Image analysis – Image compression or coding – Predictive coding
Reexamination Certificate
1999-12-10
2003-10-21
Boudreau, Leo (Department: 2621)
Image analysis
Image compression or coding
Predictive coding
C382S246000
Reexamination Certificate
active
06636641
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an encoding apparatus, a decoding apparatus and their methods for encoding and decoding picture information generated by and used in a facsimile machine, a scanner, and a computer. More specifically, the present invention relates to an encoding apparatus and a decoding apparatus having two types of encoding and decoding systems for efficiently encoding and decoding picture information by switching between the two types of encoding and decoding systems. Further, the present invention relates to an encoding method and a decoding method for encoding and decoding picture information efficiently. The present invention also relates to a picture processing apparatus having an encoding apparatus and a decoding apparatus according to the present invention. The present invention also relates to a picture processing apparatus for implementing an encoding method and a decoding method according to the present invention.
BACKGROUND ART
Related Art 1.
FIG. 66
is a block diagram showing a conventional encoding apparatus.
In
FIG. 66
, reference numeral
901
indicates a picture element memory for receiving, storing, and outputting the value of a picture element to be encoded (which will be referred to as an encoding picture element, or simply as a picture element) and for outputting the value of at least one encoded picture element already stored in the picture element memory and adjacent to the encoding picture element as the value of a reference picture element.
Reference numeral
907
indicates a predictor for calculating the prediction value for the encoding picture element by referring to the value of the at least one reference picture element.
Reference numeral
931
indicates a prediction error calculator for determining the prediction error by subtracting the prediction value calculated by the predictor
907
from the value of the encoding picture element.
Reference numeral
908
indicates an encoder for encoding the prediction error between the value of the encoding picture element and the prediction value calculated by the predictor
907
, and for outputting codewords.
Reference numeral
910
indicates a code buffer for receiving the codewords supplied from the encoder
908
and for outputting a sequence of the codewords as a code in order of the received codewords.
Next, an operation of the conventional encoding apparatus is explained.
The predictor
907
calculates the prediction value from the value of the at least one reference picture element. The calculation method may be implemented in accordance with a predetermined prediction function or by referring to a reference table. The encoder
908
encodes the prediction error (−255~+255, inclusive of zero, in the case of one picture element being represented by eight bits) which has been obtained by subtracting the calculated prediction value from the value of an encoding picture element by using a predetermined codeword table.
Related Art 2.
As another conventional related art, conversion of the prediction errors for encoding picture elements and picture elements to be decoded into binary symbol sequences, and encoding and decoding the binary symbol sequences are known. As one of the encoding and decoding methods for binary symbols, the encoding and decoding method disclosed in Japanese Patent Registered No. 1251403 will be described herein.
According to this encoding and decoding method, as shown in
FIG. 67
, one codeword is allotted to a binary symbol sequence composed of one binary symbol or a plurality of binary symbols. The term “encoding” is used in this specification to mean an operation for determining and allotting a codeword to a sequence of a certain number (which will be hereinafter referred to as the code order) of binary “0” symbols (More Probable Symbols abbreviated to MPSs) or binary “1” symbols (Less Probable Symbol abbreviated to LPSs) occurred, and for outputting the codeword therefor. At the time of encoding, the number of MPSs consecutively occurred is counted by an MPS counter (not shown) inside (or outside) the encoder. The counted value of MPSs is stored in an MPS memory (not shown), and the state numbers of binary symbol sequences (to be described hereafter) are stored in a state-number memory (not shown). The code order may be an integer greater than zero. However, it is assumed herein that the code order is restricted to 2
n
(the n-th power of 2). When the number of MPSs consecutively occurred (the count of the MPS counter) has become equal to the code order 2
n
, one-bit codeword “0” is allotted to the MPSs. On the other hand, when an LPS has occurred before the number of MPSs consecutively occurred becomes equal to the code order, the number of the MPSs consecutively occurred after outputting the latest codeword before occurring the LPS is expressed in terms of n-bit binary symbols, and, in order to differentiate from the sequence of the MPSs to which the codeword “0” is allotted, the codeword “1” is added to the beginning of the n-bit binary symbols. Accordingly, a codeword of (n+1) bits is allotted to the sequence of MPSs plus the LPS differentiating from the sequence of MPSs to which a codeword of “0” is allotted. The unit of a binary symbol sequence to which a codeword is allotted is referred to as a message. After the codeword is determined and output, the MPS counter is reset. A sequence of codewords output in this way constitutes a code. On the other hand, when a code is to be decoded, the code is supplied to the decoder and divided into individual codewords. Then, a binary symbol sequence is recreated by the decoder, and picture elements are reproduced. In this way, decoding is implemented.
In the aforementioned encoding and decoding method, the code order is changed so as to represent the appropriate code length in accordance with the occurrence probability of one of binary symbols estimated from past data on binary symbol sequences. For this reason, a further excellent encoding efficiency can be obtained.
A first example of the state transition method of determining the code order will be described now.
When a binary symbol sequence is encoded or decoded by an encoder or a decoder, the binary symbol sequence belongs to one of the sixteen states shown in FIG.
68
. The code order is determined according to the state to which each binary symbol sequence belongs. It is assumed herein that the initial value of the state number for the encoder or the decoder is set to 0. It is also assumed herein that the MPS counter of the encoder or the decoder is reset at the beginning of the encoding process or the decoding process. During the encoding process or the decoding process, the encoder or the decoder implements state transition when a codeword has been determined. When the number of MPSs consecutively occurred in a binary symbol sequence has become equal to the code order of the binary symbol sequence, the state number of the sequence is increased by one. When an LPS has occurred in a binary symbol sequence before the number of MPSs consecutively occurred becomes equal to the code order of the binary symbol sequence, the state number of the sequence is decreased by one. However, when the number of MPSs consecutively occurred in a binary symbol sequence having the state number
15
has become equal to the code order of the binary symbol sequence, or when an LPS has occurred in a binary symbol sequence having the state number
0
, the encoder or the decoder does not implement state transition, and the state number remains unchanged.
According to a second example of the method of determining the code order, there is shown a method in which the numbers of binary symbols “0” and binary symbols “1” which have occurred in a binary symbol sequence, respectively indicated by N(
0
) and N(
1
), are counted on both the transmitting side and the receiving side within the same range (such as, for example, within one line) so as to calculate the code order of the binary symbol sequence, based on the result of the count. The method of determining
Kimura Tomohiro
Matoba Narihiro
Ono Fumitaka
Ueda Kunio
Ueno Ikuro
Boudreau Leo
Dang Duy M
Mitsubishi Denki & Kabushiki Kaisha
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