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niandeng
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mangui.hls.demux {
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//import by.blooddy.crypto.Base64;
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import com.hurlant.util.Base64;
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import flash.utils.ByteArray;
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CONFIG::LOGGING {
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import org.mangui.hls.utils.Log;
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}
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public class ID3 {
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public var len : int;
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public var hasTimestamp : Boolean = false;
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public var timestamp : Number;
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public var tags : Vector.<ID3Tag> = new Vector.<ID3Tag>();
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/* create ID3 object by parsing ByteArray, looking for ID3 tag length, and timestamp */
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public function ID3(data : ByteArray) {
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var tagSize : uint = 0;
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try {
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var pos : uint = data.position;
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var header : String;
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do {
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header = data.readUTFBytes(3);
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if (header == 'ID3') {
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// skip 24 bits
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data.position += 3;
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// retrieve tag(s) length
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var byte1 : uint = data.readUnsignedByte() & 0x7f;
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var byte2 : uint = data.readUnsignedByte() & 0x7f;
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var byte3 : uint = data.readUnsignedByte() & 0x7f;
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var byte4 : uint = data.readUnsignedByte() & 0x7f;
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tagSize = (byte1 << 21) + (byte2 << 14) + (byte3 << 7) + byte4;
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var endPos : uint = data.position + tagSize;
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CONFIG::LOGGING {
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Log.debug2("ID3 tag found, size/end pos:" + tagSize + "/" + endPos);
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}
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// read ID3 tags
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_parseID3Frames(data, endPos);
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data.position = endPos;
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} else if (header == '3DI') {
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// http://id3.org/id3v2.4.0-structure chapter 3.4. ID3v2 footer
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data.position += 7;
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CONFIG::LOGGING {
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Log.debug2("3DI footer found, end pos:" + data.position);
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}
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} else {
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data.position -= 3;
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len = data.position - pos;
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CONFIG::LOGGING {
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if (len) {
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Log.debug2("ID3 len:" + len);
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if (!hasTimestamp) {
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Log.warn("ID3 tag found, but no timestamp");
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}
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}
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}
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return;
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}
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} while (true);
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} catch(e : Error) {
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}
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len = 0;
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return;
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};
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/* Each Elementary Audio Stream segment MUST signal the timestamp of
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its first sample with an ID3 PRIV tag [ID3] at the beginning of
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the segment. The ID3 PRIV owner identifier MUST be
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"com.apple.streaming.transportStreamTimestamp". The ID3 payload
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MUST be a 33-bit MPEG-2 Program Elementary Stream timestamp
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expressed as a big-endian eight-octet number, with the upper 31
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bits set to zero.
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*/
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private function _parseID3Frames(data : ByteArray, endPos : uint) : void {
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while(data.position + 8 <= endPos) {
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var tag_id : String = data.readUTFBytes(4);
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var tag_len : int = data.readUnsignedInt();
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var tag_flags : int = data.readUnsignedShort();
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CONFIG::LOGGING {
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Log.debug("ID3 tag id:" + tag_id);
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}
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switch(tag_id) {
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case "PRIV":
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// owner should be "com.apple.streaming.transportStreamTimestamp"
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if (data.readUTFBytes(44) == 'com.apple.streaming.transportStreamTimestamp') {
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// smelling even better ! we found the right descriptor
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// skip null character (string end) + 3 first bytes
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data.position += 4;
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// timestamp is 33 bit expressed as a big-endian eight-octet number, with the upper 31 bits set to zero.
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var pts_33_bit : int = data.readUnsignedByte() & 0x1;
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hasTimestamp = true;
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timestamp = (data.readUnsignedInt() / 90);
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if (pts_33_bit) {
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timestamp += 47721858.84; // 2^32 / 90
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}
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timestamp = Math.round(timestamp);
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CONFIG::LOGGING {
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Log.debug("ID3 timestamp found:" + timestamp);
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}
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}
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break;
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default:
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var tag_data : * = null;
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var base64 : Boolean;
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var firstChar : String = tag_id.charAt(0);
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if(firstChar == 'T' || firstChar == 'W') {
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base64 = false;
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var cur_tag_pos : int;
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var end_tag_pos : int = data.position + tag_len;
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// skip character encoding byte
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data.position++;
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while(data.position < end_tag_pos - 1) {
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cur_tag_pos = data.position;
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var text : String = data.readUTFBytes(end_tag_pos-cur_tag_pos);
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if(tag_data) {
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tag_data += ',' + text;
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} else {
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tag_data = text;
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}
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data.position = cur_tag_pos + text.length + 1;
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}
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data.position = end_tag_pos;
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CONFIG::LOGGING {
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Log.debug2("id/data:" + tag_id + "/" + tag_data);
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}
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} else {
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base64 = true;
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tag_data = new ByteArray();
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data.readBytes(tag_data, 0, tag_len);
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tag_data=Base64.encode(tag_data);
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}
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var id3tag : ID3Tag = new ID3Tag(tag_id,tag_flags,base64,tag_data);
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tags.push(id3tag);
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break;
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}
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}
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}
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}
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}
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