feat: add firstSequenceNumber option to Transmuxer to start sequence …

…somewhere other than zero (#395)

Adds an option `firstSequenceNumber` to Transmuxer.

Can be used like this:

new Transmuxer({ firstSequenceNumber: 10 });

This is passed in to VideoSegmentStream and AudioSegmentStream.

When mfhd boxes are constructed, the starting sequence number will be
taken from that option. The default value is zero.

This is useful for generating segmented streams out of order. Out of
oder processing allows for restart, parallelism, or random seeking into
source material.

lib/mp4/transmuxer.js

@@ -92,13 +92,15 @@ var generateSegmentTimingInfo = function(
 AudioSegmentStream = function(track, options) {
  var
  adtsFrames = [],
- sequenceNumber = 0,
+ sequenceNumber,
  earliestAllowedDts = 0,
  audioAppendStartTs = 0,
  videoBaseMediaDecodeTime = Infinity;
 
  options = options || {};
 
+ sequenceNumber = options.firstSequenceNumber || 0;
+
  AudioSegmentStream.prototype.init.call(this);
 
  this.push = function(data) {
@@ -227,14 +229,16 @@ AudioSegmentStream.prototype = new Stream();
  */
 VideoSegmentStream = function(track, options) {
  var
- sequenceNumber = 0,
+ sequenceNumber,
  nalUnits = [],
  gopsToAlignWith = [],
  config,
  pps;
 
  options = options || {};
 
+ sequenceNumber = options.firstSequenceNumber || 0;
+
  VideoSegmentStream.prototype.init.call(this);
 
  delete track.minPTS;

test/transmuxer.test.js

@@ -3427,6 +3427,64 @@ QUnit.test('no options creates combined output', function(assert) {
  assert.equal('mdat', boxes[3].type, 'generated a second mdat box');
 });
 
+QUnit.test('first sequence number option is used in mfhd box', function(assert) {
+ var
+ segments = [],
+ mfhds = [],
+ boxes,
+ transmuxer = new Transmuxer({ firstSequenceNumber: 10 });
+
+ transmuxer.on('data', function(segment) {
+ segments.push(segment);
+ });
+ transmuxer.push(packetize(PAT));
+ transmuxer.push(packetize(generatePMT({
+ hasVideo: true,
+ hasAudio: true
+ })));
+
+ transmuxer.push(packetize(audioPes([
+ 0x19, 0x47
+ ], true)));
+ transmuxer.push(packetize(videoPes([
+ 0x09, 0x01 // access_unit_delimiter_rbsp
+ ], true)));
+ transmuxer.push(packetize(videoPes([
+ 0x08, 0x01 // pic_parameter_set_rbsp
+ ], true)));
+ transmuxer.push(packetize(videoPes([
+ 0x07, // seq_parameter_set_rbsp
+ 0x27, 0x42, 0xe0, 0x0b,
+ 0xa9, 0x18, 0x60, 0x9d,
+ 0x80, 0x53, 0x06, 0x01,
+ 0x06, 0xb6, 0xc2, 0xb5,
+ 0xef, 0x7c, 0x04
+ ], false)));
+ transmuxer.push(packetize(videoPes([
+ 0x05, 0x01 // slice_layer_without_partitioning_rbsp_idr
+ ], true)));
+ transmuxer.flush();
+
+ assert.equal(segments.length, 1, 'generated a combined video and audio segment');
+ assert.equal(segments[0].type, 'combined', 'combined is the segment type');
+
+ boxes = mp4.tools.inspect(segments[0].data);
+ boxes.forEach(function(box) {
+ if (box.type === 'moof') {
+ box.boxes.forEach(function(moofBox) {
+ if (moofBox.type === 'mfhd') {
+ mfhds.push(moofBox);
+ }
+ });
+ }
+ });
+
+ assert.equal(mfhds.length, 2, 'muxed output has two mfhds');
+
+ assert.equal(mfhds[0].sequenceNumber, 10, 'first mfhd sequence starts at 10');
+ assert.equal(mfhds[1].sequenceNumber, 10, 'second mfhd sequence starts at 10');
+});
+
 QUnit.test('can specify that we want to generate separate audio and video segments', function(assert) {
  var
  segments = [],