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1 // Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // |
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15 |
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16 #include "parsers.h" |
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17 |
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18 static const TUint8 KISOEndCode = 0xB9; |
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19 static const TUint8 KPackStartCode = 0xBA; |
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20 static const TUint8 KVideoElementaryStream = 0xE0; |
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21 |
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22 #define KMPEG1PackHeaderLen 8 |
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23 #define KMPEG2PackHeaderLen 10 |
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24 |
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25 #define KMPEG1PackHeaderID 0x21 // 0010xxx1. See Doc Link 2. |
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26 #define KMPEG2PackHeaderID 0x44 // 01xxx1xx. See Doc Link 2. |
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27 |
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28 #define KStartCodeMask 0xffffff00 |
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29 #define KStartCodeIntro 0x00000100 |
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30 |
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31 #define KMPEG2StartCode1Bit KBit1 |
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32 #define KMPEG2StartCode2Bit KBit2 |
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33 #define KMPEG2VideoBit KBit3 |
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34 #define KMPEG2MPEG1Bit KBit4 |
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35 |
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36 // |
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37 // Mapping flags to a confidence level. |
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38 // |
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39 // A: extension match |
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40 // B: start-code1 |
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41 // C: start-code2 |
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42 // |
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43 // C B A -> Confidence |
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44 // ------------------- |
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45 // 0 0 0 -> ENotRecognised |
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46 // 0 0 1 -> EPossible |
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47 // 0 1 0 -> EPossible |
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48 // 0 1 1 -> EProbable |
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49 // 1 0 0 -> ENotRecognised |
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50 // 1 0 1 -> ENotRecognised |
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51 // 1 1 0 -> EProbable |
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52 // 1 1 1 -> ECertain |
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53 // |
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54 static const TInt KMPEG2FlagsToConfidence[] = |
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55 { |
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56 KConfNotRecognised, |
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57 KConfPossible, |
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58 KConfPossible, |
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59 KConfProbable, |
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60 KConfNotRecognised, |
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61 KConfNotRecognised, |
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62 KConfProbable, |
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63 KConfCertain |
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64 }; |
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65 |
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66 #define KMPEG2ConfidenceMask 0x07 // 00000111 |
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67 #define KMPEG2MimeMask 0x18 // 00011000 |
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68 #define KMPEG2MimeShift 0x03 |
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69 |
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70 static const TInt KMPEG2ExtOnlyIndex = 1; |
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71 |
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72 // |
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73 // The 'ED' bits of the flags member are used as an index into |
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74 // this table of possible MIME-types. |
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75 // |
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76 // E: MPEG1 instead of MPEG2 |
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77 // D: Video content present |
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78 // |
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79 // E D -> Mime |
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80 // ----------- |
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81 // 0 0 -> audio/mpeg2 |
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82 // 0 1 -> video/mpeg2 |
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83 // 1 0 -> audio/mpeg1 |
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84 // 1 1 -> video/mpeg1 |
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85 // |
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86 static const TText8* const KMPEG2Mimes[] = |
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87 { |
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88 KMimeMPEG2_A, |
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89 KMimeMPEG2_V, |
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90 KMimeMPEG1_A, |
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91 KMimeMPEG1_V |
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92 }; |
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93 |
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94 // |
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95 // A list of known MPEG2 file extensions. |
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96 // MPEG1 file extensions are also listed. |
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97 // |
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98 typedef struct |
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99 { |
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100 const TText* iExt; |
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101 const TText8* iMime; |
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102 } |
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103 TMPEG2Types; |
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104 |
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105 static const TMPEG2Types KMPEG2Types[] = |
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106 { |
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107 { KExtMPEG_1, KMimeMPEG2_V }, |
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108 { KExtMPEG_2, KMimeMPEG2_V }, |
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109 { KExtMPEG_3, KMimeMPEG2_V }, |
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110 { KExtMPEG_4, KMimeMPEG2_V }, |
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111 { KExtMPEG_5, KMimeMPEG2_V }, |
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112 { KExtMPEG_6, KMimeMPEG2_V }, |
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113 { KExtMPEG_7, KMimeMPEG1_V }, |
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114 { KExtMPEG_8, KMimeMPEG2_A } |
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115 }; |
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116 |
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117 #define KMPEG2ExtCount sizeof(KMPEG2Types) / sizeof(TMPEG2Types) |
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118 |
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119 |
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120 // |
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121 // |
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122 // |
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123 TMPEG2Parser::TMPEG2Parser(CReader& aReader, TFlags& aFlags) |
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124 : iReader(aReader), |
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125 iFlags(aFlags) |
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126 { |
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127 } |
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128 |
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129 |
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130 // |
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131 // Match the file's extension to known MPEG2 file extensions. |
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132 // |
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133 const TText8* TMPEG2Parser::MatchExtension(const TDesC& aExt) |
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134 { |
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135 if (aExt.Length() > 0) |
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136 { |
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137 for (TInt i = 0; i < KMPEG2ExtCount; i++) |
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138 { |
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139 if (aExt.MatchF(TPtrC(KMPEG2Types[i].iExt)) != KErrNotFound) |
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140 { |
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141 iFlags.SetExtensionFlag(); |
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142 return KMPEG2Types[i].iMime; |
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143 } |
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144 } |
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145 } |
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146 |
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147 return NULL; |
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148 } |
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149 |
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150 |
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151 // |
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152 // |
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153 // |
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154 void TMPEG2Parser::DoRecognise(const TDesC& aExt, CReader& aReader, TMatch& aMatch) |
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155 { |
