JPH11225341A - Image encoder and image decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image from deteriorating in accordance with the state of a transmission medium by adding information notifying that encoding is aborted to the encoded code and outputting it when the encoding from an upper bit of plural conversion coefficients which convert an original image is aborted at a halfway bit. SOLUTION: A sequential converting means 4 divides image data into a low frequency component band and a high frequency component band which consist of plural conversion coefficients. A conversion coefficient encoding means 5 performs reversible encoding of all of the conversion coefficients about the low frequency component, encodes the absolute value of the conversion coefficients and sign bit about the high frequency component, adds the end marker code and line number marker code of coded data and outputs them. A conversion coefficient decoding means 6 decodes high frequency component coded data based on information that is added to the coded data. A conversion coefficient correcting means 7 gets a conversion coefficient that is close to a true value and a correction conversion coefficient. An inverse converting means 8 performs inverse conversion of the correction conversion coefficient and outputs a reproduced image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding device and an image decoding device for image communication.

[0002]

2. Description of the Related Art The general concept of a conventional image communication apparatus will be briefly described. As an encoding device of a conventional image communication device, the international standardization organization ITU-T Recommendation T.T. 81 (JPE
G) there is a progressive encoding device.

[0003] The progressive encoding device is a JPE
There are two processing methods as the G progressive mode, but here, MSB (Most Significa) is used.
LSB (Lea) in order from the bit plane of (ntBit).
SA (Suc) in which coding is performed in the direction of the st Significant Bit, and the gradation of the image is gradually improved.
essential Application) method will be described. FIG. 1 is a block diagram relating to an encoding device of the SA method in the JPEG progressive mode. Reference numeral 1 denotes an image dividing unit that divides an encoding target image into blocks of 8 × 8 pixels and outputs the blocks. The divided signal divided for each block is DCT (Disc)
DCT converting means 3 for performing a transform (rete Cosine Transform);
This is encoding means for encoding 4 (8 × 8) transform coefficients and outputting an encoded bit stream.

Next, the characteristic operation processing based on the SA method will be described. The encoding means 3 performs a process of encoding a plurality of bits in the MSB direction among all the transform coefficients for each block for all the blocks. (First Scan in FIG. 2) Next, the encoding unit 3 encodes the next one bit located on the LSB side for the transform coefficients of the entire screen. (Second scan in FIG. 2) Thereafter, the encoding unit 3 sequentially encodes one bit / scan in the LSB direction.

In other words, as shown in FIG. 2, planes (bit planes) composed of certain bits of all transform coefficients in the screen are sequentially encoded. Accordingly, the encoding means 3 generates the bit stream shown in FIG. 3 from the encoded image information and outputs the bit stream to the decoding device. In this way, the encoding device encodes the image in order from the MSB to the LSB, thereby realizing the encoding in which the gradation of the conversion coefficient is gradually increased.

However, the transmission capacity of the transmission medium (wired or wireless) between the encoding device and the decoding device is not always sufficient. In particular, in wireless transmission, it is often not possible to secure a sufficient transmission capacity for transmitting an image. For example, if the bit stream encoded by the encoding device cannot be transmitted with the transmission capacity of the transmission medium, the encoding device performs LS to correspond to the transmission capacity of the transmission medium as shown in FIG.
At a predetermined position on the B side, the coded signal in the bit stream is deleted and transmitted.

On the other hand, the decoding device performs a decoding process based on the coded signal deleted on the coding device side. In this case, the decoding device approximates the transform coefficient by setting the coded signal (bit) deleted on the coding device side to 0, and performs image restoration processing based on the bit stream and the transform coefficient approximated to 0. .

[0008]

As described above, when image data is transmitted, the decoding device may receive only a part of the image data signal depending on the condition of the transmission medium. For this reason, as one method, the decoding apparatus approximates the transform coefficient by setting the coded signal (bit) deleted on the coding apparatus side to 0, and generates an image based on the bit stream and the transform coefficient approximated to 0. Is performed. But,
Since the image decoded by the decoding device is deleted and the image transmission signal is decoded based on the uniquely defined 0-bit signal, there is a problem that the image is significantly deteriorated as compared with the original image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image encoding apparatus and an image decoding apparatus capable of preventing image quality deterioration as much as possible according to the status of a transmission medium. With the goal.

