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module.audio-video.mpeg.php
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1 <?php
4 // available at http://getid3.sourceforge.net //
5 // or http://www.getid3.org //
7 // See readme.txt for more details //
9 // //
10 // module.audio-video.mpeg.php //
11 // module for analyzing MPEG files //
12 // dependencies: module.audio.mp3.php //
13 // ///
15 
16 getid3_lib::IncludeDependency(GETID3_INCLUDEPATH.'module.audio.mp3.php', __FILE__, true);
17 
18 define('GETID3_MPEG_VIDEO_PICTURE_START', "\x00\x00\x01\x00");
19 define('GETID3_MPEG_VIDEO_USER_DATA_START', "\x00\x00\x01\xB2");
20 define('GETID3_MPEG_VIDEO_SEQUENCE_HEADER', "\x00\x00\x01\xB3");
21 define('GETID3_MPEG_VIDEO_SEQUENCE_ERROR', "\x00\x00\x01\xB4");
22 define('GETID3_MPEG_VIDEO_EXTENSION_START', "\x00\x00\x01\xB5");
23 define('GETID3_MPEG_VIDEO_SEQUENCE_END', "\x00\x00\x01\xB7");
24 define('GETID3_MPEG_VIDEO_GROUP_START', "\x00\x00\x01\xB8");
25 define('GETID3_MPEG_AUDIO_START', "\x00\x00\x01\xC0");
26 
27 
28 class getid3_mpeg
29 {
30 
31  function getid3_mpeg(&$fd, &$ThisFileInfo) {
32  if ($ThisFileInfo['avdataend'] <= $ThisFileInfo['avdataoffset']) {
33  $ThisFileInfo['error'][] = '"avdataend" ('.$ThisFileInfo['avdataend'].') is unexpectedly less-than-or-equal-to "avdataoffset" ('.$ThisFileInfo['avdataoffset'].')';
34  return false;
35  }
36  $ThisFileInfo['fileformat'] = 'mpeg';
37  fseek($fd, $ThisFileInfo['avdataoffset'], SEEK_SET);
38  $MPEGstreamData = fread($fd, min(100000, $ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']));
39  $MPEGstreamDataLength = strlen($MPEGstreamData);
40 
41  $foundVideo = true;
42  $VideoChunkOffset = 0;
43  while (substr($MPEGstreamData, $VideoChunkOffset++, 4) !== GETID3_MPEG_VIDEO_SEQUENCE_HEADER) {
44  if ($VideoChunkOffset >= $MPEGstreamDataLength) {
45  $foundVideo = false;
46  break;
47  }
48  }
49  if ($foundVideo) {
50 
51  // Start code 32 bits
52  // horizontal frame size 12 bits
53  // vertical frame size 12 bits
54  // pixel aspect ratio 4 bits
55  // frame rate 4 bits
56  // bitrate 18 bits
57  // marker bit 1 bit
58  // VBV buffer size 10 bits
59  // constrained parameter flag 1 bit
60  // intra quant. matrix flag 1 bit
61  // intra quant. matrix values 512 bits (present if matrix flag == 1)
62  // non-intra quant. matrix flag 1 bit
63  // non-intra quant. matrix values 512 bits (present if matrix flag == 1)
64 
65  $ThisFileInfo['video']['dataformat'] = 'mpeg';
66 
67  $VideoChunkOffset += (strlen(GETID3_MPEG_VIDEO_SEQUENCE_HEADER) - 1);
68 
69  $FrameSizeDWORD = getid3_lib::BigEndian2Int(substr($MPEGstreamData, $VideoChunkOffset, 3));
70  $VideoChunkOffset += 3;
71 
72  $AspectRatioFrameRateDWORD = getid3_lib::BigEndian2Int(substr($MPEGstreamData, $VideoChunkOffset, 1));
73  $VideoChunkOffset += 1;
74 
75  $assortedinformation = getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 4));
76  $VideoChunkOffset += 4;
77 
78  $ThisFileInfo['mpeg']['video']['raw']['framesize_horizontal'] = ($FrameSizeDWORD & 0xFFF000) >> 12; // 12 bits for horizontal frame size
79  $ThisFileInfo['mpeg']['video']['raw']['framesize_vertical'] = ($FrameSizeDWORD & 0x000FFF); // 12 bits for vertical frame size
80  $ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio'] = ($AspectRatioFrameRateDWORD & 0xF0) >> 4;
81  $ThisFileInfo['mpeg']['video']['raw']['frame_rate'] = ($AspectRatioFrameRateDWORD & 0x0F);
82 
83  $ThisFileInfo['mpeg']['video']['framesize_horizontal'] = $ThisFileInfo['mpeg']['video']['raw']['framesize_horizontal'];
84  $ThisFileInfo['mpeg']['video']['framesize_vertical'] = $ThisFileInfo['mpeg']['video']['raw']['framesize_vertical'];
85 
86  $ThisFileInfo['mpeg']['video']['pixel_aspect_ratio'] = $this->MPEGvideoAspectRatioLookup($ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio']);
