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<div class="title">h26x_bit_reader.h</div> </div>
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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// Copyright 2014 The Chromium Authors. All rights reserved.</span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">// Use of this source code is governed by a BSD-style license that can be</span></div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// found in the LICENSE file.</span></div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment">//</span></div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment">// This file contains an implementation of an H264 Annex-B video stream parser.</span></div>
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<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> </div>
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<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="preprocessor">#ifndef MEDIA_CODECS_H264_BIT_READER_H_</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="preprocessor"></span><span class="preprocessor">#define MEDIA_CODECS_H264_BIT_READER_H_</span></div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="preprocessor"></span></div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="preprocessor">#include <stdint.h></span></div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="preprocessor">#include <sys/types.h></span></div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> </div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="preprocessor">#include "packager/base/macros.h"</span></div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> </div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="keyword">namespace </span>shaka {</div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="keyword">namespace </span>media {</div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> </div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment">// A class to provide bit-granularity reading of H.264/H.265 streams.</span></div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="comment">// This is not a generic bit reader class, as it takes into account</span></div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="comment">// H.264 stream-specific constraints, such as skipping emulation-prevention</span></div>
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<div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="comment">// bytes and stop bits. See spec for more details.</span></div>
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<div class="line"><a name="l00022"></a><span class="lineno"><a class="line" href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html"> 22</a></span> <span class="keyword">class </span><a class="code" href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html">H26xBitReader</a> {</div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  <span class="keyword">public</span>:</div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>  <a class="code" href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html">H26xBitReader</a>();</div>
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<div class="line"><a name="l00025"></a><span class="lineno"> 25</span>  ~<a class="code" href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html">H26xBitReader</a>();</div>
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<div class="line"><a name="l00026"></a><span class="lineno"> 26</span> </div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>  <span class="comment">// Initialize the reader to start reading at |data|, |size| being size</span></div>
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<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  <span class="comment">// of |data| in bytes.</span></div>
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<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>  <span class="comment">// Return false on insufficient size of stream..</span></div>
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<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>  <span class="keywordtype">bool</span> Initialize(<span class="keyword">const</span> uint8_t* data, off_t size);</div>
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<div class="line"><a name="l00031"></a><span class="lineno"> 31</span> </div>
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<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>  <span class="comment">// Read |num_bits| next bits from stream and return in |*out|, first bit</span></div>
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<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  <span class="comment">// from the stream starting at |num_bits| position in |*out|.</span></div>
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<div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  <span class="comment">// |num_bits| may be 1-32, inclusive.</span></div>
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<div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="comment">// Return false if the given number of bits cannot be read (not enough</span></div>
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<div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="comment">// bits in the stream), true otherwise.</span></div>
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<div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  <span class="keywordtype">bool</span> ReadBits(<span class="keywordtype">int</span> num_bits, <span class="keywordtype">int</span>* out);</div>
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<div class="line"><a name="l00038"></a><span class="lineno"> 38</span> </div>
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<div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <span class="comment">// Read a single bit and return in |*out|.</span></div>
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<div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  <span class="comment">// Return false if the bit cannot be read (not enough bits in the stream),</span></div>
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<div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  <span class="comment">// true otherwise.</span></div>
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<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  <span class="keywordtype">bool</span> ReadBool(<span class="keywordtype">bool</span>* out) {</div>
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<div class="line"><a name="l00043"></a><span class="lineno"> 43</span>  <span class="keywordtype">int</span> value;</div>
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<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  <span class="keywordflow">if</span> (!ReadBits(1, &value))</div>
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<div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
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<div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  *out = (value != 0);</div>
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<div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
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<div class="line"><a name="l00048"></a><span class="lineno"> 48</span>  }</div>
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<div class="line"><a name="l00049"></a><span class="lineno"> 49</span> </div>
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<div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  <span class="comment">// Skips the given number of bits (does not have to be less than 32 bits).</span></div>
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<div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  <span class="comment">// Return false if there aren't enough bits in the stream, true otherwise.</span></div>
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<div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  <span class="keywordtype">bool</span> SkipBits(<span class="keywordtype">int</span> num_bits);</div>
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<div class="line"><a name="l00053"></a><span class="lineno"> 53</span> </div>
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<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  <span class="comment">// Exp-Golomb code parsing as specified in chapter 9.1 of the spec.</span></div>
