qccenthuffmanencode.3

spiht for linux this is used to decod and encode vedio i wich all enjoy

.TH QCCENTHUFFMANENCODE 3 "QCCPACK" ""
.SH NAME
QccENTHuffmanEncode, QccENTHuffmanDecode \- 
Huffman encoding and decoding
.SH SYNOPSIS
.B #include "libQccPack.h"
.sp
.BI "int QccENTHuffmanEncode(QccBitBuffer *" output_buffer ", const int *" symbols ", int " num_symbols ", const QccENTHuffmanTable *" table );
.br
.BI "int QccENTHuffmanDecode(QccBitBuffer *" input_buffer ", int *" symbols ", int " num_symbols ", const QccENTHuffmanTable *" table );
.SH DESCRIPTION
.BR QccENTHuffmanEncode()
performs Huffman coding of the symbol stream in
.IR symbols ,
outputting the binary codewords to
.IR output_buffer .
.I num_symbols
indicates how many symbols are in the symbol stream (which can be
as short as one symbol).
.I output_buffer
must be a
.BR QccBitBuffer
that has been opened for writing prior to calling
.BR QccENTHuffmanEncode() .
Finally,
.I table
gives the table of Huffman codewords for the alphabet of possible
symbols.
.BR QccENTHuffmanDesign (3)
can be used to design this table from a probability distribution
of the symbols.
.I table
must be an encoding table;
i.e.,
.IR table -> table_type
must be
.BR QCCENTHUFFMAN_ENCODETABLE .
After calling
.BR QccENTHuffmanEncode() ,
.BR QccBitBufferFlush (3)
must be called 
to ensure that the last few bits of the bitstream are actually written
to the output file.
.LP
.BR QccENTHuffmanDecode()
performs Huffman decoding of the bits in the bitstream
.IR input_buffer ,
producing a output stream of symbols that are stored in
.I symbols .
The
.I symbols 
array must be allocated with space sufficient for holding
.I num_symbols
integers; this allocation must be done prior to calling
.BR QccENTHuffmanDecode() .
Additionally,
.I input_buffer
must be opened for reading prior to calling
.BR QccENTHuffmanDecode() .
.SH "NOTES"
Multiple successive calls to
.BR QccENTHuffmanEncode()
are possible; in this case, the individual bitstreams produced by each
encoding appear concatenated in the final output bitstream.
.BR QccBitBufferFlush (3)
must be called after the
.I final
call to
.BR QccENTHuffmanEncode()
(but not after any of the preceeding calls to
.BR QccENTHuffmanEncode() )
to ensure that the last few bits of the
concatenated bitstream are actually written
to the output file.
Multiple calls to
.BR QccENTHuffmanDecode()
can be used to decode the concatenated bitstream produced in this fashion,
or a single call (with an appropriately larger
.IR num_symbols
value) will work too.
.LP
These routines are based upon the implementations of Huffman encoding and
decoding suggested in Annexes C & F of the JPEG
standard, ISO/IEC 10918.
.SH "RETURN VALUE"
These routines return 0 on success, and 1 on failure.
.LP
.BR QccENTHuffmanEncode()
will fail if it encounters an invalid symbol (a symbol that is
outside of the permissible range of 0 to 
.BR QCCENTHUFFMAN_MAXSYMBOL ,
or a symbol that does not have a valid codeword assigned to it in
the Huffman table).
.LP
.BR QccENTHuffmanDecode()
will fail if it encounters a bit pattern in the bitstream that does
not correspond to a valid codeword in the Huffman table.
.SH "SEE ALSO"
.BR QccENTHuffmanDesign (3),
.BR QccENTHuffmanTable (3),
.BR QccPackENT (3),
.BR QccPack (3)
.LP
D. A. Huffman, "A Method for the Construction of Minimum-Redundancy Codes,"
.IR "Proceedings of the IRE" ,
vol. 40, pp. 1098-1101, September 1952.
.LP
ISO/IEC 10918,
.IR "Digital compression and coding of continuous-tone still images" ,
1994.
.SH AUTHOR
Copyright (C) 1997-2009  James E. Fowler
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