87  $ThisFileInfo['mpeg']['video']['pixel_aspect_ratio_text'] = $this->MPEGvideoAspectRatioTextLookup($ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio']);
88  $ThisFileInfo['mpeg']['video']['frame_rate'] = $this->MPEGvideoFramerateLookup($ThisFileInfo['mpeg']['video']['raw']['frame_rate']);
89 
90  $ThisFileInfo['mpeg']['video']['raw']['bitrate'] = getid3_lib::Bin2Dec(substr($assortedinformation, 0, 18));
91  $ThisFileInfo['mpeg']['video']['raw']['marker_bit'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 18, 1));
92  $ThisFileInfo['mpeg']['video']['raw']['vbv_buffer_size'] = getid3_lib::Bin2Dec(substr($assortedinformation, 19, 10));
93  $ThisFileInfo['mpeg']['video']['raw']['constrained_param_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 29, 1));
94  $ThisFileInfo['mpeg']['video']['raw']['intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 30, 1));
95  if ($ThisFileInfo['mpeg']['video']['raw']['intra_quant_flag']) {
96 
97  // read 512 bits
98  $ThisFileInfo['mpeg']['video']['raw']['intra_quant'] = getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 64));
99  $VideoChunkOffset += 64;
100 
101  $ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($ThisFileInfo['mpeg']['video']['raw']['intra_quant'], 511, 1));
102  $ThisFileInfo['mpeg']['video']['raw']['intra_quant'] = getid3_lib::Bin2Dec(substr($assortedinformation, 31, 1)).substr(getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 64)), 0, 511);
103 
104  if ($ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag']) {
105  $ThisFileInfo['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData, $VideoChunkOffset, 64);
106  $VideoChunkOffset += 64;
107  }
108 
109  } else {
110 
111  $ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 31, 1));
112  if ($ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag']) {
113  $ThisFileInfo['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData, $VideoChunkOffset, 64);
114  $VideoChunkOffset += 64;
115  }
116 
117  }
118 
119  if ($ThisFileInfo['mpeg']['video']['raw']['bitrate'] == 0x3FFFF) { // 18 set bits
120 
121  $ThisFileInfo['warning'][] = 'This version of getID3() ['.GETID3_VERSION.'] cannot determine average bitrate of VBR MPEG video files';
122  $ThisFileInfo['mpeg']['video']['bitrate_mode'] = 'vbr';
123 
124  } else {
125 
126  $ThisFileInfo['mpeg']['video']['bitrate'] = $ThisFileInfo['mpeg']['video']['raw']['bitrate'] * 400;
127  $ThisFileInfo['mpeg']['video']['bitrate_mode'] = 'cbr';
128  $ThisFileInfo['video']['bitrate'] = $ThisFileInfo['mpeg']['video']['bitrate'];
129 
130  }
131 
132  $ThisFileInfo['video']['resolution_x'] = $ThisFileInfo['mpeg']['video']['framesize_horizontal'];
133  $ThisFileInfo['video']['resolution_y'] = $ThisFileInfo['mpeg']['video']['framesize_vertical'];
134  $ThisFileInfo['video']['frame_rate'] = $ThisFileInfo['mpeg']['video']['frame_rate'];
135  $ThisFileInfo['video']['bitrate_mode'] = $ThisFileInfo['mpeg']['video']['bitrate_mode'];
136  $ThisFileInfo['video']['pixel_aspect_ratio'] = $ThisFileInfo['mpeg']['video']['pixel_aspect_ratio'];
137  $ThisFileInfo['video']['lossless'] = false;
138  $ThisFileInfo['video']['bits_per_sample'] = 24;
139 
140  } else {
141 
142  $ThisFileInfo['error'][] = 'Could not find start of video block in the first 100,000 bytes (or before end of file) - this might not be an MPEG-video file?';
143 
144  }
145 
146  //0x000001B3 begins the sequence_header of every MPEG video stream.
147  //But in MPEG-2, this header must immediately be followed by an
148  //extension_start_code (0x000001B5) with a sequence_extension ID (1).
149  //(This extension contains all the additional MPEG-2 stuff.)
150  //MPEG-1 doesn't have this extension, so that's a sure way to tell the
151  //difference between MPEG-1 and MPEG-2 video streams.