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<div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  <span class="comment">// Read one unsigned exp-Golomb code from the stream and return in |*val|.</span></div>
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<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="keywordtype">bool</span> ReadUE(<span class="keywordtype">int</span>* val);</div>
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<div class="line"><a name="l00057"></a><span class="lineno"> 57</span> </div>
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<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>  <span class="comment">// Read one signed exp-Golomb code from the stream and return in |*val|.</span></div>
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<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  <span class="keywordtype">bool</span> ReadSE(<span class="keywordtype">int</span>* val);</div>
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<div class="line"><a name="l00060"></a><span class="lineno"> 60</span> </div>
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<div class="line"><a name="l00061"></a><span class="lineno"> 61</span>  <span class="comment">// Return the number of bits left in the stream.</span></div>
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<div class="line"><a name="l00062"></a><span class="lineno"> 62</span>  off_t NumBitsLeft();</div>
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<div class="line"><a name="l00063"></a><span class="lineno"> 63</span> </div>
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<div class="line"><a name="l00064"></a><span class="lineno"> 64</span>  <span class="comment">// See the definition of more_rbsp_data() in spec.</span></div>
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<div class="line"><a name="l00065"></a><span class="lineno"> 65</span>  <span class="keywordtype">bool</span> HasMoreRBSPData();</div>
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<div class="line"><a name="l00066"></a><span class="lineno"> 66</span> </div>
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<div class="line"><a name="l00067"></a><span class="lineno"> 67</span>  <span class="comment">// Return the number of emulation prevention bytes already read.</span></div>
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<div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  <span class="keywordtype">size_t</span> NumEmulationPreventionBytesRead();</div>
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<div class="line"><a name="l00069"></a><span class="lineno"> 69</span> </div>
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<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keyword">private</span>:</div>
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<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  <span class="comment">// Advance to the next byte, loading it into curr_byte_.</span></div>
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<div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  <span class="comment">// Return false on end of stream.</span></div>
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<div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  <span class="keywordtype">bool</span> UpdateCurrByte();</div>
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<div class="line"><a name="l00074"></a><span class="lineno"> 74</span> </div>
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<div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <span class="comment">// Pointer to the next unread (not in curr_byte_) byte in the stream.</span></div>
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<div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="keyword">const</span> uint8_t* data_;</div>
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<div class="line"><a name="l00077"></a><span class="lineno"> 77</span> </div>
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<div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="comment">// Bytes left in the stream (without the curr_byte_).</span></div>
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<div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  off_t bytes_left_;</div>
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<div class="line"><a name="l00080"></a><span class="lineno"> 80</span> </div>
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<div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  <span class="comment">// Contents of the current byte; first unread bit starting at position</span></div>
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<div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  <span class="comment">// 8 - num_remaining_bits_in_curr_byte_ from MSB.</span></div>
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<div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  <span class="keywordtype">int</span> curr_byte_;</div>
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<div class="line"><a name="l00084"></a><span class="lineno"> 84</span> </div>
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<div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  <span class="comment">// Number of bits remaining in curr_byte_</span></div>
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<div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  <span class="keywordtype">int</span> num_remaining_bits_in_curr_byte_;</div>
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<div class="line"><a name="l00087"></a><span class="lineno"> 87</span> </div>
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<div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  <span class="comment">// Used in emulation prevention three byte detection (see spec).</span></div>
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<div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  <span class="comment">// Initially set to 0xffff to accept all initial two-byte sequences.</span></div>
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<div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  <span class="keywordtype">int</span> prev_two_bytes_;</div>
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<div class="line"><a name="l00091"></a><span class="lineno"> 91</span> </div>
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<div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  <span class="comment">// Number of emulation preventation bytes (0x000003) we met.</span></div>
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<div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  <span class="keywordtype">size_t</span> emulation_prevention_bytes_;</div>
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<div class="line"><a name="l00094"></a><span class="lineno"> 94</span> </div>
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<div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  DISALLOW_COPY_AND_ASSIGN(<a class="code" href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html">H26xBitReader</a>);</div>
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<div class="line"><a name="l00096"></a><span class="lineno"> 96</span> };</div>
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<div class="line"><a name="l00097"></a><span class="lineno"> 97</span> </div>
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<div class="line"><a name="l00098"></a><span class="lineno"> 98</span> } <span class="comment">// namespace media</span></div>
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<div class="line"><a name="l00099"></a><span class="lineno"> 99</span> } <span class="comment">// namespace shaka</span></div>
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<div class="line"><a name="l00100"></a><span class="lineno"> 100</span> </div>
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<div class="line"><a name="l00101"></a><span class="lineno"> 101</span> <span class="preprocessor">#endif // MEDIA_CODECS_H264_BIT_READER_H_</span></div>
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<div class="ttc" id="classshaka_1_1media_1_1H26xBitReader_html"><div class="ttname"><a href="../../de/db4/classshaka_1_1media_1_1H26xBitReader.html">shaka::media::H26xBitReader</a></div><div class="ttdef"><b>Definition:</b> <a href="../../d1/dc2/h26x__bit__reader_8h_source.html#l00022">h26x_bit_reader.h:22</a></div></div>
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