refactor: dedupe code into modules for smaller vhs bundle (videojs#345)

starsw001 · Jun 16, 2020 · 040c506 · 040c506
1 parent 073e203
commit 040c506
Show file tree

Hide file tree

Showing 10 changed files with 312 additions and 270 deletions.
diff --git a/lib/mp4/caption-parser.js b/lib/mp4/caption-parser.js
@@ -11,7 +11,10 @@
 
 var discardEmulationPreventionBytes = require('../tools/caption-packet-parser').discardEmulationPreventionBytes;
 var CaptionStream = require('../m2ts/caption-stream').CaptionStream;
-var inspect = require('../tools/mp4-inspector');
+var findBox = require('../mp4/find-box.js');
+var parseTfdt = require('../tools/parse-tfdt.js');
+var parseTrun = require('../tools/parse-trun.js');
+var parseTfhd = require('../tools/parse-tfhd.js');
 
 /**
   * Maps an offset in the mdat to a sample based on the the size of the samples.
@@ -133,7 +136,7 @@ var parseSamples = function(truns, baseMediaDecodeTime, tfhd) {
     // Note: We currently do not parse the sample table as well
     // as the trun. It's possible some sources will require this.
     // moov > trak > mdia > minf > stbl
-    var trackRun = inspect.parseTrun(trun);
+    var trackRun = parseTrun(trun);
     var samples = trackRun.samples;
 
     samples.forEach(function(sample) {
@@ -169,9 +172,9 @@ var parseSamples = function(truns, baseMediaDecodeTime, tfhd) {
  **/
 var parseCaptionNals = function(segment, videoTrackId) {
   // To get the samples
-  var trafs = inspect.findBox(segment, ['moof', 'traf']);
+  var trafs = findBox(segment, ['moof', 'traf']);
   // To get SEI NAL units
-  var mdats = inspect.findBox(segment, ['mdat']);
+  var mdats = findBox(segment, ['mdat']);
   var captionNals = {};
   var mdatTrafPairs = [];
 
@@ -187,14 +190,14 @@ var parseCaptionNals = function(segment, videoTrackId) {
   mdatTrafPairs.forEach(function(pair) {
     var mdat = pair.mdat;
     var traf = pair.traf;
-    var tfhd = inspect.findBox(traf, ['tfhd']);
+    var tfhd = findBox(traf, ['tfhd']);
     // Exactly 1 tfhd per traf
-    var headerInfo = inspect.parseTfhd(tfhd[0]);
+    var headerInfo = parseTfhd(tfhd[0]);
     var trackId = headerInfo.trackId;
-    var tfdt = inspect.findBox(traf, ['tfdt']);
+    var tfdt = findBox(traf, ['tfdt']);
     // Either 0 or 1 tfdt per traf
-    var baseMediaDecodeTime = (tfdt.length > 0) ? inspect.parseTfdt(tfdt[0]).baseMediaDecodeTime : 0;
-    var truns = inspect.findBox(traf, ['trun']);
+    var baseMediaDecodeTime = (tfdt.length > 0) ? parseTfdt(tfdt[0]).baseMediaDecodeTime : 0;
+    var truns = findBox(traf, ['trun']);
     var samples;
     var seiNals;
 

diff --git a/lib/mp4/find-box.js b/lib/mp4/find-box.js
@@ -0,0 +1,44 @@
+var toUnsigned = require('../utils/bin').toUnsigned;
+var parseType = require('./parse-type.js');
+
+var findBox = function(data, path) {
+  var results = [],
+    i, size, type, end, subresults;
+
+  if (!path.length) {
+    // short-circuit the search for empty paths
+    return null;
+  }
+
+  for (i = 0; i < data.byteLength;) {
+    size = toUnsigned(data[i]     << 24 |
+      data[i + 1] << 16 |
+      data[i + 2] <<  8 |
+      data[i + 3]);
+
+    type = parseType(data.subarray(i + 4, i + 8));
+
+    end = size > 1 ? i + size : data.byteLength;
+
+    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.subarray(i + 8, end));
+      } else {
+        // recursively search for the next box along the path
+        subresults = findBox(data.subarray(i + 8, end), path.slice(1));
+        if (subresults.length) {
+          results = results.concat(subresults);
+        }
+      }
+    }
+    i = end;
+  }
+
+  // we've finished searching all of data
+  return results;
+};
+
+module.exports = findBox;
+
diff --git a/lib/mp4/parse-type.js b/lib/mp4/parse-type.js
@@ -0,0 +1,11 @@
+var parseType = function(buffer) {
+  var result = '';
+  result += String.fromCharCode(buffer[0]);
+  result += String.fromCharCode(buffer[1]);
+  result += String.fromCharCode(buffer[2]);
+  result += String.fromCharCode(buffer[3]);
+  return result;
+};
+
+
+module.exports = parseType;
diff --git a/lib/mp4/probe.js b/lib/mp4/probe.js
@@ -10,7 +10,11 @@
 
 var toUnsigned = require('../utils/bin').toUnsigned;
 var toHexString = require('../utils/bin').toHexString;
-var mp4Inspector = require('../tools/mp4-inspector.js');
+var findBox = require('../mp4/find-box.js');
+var parseType = require('../mp4/parse-type.js');
+var parseTfhd = require('../tools/parse-tfhd.js');
+var parseTrun = require('../tools/parse-trun.js');
+var parseTfdt = require('../tools/parse-tfdt.js');
 var timescale, startTime, compositionStartTime, getVideoTrackIds, getTracks,
   getTimescaleFromMediaHeader;
 
