1 /* |
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2 * Copyright (c) 2010 Ixonos Plc. |
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3 * All rights reserved. |
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4 * This component and the accompanying materials are made available |
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5 * under the terms of the "Eclipse Public License v1.0" |
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6 * which accompanies this distribution, and is available |
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7 * at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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8 * |
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9 * Initial Contributors: |
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10 * Nokia Corporation - Initial contribution |
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11 * |
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12 * Contributors: |
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13 * Ixonos Plc |
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14 * |
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15 * Description: |
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16 * H.263 sync code functions. |
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17 * |
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18 */ |
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19 |
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20 |
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21 |
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22 |
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23 #include "h263dConfig.h" |
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24 |
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25 #include "sync.h" |
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26 #include "errcodes.h" |
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27 #include "debug.h" |
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28 #include "biblin.h" |
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29 |
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30 |
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31 |
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32 /* |
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33 * Global functions |
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34 */ |
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35 |
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36 /* {{-output"sncCheckSync.txt"}} */ |
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37 /* |
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38 * sncCheckSync |
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39 * |
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40 * |
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41 * Parameters: |
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42 * buffer a pointer to a bit buffer structure |
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43 * numStuffBits the number of stuffing bits |
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44 * error error code |
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45 * |
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46 * Function: |
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47 * This function checks if the Picture Start Code (PSC), |
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48 * the End Of Sequence code (EOS) or the GOB synchronization code (GBSC) |
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49 * are the next codes in the bit buffer. |
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50 * Stuffing (PSTUF, ESTUF or GSTUF) is allowed before the code and |
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51 * the number of stuffing bits is returned in numStuffBits parameter. |
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52 * The code is not flushed from the buffer. |
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53 * |
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54 * Returns: |
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55 * SNC_NO_SYNC if no sync code is found |
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56 * SNC_PSC if PSC is found |
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57 * SNC_GBSC if GBSC is found |
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58 * SNC_EOS if EOS is found |
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59 * SNC_STUFFING if there are less than 8 zeros starting from |
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60 * the current position and after |
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61 * them the buffer ends |
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62 * |
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63 * Error codes: |
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64 * Error codes returned by bibFlushBits/bibGetBits/bibShowBits. |
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65 * |
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66 */ |
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67 |
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68 int sncCheckSync(bibBuffer_t *buffer, int *numStuffBits, int16 *error) |
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69 /* {{-output"sncCheckSync.txt"}} */ |
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70 { |
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71 u_int32 result; |
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72 int numBitsGot, i; |
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73 int16 newError = 0; |
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74 int bitErrorIndication = 0; |
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75 |
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76 for(i = 0; i < 8; i++) { |
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77 bitErrorIndication = 0; |
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78 result = bibShowBits(i + 22, buffer, &numBitsGot, &bitErrorIndication, |
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79 &newError); |
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80 if (result == 32) { |
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81 /* PSC */ |
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82 *numStuffBits = i; |
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83 return SNC_PSC; |
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84 } |
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85 |
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86 else if (result == 63) { |
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87 /* EOS */ |
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88 *numStuffBits = i; |
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89 return SNC_EOS; |
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90 } |
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91 |
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92 else if (result > 32 && result < 63) { |
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93 /* GBSC */ |
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94 /* Notice that the allowed Group Numbers are listed in section 5.2.3 |
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95 of the H.263 recommendation. They are not checked here but rather |
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96 they are assumed to be checked in the corresponding header reading |
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97 function, e.g. vdxGetGOBHeader. */ |
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98 *numStuffBits = i; |
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99 return SNC_GBSC; |
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100 } |
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101 |
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102 else if (result >= 64) { |
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103 return SNC_NO_SYNC; |
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104 } |
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105 else if ( buffer->error ) |
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106 { |
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107 // out of bits |
