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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 flash.utils.ByteArray;
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CONFIG::LOGGING {
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import org.mangui.hls.HLSSettings;
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import org.mangui.hls.utils.Log;
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}
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/** Constants and utilities for the H264 video format. **/
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public class Nalu {
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private static var _audNalu : ByteArray;
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// static initializer
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{
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_audNalu = new ByteArray();
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_audNalu.length = 2;
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_audNalu.writeByte(0x09);
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_audNalu.writeByte(0xF0);
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};
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/** Return an array with NAL delimiter indexes. **/
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public static function getNALU(nalu : ByteArray, position : uint) : Vector.<VideoFrame> {
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var len : uint = nalu.length,i : uint = position;
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var unitHeader : int,lastUnitHeader : int = 0;
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var unitStart : int,lastUnitStart : int = 0;
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var unitType : int,lastUnitType : int = 0;
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var audFound : Boolean = false;
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var value : uint,state : uint = 0;
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var units : Vector.<VideoFrame> = new Vector.<VideoFrame>();
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// Loop through data to find NAL startcodes.
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while (i < len) {
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// finding 3 or 4-byte start codes (00 00 01 OR 00 00 00 01)
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value = nalu[i++];
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switch(state)
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{
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case 0:
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if(!value) {
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state = 1;
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// unitHeader is NAL header offset
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unitHeader=i-1;
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}
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break;
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case 1:
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if(value) {
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state = 0;
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} else {
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state = 2;
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}
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break;
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case 2:
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case 3:
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if(value) {
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if(value === 1 && i < len) {
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unitType = nalu[i] & 0x1f;
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if(unitType == 9) {
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audFound = true;
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}
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if(lastUnitStart) {
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// use Math.min(4,...) as max header size is 4.
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// in case there are any leading zeros
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// such as 00 00 00 00 00 00 01
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// ^^
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// we need to ignore them as they are part of previous NAL unit
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units.push(new VideoFrame(Math.min(4,lastUnitStart-lastUnitHeader), i-state-1-lastUnitStart, lastUnitStart, lastUnitType));
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}
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lastUnitStart = i;
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lastUnitType = unitType;
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lastUnitHeader = unitHeader;
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if(audFound == true && (unitType === 1 || unitType === 5)) {
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// OPTI !!! if AUD unit already parsed and if IDR/NDR unit, consider it is last NALu
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i = len;
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}
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}
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state = 0;
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} else {
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state = 3;
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}
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break;
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default:
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break;
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}
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}
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//push last unit
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if(lastUnitStart) {
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units.push(new VideoFrame(Math.min(4,lastUnitStart-lastUnitHeader), len-lastUnitStart, lastUnitStart, lastUnitType));
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}
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// Reset position and return results.
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CONFIG::LOGGING {
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if (HLSSettings.logDebug2) {
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/** H264 NAL unit names. **/
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const NAMES : Array = ['Unspecified',// 0
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'NDR', // 1
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'Partition A', // 2
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'Partition B', // 3
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'Partition C', // 4
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'IDR', // 5
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'SEI', // 6
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'SPS', // 7
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'PPS', // 8
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'AUD', // 9
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'End of Sequence', // 10
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'End of Stream', // 11
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'Filler Data'// 12
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];
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if (units.length) {
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var txt : String = "AVC: ";
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for (i = 0; i < units.length; i++) {
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txt += NAMES[units[i].type] + ","; //+ ":" + units[i].length
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}
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Log.debug2(txt.substr(0,txt.length-1) + " slices");
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} else {
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Log.debug2('AVC: no NALU slices found');
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}
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}
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}
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nalu.position = position;
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return units;
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};
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public static function get AUD():ByteArray {
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return _audNalu;
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}
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/**
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* remove Emulation Prevention bytes from a RBSP
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*/
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public static function unescapeStream(data : ByteArray):ByteArray {
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var length : uint = data.length;
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var EPBPositions : Vector.<uint> = new Vector.<uint>();
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var i : uint = 1;
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var newLength : uint;
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var newData : ByteArray;
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// Find all `Emulation Prevention Bytes`
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while (i < length - 2) {
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if (data[i] === 0 &&
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data[i + 1] === 0 &&
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data[i + 2] === 0x03) {
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EPBPositions.push(i + 2);
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i += 2;
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} else {
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i++;
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}
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}
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// If no Emulation Prevention Bytes were found just return the original
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// array
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if (EPBPositions.length === 0) {
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return data;
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}
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// Create a new array to hold the NAL unit data
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newLength = length - EPBPositions.length;
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newData = new ByteArray();
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newData.length = newLength;
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var sourceIndex : uint = 0;
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for (i = 0; i < newLength; sourceIndex++, i++) {
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if (EPBPositions.length && sourceIndex === EPBPositions[0]) {
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// Skip this byte
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sourceIndex++;
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// Remove this position index
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EPBPositions.shift();
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}
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newData[i] = data[sourceIndex];
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}
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return newData;
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}
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}
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}
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