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156 TFlags flags; |
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157 TMPEG2Parser parser(aReader, flags); |
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158 |
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159 const TText8* extMime = parser.MatchExtension(aExt); |
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160 TRAP_IGNORE(parser.ParseL()); |
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161 |
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162 TInt confIndex = flags.GetBitField(KMPEG2ConfidenceMask); |
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163 aMatch.iConfidence = KMPEG2FlagsToConfidence[confIndex]; |
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164 if (aMatch.iConfidence != KConfNotRecognised) |
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165 { |
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166 if (confIndex == KMPEG2ExtOnlyIndex) |
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167 { |
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168 // The content is corrupt, but the extension was recognised. |
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169 aMatch.iMime = extMime; |
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170 } |
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171 else |
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172 { |
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173 TInt mimeIndex = flags.GetBitField(KMPEG2MimeMask, KMPEG2MimeShift); |
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174 aMatch.iMime = KMPEG2Mimes[mimeIndex]; |
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175 } |
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176 } |
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177 } |
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178 |
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179 |
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180 // |
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181 // Attempts to parse an MPEG2 file by looking for start-codes. |
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182 // |
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183 void TMPEG2Parser::ParseL() |
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184 { |
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185 TBool finished; |
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186 |
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187 // Assume there's video content if we only have a buffer. |
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188 if (iReader.Type() == CReader::EBuffer) |
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189 { |
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190 iFlags.SetBit(KMPEG2VideoBit); |
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191 } |
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192 |
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193 do |
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194 { |
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195 finished = NextStartCodeL(); |
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196 } |
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197 while (!finished); |
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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 // Skips over the current start-code box. |
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203 // |
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204 void TMPEG2Parser::SkipL() |
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205 { |
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206 TUint16 size; |
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207 |
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208 iReader.Read16L(size); |
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209 iReader.SeekL((TInt)size); |
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210 } |
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211 |
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212 |
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213 /* |
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214 ** Expects an MPEG2 Pack Header at the current location. |
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215 ** The Pack Header is used to determine between MPEG1 and MPEG2. |
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216 */ |
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217 void TMPEG2Parser::ReadPackHeaderL() |
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218 { |
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219 TUint8 byte; |
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220 TBuf8<KMPEG2PackHeaderLen> header; // Size is of whichever is larger. |
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221 |
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222 iReader.ReadByteL(byte); |
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223 |
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224 if ((byte & KMPEG1PackHeaderID) == KMPEG1PackHeaderID) |
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225 { |
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226 iFlags.SetBit(KMPEG2MPEG1Bit); |
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227 header.SetLength(KMPEG1PackHeaderLen - 1); // We've already read a byte. |
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228 iReader.ReadBytesL(header); |
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229 } |
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230 else if ((byte & KMPEG2PackHeaderID) == KMPEG2PackHeaderID) |
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231 { |
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232 header.SetLength(KMPEG2PackHeaderLen - 1); // We've already read a byte. |
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233 iReader.ReadBytesL(header); |
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234 |
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235 // The lowest 3 bits of the last byte say how much stuffing is present. |
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236 TInt stuffing = header[8] & 0x07; // 00000111 |
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237 if (stuffing) |
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238 { |
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239 iReader.SeekL(stuffing); |
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240 } |
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241 } |
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242 else |
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243 { |
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244 User::Leave(KErrCorrupt); |
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245 } |
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246 |
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247 } |
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248 |
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249 // |
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250 // Start codes are bit patterns that do not occur in the video stream. |
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251 // The start-code sequence is expected to be at the current CReader position. |
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252 // |
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253 TBool TMPEG2Parser::NextStartCodeL() |
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254 { |
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255 TUint32 data; |
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256 |
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257 iReader.Read32L(data); |
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258 |
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259 // Start codes must begin with 0x000001ss, where 'ss' is the start code. |
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260 if ((data & KStartCodeMask) != KStartCodeIntro) |
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261 { |
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262 User::Leave(KErrCorrupt); |
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263 } |
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264 |
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265 if (!iFlags.GetBitField(KMPEG2StartCode1Bit)) |
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266 { |
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267 iFlags.SetBit(KMPEG2StartCode1Bit); |
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268 } |
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269 else |
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270 { |
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271 if (!iFlags.GetBitField(KMPEG2StartCode2Bit)) |
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272 { |
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273 iFlags.SetBit(KMPEG2StartCode2Bit); |
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274 } |
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275 } |
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276 |
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277 // Try to identify the start code. |
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278 switch (LOW_BYTE(data)) |
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279 { |
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280 case KPackStartCode: |
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281 ReadPackHeaderL(); |
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282 break; |
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283 |
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284 case KVideoElementaryStream: |
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285 iFlags.SetBit(KMPEG2VideoBit); |
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286 return ETrue; |
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287 |
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288 case KISOEndCode: |
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289 // This code should occur at the end of the file and |
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290 // it cannot be skipped over. |
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291 return ETrue; |
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292 |
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293 default: |
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294 SkipL(); |
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295 } |
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296 |
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297 return EFalse; |
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298 } |
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299 |