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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 | 1x | /** * MP4 demuxer */ import { logger } from '../utils/logger'; import Event from '../events'; const UINT32_MAX = Math.pow(2, 32) - 1; class MP4Demuxer { constructor (observer, remuxer) { this.observer = observer; this.remuxer = remuxer; } resetTimeStamp (initPTS) { this.initPTS = initPTS; } resetInitSegment (initSegment, audioCodec, videoCodec, duration) { // jshint unused:false if (initSegment && initSegment.byteLength) { const initData = this.initData = MP4Demuxer.parseInitSegment(initSegment); // default audio codec if nothing specified // TODO : extract that from initsegment if (audioCodec == null) audioCodec = 'mp4a.40.5'; if (videoCodec == null) videoCodec = 'avc1.42e01e'; const tracks = {}; if (initData.audio && initData.video) { tracks.audiovideo = { container: 'video/mp4', codec: audioCodec + ',' + videoCodec, initSegment: duration ? initSegment : null }; } else { if (initData.audio) tracks.audio = { container: 'audio/mp4', codec: audioCodec, initSegment: duration ? initSegment : null }; if (initData.video) tracks.video = { container: 'video/mp4', codec: videoCodec, initSegment: duration ? initSegment : null }; } this.observer.trigger(Event.FRAG_PARSING_INIT_SEGMENT, { tracks }); } else { if (audioCodec) this.audioCodec = audioCodec; if (videoCodec) this.videoCodec = videoCodec; } } static probe (data) { // ensure we find a moof box in the first 16 kB return MP4Demuxer.findBox({ data: data, start: 0, end: Math.min(data.length, 16384) }, ['moof']).length > 0; } static bin2str (buffer) { return String.fromCharCode.apply(null, buffer); } static readUint16 (buffer, offset) { if (buffer.data) { offset += buffer.start; buffer = buffer.data; } const val = buffer[offset] << 8 | buffer[offset + 1]; return val < 0 ? 65536 + val : val; } static readUint32 (buffer, offset) { if (buffer.data) { offset += buffer.start; buffer = buffer.data; } const val = buffer[offset] << 24 | buffer[offset + 1] << 16 | buffer[offset + 2] << 8 | buffer[offset + 3]; return val < 0 ? 4294967296 + val : val; } static writeUint32 (buffer, offset, value) { if (buffer.data) { offset += buffer.start; buffer = buffer.data; } buffer[offset] = value >> 24; buffer[offset + 1] = (value >> 16) & 0xff; buffer[offset + 2] = (value >> 8) & 0xff; buffer[offset + 3] = value & 0xff; } // Find the data for a box specified by its path static findBox (data, path) { let results = [], i, size, type, end, subresults, start, endbox; if (data.data) { start = data.start; end = data.end; data = data.data; } else { start = 0; end = data.byteLength; } if (!path.length) { // short-circuit the search for empty paths return null; } for (i = start; i < end;) { size = MP4Demuxer.readUint32(data, i); type = MP4Demuxer.bin2str(data.subarray(i + 4, i + 8)); endbox = size > 1 ? i + size : end; if (type === path[0]) { if (path.length === 1) { // this is the end of the path and we've found the box we were // looking for results.push({ data: data, start: i + 8, end: endbox }); } else { // recursively search for the next box along the path subresults = MP4Demuxer.findBox({ data: data, start: i + 8, end: endbox }, path.slice(1)); if (subresults.length) results = results.concat(subresults); } } i = endbox; } // we've finished searching all of data return results; } static parseSegmentIndex (initSegment) { const moov = MP4Demuxer.findBox(initSegment, ['moov'])[0]; const moovEndOffset = moov ? moov.end : null; // we need this in case we need to chop of garbage of the end of current data let index = 0; let sidx = MP4Demuxer.findBox(initSegment, ['sidx']); let references; if (!sidx || !sidx[0]) return null; references = []; sidx = sidx[0]; const version = sidx.data[0]; // set initial offset, we skip the reference ID (not needed) index = version === 0 ? 8 : 16; const timescale = MP4Demuxer.readUint32(sidx, index); index += 4; // TODO: parse earliestPresentationTime and firstOffset // usually zero in our case let earliestPresentationTime = 0; let firstOffset = 0; if (version === 0) index += 8; else index += 16; // skip reserved index += 2; let startByte = sidx.end + firstOffset; const referencesCount = MP4Demuxer.readUint16(sidx, index); index += 2; for (let i = 0; i < referencesCount; i++) { let referenceIndex = index; const referenceInfo = MP4Demuxer.readUint32(sidx, referenceIndex); referenceIndex += 4; const referenceSize = referenceInfo & 0x7FFFFFFF; const referenceType = (referenceInfo & 0x80000000) >>> 31; if (referenceType === 1) { console.warn('SIDX has hierarchical references (not supported)'); return; } const subsegmentDuration = MP4Demuxer.readUint32(sidx, referenceIndex); referenceIndex += 4; references.push({ referenceSize, subsegmentDuration, // unscaled info: { duration: subsegmentDuration / timescale, start: startByte, end: startByte + referenceSize - 1 } }); startByte += referenceSize; // Skipping 1 bit for |startsWithSap|, 3 bits for |sapType|, and 28 bits // for |sapDelta|. referenceIndex += 4; // skip to next ref index = referenceIndex; } return { earliestPresentationTime, timescale, version, referencesCount, references, moovEndOffset }; } /** * Parses an MP4 initialization segment and extracts stream type and * timescale values for any declared tracks. Timescale values