1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
8 * @param {MetadataDispatcher} parent Parent object.
11 function MpegParser(parent) {
12 MetadataParser.call(this, parent, 'mpeg', /\.(mp4|m4v|m4a|mpe?g4?)$/i);
13 this.mimeType = 'video/mpeg';
16 MpegParser.prototype = {__proto__: MetadataParser.prototype};
19 * Size of the atom header.
21 MpegParser.HEADER_SIZE = 8;
24 * @param {ByteReader} br ByteReader instance.
25 * @param {number=} opt_end End of atom position.
26 * @return {number} Atom size.
28 MpegParser.readAtomSize = function(br, opt_end) {
32 // Assert that opt_end <= buffer end.
33 // When supplied, opt_end is the end of the enclosing atom and is used to
34 // check the correct nesting.
35 br.validateRead(opt_end - pos);
38 var size = br.readScalar(4, false, opt_end);
40 if (size < MpegParser.HEADER_SIZE)
41 throw 'atom too short (' + size + ') @' + pos;
43 if (opt_end && pos + size > opt_end)
44 throw 'atom too long (' + size + '>' + (opt_end - pos) + ') @' + pos;
50 * @param {ByteReader} br ByteReader instance.
51 * @param {number=} opt_end End of atom position.
52 * @return {string} Atom name.
54 MpegParser.readAtomName = function(br, opt_end) {
55 return br.readString(4, opt_end).toLowerCase();
59 * @param {Object} metadata Metadata object.
60 * @return {Object} Root of the parser tree.
62 MpegParser.createRootParser = function(metadata) {
63 function findParentAtom(atom, name) {
66 if (!atom) return null;
67 if (atom.name == name) return atom;
71 function parseFtyp(br, atom) {
72 metadata.brand = br.readString(4, atom.end);
75 function parseMvhd(br, atom) {
76 var version = br.readScalar(4, false, atom.end);
77 var offset = (version == 0) ? 8 : 16;
78 br.seek(offset, ByteReader.SEEK_CUR);
79 var timescale = br.readScalar(4, false, atom.end);
80 var duration = br.readScalar(4, false, atom.end);
81 metadata.duration = duration / timescale;
84 function parseHdlr(br, atom) {
85 br.seek(8, ByteReader.SEEK_CUR);
86 findParentAtom(atom, 'trak').trackType = br.readString(4, atom.end);
89 function parseStsd(br, atom) {
90 var track = findParentAtom(atom, 'trak');
91 if (track && track.trackType == 'vide') {
92 br.seek(40, ByteReader.SEEK_CUR);
93 metadata.width = br.readScalar(2, false, atom.end);
94 metadata.height = br.readScalar(2, false, atom.end);
98 function parseDataString(name, br, atom) {
99 br.seek(8, ByteReader.SEEK_CUR);
100 metadata[name] = br.readString(atom.end - br.tell(), atom.end);
103 function parseCovr(br, atom) {
104 br.seek(8, ByteReader.SEEK_CUR);
105 metadata.thumbnailURL = br.readImage(atom.end - br.tell(), atom.end);
108 // 'meta' atom can occur at one of the several places in the file structure.
111 '©nam': { data: parseDataString.bind(null, 'title') },
112 '©alb': { data: parseDataString.bind(null, 'album') },
113 '©art': { data: parseDataString.bind(null, 'artist') },
114 'covr': { data: parseCovr }
119 // main parser for the entire file structure.
146 * @param {File} file File.
147 * @param {Object} metadata Metadata.
148 * @param {function(Object)} callback Success callback.
149 * @param {function} onError Error callback.
151 MpegParser.prototype.parse = function(file, metadata, callback, onError) {
152 this.rootParser_ = MpegParser.createRootParser(metadata);
154 // Kick off the processing by reading the first atom's header.
155 this.requestRead(file, 0, MpegParser.HEADER_SIZE, null,
156 onError, callback.bind(null, metadata));
160 * @param {function(ByteReader, Object)|Object} parser Parser tree node.
161 * @param {ByteReader} br ByteReader instance.
162 * @param {Object} atom Atom descriptor.
163 * @param {number} filePos File position of the atom start.