@@ -35,13 +39,13 @@ var timescale, startTime, compositionStartTime, getVideoTrackIds, getTracks,
 timescale = function(init) {
   var
     result = {},
-    traks = mp4Inspector.findBox(init, ['moov', 'trak']);
+    traks = findBox(init, ['moov', 'trak']);
 
   // mdhd timescale
   return traks.reduce(function(result, trak) {
     var tkhd, version, index, id, mdhd;
 
-    tkhd = mp4Inspector.findBox(trak, ['tkhd'])[0];
+    tkhd = findBox(trak, ['tkhd'])[0];
     if (!tkhd) {
       return null;
     }
@@ -52,7 +56,7 @@ timescale = function(init) {
                     tkhd[index + 2] <<  8 |
                     tkhd[index + 3]);
 
-    mdhd = mp4Inspector.findBox(trak, ['mdia', 'mdhd'])[0];
+    mdhd = findBox(trak, ['mdia', 'mdhd'])[0];
     if (!mdhd) {
       return null;
     }
@@ -86,11 +90,11 @@ startTime = function(timescale, fragment) {
   var trafs, baseTimes, result;
 
   // we need info from two childrend of each track fragment box
-  trafs = mp4Inspector.findBox(fragment, ['moof', 'traf']);
+  trafs = findBox(fragment, ['moof', 'traf']);
 
   // determine the start times for each track
   baseTimes = [].concat.apply([], trafs.map(function(traf) {
-    return mp4Inspector.findBox(traf, ['tfhd']).map(function(tfhd) {
+    return findBox(traf, ['tfhd']).map(function(tfhd) {
       var id, scale, baseTime;
 
       // get the track id from the tfhd
@@ -102,7 +106,7 @@ startTime = function(timescale, fragment) {
       scale = timescale[id] || 90e3;
 
       // get the base media decode time from the tfdt
-      baseTime = mp4Inspector.findBox(traf, ['tfdt']).map(function(tfdt) {
+      baseTime = findBox(traf, ['tfdt']).map(function(tfdt) {
         var version, result;
 
         version = tfdt[0];
@@ -151,7 +155,7 @@ startTime = function(timescale, fragment) {
  * @return {number} the composition start time for the fragment, in seconds
  **/
 compositionStartTime = function(timescales, fragment) {
-  var trafBoxes = mp4Inspector.findBox(fragment, ['moof', 'traf']);
+  var trafBoxes = findBox(fragment, ['moof', 'traf']);
   var baseMediaDecodeTime = 0;
   var compositionTimeOffset = 0;
   var trackId;
@@ -160,15 +164,27 @@ compositionStartTime = function(timescales, fragment) {
     // The spec states that track run samples contained within a `traf` box are contiguous, but
     // it does not explicitly state whether the `traf` boxes themselves are contiguous.
     // We will assume that they are, so we only need the first to calculate start time.
-    var parsedTraf = mp4Inspector.parseTraf(trafBoxes[0]);
-
-    for (var i = 0; i < parsedTraf.boxes.length; i++) {
-      if (parsedTraf.boxes[i].type === 'tfhd') {
-        trackId = parsedTraf.boxes[i].trackId;
-      } else if (parsedTraf.boxes[i].type === 'tfdt') {
-        baseMediaDecodeTime = parsedTraf.boxes[i].baseMediaDecodeTime;
-      } else if (parsedTraf.boxes[i].type === 'trun' && parsedTraf.boxes[i].samples.length) {
-        compositionTimeOffset = parsedTraf.boxes[i].samples[0].compositionTimeOffset || 0;
+    var tfhd = findBox(trafBoxes[0], ['tfhd'])[0];
+    var trun = findBox(trafBoxes[0], ['trun'])[0];
+    var tfdt = findBox(trafBoxes[0], ['tfdt'])[0];
+
+    if (tfhd) {
+      var parsedTfhd = parseTfhd(tfhd);
+
+      trackId = parsedTfhd.trackId;
+    }
+
+    if (tfdt) {
+      var parsedTfdt = parseTfdt(tfdt);
+
+      baseMediaDecodeTime = parsedTfdt.baseMediaDecodeTime;
+    }
+
+    if (trun) {
+      var parsedTrun = parseTrun(trun);
+
+      if (parsedTrun.samples && parsedTrun.samples.length) {
+        compositionTimeOffset = parsedTrun.samples[0].compositionTimeOffset || 0;
       }
     }
   }
@@ -193,15 +209,15 @@ compositionStartTime = function(timescales, fragment) {
   * @see ISO-BMFF-12/2015, Section 8.4.3
  **/
 getVideoTrackIds = function(init) {
-  var traks = mp4Inspector.findBox(init, ['moov', 'trak']);
+  var traks = findBox(init, ['moov', 'trak']);
   var videoTrackIds = [];
 
