sfqencode.1

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

.TH SFQENCODE 1 "QCCPACK" ""
.SH NAME
sfqencode, sfqdecode \- encode/decode an image using the SFQ algorithm
.SH SYNOPSIS
.B sfqencode
.RB "[\|" \-w
.IR  wavelet "\|]"
.RB "[\|" \-b
.IR  boundary "\|]"
.RB "[\|" \-l
.IR  lambda "\|]"
.RB "[\|" \-bbq
.IR  baseband\_quantizer\_stepsize "\|]"
.RB "[\|" \-hpq
.IR  highpass\_quantizer\_stepsize "\|]"
.RB "[\|" \-pw
.IR  pcpfile "\|]"
.RB "[\|" \-nl
.IR  levels "\|]"
.RB "[\|" \-vo "\|]"
.I imgfile
.I bitstream
.LP
.B sfqdecode
.RB "[\|" \-w
.IR  wavelet "\|]"
.RB "[\|" \-b
.IR  boundary "\|]"
.RB "[\|" \-pw
.IR  pcpfile "\|]"
.I bitstream
.I imgfile
.SH OPTIONS
.TP
.BI \-w " wavelet"
String. 
Name of the wavelet file
.RB ( FBK
or
.B LFT
format); default = "CohenDaubechiesFeauveau.9-7.lft"
.TP
.BI \-b " boundary"
String. Type of boundary extension; default = "symmetric".
.TP
.BI \-l " lambda"
Float. Rate-distortion parameter.  Default is 1.0.
.TP
.BI \-bbq " baseband\_quantizer\_stepsize"
Float.  Default is to search all allowable stepsizes.
.TP
.BI \-hpq " highpass\_quantizer\_stepsize"
Float.  Default is to search all allowable stepsizes.
.TP
.BI \-pw " pcpfile
String. Name of file containing perceptual weights.
.TP 
.BI \-nl " levels"
Integer. Number of levels of dyadic decomposition.
Default value is 3 levels.
.TP
.B \-vo
Print only the value of the rate to stdout (terse output).
Default is verbose output.
.SH DESCRIPTION
.LP
.B sfqencode
codes an image,
.IR imgfile ,
using the space-frequency-quantization (SFQ) algorithm of Xiong
.IR "et al" .
The SFQ algorithm involves a 2D DWT followed by the
identification of zerotrees based on a rate-distortion criterion.
The zerotree structure indicates which wavelet coefficients are 
"insignificant."
Coding these
insignificant coefficients costs more in bit rate
than the possible gain in distortion performance;
consequently, these insignificant coefficients are set to zero.
Uniform scalar quantization 
followed by arithmetic entropy coding
is used to code all remaining significant coefficients.
.LP
The DWT is performed as described for
.BR imgdwt (1).
Option
.B \-w
specifies the wavelet, 
option
.B \-b
specifies the boundary extension, and option
.B \-pw
indicates whether perceptual weighting is to be used.
See 
.BR imgdwt (1)
for more details.
.LP
The SFQ algorithm operates using a Lagrangian cost formulation
of the form
.I "J = D + lambda * R"
where 
.I D
is distortion,
.I R
is rate,
and
.I lambda
is the Lagrangian rate-distortion parameter given by
the
.B \-l
option.
.I lambda 
determines the balance between rate and distortion in the
algorithm:  large values of
.I lambda
emphasize reduction of bit rate over distortion; small values of
.I lambda
produce codings with lower distortion but at a consequently higher rate.
Varying
.I lambda
from 0 to infinity will trace out the rate-distortion performance curve
of the SFQ algorithm for a particular input image and for a
particular scalar-quantizer stepsize; a single
.I lambda
thus specifies an operating point on this rate-distortion curve.
.LP
The performance of the SFQ algorithm depends not only on 
.I lambda
but also on the chosen scalar-quantizer stepsizes.
The option
.B \-hpq
specifies the scalar-quantizer stepsize to be used in the coding
of the highpass subbands; the baseband, coded independently from the
highpass subbands, uses the stepsize given by the
.B \-bbq
option.
If a highpass stepsize is not specified (i.e., no
.B \-hpq
option given), 
.B sfqencode
determines an "optimal" stepsize by searching in
a set of 245 stepsizes between 7.6 and 32.
The optimal stepsize is the one in the set found to
minimize the rate-distortion cost criterion
.I J
(see above).
Note: this search process essentially implies coding the highpass
subbands 245 times and
choosing the best coding; it is consequently quite slow.
A similar search is performed for the baseband stepsize in the
case that the
.B \-bbq
option is not given.
.LP
.B sfqencode
normally prints to stdout a small amount of information
concerning the encoding being performed, most notably the bit rate,
expressed in bits per pixel,
achieved by the program.  If the 
.B \-vo
(value-only) option is given, this printed output is suppressed except for
the bit rate.
.LP
Note: the original presentation of SFQ given by Xiong 
.IR "et al" .
describes a method for predicting portions of the zerotree for
high-frequency subbands based on the zerotree for
lower-frequency subbands.
.BR sfqencode ,
as currently implemented, does not perform this zerotree prediction.
.LP
Note: the original presentation of SFQ given by Xiong
.IR "et al" .
does not include perceptual weighting as allowed by
.B sfqencode
(the 
.B \-pw
option).  Refer to
.BR imgdwt (1)
and
.BR QccWAVPerceptualWeights (3)
for details on the implementation of perceptual weighting.
.LP
Note:
.BR sfqencode
currently achieves rate-distortion performance slightly below that reported
by Xiong
.IR "et al" .
For instance, when coding the "Barbara" 
image at 0.5 bits/pixel, 
.B sfqencode 
achieves a PSNR about 1dB below the reported figure.
The reasons for this performance gap are currently being investigated,
although it is probably due in part to the lack of tree prediction
as described above.
.SH "SEE ALSO"
.BR imgdwt (1),
.BR QccWAVPerceptualWeights (3),
.BR QccWAVSubbandPyramid (3),
.BR QccPackWAV (3),
.BR QccPackIMG (3),
.BR QccPack (3)

Z. Xiong, K. Ramchandran, and M. T. Orchard,
"Space-Frequency Quantization for Wavelet Image Coding,"
.IR "IEEE Transactions on Image Processing" ,
vol. 6, no. 5, pp. 677-693, May 1997.

.SH AUTHOR
Copyright (C) 1997-2009  James E. Fowler
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