152 
153  if (substr($MPEGstreamData, $VideoChunkOffset, 4) == GETID3_MPEG_VIDEO_EXTENSION_START) {
154  $ThisFileInfo['video']['codec'] = 'MPEG-2';
155  } else {
156  $ThisFileInfo['video']['codec'] = 'MPEG-1';
157  }
158 
159 
160  $AudioChunkOffset = 0;
161  while (true) {
162  while (substr($MPEGstreamData, $AudioChunkOffset++, 4) !== GETID3_MPEG_AUDIO_START) {
163  if ($AudioChunkOffset >= $MPEGstreamDataLength) {
164  break 2;
165  }
166  }
167 
168  for ($i = 0; $i <= 7; $i++) {
169  // some files have the MPEG-audio header 8 bytes after the end of the $00 $00 $01 $C0 signature, some have it up to 13 bytes (or more?) after
170  // I have no idea why or what the difference is, so this is a stupid hack.
171  // If anybody has any better idea of what's going on, please let me know - info@getid3.org
172 
173  $dummy = $ThisFileInfo;
174  if (getid3_mp3::decodeMPEGaudioHeader($fd, ($AudioChunkOffset + 3) + 8 + $i, $dummy, false)) {
175  $ThisFileInfo = $dummy;
176  $ThisFileInfo['audio']['bitrate_mode'] = 'cbr';
177  $ThisFileInfo['audio']['lossless'] = false;
178  break 2;
179 
180  }
181  }
182  }
183 
184  // Temporary hack to account for interleaving overhead:
185  if (!empty($ThisFileInfo['video']['bitrate']) && !empty($ThisFileInfo['audio']['bitrate'])) {
186  $ThisFileInfo['playtime_seconds'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / ($ThisFileInfo['video']['bitrate'] + $ThisFileInfo['audio']['bitrate']);
187 
188  // Interleaved MPEG audio/video files have a certain amount of overhead that varies
189  // by both video and audio bitrates, and not in any sensible, linear/logarithmic patter
190  // Use interpolated lookup tables to approximately guess how much is overhead, because
191  // playtime is calculated as filesize / total-bitrate
192  $ThisFileInfo['playtime_seconds'] *= $this->MPEGsystemNonOverheadPercentage($ThisFileInfo['video']['bitrate'], $ThisFileInfo['audio']['bitrate']);
193 
194  //switch ($ThisFileInfo['video']['bitrate']) {
195  // case('5000000'):
196  // $multiplier = 0.93292642112380355828048824319889;
197  // break;
198  // case('5500000'):
199  // $multiplier = 0.93582895375200989965359777343219;
200  // break;
201  // case('6000000'):
202  // $multiplier = 0.93796247714820932532911373859139;
203  // break;
204  // case('7000000'):
205  // $multiplier = 0.9413264083635103463010117778776;
206  // break;
207  // default:
208  // $multiplier = 1;
209  // break;
210  //}
211  //$ThisFileInfo['playtime_seconds'] *= $multiplier;
212  //$ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be inaccurate. With current hack should be within a few seconds of accurate. Report to info@getid3.org if off by more than 10 seconds.';
213  if ($ThisFileInfo['video']['bitrate'] < 50000) {
214  $ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be slightly inaccurate for video bitrates below 100kbps. Except in extreme low-bitrate situations, error should be less than 1%. Report to info@getid3.org if greater than this.';
215  }
216  }
217 
218  return true;
219  }
220 
221 
222  function MPEGsystemNonOverheadPercentage($VideoBitrate, $AudioBitrate) {
223  $OverheadPercentage = 0;
224 
225  $AudioBitrate = max(min($AudioBitrate / 1000, 384), 32); // limit to range of 32kbps - 384kbps (should be only legal bitrates, but maybe VBR?)
