Generate an mfhd with a valid sequence number

Allow sequence numbers to be passed in during moof generation. Hook up the transmuxer to specify increasing sequence numbers as media segments are built.

 (function(window, videojs, undefined) {
 'use strict';
 
-var box, dinf, ftyp, mdat, minf, moof, moov, mvex, mvhd, trak, tkhd, mdia, mdhd, hdlr, stbl,
+var box, dinf, ftyp, mdat, mfhd, minf, moof, moov, mvex, mvhd, trak, tkhd, mdia, mdhd, hdlr, stbl,
     stsd, styp, types, MAJOR_BRAND, MINOR_VERSION, VIDEO_HDLR, AUDIO_HDLR, HDLR_TYPES, VMHD, DREF, STCO, STSC, STSZ, STTS, TREX,
     Uint8Array, DataView;
 
@@ -188,10 +188,20 @@ mdhd = function(duration) {
 mdia = function(duration, width, height, type) {
   return box(types.mdia, mdhd(duration), hdlr(type), minf(width, height));
 };
+mfhd = function(sequenceNumber) {
+  return box(types.mfhd, new Uint8Array([
+    0x00,
+    0x00, 0x00, 0x00, // flags
+    (sequenceNumber & 0xFF000000) >> 24,
+    (sequenceNumber & 0xFF0000) >> 16,
+    (sequenceNumber & 0xFF00) >> 8,
+    sequenceNumber & 0xFF, // sequence_number
+  ]));
+};
 minf = function(width, height) {
   return box(types.minf, box(types.vmhd, VMHD), dinf(), stbl(width, height));
 };
-moof = function(tracks) {
+moof = function(sequenceNumber, tracks) {
   var
     trafCall = [],
     i = tracks.length;
@@ -208,7 +218,7 @@ moof = function(tracks) {
   }
   trafCall.unshift(types.traf);
   return box(types.moof,
-             box(types.mfhd),
+             mfhd(sequenceNumber),
              box.apply(null, trafCall));
 };
 moov = function(duration, width, height, type) {

@@ -421,7 +421,10 @@ H264Stream.prototype = new videojs.Hls.Stream();
 
 
 Transmuxer = function() {
-  var self = this, packetStream, parseStream, programStream, aacStream, h264Stream;
+  var
+    self = this,
+    sequenceNumber = 0,
+    packetStream, parseStream, programStream, aacStream, h264Stream;
   Transmuxer.prototype.init.call(this);
 
   // set up the parsing pipeline
@@ -443,10 +446,15 @@ Transmuxer = function() {
   });
   h264Stream.on('data', function(data) {
     var
-      moof = mp4.moof([]),
+      moof = mp4.moof(sequenceNumber, []),
       mdat = mp4.mdat(data.data),
+      // it would be great to allocate this array up front instead of
+      // throwing away hundreds of media segment fragments
       boxes = new Uint8Array(moof.byteLength + mdat.byteLength);
 
+    // bump the sequence number for next time
+    sequenceNumber++;
+
     boxes.set(moof);
     boxes.set(mdat, moof.byteLength);
 

@@ -246,7 +246,7 @@ test('generates an initialization segment', function() {
 
 test('generates a minimal moof', function() {
   var
-    data = mp4.moof([{
+    data = mp4.moof(7, [{
       trackId: 1
     }, {
       trackId: 2
@@ -257,6 +257,7 @@ test('generates a minimal moof', function() {
   equal(moof[0].type, 'moof', 'generated a moof box');
   equal(moof[0].boxes.length, 2, 'generated two child boxes');
   equal(moof[0].boxes[0].type, 'mfhd', 'generated an mfhd box');
+  equal(moof[0].boxes[0].sequenceNumber, 7, 'included the sequence_number');
   equal(moof[0].boxes[1].type, 'traf', 'generated a traf box');
   equal(moof[0].boxes[1].boxes.length, 2, 'generated two fragment headers');
   equal(moof[0].boxes[1].boxes[0].type, 'tfhd', 'generated a tfhd box');
@@ -274,5 +275,4 @@ test('generates an mdat', function() {
   deepEqual(mdat[0].byteLength, 4, 'encapsulated the data');
 });
 
-
 })(window, window.videojs);

@@ -643,7 +643,10 @@ test('generates an init segment', function() {
 });
 
 test('parses an example mp2t file and generates media segments', function() {
-  var segments = [], i, boxes;
+  var
+    segments = [],
+    sequenceNumber = window.Infinity,
+    i, boxes, mfhd, traf, mdat;
   transmuxer.on('data', function(segment) {
     segments.push(segment);
   });
@@ -656,9 +659,16 @@ test('parses an example mp2t file and generates media segments', function() {
     boxes = videojs.inspectMp4(segments[i].data);
     equal(boxes.length, 2, 'segments are composed of two boxes');
     equal(boxes[0].type, 'moof', 'first box is a moof');
-    equal(boxes[0].boxes.length, 2, 'moof has three children');
-    equal(boxes[0].boxes[0].type, 'mfhd', 'mfhd is a child of the moof');
-    equal(boxes[0].boxes[1].type, 'traf', 'traf is a child of the moof');
+    equal(boxes[0].boxes.length, 2, 'the moof has two children');
+
+    mfhd = boxes[0].boxes[0];
+    equal(mfhd.type, 'mfhd', 'mfhd is a child of the moof');
+    ok(mfhd.sequenceNumber < sequenceNumber, 'sequence numbers are increasing');
+    sequenceNumber = mfhd.sequenceNumber;
+
+    traf = boxes[0].boxes[1];
+    equal(traf.type, 'traf', 'traf is a child of the moof');
+
     equal(boxes[1].type, 'mdat', 'second box is an mdat');
   }
 });