qccimgimagecomponentdpcmencode.3

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

.TH QCCIMGIMAGECOMPONENTDPCMENCODE 3 "QCCPACK" ""
.SH NAME
QccIMGImageComponentDPCMEncode,
QccIMGImageComponentDPCMDecode,
QccIMGImageDPCMEncode,
QccIMGImageDPCMDecode
\- 
DPCM encoding and decoding of images and image components
.SH SYNOPSIS
.B #include "libQccPack.h"
.sp
.BI "int QccIMGImageComponentDPCMEncode(const QccIMGImageComponent *" image_component ", const QccSQScalarQuantizer *" quantizer ", double " out_of_bound_value ", int " predictor_code ", QccIMGImageComponent *" difference_image ", QccChannel *" channel );
.br
.BI "int QccIMGImageComponentDPCMDecode(QccChannel *" channel ", const QccSQScalarQuantizer *" quantizer ", double " out_of_bound_value ", int " predictor_code ", QccIMGImageComponent *" image_component );
.br
.sp
.BI "int QccIMGImageDPCMEncode(const QccIMGImage *" image ", const QccSQScalarQuantizer *" quantizers ", const QccVector " out_of_bound_values ", int " predictor_code ", QccIMGImage *" difference_image ", QccChannel *" channels );
.br
.BI "int QccIMGImageDPCMDecode(QccChannel *" channels ", const QccSQScalarQuantizer *" quantizers ", const QccVector " out_of_bound_values ", int " predictor_code ", QccIMGImage *" image);
.SH DESCRIPTION
.IR QccIMGImageComponentDPCMEncode()
and
.IR QccIMGImageComponentDPCMDecode()
implement differential pulse-code modulation (DPCM) of an
.IR image_component .
In essence, DPCM encoding consists of making a prediction of the current
pixel, subtracting the prediction from the current pixel,
and scalar-quantizing the resulting difference value to produce a
quantization index. This procedure is repeated in a raster-scan fashion
throughout the image.
DPCM decoding reverses the procedure by inverse scalar-quantizing the
index to produce a reconstructed difference and then adding
this reconstructed difference to a prediction to reconstruct the
current pixel. See "PREDICTION" below for more detail on the
predictors used in the DPCM encoder and decoder.
.LP
.IR QccIMGImageComponentDPCMEncode()
encodes
.IR image_component
with DPCM using the predictor specified by
.IR predictor_code ,
quantizing difference values with
.IR quantizer ,
and outputting the resulting quantizer indices to
.IR channel .
.IR QccChannelNormalize (3)
is called if the quantization indices consist of both positive and
negative numbers, which is the case unless
.IR quantizer->type
is
.BR QCCSQSCALARQUANTIZER_GENERAL .
If
.IR difference_image
is 
.RB non- NULL ,
the image of difference values is returned.
.IR channel
must be allocated with sufficient storage space to hold all
the quantizer indices (i.e., one for each pixel in
.IR image_component )
prior to calling
.BR QccIMGImageComponentDPCMEncode() .
.LP
.BR QccIMGImageComponentDPCMDecode()
decodes the
.IR channel
produced by
.BR QccIMGImageComponentDPCMEncode() ,
reconstructing
.IR image_component .
For sane results,
.IR predictor_code ,
.IR out_of_bound_value ,
and
.IR quantizer
must be the same as those used by
.BR QccIMGImageComponentDPCMEncode() .
.IR image_component
must be allocated prior to calling
.BR QccIMGImageComponentDPCMDecode() .
.LP
.BR QccIMGImageDPCMEncode()
and
.BR QccIMGImageDPCMDecode()
implement DPCM encoding and decoding, respectively, for
.IR image .
Essentially,
.BR QccIMGImageDPCMEncode()
calls
.BR QccIMGImageComponentDPCMEncode()
for each of the
.IR Y ,
.IR U ,
and
.IR V
image components of
.IR image .
.IR out_of_bound_values
is a vector of three values to use in the predictor,
.IR quantizers
is an array of three quantizers to apply to the prediction
residuals, and 
.IR channels
is an array of three channels used to store the quantization
indices for each of the three components.
Similarly,
.BR QccIMGImageDPCMDecode()
calls
.BR QccIMGImageComponentDPCMDecode()
for each of the
.IR Y ,
.IR U ,
and
.IR V
image components of
.IR image .
.SH "PREDICTION"
For best performance, 
it is necessary for the DPCM encoder and decoder to stay synchronized
throughout the coding of an image component.
Thus, the encoder and decoder must
use exactly the same predictions. Consequently, both the encoder
and decoder calculate a prediction of the current pixel based on
previously encoded and reconstructed pixels in the causal neighborhood
surrounding the current pixel in the raster scan.
.LP
Jain identifies six linear predictors as being particularly useful for
image coding. These predictors use four pixels
.IR A , " B" , " C" ", and " D
in the causal neighborhood surrounding current pixel
.IR X
as illustrated below.
.nf

.RI "previous line    ... *   *   *   " B "   " C "   " D "   *   *   * ..."
.RI " current line    ... *   *   *   " A "   " X "   -   -   -   - ..."
    next line    ... -   -   -   -   -   -   -   -   - ...

.IR "" "         *: previously encoded pixels"
.IR "" "         -: pixels not yet encoded"
.IR A ", " B ", " C ", " D ": previously encoded pixels used by predictor"
.IR "         X" ": current pixel (to be predicted)

.fi
The different predictors, specified by
.IR predictor_code
in these routines, are as follows, where
.I P
is the predicted value of the current pixel,
.IR X .
.TP
Predictor code: 0
.IR P " = " A
.TP
Predictor code: 1
.IR P " = (" A " + " D ") / 2"
.TP
Predictor code: 2
.IR P " = (" A " + " C ") / 2"
.TP
Predictor code: 3
.IR P " = ((" A " + (" C " + " D ")/2) / 2)"
.TP
Predictor code: 4
.IR P " = " A " + (" C " - " B ")"
.TP
Predictor code: 5
.IR P " = " A " + (" D " - " B ")/2"
.LP
In the event that the current pixel is close to the boundaries
of the image component, one or more of the
.IR A , " B" , " C" ", or " D
pixels may not be available for these predictors. In this case,
the predictor substitutes
.IR out_of_bound_value
for the missing pixel in the prediction formula.
.SH "RETURN VALUE"
These routines return 0 on success, 1 on failure.
.SH "SEE ALSO"
.BR QccSQScalarQuantization (3),
.BR QccChannelNormalize (3),
.BR QccIMGImageComponent (3),
.BR QccIMGImage (3),
.BR QccChannel (3),
.BR QccPackIMG (3),
.BR QccPack (3)

A. K. Jain,
.IR "Fundamentals of Digital Image Processing" .
Englewood Cliffs, NJ: Prentice Hall, 1989.

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