165 MpegParser.prototype.applyParser = function(parser, br, atom, filePos) {
167 var path = atom.name;
168 for (var p = atom.parent; p && p.name; p = p.parent) {
169 path = p.name + '.' + path;
174 action = 'skipping ';
175 } else if (parser instanceof Function) {
178 action = 'recursing';
181 var start = atom.start - MpegParser.HEADER_SIZE;
182 this.vlog(path + ': ' +
183 '@' + (filePos + start) + ':' + (atom.end - start),
188 if (parser instanceof Function) {
189 br.pushSeek(atom.start);
193 if (parser.versioned) {
196 this.parseMpegAtomsInRange(parser, br, atom, filePos);
202 * @param {function(ByteReader, Object)|Object} parser Parser tree node.
203 * @param {ByteReader} br ByteReader instance.
204 * @param {Object} parentAtom Parent atom descriptor.
205 * @param {number} filePos File position of the atom start.
207 MpegParser.prototype.parseMpegAtomsInRange = function(
208 parser, br, parentAtom, filePos) {
210 for (var offset = parentAtom.start; offset != parentAtom.end;) {
211 if (count++ > 100) // Most likely we are looping through a corrupt file.
212 throw 'too many child atoms in ' + parentAtom.name + ' @' + offset;
215 var size = MpegParser.readAtomSize(br, parentAtom.end);
216 var name = MpegParser.readAtomName(br, parentAtom.end);
221 { start: offset + MpegParser.HEADER_SIZE,
234 * @param {File} file File.
235 * @param {number} filePos Start position in the file.
236 * @param {number} size Atom size.
237 * @param {string} name Atom name.
238 * @param {function} onError Error callback.
239 * @param {function} onSuccess Success callback.
241 MpegParser.prototype.requestRead = function(
242 file, filePos, size, name, onError, onSuccess) {
244 var reader = new FileReader();
245 reader.onerror = onError;
246 reader.onload = function(event) {
247 self.processTopLevelAtom(
248 reader.result, file, filePos, size, name, onError, onSuccess);
250 this.vlog('reading @' + filePos + ':' + size);
251 reader.readAsArrayBuffer(file.slice(filePos, filePos + size));
255 * @param {ArrayBuffer} buf Data buffer.
256 * @param {File} file File.
257 * @param {number} filePos Start position in the file.
258 * @param {number} size Atom size.
259 * @param {string} name Atom name.
260 * @param {function} onError Error callback.
261 * @param {function} onSuccess Success callback.
263 MpegParser.prototype.processTopLevelAtom = function(
264 buf, file, filePos, size, name, onError, onSuccess) {
266 var br = new ByteReader(buf);
268 // the header has already been read.
269 var atomEnd = size - MpegParser.HEADER_SIZE;
271 var bufLength = buf.byteLength;
273 // Check the available data size. It should be either exactly
274 // what we requested or HEADER_SIZE bytes less (for the last atom).
275 if (bufLength != atomEnd && bufLength != size) {
276 throw 'Read failure @' + filePos + ', ' +
277 'requested ' + size + ', read ' + bufLength;
280 // Process the top level atom.
281 if (name) { // name is null only the first time.
283 this.rootParser_[name],
285 {start: 0, end: atomEnd, name: name},
290 filePos += bufLength;
291 if (bufLength == size) {
292 // The previous read returned everything we asked for, including
293 // the next atom header at the end of the buffer.
294 // Parse this header and schedule the next read.
295 br.seek(-MpegParser.HEADER_SIZE, ByteReader.SEEK_END);
296 var nextSize = MpegParser.readAtomSize(br);
297 var nextName = MpegParser.readAtomName(br);
299 // If we do not have a parser for the next atom, skip the content and
300 // read only the header (the one after the next).
301 if (!this.rootParser_[nextName]) {
302 filePos += nextSize - MpegParser.HEADER_SIZE;
303 nextSize = MpegParser.HEADER_SIZE;
306 this.requestRead(file, filePos, nextSize, nextName, onError, onSuccess);
308 // The previous read did not return the next atom header, EOF reached.
309 this.vlog('EOF @' + filePos);
313 onError(e.toString());
317 MetadataDispatcher.registerParserClass(MpegParser);