indicate the * number of clock ticks per second to assume for time-based values * elsewhere in the MP4. * * To determine the start time of an MP4, you need two pieces of * information: the timescale unit and the earliest base media decode * time. Multiple timescales can be specified within an MP4 but the * base media decode time is always expressed in the timescale from * the media header box for the track: * ``` * moov > trak > mdia > mdhd.timescale * moov > trak > mdia > hdlr * ``` * @param init {Uint8Array} the bytes of the init segment * @return {object} a hash of track type to timescale values or null if * the init segment is malformed. */ static parseInitSegment (initSegment) { let result = []; let traks = MP4Demuxer.findBox(initSegment, ['moov', 'trak']); traks.forEach(trak => { const tkhd = MP4Demuxer.findBox(trak, ['tkhd'])[0]; if (tkhd) { let version = tkhd.data[tkhd.start]; let index = version === 0 ? 12 : 20; let trackId = MP4Demuxer.readUint32(tkhd, index); const mdhd = MP4Demuxer.findBox(trak, ['mdia', 'mdhd'])[0]; if (mdhd) { version = mdhd.data[mdhd.start]; index = version === 0 ? 12 : 20; const timescale = MP4Demuxer.readUint32(mdhd, index); const hdlr = MP4Demuxer.findBox(trak, ['mdia', 'hdlr'])[0]; if (hdlr) { const hdlrType = MP4Demuxer.bin2str(hdlr.data.subarray(hdlr.start + 8, hdlr.start + 12)); let type = { 'soun': 'audio', 'vide': 'video' }[hdlrType]; if (type) { // extract codec info. TODO : parse codec details to be able to build MIME type let codecBox = MP4Demuxer.findBox(trak, ['mdia', 'minf', 'stbl', 'stsd']); if (codecBox.length) { codecBox = codecBox[0]; let codecType = MP4Demuxer.bin2str(codecBox.data.subarray(codecBox.start + 12, codecBox.start + 16)); logger.log(`MP4Demuxer:${type}:${codecType} found`); } result[trackId] = { timescale: timescale, type: type }; result[type] = { timescale: timescale, id: trackId }; } } } } }); return result; } /** * Determine the base media decode start time, in seconds, for an MP4 * fragment. If multiple fragments are specified, the earliest time is * returned. * * The base media decode time can be parsed from track fragment * metadata: * ``` * moof > traf > tfdt.baseMediaDecodeTime * ``` * It requires the timescale value from the mdhd to interpret. * * @param timescale {object} a hash of track ids to timescale values. * @return {number} the earliest base media decode start time for the * fragment, in seconds */ static getStartDTS (initData, fragment) { let trafs, baseTimes, result; // we need info from two childrend of each track fragment box trafs = MP4Demuxer.findBox(fragment, ['moof', 'traf']); // determine the start times for each track baseTimes = [].concat.apply([], trafs.map(function (traf) { return MP4Demuxer.findBox(traf, ['tfhd']).map(function (tfhd) { let id, scale, baseTime; // get the track id from the tfhd id = MP4Demuxer.readUint32(tfhd, 4); // assume a 90kHz clock if no timescale was specified scale = initData[id].timescale || 90e3; // get the base media decode time from the tfdt baseTime = MP4Demuxer.findBox(traf, ['tfdt']).map(function (tfdt) { let version, result; version = tfdt.data[tfdt.start]; result = MP4Demuxer.readUint32(tfdt, 4); if (version === 1) { result *= Math.pow(2, 32); result += MP4Demuxer.readUint32(tfdt, 8); } return result; })[0]; // convert base time to seconds return baseTime / scale; }); })); // return the minimum result = Math.min.apply(null, baseTimes); return isFinite(result) ? result : 0; } static offsetStartDTS (initData, fragment, timeOffset) { MP4Demuxer.findBox(fragment, ['moof', 'traf']).map(function (traf) { return MP4Demuxer.findBox(traf, ['tfhd']).map(function (tfhd) { // get the track id from the tfhd let id = MP4Demuxer.readUint32(tfhd, 4); // assume a 90kHz clock if no timescale was specified let timescale = initData[id].timescale || 90e3; // get the base media decode time from the tfdt MP4Demuxer.findBox(traf, ['tfdt']).map(function (tfdt) { let version = tfdt.data[tfdt.start]; let baseMediaDecodeTime = MP4Demuxer.readUint32(tfdt, 4); if (version === 0) { MP4Demuxer.writeUint32(tfdt, 4, baseMediaDecodeTime - timeOffset * timescale); } else { baseMediaDecodeTime *= Math.pow(2, 32); baseMediaDecodeTime += MP4Demuxer.readUint32(tfdt, 8); baseMediaDecodeTime -= timeOffset * timescale; baseMediaDecodeTime = Math.max(baseMediaDecodeTime, 0); const upper = Math.floor(baseMediaDecodeTime / (UINT32_MAX + 1)); const lower = Math.floor(baseMediaDecodeTime % (UINT32_MAX + 1)); MP4Demuxer.writeUint32(tfdt, 4, upper); MP4Demuxer.writeUint32(tfdt, 8, lower); } }); }); }); } // feed incoming data to the front of the parsing pipeline append (data, timeOffset, contiguous, accurateTimeOffset) { let initData = this.initData; if (!initData) { this.resetInitSegment(data, this.audioCodec, this.videoCodec, false); initData = this.initData; } let startDTS, initPTS = this.initPTS; if (initPTS === undefined) { let startDTS = MP4Demuxer.getStartDTS(initData, data); this.initPTS = initPTS = startDTS - timeOffset; this.observer.trigger(Event.INIT_PTS_FOUND, { initPTS: initPTS }); } MP4Demuxer.offsetStartDTS(initData, data, initPTS); startDTS = MP4Demuxer.getStartDTS(initData, data); this.remuxer.remux(initData.audio, initData.video, null, null, startDTS, contiguous, accurateTimeOffset, data); } destroy () {} } export default MP4Demuxer; |