org.red5.io.mp3.MP3Header Maven / Gradle / Ivy
package org.red5.io.mp3;
/*
* RED5 Open Source Flash Server - http://code.google.com/p/red5/
*
* Copyright (c) 2006-2010 by respective authors (see below). All rights reserved.
*
* This library is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free Software
* Foundation; either version 2.1 of the License, or (at your option) any later
* version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
* PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along
* with this library; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/**
* Header of a MP3 frame.
*
* @author The Red5 Project ([email protected])
* @author Joachim Bauch ([email protected])
* @see File format
*/
public class MP3Header {
/**
* MP3 bitrates
*/
private static final int[][] BITRATES = {
{ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416,
448, -1 },
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320,
384, -1 },
{ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320,
-1 },
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224,
256, -1 },
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, -1 }, };
/**
* Sample rates
*/
private static final int[][] SAMPLERATES = {
// Version 2.5
{ 11025, 12000, 8000, -1 },
// Unknown version
{ -1, -1, -1, -1 },
// Version 2
{ 22050, 24000, 16000, -1 },
// Version 1
{ 44100, 48000, 32000, -1 }, };
/**
* Frame sync data
*/
private int data;
/**
* Audio version id
*/
private byte audioVersionId;
/**
* Layer description
*/
private byte layerDescription;
/**
* Protection bit
*/
private boolean protectionBit;
/**
* Bitrate used (index in array of bitrates)
*/
private byte bitRateIndex;
/**
* Sampling rate used (index in array of sample rates)
*/
private byte samplingRateIndex;
/**
* Padding bit
*/
private boolean paddingBit;
/**
* Channel mode
*/
private byte channelMode;
/**
* Creates MP3 header from frame sync value
* @param data Frame sync data
* @throws Exception On invalid frame synchronization
*/
public MP3Header(int data) throws Exception {
if ((data & 0xffe00000) != 0xffe00000) {
throw new Exception("invalid frame sync word");
}
this.data = data;
// Strip signed bit
data &= 0x1fffff;
audioVersionId = (byte) ((data >> 19) & 3);
layerDescription = (byte) ((data >> 17) & 3);
protectionBit = ((data >> 16) & 1) == 0;
bitRateIndex = (byte) ((data >> 12) & 15);
samplingRateIndex = (byte) ((data >> 10) & 3);
paddingBit = ((data >> 9) & 1) != 0;
channelMode = (byte) ((data >> 6) & 3);
}
/**
* Getter for frame sync word data
*
* @return Frame sync word data
*/
public int getData() {
return data;
}
/**
* Whether stereo playback mode is used
*
* @return true if stereo mode is used, false otherwise
*/
public boolean isStereo() {
return (channelMode != 3);
}
/**
* Whether MP3 has protection bit
*
* @return true if MP3 has protection bit, false otherwise
*/
public boolean isProtected() {
return protectionBit;
}
/**
* Getter for bitrate
*
* @return File bitrate
*/
public int getBitRate() {
int result;
switch (audioVersionId) {
case 1:
// Unknown
return -1;
case 0:
case 2:
// Version 2 or 2.5
if (layerDescription == 3) {
// Layer 1
result = BITRATES[3][bitRateIndex];
} else if (layerDescription == 2 || layerDescription == 1) {
// Layer 2 or 3
result = BITRATES[4][bitRateIndex];
} else {
// Unknown layer
return -1;
}
break;
case 3:
// Version 1
if (layerDescription == 3) {
// Layer 1
result = BITRATES[0][bitRateIndex];
} else if (layerDescription == 2) {
// Layer 2
result = BITRATES[1][bitRateIndex];
} else if (layerDescription == 1) {
// Layer 3
result = BITRATES[2][bitRateIndex];
} else {
// Unknown layer
return -1;
}
break;
default:
// Unknown version
return -1;
}
return result * 1000;
}
/**
* Getter for sample rate
*
* @return Sampling rate
*/
public int getSampleRate() {
return SAMPLERATES[audioVersionId][samplingRateIndex];
}
/**
* Calculate the size of a MP3 frame for this header.
*
* @return size of the frame including the header
*/
public int frameSize() {
switch (layerDescription) {
case 3:
// Layer 1
return (12 * getBitRate() / getSampleRate() + (paddingBit ? 1
: 0)) * 4;
case 2:
case 1:
// Layer 2 and 3
if (audioVersionId == 3) {
// MPEG 1
return 144 * getBitRate() / getSampleRate()
+ (paddingBit ? 1 : 0);
} else {
// MPEG 2 or 2.5
return 72 * getBitRate() / getSampleRate()
+ (paddingBit ? 1 : 0);
}
default:
// Unknown
return -1;
}
}
/**
* Return the duration of the frame for this header.
*
* @return The duration in milliseconds
*/
public double frameDuration() {
switch (layerDescription) {
case 3:
// Layer 1
return 384 / (getSampleRate() * 0.001);
case 2:
case 1:
if (audioVersionId == 3) {
// MPEG 1, Layer 2 and 3
return 1152 / (getSampleRate() * 0.001);
} else {
// MPEG 2 or 2.5, Layer 2 and 3
return 576 / (getSampleRate() * 0.001);
}
default:
// Unknown
return -1;
}
}
}
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