[0010]

According to a first aspect of the present invention, there is provided an image coding apparatus for converting an original image into a plurality of conversion coefficients, and converting the conversion coefficients converted by the conversion means from upper bits thereof. Encoding means for encoding and outputting a code, wherein the encoding means adds, when the encoding of the transform coefficient is discontinued up to the middle bit, information notifying that the encoding has been discontinued to the code. Output.

According to a second aspect of the present invention, there is provided an image encoding apparatus, comprising: a transforming means for transforming a transform coefficient which has been transformed; Encoding means for converting, when the encoding of the transform coefficient is interrupted up to the middle bit, information for notifying that the encoding has been interrupted is added to the code and outputted. .

According to a third aspect of the present invention, there is provided an image encoding apparatus comprising:
The conversion means divides the original image or the converted conversion coefficient into a low-frequency component and a high-frequency component by band filtering.

According to a fourth aspect of the present invention, there is provided an image encoding apparatus comprising:
The encoding means adds a first marker code indicating the end of the code and a second marker code indicating the coding cutoff information to the code sequence and outputs the code sequence.

According to a fifth aspect of the present invention, there is provided an image encoding apparatus comprising:
The second marker code uses the bit plane position encoded until the transmission is terminated as position information.

In the image encoding apparatus according to a sixth aspect of the present invention, the number of transform coefficients obtained by encoding the second marker code until the transmission is terminated is used as position information.

According to a seventh aspect of the present invention, there is provided an image encoding apparatus comprising:
The number of pixels obtained by encoding the second marker code until the transmission is terminated is expressed in units of lines, and this expression is used as the position information of the conversion coefficient.

An image coding apparatus according to an eighth aspect of the present invention comprises:
The number of transform coefficients encoded before the transmission of the second marker code is terminated is expressed in units of rectangular areas, and this representation is used as position information of the transform coefficients.

According to a ninth aspect of the present invention, there is provided an image decoding apparatus comprising:
A decoding means for decoding the code, reproducing the transform coefficient and outputting a decoded transform coefficient, and detecting the coding cut-off information added to the code, and the decoding means detecting the coding cut-off information A correction means for estimating and correcting the decoded transform coefficient by statistical data, and outputting the corrected transform coefficient as a corrected transform coefficient; and, when the decoding means detects the coding cutoff information, performing an inverse transform on the corrected transform coefficient. And outputting a reproduced image, and performing inverse transform on the decoded transform coefficient when the decoding means does not detect the encoded cut-off information, and providing an inverse transform means for outputting a reproduced image. Things.

According to a tenth aspect of the present invention, in the image decoding apparatus, the correcting means accumulates the decoded transform coefficients and corrects the decoded transform coefficients based on the accumulated value.

An image decoding apparatus according to an eleventh aspect of the present invention decodes a code, reproduces a transform coefficient, outputs a decoded transform coefficient, and detects coding cutoff information added to the code. And first correcting means for estimating and correcting the decoded transform coefficient by statistical data when the decoding means detects the coding cut-off information, and outputting the corrected transform coefficient as a corrected transform coefficient. Is detected by the decoding unit, and when the correction conversion coefficient of the correction unit is 0, the correction conversion coefficient of the first correction unit is estimated by referring to a nearby correction conversion coefficient. A second correction means for re-correcting the correction conversion coefficient and outputting a re-correction conversion coefficient; And performing a reverse conversion on the decoded transform coefficient when the decoding means does not detect the encoding cutoff information, and outputting a reproduced image. It is a thing.

According to a twelfth aspect of the present invention, in the image decoding apparatus, the first correction means accumulates the decoded conversion coefficients and corrects the decoding conversion based on the accumulated value.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 4, reference numeral 4 denotes a forward transform unit for dividing an original image signal or already transformed transform coefficients into transform coefficients of a plurality of bands by band filtering, and 5 a transform coefficient for independently encoding transform coefficients of a plurality of bands. Encoding means, 6 is a transform coefficient decoding means for decoding the transmitted (or accumulated) coded data into transform coefficients, 7 is a transform coefficient correcting means for correcting the value of a reproduced transform coefficient which has been decoded and whose accuracy has decreased, and 8 is a plurality of transform coefficient correcting means. This is an inverse conversion means for reconstructing an image signal from the corrected conversion coefficient of the band. The forward transform unit 4 and the transform encoding unit 5 constitute an image encoding device. The transform coefficient decoding means 6, the transform coefficient correcting means 7, and the inverse transform means 8 constitute an image decoding device.

