Function WebM_Extract

runtime/html5/static/recorder-core.js:1273–1412

(inBytes, scope)

//=======从WebM字节流中提取pcm数据，提取成功返回Float32Array，失败返回null||-1=====
var WebM_Extract=function(inBytes, scope){
	if(!scope.pos){
		scope.pos=[0]; scope.tracks={}; scope.bytes=[];
	};
	var tracks=scope.tracks, position=[scope.pos[0]];
	var endPos=function(){ scope.pos[0]=position[0] };
	
	var sBL=scope.bytes.length;
	var bytes=new Uint8Array(sBL+inBytes.length);
	bytes.set(scope.bytes); bytes.set(inBytes,sBL);
	scope.bytes=bytes;
	
	//先读取文件头和Track信息
	if(!scope._ht){
		readMatroskaVInt(bytes, position);//EBML Header
		readMatroskaBlock(bytes, position);//跳过EBML Header内容
		if(!BytesEq(readMatroskaVInt(bytes, position), [0x18,0x53,0x80,0x67])){
			return;//未识别到Segment
		}
		readMatroskaVInt(bytes, position);//跳过Segment长度值
		while(position[0]<bytes.length){
			var eid0=readMatroskaVInt(bytes, position);
			var bytes0=readMatroskaBlock(bytes, position);
			var pos0=[0],audioIdx=0;
			if(!bytes0)return;//数据不全，等待缓冲
			//Track完整数据，循环读取TrackEntry
			if(BytesEq(eid0, [0x16,0x54,0xAE,0x6B])){
				while(pos0[0]<bytes0.length){
					var eid1=readMatroskaVInt(bytes0, pos0);
					var bytes1=readMatroskaBlock(bytes0, pos0);
					var pos1=[0],track={channels:0,sampleRate:0};
					if(BytesEq(eid1, [0xAE])){//TrackEntry
						while(pos1[0]<bytes1.length){
							var eid2=readMatroskaVInt(bytes1, pos1);
							var bytes2=readMatroskaBlock(bytes1, pos1);
							var pos2=[0];
							if(BytesEq(eid2, [0xD7])){//Track Number
								var val=BytesInt(bytes2);
								track.number=val;
								tracks[val]=track;
							}else if(BytesEq(eid2, [0x83])){//Track Type
								var val=BytesInt(bytes2);
								if(val==1) track.type="video";
								else if(val==2) {
									track.type="audio";
									if(!audioIdx) scope.track0=track;
									track.idx=audioIdx++;
								}else track.type="Type-"+val;
							}else if(BytesEq(eid2, [0x86])){//Track Codec
								var str="";
								for(var i=0;i<bytes2.length;i++){
									str+=String.fromCharCode(bytes2[i]);
								}
								track.codec=str;
							}else if(BytesEq(eid2, [0xE1])){
								while(pos2[0]<bytes2.length){//循环读取 Audio 属性
									var eid3=readMatroskaVInt(bytes2, pos2);
									var bytes3=readMatroskaBlock(bytes2, pos2);