144 lines
3.7 KiB
JavaScript
144 lines
3.7 KiB
JavaScript
/**
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* mux.js
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*
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* Copyright (c) 2016 Brightcove
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* All rights reserved.
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*
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* A stream-based aac to mp4 converter. This utility can be used to
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* deliver mp4s to a SourceBuffer on platforms that support native
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* Media Source Extensions.
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*/
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'use strict';
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var Stream = require('../utils/stream.js');
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// Constants
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var AacStream;
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/**
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* Splits an incoming stream of binary data into ADTS and ID3 Frames.
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*/
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AacStream = function() {
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var
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everything = new Uint8Array(),
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timeStamp = 0;
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AacStream.prototype.init.call(this);
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this.setTimestamp = function(timestamp) {
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timeStamp = timestamp;
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};
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this.parseId3TagSize = function(header, byteIndex) {
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var
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returnSize = (header[byteIndex + 6] << 21) |
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(header[byteIndex + 7] << 14) |
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(header[byteIndex + 8] << 7) |
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(header[byteIndex + 9]),
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flags = header[byteIndex + 5],
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footerPresent = (flags & 16) >> 4;
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if (footerPresent) {
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return returnSize + 20;
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}
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return returnSize + 10;
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};
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this.parseAdtsSize = function(header, byteIndex) {
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var
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lowThree = (header[byteIndex + 5] & 0xE0) >> 5,
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middle = header[byteIndex + 4] << 3,
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highTwo = header[byteIndex + 3] & 0x3 << 11;
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return (highTwo | middle) | lowThree;
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};
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this.push = function(bytes) {
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var
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frameSize = 0,
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byteIndex = 0,
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bytesLeft,
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chunk,
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packet,
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tempLength;
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// If there are bytes remaining from the last segment, prepend them to the
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// bytes that were pushed in
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if (everything.length) {
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tempLength = everything.length;
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everything = new Uint8Array(bytes.byteLength + tempLength);
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everything.set(everything.subarray(0, tempLength));
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everything.set(bytes, tempLength);
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} else {
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everything = bytes;
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}
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while (everything.length - byteIndex >= 3) {
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if ((everything[byteIndex] === 'I'.charCodeAt(0)) &&
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(everything[byteIndex + 1] === 'D'.charCodeAt(0)) &&
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(everything[byteIndex + 2] === '3'.charCodeAt(0))) {
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// Exit early because we don't have enough to parse
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// the ID3 tag header
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if (everything.length - byteIndex < 10) {
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break;
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}
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// check framesize
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frameSize = this.parseId3TagSize(everything, byteIndex);
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// Exit early if we don't have enough in the buffer
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// to emit a full packet
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if (frameSize > everything.length) {
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break;
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}
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chunk = {
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type: 'timed-metadata',
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data: everything.subarray(byteIndex, byteIndex + frameSize)
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};
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this.trigger('data', chunk);
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byteIndex += frameSize;
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continue;
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} else if ((everything[byteIndex] & 0xff === 0xff) &&
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((everything[byteIndex + 1] & 0xf0) === 0xf0)) {
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// Exit early because we don't have enough to parse
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// the ADTS frame header
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if (everything.length - byteIndex < 7) {
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break;
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}
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frameSize = this.parseAdtsSize(everything, byteIndex);
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// Exit early if we don't have enough in the buffer
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// to emit a full packet
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if (frameSize > everything.length) {
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break;
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}
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packet = {
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type: 'audio',
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data: everything.subarray(byteIndex, byteIndex + frameSize),
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pts: timeStamp,
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dts: timeStamp
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};
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this.trigger('data', packet);
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byteIndex += frameSize;
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continue;
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}
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byteIndex++;
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}
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bytesLeft = everything.length - byteIndex;
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if (bytesLeft > 0) {
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everything = everything.subarray(byteIndex);
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} else {
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everything = new Uint8Array();
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}
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};
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};
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AacStream.prototype = new Stream();
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module.exports = AacStream;
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