Next, the operation of the image coding apparatus will be described. First, the forward conversion unit 4 divides the entire image data to be transmitted into a plurality of band components. The forward transforming unit 4 performs filtering in the horizontal direction on the entire image data to be transmitted as shown in Expressions 1 and 2, and divides the image data into an L component (low-frequency component) and an H component (high-frequency component). Equation 1 and Equation 2
As shown in (1), the divided original image (transmission target image data xn) is divided into L component (sn) and H component (dn) transform coefficients.

[0024]

(Equation 1)

[0025]

(Equation 2)

(However, [•] indicates truncation below the decimal point.)

That is, as shown in FIG.
, An image composed of M × N pixels is represented by M × (N / 2)
It is divided into two bands of an L component and an H component consisting of a number of transform coefficients. Next, the transform coefficient coding means 5 losslessly codes all the transform coefficients sn of the L component, that is, codes and transmits the error so that no error occurs on the receiving side. The lossless encoding method is JPEG defined as an international standard.
An arbitrary lossless encoding method such as a lossless encoding method is applied.
Further, the transform coefficient encoding means 5 converts the H-component transform coefficient d.
The absolute value and the sign bit (positive or negative) of the transform coefficient represented by n (see FIG. 6) expressed in binary are encoded and transmitted.

At this time, the transform coefficient coding means 5 performs binary entropy coding of the absolute value for each bit plane. That is, as shown in FIG. 7, a plane (bit plane) composed of each bit of the absolute value of all the transform coefficients is represented by the MSB (Most S).
Binary entropy coding is performed in order from the plane of the (ignitant Bit). This bit plane encoding is performed using LSB (Least Significant B).
It is possible to abort at a desired bit plane without performing the bit plane of (it). If the bit plane coding is aborted at the bit plane before the LSB, a part of the information is not transmitted, so that the reproduced image and the original image are irreversible, and if the entire LSB bit plane is coded, the lossless coding is performed. Encoding.

The transform coefficient coding means 5 performs binary entropy coding of the sign bit as 0 for positive and 1 for negative immediately after the first appearance of bit 1 in a certain transform coefficient. If the absolute value is 0, there is no need to transmit the sign bit. The binary entropy encoding method is as follows.
ITU-T International Standard Recommendation T. An arbitrary binary entropy coding method such as QM-coder, which is an arithmetic code defined in 82, is applied. As described above, bit plane encoding of a plane (bit plane) composed of each bit of the absolute value of all transform coefficients is performed using LSB (Least Sign).
If the process is terminated at a desired bit plane without performing the process up to the bit plane of the (determinant Bit), it is necessary for the receiving side (decoding device side) to know how far the coding has been performed. Therefore, at the end of the encoded data to be transmitted, the data size, for example, the number of encoded symbols, the number of lines,
The number of units such as the number of blocks is added as information, and the encoding means of the image encoding device transmits the information.

The transform coefficient coding means 5 of the image coding apparatus generates a marker code indicating the end of the coded data after finishing the coding on a predetermined line of a predetermined bit plane, as shown in FIG. As described above, an end marker code indicating the end of the encoded data and a line number marker code are added to the end of the encoded data of the H component and output. Note that the line number marker code indicates the position information of the termination of the code.

Here, the structure of the encoded data in FIG. 8 will be described. In this embodiment, the end marker code is set to 0xf using a QM-coder defined as an international standard as an encoder and its marker code.
f02 (0x represents a hexadecimal number), the line number marker code is 0xff05, and the coding line number is 4
Expressed in bytes. Therefore, the number of coding lines is 0x100
In the case of the 0 line, ff 02 f
The 8-byte data of f 05 00 0010 00 is added.

Although the QM-coder and its marker code have been described above, a marker code having a value other than the above may be used as long as the marker code does not occur as encoded data. Regarding the arrangement relationship between the marker code and the encoded data, the end marker code may be arranged first by the line number marker code and its additional information. In addition, information indicating up to which bit plane or up to which transform coefficient has been encoded may be added to the encoded data instead of information indicating up to which line the encoding has been performed.

More specifically, the line number marker code uses, as position information, the number of transform coefficients encoded before transmission is terminated. The line number marker code represents the number of pixels of the conversion coefficient coded by the time the transmission is terminated in units of lines, and this representation is used as the position information of the conversion coefficient. The line number marker code expresses the number of pixels of the transform coefficient coded before the transmission is stopped in units of rectangular areas, and this representation is used as the position information of the transform coefficient. Furthermore, the line number marker code is expressed in units of the number of bit planes of the conversion coefficient coded before the transmission is terminated, and this expression is used as the position information of the conversion coefficient. The image coding apparatus according to the present embodiment may determine the number of coding lines for transform coefficients according to the state of the transmission medium (transmission capacity, bandwidth). The above is the operation of the image encoding device.