   traks.forEach(function(trak) {
-    var hdlrs = mp4Inspector.findBox(trak, ['mdia', 'hdlr']);
-    var tkhds = mp4Inspector.findBox(trak, ['tkhd']);
+    var hdlrs = findBox(trak, ['mdia', 'hdlr']);
+    var tkhds = findBox(trak, ['tkhd']);
 
     hdlrs.forEach(function(hdlr, index) {
-      var handlerType = mp4Inspector.parseType(hdlr.subarray(8, 12));
+      var handlerType = parseType(hdlr.subarray(8, 12));
       var tkhd = tkhds[index];
       var view;
       var version;
@@ -238,12 +254,12 @@ getTimescaleFromMediaHeader = function(mdhd) {
  * mp4 segment
  */
 getTracks = function(init) {
-  var traks = mp4Inspector.findBox(init, ['moov', 'trak']);
+  var traks = findBox(init, ['moov', 'trak']);
   var tracks = [];
 
   traks.forEach(function(trak) {
     var track = {};
-    var tkhd = mp4Inspector.findBox(trak, ['tkhd'])[0];
+    var tkhd = findBox(trak, ['tkhd'])[0];
     var view, tkhdVersion;
 
     // id
@@ -254,11 +270,11 @@ getTracks = function(init) {
       track.id = (tkhdVersion === 0) ? view.getUint32(12) : view.getUint32(20);
     }
 
-    var hdlr = mp4Inspector.findBox(trak, ['mdia', 'hdlr'])[0];
+    var hdlr = findBox(trak, ['mdia', 'hdlr'])[0];
 
     // type
     if (hdlr) {
-      var type = mp4Inspector.parseType(hdlr.subarray(8, 12));
+      var type = parseType(hdlr.subarray(8, 12));
 
       if (type === 'vide') {
         track.type = 'video';
@@ -271,14 +287,14 @@ getTracks = function(init) {
 
 
     // codec
-    var stsd = mp4Inspector.findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];
+    var stsd = findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];
 
     if (stsd) {
       var sampleDescriptions = stsd.subarray(8);
       // gives the codec type string
-      track.codec = mp4Inspector.parseType(sampleDescriptions.subarray(4, 8));
+      track.codec = parseType(sampleDescriptions.subarray(4, 8));
 
-      var codecBox = mp4Inspector.findBox(sampleDescriptions, [track.codec])[0];
+      var codecBox = findBox(sampleDescriptions, [track.codec])[0];
       var codecConfig, codecConfigType;
 
       if (codecBox) {
@@ -287,7 +303,7 @@ getTracks = function(init) {
           // we don't need anything but the "config" parameter of the
           // avc1 codecBox
           codecConfig = codecBox.subarray(78);
-          codecConfigType = mp4Inspector.parseType(codecConfig.subarray(4, 8));
+          codecConfigType = parseType(codecConfig.subarray(4, 8));
 
           if (codecConfigType === 'avcC' && codecConfig.length > 11) {
             track.codec += '.';
@@ -307,7 +323,7 @@ getTracks = function(init) {
         } else if ((/^mp4[a,v]$/i).test(track.codec)) {
           // we do not need anything but the streamDescriptor of the mp4a codecBox
           codecConfig = codecBox.subarray(28);
-          codecConfigType = mp4Inspector.parseType(codecConfig.subarray(4, 8));
+          codecConfigType = parseType(codecConfig.subarray(4, 8));
 
           if (codecConfigType === 'esds' && codecConfig.length > 20 && codecConfig[19] !== 0) {
             track.codec += '.' + toHexString(codecConfig[19]);
@@ -324,7 +340,7 @@ getTracks = function(init) {
       }
     }
 
-    var mdhd = mp4Inspector.findBox(trak, ['mdia', 'mdhd'])[0];
+    var mdhd = findBox(trak, ['mdia', 'mdhd'])[0];
 
     if (mdhd) {
       track.timescale = getTimescaleFromMediaHeader(mdhd);
@@ -338,8 +354,8 @@ getTracks = function(init) {
 
 module.exports = {
   // export mp4 inspector's findBox and parseType for backwards compatibility
-  findBox: mp4Inspector.findBox,
-  parseType: mp4Inspector.parseType,
+  findBox: findBox,
+  parseType: parseType,
   timescale: timescale,
   startTime: startTime,
   compositionStartTime: compositionStartTime,