gyencode.1

QccPack implementation in C

.TH GYENCODE 1 "QCCPACK" ""
.SH NAME
gyencode \- encode using Gersho and Yano's AVQ algorithm
.SH SYNOPSIS
.B gyencode
.RB "[\|" \-i
.IR  adaption\_interval "\|]"
.RB "[\|" \-fc
.IR final\_codebook "\|]"
.I datfile
.I codebook
.I codebook\_coder
.I channelfile
.I sideinfofile
.SH OPTIONS
.TP
.BI \-i " adaption\_interval"
Integer.  Number of vectors in an adaption interval.  Default value = 1000.
.TP
.BI \-fc " final\_codebook"
String. Output the final state of the codebook after encoding to
.IR final\_codebook .
.SH DESCRIPTION
.LP
.B gyencode
implements the simple version of Gersho and Yano's algorithm.
The vectors of
.I datfile
(DAT format)
are encoded using the Gersho-Yano algorithm, with
.I codebook
(CBK format)
being the initial codebook.
.B gyencode
outputs a channel of VQ indices,
.I channelfile
(CHN format), and side information,
.I sideinfofile
(SID format).
.I codebook\_coder
(SQ format) gives the scalar quantizer used to produce the
side information (see below).
.LP
The Gersho-Yano algorithm operates as follows.
Over the vectors of each adaption interval (the length of which is
given by
.IR adaption\_interval),
the partition with
the greatest partial distortion is split. 
An iteration of the generalized Lloyd algorithm is run to
refine the locations of the two new codewords.  One codeword replaces
the split codeword; the other replaces the codeword with the smallest
partial distortion.
.LP
.B gydecode
is used for the corresponding decoding of 
.I channelfile 
and
.IR sideinfofile ;
.B avqrate
calculates the bit rate for the Gersho-Yano algorithm as represented by
this channel and the side information.
See
.BR gydecode (1)
and
.BR avqrate (1)
for more details.
.LP
Note: If the number of the vectors in
.I datfile
is not a multiple of 
.IR adaption\_interval ,
then 
the final adaption interval will contain fewer than
.I adaption\_interval 
vectors.
.LP
If option
.B \-fc
is specified, 
.B gyencode
outputs the final state of the codebook, taking into account all codebook
updates performed during coding, to
.IR final\_codebook .
.SH "SIDE INFORMATION"
.LP
The side information output by
.B gyencode
consists of a series of 
addresses and vectors.
.B gyencode
updates two vectors per adaption interval.
Thus, for each adaption interval,
.I sideinfofile
contains two vectors, which update the codebook,
as well as their corresponding addresses in the codebook.
.LP
The side-information file,
.IR sideinfofile ,
consists of a sequence of symbols of the following form:
.nf

.I "    <symbol type>" <symbol value>

.fi
where
.I <symbol type>
is 2 for an address, and 3 for an update vector.
The symbols are stored in pairs:  first an address which is then followed by
its correspomding update vector.
For an address,
.I <symbol type>
= 2, and
.I <symbol value>
is an integer (0 through codebook size - 1) denoting the address
in the codebook to which the following vector is assigned.
If
.I <symbol type>
= 3, then the current symbol is a vector.
In this case,
.I <symbol value>
= 
.IR "v[1] v[2] " \|.\|.\|. " v[dim]".
The scalar quantizer 
.I codebook\_coder 
(SQ format) is used to
quantize each component of the vector that updates the
codebook.
Thus, each
.I v[i]
is an index output from this scalar quantizer.
Note:
.I dim
is the vector dimension specified in the header of 
.I sideinfofile
(see
.BR QccPack (1)).
Note: in all instances,
.I <symbol value>
and 
.I <symbol type>
are stored in ASCII characters.
.LP
Note:
The value of
.I adaption\_interval
is stored in the header of
.I sideinfofile
as
.I N
(see
.BR QccPack (1)).
.IR sideinfofile .
.SH "SEE ALSO"
.BR gydecode (1),
.BR avqrate (1),
.BR QccPackAVQ (3),
.BR QccPack (3)

A. Gersho and M. Yano, "Adaptive Vector Quantization by Progressive
Codevector Replacement," Proc. ICASSP, pp. 133-136, 1985.

.SH AUTHOR
Copyright (C) 1997-2005  James E. Fowler
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A. Gersho and M. Yano, "Adaptive Vector Quantization by Progressive
Codevector Replacement," Proc. ICASSP, pp. 133-136, 1985.