Next, the operation of the image decoding apparatus will be described. 4, the transform coefficient decoding means 6 performs entropy decoding on the code data to calculate a decoded transform coefficient s'n and a corrected transform coefficient d "n. For the L component, the transform coefficient is used in order to apply lossless encoding. The sn and the decoding transform coefficient s'n completely match (hereinafter, the decoding transform coefficient is also denoted by sn). On the other hand, the H component is not necessarily up to the LSB bit plane as described in the above-described image encoding apparatus. Since it is not encoded, the decoded transform coefficient d'n may not coincide with the true value, that is, the transform coefficient dn calculated by the image encoding device.

The transform coefficient decoding means 6 converts the information added to the coded data (information indicating up to which bit plane or which H component transform coefficient has been coded, that is, the coding cutoff information) into the H component code. If it is detected in the decoding of the coded data, the decoding of the H component coded data is performed up to a predetermined number of lines based on the above information. This allows the image decoding apparatus to determine how far the H component encoded data is to be decoded. In short, the transform coefficient decoding means 6 of the image decoding apparatus detects information on lower bits of the missing transform coefficient.

Therefore, when all the bit planes of the H component have not been coded, the transform coefficient correcting means 7 corrects the decoded transform coefficient d'n by a method described later to obtain a transform coefficient closer to the true value. Then, the transform coefficient d ″ n is obtained. Next, the inverse transform means 8 uses the inverse transform equations shown in Equations 3 and 4 to obtain
By performing an inverse transform on the correction transform coefficient, a reproduced image x'n is calculated (output). When the transform coefficient decoding unit 6 does not detect the above-mentioned encoded cutoff information,
The decoded transform coefficients s'n and d'n are output to the inverse transform means 8 without being processed by the transform coefficient correction means 7. Then, the inverse transform means 8 calculates the reproduced image x'n by performing inverse transform on the decoded transform coefficients s'n and d'n using the inverse transform formulas shown in Expressions 3 and 4.

[0037]

(Equation 3)

[0038]

(Equation 4)

FIG. 9 shows the conversion coefficient correcting means 7 in FIG.
FIG. 4 is a block diagram showing the details of. First, the configuration of FIG. 9 will be described. Reference numerals 6, 7, and 8 denote transform coefficient decoding means, transform coefficient correction means, and inverse transform means, respectively.
7 and 8. Reference numeral 9 denotes a correction circuit for correcting the decoded transform coefficient of the H component.

Next, the operation of the correction circuit will be described. The transform coefficient decoding means 6 can decode the losslessly encoded L component without error using the transmitted code data.
When all the bit planes are not coded, only the coded upper bit plane is decoded for the H component (lower undecoded bits of the decoded transform coefficient d'n are regarded as 0 for convenience). ). Therefore, the correcting means A9 estimates the lower bits that have not been decoded from the upper bits that have been decoded, and corrects the value of the decoded transform coefficient d'n.

Here, as an example of the correction method, if all the decoded upper bits are 0, it is estimated that all the lower bits are 0. In addition, when the decoded upper bits include “1”, it is estimated that the lower two bits from the least significant bit of the decoded bits are “1” and the other bits are “0”. FIG. 10 shows an example in which only the upper 3 bits of the 8-bit H component are decoded with the absolute value precision. At this time, assuming that the upper 3 bits are 001, the remaining lower 5 bits are 01000, and the correction conversion coefficient d "n is 0010.
It becomes 1000. That is, the bits estimated by the statistical data based on the decoded bits (upper bits) are regarded as undecoded values, and the corrected transform coefficients (estimated values)
Is calculated.

In addition to the above-mentioned correction method, other correction methods can be applied. For example, when all the decoded upper bits are 0, all the lower bits include 0 and the decoded upper bits include 1. If the bits are lower, two bits lower and three bits lower than the least significant bit of the decoded bit are used.
It can also be assumed that one bit is 1 and the other bits are 0. The above is the operation of the image decoding apparatus according to the present embodiment.