226  $VideoBitrate = max(min($VideoBitrate / 1000, 10000), 10); // limit to range of 10kbps - 10Mbps (beyond that curves flatten anyways, no big loss)
227 
228 
229  //OMBB[audiobitrate] = array(video-10kbps, video-100kbps, video-1000kbps, video-10000kbps)
230  $OverheadMultiplierByBitrate[32] = array(0, 0.9676287944368530, 0.9802276264360310, 0.9844916183244460, 0.9852821845179940);
231  $OverheadMultiplierByBitrate[48] = array(0, 0.9779100089209830, 0.9787770035359320, 0.9846738664076130, 0.9852683013799960);
232  $OverheadMultiplierByBitrate[56] = array(0, 0.9731249855367600, 0.9776624308938040, 0.9832606361852130, 0.9843922606633340);
233  $OverheadMultiplierByBitrate[64] = array(0, 0.9755642683275760, 0.9795256705493390, 0.9836573009193170, 0.9851122539404470);
234  $OverheadMultiplierByBitrate[96] = array(0, 0.9788025247497290, 0.9798553314148700, 0.9822956869792560, 0.9834815119124690);
235  $OverheadMultiplierByBitrate[128] = array(0, 0.9816940050925480, 0.9821675936072120, 0.9829756927470870, 0.9839763420152050);
236  $OverheadMultiplierByBitrate[160] = array(0, 0.9825894094561180, 0.9820913399073960, 0.9823907143253970, 0.9832821783651570);
237  $OverheadMultiplierByBitrate[192] = array(0, 0.9832038474336260, 0.9825731694317960, 0.9821028622712400, 0.9828262076447620);
238  $OverheadMultiplierByBitrate[224] = array(0, 0.9836516298538770, 0.9824718601823890, 0.9818302180625380, 0.9823735101626480);
239  $OverheadMultiplierByBitrate[256] = array(0, 0.9845863022094920, 0.9837229411967540, 0.9824521662210830, 0.9828645172100790);
240  $OverheadMultiplierByBitrate[320] = array(0, 0.9849565280263180, 0.9837683142805110, 0.9822885275960400, 0.9824424382727190);
241  $OverheadMultiplierByBitrate[384] = array(0, 0.9856094774357600, 0.9844573394432720, 0.9825970399837330, 0.9824673808303890);
242 
243  $BitrateToUseMin = 32;
244  $BitrateToUseMax = 32;
245  $previousBitrate = 32;
246  foreach ($OverheadMultiplierByBitrate as $key => $value) {
247  if ($AudioBitrate >= $previousBitrate) {
248  $BitrateToUseMin = $previousBitrate;
249  }
250  if ($AudioBitrate < $key) {
251  $BitrateToUseMax = $key;
252  break;
253  }
254  $previousBitrate = $key;
255  }
256  $FactorA = ($BitrateToUseMax - $AudioBitrate) / ($BitrateToUseMax - $BitrateToUseMin);
257 
258  $VideoBitrateLog10 = log10($VideoBitrate);
259  $VideoFactorMin1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][floor($VideoBitrateLog10)];
260  $VideoFactorMin2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][floor($VideoBitrateLog10)];
261  $VideoFactorMax1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][ceil($VideoBitrateLog10)];
262  $VideoFactorMax2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][ceil($VideoBitrateLog10)];
263  $FactorV = $VideoBitrateLog10 - floor($VideoBitrateLog10);
264 
265  $OverheadPercentage = $VideoFactorMin1 * $FactorA * $FactorV;
266  $OverheadPercentage += $VideoFactorMin2 * (1 - $FactorA) * $FactorV;
267  $OverheadPercentage += $VideoFactorMax1 * $FactorA * (1 - $FactorV);
268  $OverheadPercentage += $VideoFactorMax2 * (1 - $FactorA) * (1 - $FactorV);
269 
270  return $OverheadPercentage;
271  }
272 
273 
274  function MPEGvideoFramerateLookup($rawframerate) {
275  $MPEGvideoFramerateLookup = array(0, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60);
276  return (isset($MPEGvideoFramerateLookup[$rawframerate]) ? (float) $MPEGvideoFramerateLookup[$rawframerate] : (float) 0);
277  }
278 
279  function MPEGvideoAspectRatioLookup($rawaspectratio) {
280  $MPEGvideoAspectRatioLookup = array(0, 1, 0.6735, 0.7031, 0.7615, 0.8055, 0.8437, 0.8935, 0.9157, 0.9815, 1.0255, 1.0695, 1.0950, 1.1575, 1.2015, 0);
281  return (isset($MPEGvideoAspectRatioLookup[$rawaspectratio]) ? (float) $MPEGvideoAspectRatioLookup[$rawaspectratio] : (float) 0);
282  }
283 
284  function MPEGvideoAspectRatioTextLookup($rawaspectratio) {
285  $MPEGvideoAspectRatioTextLookup = array('forbidden', 'square pixels', '0.6735', '16:9, 625 line, PAL', '0.7615', '0.8055', '16:9, 525 line, NTSC', '0.8935', '4:3, 625 line, PAL, CCIR601', '0.9815', '1.0255', '1.0695', '4:3, 525 line, NTSC, CCIR601', '1.1575', '1.2015', 'reserved');
286  return (isset($MPEGvideoAspectRatioTextLookup[$rawaspectratio]) ? $MPEGvideoAspectRatioTextLookup[$rawaspectratio] : '');
287  }
288 
289 }
290 
291 
292 ?>