isobmffManager.js

define(function() {
	
	var extractinit = function (ab) {
	  var d = new DataView(ab);
	  var pos = 0;
	  while (pos < ab.byteLength) {
		var type = d.getUint32(pos+4, false);
		if (type == 0x73696478 || type == 0x6d6f6f66)
		  break;
		pos += d.getUint32(pos, false);
	  }
	  return new Uint8Array(ab.slice(0, pos));
	}

	var parsesidx = function(ab, ab_first_byte_offset) {
	  var d = new DataView(ab);
	  var pos = 0;
	  while (d.getUint32(pos+4, false) != 0x73696478) {
		pos += d.getUint32(pos, false);
		if (pos >= ab.byteLength) throw "Could not find sidx";
	  }
	
	  var sidxEnd = d.getUint32(pos, false) + pos;
	  if (sidxEnd > ab.byteLength) throw "sidx terminates after array buffer";
	  var version = d.getUint8(pos+8);
	  pos += 12;
	
	  // skipped reference_ID(32)
	  var timescale = d.getUint32(pos+4, false);
	  pos += 8;
	
	  var earliest_presentation_time, first_offset;
	  if (version == 0) {
		earliest_presentation_time = d.getUint32(pos, false);
		first_offset = d.getUint32(pos+4, false);
		pos += 8;
	  } else {
		// TODO(strobe): Overflow checks
		earliest_presentation_time =
			(d.getUint32(pos, false) << 32) + d.getUint32(pos+4, false);
		first_offset =
			(d.getUint32(pos+8, false) << 32) + d.getUint32(pos+12, false);
		pos += 16;
	  }
	  first_offset += sidxEnd + (ab_first_byte_offset || 0);
	
	  // skipped reserved(16)
	  var reference_count = d.getUint16(pos+2, false);
	  pos += 4;
	
	  var offset = first_offset;
	  var time = earliest_presentation_time;
	  var references = [];
	  for (var i = 0; i < reference_count; i++) {
		var ref_size = d.getUint32(pos, false);
		var ref_type = ref_size & 0x80000000;
		if (ref_type) throw "Unhandled indirect reference";
		ref_size = ref_size & 0x7fffffff;
		var ref_dur = d.getUint32(pos+4, false);
		pos += 12;
		references.push({'size': ref_size, 'offset': offset,
						 'duration': ref_dur / timescale,
						 'time': time / timescale});
		offset += ref_size;
		time += ref_dur;
	  }
	  if (pos != sidxEnd)
		throw "Error: final pos " + pos + " differs from SIDX end " + sidxEnd;
	  return references;
	};
	
	return { parseSIDX : parsesidx, extractInit : extractinit };

} );