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108 *error = (int16)buffer->error; |
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109 return SNC_NO_SYNC; |
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110 } |
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111 } |
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112 |
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113 return SNC_NO_SYNC; |
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114 } |
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115 |
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116 |
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117 /* {{-output"sncRewindAndSeekNewSync.txt"}} */ |
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118 /* |
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119 * sncRewindAndSeekNewSync |
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120 * |
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121 * |
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122 * Parameters: |
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123 * earliestBitPos location of previously found sync code |
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124 * so no sense to rewind over it |
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125 * buffer a pointer to a bit buffer structure |
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126 * error error code |
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127 * |
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128 * Function: |
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129 * This function is intended to be called after GOB header is corrupted. |
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130 * It rewinds some (already read) bits in order not to miss any sync code. |
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131 * Then, this function finds the next Picture Start Code (PSC), |
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132 * End Of Sequence code (EOS) or Group of Blocks Start Code (GBSC) |
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133 * The function discards the bits before the synchronization code |
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134 * but does not remove the found code from the buffer. |
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135 * |
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136 * Returns: |
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137 * SNC_NO_SYNC if no PSC, EOS either GBSC was found and |
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138 * no more bits are available |
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139 * SNC_PSC if PSC is found |
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140 * SNC_GBSC if GBSC is found |
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141 * SNC_EOS if EOS is found |
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142 * |
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143 * Error codes: |
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144 * Error codes returned by bibFlushBits/bibGetBits/bibShowBits. |
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145 * |
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146 */ |
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147 |
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148 int sncRewindAndSeekNewSync(u_int32 earliestBitPos, bibBuffer_t *buffer, |
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149 int16 *error) |
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150 /* {{-output"sncRewindAndSeekNewSync.txt"}} */ |
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151 { |
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152 int sncCode; /* found sync code */ |
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153 u_int32 numRewindableBits; /* number of bits which can be rewinded */ |
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154 u_int32 bitPosBeforeRewinding; /* initial buffer bit index */ |
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155 u_int32 numBitsToRewind; /* number of bits to rewind before seeking the sync code */ |
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156 |
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157 *error = 0; |
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158 |
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159 bitPosBeforeRewinding = bibNumberOfFlushedBits(buffer); |
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160 |
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161 if ( bitPosBeforeRewinding > earliestBitPos+17 ) { |
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162 numBitsToRewind = bitPosBeforeRewinding - earliestBitPos - 17; |
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163 /* 17 is the sync code length, and one sync code exists in earliestBitPos => do not read it again */ |
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164 } |
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165 else if ( bitPosBeforeRewinding > earliestBitPos ) { |
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166 /* This might be possible in slice mode */ |
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167 numBitsToRewind = bitPosBeforeRewinding - earliestBitPos; |
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168 } |
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169 else { |
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170 /* Bit counter overrun? */ |
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171 numBitsToRewind = bitPosBeforeRewinding + (0xffffffff - earliestBitPos) - 17; |
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172 } |
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173 numRewindableBits = bibNumberOfRewBits(buffer); |
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174 |
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175 if (numRewindableBits < (u_int32) numBitsToRewind) |
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176 numBitsToRewind = (int) numRewindableBits; |
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177 |
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178 bibRewindBits(numBitsToRewind, buffer, error); |
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179 if (*error) |
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180 return SNC_NO_SYNC; |
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181 |
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182 /* Seek the next synchronization code */ |
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183 sncCode = sncSeekSync(buffer, error); |
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184 if (*error) |
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185 return sncCode; |
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186 |
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187 return sncCode; |
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188 } |
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189 |
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190 |
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191 /* {{-output"sncSeekFrameSync.txt"}} */ |
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192 /* |
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193 * sncSeekFrameSync |
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194 * |
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195 * |
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196 * Parameters: |
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197 * buffer a pointer to a bit buffer structure |
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198 * error error code |
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199 * |
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200 * Function: |
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201 * This function finds the next Picture Start Code (PSC) or |
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202 * End Of Sequence code (EOS) from the bit buffer. The function skips |
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203 * any other codes. It discards the bits before the found synchronization |
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204 * code but does not remove the found code from the buffer. |
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205 * |