In the image coding apparatus and the image decoding apparatus according to the present embodiment, horizontal conversion is performed as band division.
Although the example of dividing into two band components has been shown, the same conversion is performed in the vertical direction, or the converted band components are converted, and the division is further finely divided. It is also possible to perform the same processing as that performed for the same. In other words, horizontal and vertical conversions are
If the encoding side and the decoding side match each other, the combination and order may be performed in any manner. Also, L
For the component, it is also possible to perform the same treatment as that performed on the H component. In the present embodiment, the conversions shown in Expressions 1, 2, 3, and 4 have been described as conversion expressions, but other conversion expressions can be used. Furthermore, in the present embodiment, an example of the progressive encoding scheme in which the accuracy is improved by a power of 2 called bit plane encoding has been described.
It is not necessary to increase the precision by exponentiation, and a progressive coding scheme in which the precision is improved at an arbitrary precision is also applicable.

Embodiment 2 An image encoding device and an image decoding device according to Embodiment 2 of the present invention will be described.
However, since the configuration operation of the image encoding / decoding apparatus is the same as in FIGS. 4 and 9 except for the conversion coefficient correction unit, only the operation of the conversion coefficient correction unit which is a characteristic configuration of the present embodiment will be described. 11 will be described. First, the configuration of FIG. 11 will be described. Reference numerals 6, 7, and 8 denote transform coefficient decoding means, transform coefficient correction means, and inverse transform means, respectively, and correspond to 6, 7, and 8 in FIGS. 9 is a decoding transform coefficient d ′ of the H component
n is a correction means for correcting n (corresponding to a first correction means of claim 11), and 10 is an output signal dAn from the correction means 9.
Is a second correction unit that further corrects.

Next, the operation of the conversion coefficient correction means 7 will be described. In the same manner as in the first embodiment, the transform coefficient decoding unit 6 can decode the losslessly encoded L component without error using the transmitted code data. If the bit plane has not been encoded, the transform coefficient decoding means 6 can decode only the upper bit plane of the encoded data. Therefore, first, the correction means 9 estimates the lower bits of the undecoded H component from the decoded upper bits, and corrects the value of the transform coefficient, as in the first embodiment. To show an example of the correction method, if all the decoded upper bits are 0, the lower bits are all assumed to be 0, and 1 is added to the decoded upper bits.
Is included, it is estimated that the lower two bits from the least significant bit of the decoded bits are 1, and the other bits are 0.

Next, in the second correction means 10, when all the bit planes of the H component are not coded and the coded upper bits of the decoded transform coefficient d'n are all 0, the following equation (5) is obtained. , The decoded transform coefficient is corrected using the output of the correcting means 9 and the transform coefficient of the L component, and the corrected transform coefficient d ″
Calculate n. In addition, in the second correction unit 10, except for the case where all the bit planes of the H component are not coded and the coded upper bits of the decoded transform coefficient d′ n are all 0, The output correction conversion coefficient d "n is output to the inverse conversion means without any processing.

[0047]

(Equation 5)

Further, the correction conversion coefficient d "n processed by the second correction means 10 is input to the inverse conversion means 8, and the inverse conversion means 8 is processed by the second correction means 10. The corrected transform coefficient d "n and the transform coefficient sn of the S component are inversely transformed using the above-described equations (3) and (4) to obtain a reproduced image x'n. In the correcting means 9 according to the second embodiment, the estimated bits are all 0, or the lower two bits from the least significant bit of the decoded bits are 1, and the other bits are 0.
However, similar to the first embodiment, other methods are also possible. Also, in the present embodiment, an example has been described in which horizontal conversion is performed as band division and division is performed into two band components, but similar conversion is performed in the vertical direction, or
It is also possible to apply conversion to the converted band components and further divide the components, and to perform the same processing as that performed on the H component for each component. The conversion in the horizontal and vertical directions may be performed in any combination and order as long as they match on both the encoding side and the decoding side. The same processing as that performed on the H component can also be performed on the L component.

In this embodiment, the second correction means 1
Equation 5 is used as the equation for calculating the correction conversion coefficient d "n at 0, but other equations may be used.
Further, in the present embodiment, the conversions shown in Expression 1, Expression 2, Expression 3, and Expression 4 are shown as conversion expressions, but other conversion expressions can also be used. Furthermore, in the present embodiment, an example of the progressive encoding method in which the accuracy is improved by a power of 2 called bit plane encoding has been described. However, the accuracy does not necessarily need to be increased by the power of 2; A progressive coding method in which the accuracy is improved at an arbitrary accuracy is applicable.

Embodiment 3 An image encoding device and an image decoding device according to Embodiment 3 of the present invention will be described. However, the configuration operation of the image encoding / decoding device is based on the correction means 9
4 and 9 except for the above, only the operation of the correcting means 9 which is a characteristic configuration of the present embodiment will be described.

