fi.helsinki.cs.ohtu.mpeg2.video
Class VLC

java.lang.Object
  fi.helsinki.cs.ohtu.mpeg2.video.VLC

public class VLC
extends java.lang.Object

VLC contains methods for writing to a BitOutputStream the various variable length codes used in MPEG-2 encoding.

Nested Class Summary

static class	VLC.DCTCoefficientTable These are the two variable length code tables used for coding DCT coefficients.
static class	VLC.IntraVLCFormat These are the two intra VLC format options.

Field Summary

private BitOutputStream

output

Constructor Summary

VLC(BitOutputStream bitStream)
Class constructor.

Method Summary

private int	abs(int a)
VLC.DCTCoefficientTable	getIntraTable(VLC.IntraVLCFormat format) Returns the variable length code table to use for intra blocks.
VLC.DCTCoefficientTable	getNonIntraTable() Returns the variable length code table to use for non intra blocks.
BitOutputStream	getStream() Gets the underlying stream the variable length codes are written to.
void	setStream(BitOutputStream stream) Sets the stream the variable length codes are written to.
void	writeCodedBlockPattern(boolean[] coded) Writes the coded block pattern variable length code to the stream.
void	writeDCTCoefficient(int run, int level, VLC.DCTCoefficientTable tableToUse, boolean dcCoefficient) Writes a single variable length code for a given run and level.
private void	writeDCTCoefficientTableOne(int run, int level)
private void	writeDCTCoefficientTableZero(int run, int level, boolean dcCoefficient)
void	writeDCTDcSizeChrominance(int dcSize) Writes the variable length code for a given size of a DC coefficient (in an intra block).
void	writeDCTDcSizeLuminance(int dcSize) Writes the variable length code for a given size of a DC coefficient (in an intra block).
void	writeDCTEndOfBlock(VLC.DCTCoefficientTable tableToUse)
private void	writeEscapedDCTCoefficient(int run, int level)
void	writeMacroblockAddressIncrement(int addressIncrement) Writes the variable length code of the given macroblock address increment to the stream.

Methods inherited from class java.lang.Object

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

Field Detail

output

private BitOutputStream output

Constructor Detail

VLC

public VLC(BitOutputStream bitStream)

Class constructor.

Parameters:

bitStream - The stream to write the variable length codes to

Method Detail

getStream

public BitOutputStream getStream()

Gets the underlying stream the variable length codes are written to. This is most useful for writing writeTo methods for things such as macroblocks, some fields of which are VL-coded while others are not. Naturally, both are always written to the same stream, so the stream returned by this function can be used for writing the non-VL-coded parts.

Returns:

The stream.

setStream

public void setStream(BitOutputStream stream)

Sets the stream the variable length codes are written to.

Parameters:

stream - The new stream to write to.

writeMacroblockAddressIncrement

public void writeMacroblockAddressIncrement(int addressIncrement)
                                     throws java.io.IOException

Writes the variable length code of the given macroblock address increment to the stream. This method writes a macroblock escape code floor(addressIncrement/33) times and then writes the variable length code for addressIncrement mod 33.

Parameters:

addressIncrement - The macroblock address increment to write. Must be greater than zero.

Throws:

java.io.IOException - Exception from the underlying stream

writeCodedBlockPattern

public void writeCodedBlockPattern(boolean[] coded)
                            throws java.io.IOException

Writes the coded block pattern variable length code to the stream. The order of the blocks is as follows:

Y:

0	1
2	3

Cb:

4

Cr:

5

Parameters:

coded - Indicates whether a given block is to be marked as coded. If coded[i], where i is a the number of the block, equals true then that block is coded in its macroblock.

Throws:

java.io.IOException - Exception from the underlying stream

writeDCTDcSizeLuminance

public void writeDCTDcSizeLuminance(int dcSize)
                             throws java.io.IOException

Writes the variable length code for a given size of a DC coefficient (in an intra block). This method is used for luminance blocks.

Parameters:

dcSize - Must be in range [0,11]

Throws:

java.io.IOException - Exception from the underlying stream

writeDCTDcSizeChrominance

public void writeDCTDcSizeChrominance(int dcSize)
                               throws java.io.IOException

Writes the variable length code for a given size of a DC coefficient (in an intra block). This method is used for chrominance blocks.

Parameters:

dcSize - Must be in range [0,11]

Throws:

java.io.IOException - Exception from the underlying stream

getIntraTable

public VLC.DCTCoefficientTable getIntraTable(VLC.IntraVLCFormat format)

Returns the variable length code table to use for intra blocks.

Parameters:

format - The intra VLC format to be used.

Returns:

The table that should be used.

getNonIntraTable

public VLC.DCTCoefficientTable getNonIntraTable()

Returns the variable length code table to use for non intra blocks.

Returns:

The table that should be used.

writeDCTCoefficient

public void writeDCTCoefficient(int run,
                                int level,
                                VLC.DCTCoefficientTable tableToUse,
                                boolean dcCoefficient)
                         throws java.io.IOException

Writes a single variable length code for a given run and level. The variable length code table zero uses an alternate code for DC coefficients of level 1.

Parameters:

run - The number of zeros preceding the non-zero coefficient. Must be in range [0,63].

level - The level of the non-zero coefficient. Must be in range [-2047,2047] and shall not be zero.

tableToUse - The variable length code table to use.

dcCoefficient - Whether the coefficient to be written is the DC coefficient of the block.

Throws:

java.io.IOException - Exception from the underlying stream

writeDCTEndOfBlock

public void writeDCTEndOfBlock(VLC.DCTCoefficientTable tableToUse)
                        throws java.io.IOException

Throws:

java.io.IOException

writeDCTCoefficientTableZero

private void writeDCTCoefficientTableZero(int run,
                                          int level,
                                          boolean dcCoefficient)
                                   throws java.io.IOException

Throws:

java.io.IOException

writeDCTCoefficientTableOne

private void writeDCTCoefficientTableOne(int run,
                                         int level)
                                  throws java.io.IOException

Throws:

java.io.IOException

abs

private int abs(int a)

writeEscapedDCTCoefficient

private void writeEscapedDCTCoefficient(int run,
                                        int level)
                                 throws java.io.IOException

Throws:

java.io.IOException