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206 * Returns: |
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207 * SNC_NO_SYNC if no PSC or EOS was found and |
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208 * no more bits are available |
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209 * SNC_PSC if PSC is found |
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210 * SNC_EOS if EOS is found |
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211 * |
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212 * Error codes: |
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213 * Error codes returned by bibFlushBits/bibGetBits/bibShowBits. |
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214 * |
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215 */ |
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216 |
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217 int sncSeekFrameSync(bibBuffer_t *buffer, int16 *error) |
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218 /* {{-output"sncSeekFrameSync.txt"}} */ |
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219 { |
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220 int numBitsGot, syncCode, bitErrorIndication = 0; |
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221 int16 newError = 0; |
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222 |
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223 for (;;) { |
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224 syncCode = sncSeekSync(buffer, &newError); |
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225 |
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226 if (newError) { |
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227 *error = newError; |
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228 return SNC_NO_SYNC; |
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229 } |
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230 |
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231 if (syncCode == SNC_GBSC) { |
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232 bibFlushBits(17, buffer, &numBitsGot, &bitErrorIndication, &newError); |
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233 } |
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234 |
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235 else |
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236 return syncCode; |
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237 } |
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238 } |
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239 |
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240 |
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241 /* {{-output"sncSeekSync.txt"}} */ |
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242 /* |
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243 * sncSeekSync |
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244 * |
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245 * |
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246 * Parameters: |
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247 * buffer a pointer to a bit buffer structure |
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248 * error error code |
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249 * |
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250 * Function: |
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251 * This function finds the next Picture Start Code (PSC), |
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252 * End Of Sequence code (EOS) or Group of Blocks Start Code (GBSC) |
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253 * from the bit buffer. It discards the bits before the synchronization |
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254 * code but does not remove the found code from the buffer. |
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255 * |
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256 * Returns: |
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257 * SNC_NO_SYNC if no PSC, EOS either GBSC was found and |
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258 * no more bits are available |
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259 * SNC_PSC if PSC is found |
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260 * SNC_GBSC if GBSC is found |
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261 * SNC_EOS if EOS is found |
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262 * |
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263 * Error codes: |
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264 * Error codes returned by bibFlushBits/bibGetBits/bibShowBits. |
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265 * |
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266 */ |
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267 |
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268 int sncSeekSync(bibBuffer_t *buffer, int16 *error) |
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269 /* {{-output"sncSeekSync.txt"}} */ |
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270 { |
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271 u_int32 result; |
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272 int numBitsGot; |
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273 int16 newError = 0; |
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274 int bitErrorIndication = 0; |
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275 |
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276 for (;;) { |
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277 bitErrorIndication = 0; |
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278 result = bibShowBits(22, buffer, &numBitsGot, &bitErrorIndication, |
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279 &newError); |
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280 |
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281 |
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282 if (result == 32) { |
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283 /* PSC */ |
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284 return SNC_PSC; |
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285 } |
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286 |
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287 else if (result == 63) { |
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288 /* EOS */ |
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289 return SNC_EOS; |
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290 } |
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291 |
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292 else if (result > 32 && result < 63) { |
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293 /* GBSC */ |
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294 /* Notice that the allowed Group Numbers are listed in section 5.2.3 |
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295 of the H.263 recommendation. They are not checked here but rather |
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296 they are assumed to be checked in the corresponding header reading |
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297 function, e.g. vdxGetGOBHeader. */ |
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298 return SNC_GBSC; |
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299 } |
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300 else if ( buffer->error ) |
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301 { |
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302 // out of bits |
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303 *error = (int16)buffer->error; |
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304 return SNC_NO_SYNC; |
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305 } |
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306 |
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307 bibFlushBits(1, buffer, &numBitsGot, &bitErrorIndication, error); |
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308 } |
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309 } |
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310 |
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311 // End of file |
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