org.monte.media.mp3

Class MP3ElementaryInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

org.monte.media.mp3.MP3ElementaryInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class MP3ElementaryInputStream
extends FilterInputStream

Facilitates reading of an MP3 elementary stream frame by frame.

An MP3 frame has a 32-bit header with the following contents in big endian order:

• bit 31-21, MP3 Sync Word, all bits must be set
• bit 20-19, Version, 00=MPEG 2.5,01=reserved,10=MPEG 2, 11=MPEG 1
• bit 18-17, Layer, 00=reserved, 01=layer 3, 10=layer 2, 11=layer 1
• bit 16, Error protection, 0=16 bit CRC follows header, 1=Not protected
• bit 15-12, Bit Rate in kbps, interpretation depends on version and layer
• bit 11-10, Frequency, interpretation depends on version
• bit 9, Pad Bit, 0=frame is not padded, 1=frame is padded to exactly fit the bit rate
• bit 8, Private bit, only informative
• bit 7-6, Channel Mode, 00=stereo, 01=joint stereo, 10=dual channel (2 mono channels), 11=single channel (mono)
• bit 5-4, Mode Extension (only used with Joint Stereo), interpretation depends on version and layer
• bit 3, Copyright, 0=not copyrighted, 1=copyrighted
• bit 2, Original, 0=Copy of original media,1=original media
• bit 1-0, Emphasis, 00=none,01=50/15ms,10=reserved,11=CCIT J.17

Reference:
http://en.wikipedia.org/wiki/MP3
http://www.datavoyage.com/mpgscript/mpeghdr.htm
http://www.mp3-tech.org/programmer/frame_header.html
http://lame.sourceforge.net/tech-FAQ.txt
http://www.altera.com/literature/dc/1.4-2005_Taiwan_2nd_SouthernTaiwanU-web.pdf

Version:

1.1 2011-01-17 Renamed getHeader() to getHeaderCode().
1.0 2011-01-03 Created.

Author:

Werner Randelshofer

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MP3ElementaryInputStream.Frame An elementary frame.

Field Summary

Fields

Modifier and Type	Field and Description
static AudioFormat.Encoding	MP3 Defines the "MP3" encoding.

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor and Description
MP3ElementaryInputStream(File file)
MP3ElementaryInputStream(InputStream in)

Method Summary

Methods

Modifier and Type	Method and Description
AudioFormat	getFormat() Gets the format of the current frame.
MP3ElementaryInputStream.Frame	getFrame() Returns the current frame.
MP3ElementaryInputStream.Frame	getNextFrame() Gets the next frame from the input stream.
long	getStreamPosition() Returns the current position in the stream.
int	read() Reads a byte from the current frame (its header and its data).
int	read(byte[] b, int off, int len) Reads up to len bytes from the current frame (its header and its data).
void	readFully(byte[] b) Reads b.length bytes from the current frame (its header and its data).
void	readFully(byte[] b, int off, int len) Reads len bytes from the current frame (its header and its data).
long	skip(long n) Skips up to n bytes from the current frame (its header and its data).

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, read, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MP3

public static final AudioFormat.Encoding MP3

Defines the "MP3" encoding.

Constructor Detail

MP3ElementaryInputStream

public MP3ElementaryInputStream(File file)
                         throws IOException

Throws:

IOException

MP3ElementaryInputStream

public MP3ElementaryInputStream(InputStream in)

Method Detail

getNextFrame

public MP3ElementaryInputStream.Frame getNextFrame()
                                            throws IOException

Gets the next frame from the input stream. Positions the stream in front of the frame header.

Throws:

IOException

getFrame

public MP3ElementaryInputStream.Frame getFrame()

Returns the current frame.

getFormat

public AudioFormat getFormat()

Gets the format of the current frame. Returns null if the input stream is not positioned on a frame, or the frame is not valid.

Returns:

AudioFormat of current frame or null.

read

public int read()
         throws IOException

Reads a byte from the current frame (its header and its data). Returns -1 on an attempt to read past the end of the frame.

Overrides:

read in class FilterInputStream

Throws:

IOException

read

public int read(byte[] b,
       int off,
       int len)
         throws IOException

Reads up to len bytes from the current frame (its header and its data). May read less then len bytes. Returns the actual number of bytes read. Returns -1 on an attempt to read past the end of the frame.

Overrides:

read in class FilterInputStream

Throws:

IOException

readFully

public final void readFully(byte[] b)
                     throws IOException

Reads b.length bytes from the current frame (its header and its data).

Throws:

{@code - IOException} on an attempt to read past the end of the frame.

IOException

readFully

public final void readFully(byte[] b,
             int off,
             int len)
                     throws IOException

Reads len bytes from the current frame (its header and its data).

Throws:

{@code - IOException} on an attempt to read past the end of the frame.

IOException

skip

public long skip(long n)
          throws IOException

Skips up to n bytes from the current frame (its header and its data). Returns the actual number of bytes that have been skipped. Returns -1 on an attempt to skip past the end of the frame.

Overrides:

skip in class FilterInputStream

Throws:

IOException

getStreamPosition

public long getStreamPosition()

Returns the current position in the stream.

Returns:

The stream position.