;
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302 | this.clow &= 0xffff;
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303 | }
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304 | }
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305 |
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306 | readBit(contexts, pos) {
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307 | let cx_index = contexts[pos] >> 1,
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308 | cx_mps = contexts[pos] & 1;
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309 | const qeTableIcx = QeTable[cx_index];
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310 | const qeIcx = qeTableIcx.qe;
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311 | let d;
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312 | let a = this.a - qeIcx;
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313 |
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314 | if (this.chigh < qeIcx) {
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315 | if (a < qeIcx) {
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316 | a = qeIcx;
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317 | d = cx_mps;
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318 | cx_index = qeTableIcx.nmps;
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319 | } else {
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320 | a = qeIcx;
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321 | d = 1 ^ cx_mps;
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322 |
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323 | if (qeTableIcx.switchFlag === 1) {
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324 | cx_mps = d;
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325 | }
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326 |
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327 | cx_index = qeTableIcx.nlps;
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328 | }
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329 | } else {
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330 | this.chigh -= qeIcx;
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331 |
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332 | if ((a & 0x8000) !== 0) {
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333 | this.a = a;
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334 | return cx_mps;
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335 | }
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336 |
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337 | if (a < qeIcx) {
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338 | d = 1 ^ cx_mps;
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339 |
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340 | if (qeTableIcx.switchFlag === 1) {
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341 | cx_mps = d;
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342 | }
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343 |
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344 | cx_index = qeTableIcx.nlps;
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345 | } else {
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346 | d = cx_mps;
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347 | cx_index = qeTableIcx.nmps;
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348 | }
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349 | }
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350 |
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351 | do {
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352 | if (this.ct === 0) {
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353 | this.byteIn();
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354 | }
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355 |
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356 | a <<= 1;
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357 | this.chigh = this.chigh << 1 & 0xffff | this.clow >> 15 & 1;
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358 | this.clow = this.clow << 1 & 0xffff;
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359 | this.ct--;
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360 | } while ((a & 0x8000) === 0);
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361 |
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362 | this.a = a;
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363 | contexts[pos] = cx_index << 1 | cx_mps;
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364 | return d;
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365 | }
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366 |
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367 | }
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368 |
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369 | exports.ArithmeticDecoder = ArithmeticDecoder; |
\ | No newline at end of file |