FIG. 12 is a block diagram showing details of the correction means 9 in the present embodiment. 11 is an appearance bit counter A for storing the cumulative number of occurrences of {1} among the decoded bits, and 12 is an appearance bit counter B for storing the cumulative number of occurrences of the decoded bits (both {0} and {1}). , 1
3 is a decoding transform coefficient d based on the cumulative number of bits stored in the appearance bit counter A and the appearance bit counter B.
(2) A correction value calculating means for correcting n.

Next, the operation of the correcting means 9 will be described. As in the first embodiment, the transform coefficient decoding unit 6
In the above, the losslessly encoded L component can be decoded without error using the transmitted code data, but if all bit planes of the H component are not encoded on the image encoding device side,
The transform coefficient decoding means 6 can decode only the upper bit plane of the encoded data. Therefore, the correction unit 9 estimates the lower bits of the H component that have not been decoded, based on the decoded upper bits and the bits of another already decoded transform coefficient in the current bit plane.

In the appearance bit counter A11, every time a bit is decoded, if the bit is {1}, 1 is added to the counter value N _A, and if the bit is {0}, the counter value N _A is not changed. On the other hand, the appearance-bit counter B 12, each for decoding a bit, adds 1 to the counter value N _B regardless of the bit ■ 1 ■ or ■ 0 ■ or. When N _B reaches a predetermined constant (for example, 64), N _A , N _B
Are N _A / 2 and N _B / 2, respectively. The initial value of N _A, N _B may be set such _{N A = 0, N B =} 1, any non-negative integer that satisfies N _A ≦ N _B and N _B ≠ 0.

Next, the correction value calculating means 13 corrects the decoding conversion coefficient d ■ n to the correction conversion coefficient d ■ n according to the equation (6). Here, i in Expression 6 is a bit position representing a bit plane to be decoded. When the third bit is decoded from the MSB with an 8-bit precision conversion coefficient as in the example of FIG. = 5. In the example of FIG. 13, N _A = 5, N _B
In the case of = 15, [2 ⁵ × 5/15] = 10, and the lower 5 bits of the correction conversion coefficient are represented by a binary number of 1001010.
Becomes That is, 10 is added to the decoded transform coefficient d ■ n = 32, and the corrected transform coefficient d ■ n = 42 is obtained.

[0055]

(Equation 6)

(However, [•] indicates truncation below the decimal point.)

In the present embodiment, an example has been shown in which horizontal conversion is performed as band division and division is performed into two band components. However, similar division is performed in the vertical direction, or conversion into converted band components is performed. It is also possible to perform the same processing as that performed on the H component in each component by further dividing the data. The horizontal and vertical conversions may be performed in any combination and order as long as they match on both the encoding side and the decoding side.
The same processing as that performed on the H component can also be performed on the L component.

Further, in the present embodiment, Equation 6 is used as the equation for calculating the correction conversion coefficient d ■ n in the correction value calculating means. However, other equations may be used. Furthermore, the correcting means 9 used in this embodiment is different from the correcting means 9 shown in FIG.
It is also possible to use the correction means 9 of the embodiment shown in FIG.

[0059]

According to the present invention, it is possible to provide an image encoding apparatus and an image decoding apparatus which can prevent image quality deterioration as much as possible according to the status of the transmission medium.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a conventional image encoding device.

FIG. 2 is a diagram illustrating a conventional image encoding process.

FIG. 3 is a diagram showing a conventional encoded signal.

FIG. 4 is a block diagram illustrating an image encoding device and an image decoding device according to Embodiment 1.

FIG. 5 is a diagram illustrating transform coefficients of the image encoding device according to the first embodiment.

FIG. 6 is a diagram illustrating an encoded signal output from the image encoding device according to the first embodiment.

FIG. 7 is a diagram illustrating an image encoding process according to the first embodiment.

FIG. 8 is a diagram illustrating an encoded signal output from the image encoding device according to the first embodiment.

FIG. 9 is a detailed block diagram of an image decoding device according to the first embodiment.

FIG. 10 is a diagram illustrating a correction process of a correction unit according to the first embodiment.

FIG. 11 is a detailed block diagram of an image decoding device according to a second embodiment.

FIG. 12 is a block diagram illustrating details of a correction unit 9 according to the third embodiment.

FIG. 13 is a diagram illustrating a correction process of a correction unit according to the third embodiment.

[Explanation of symbols]

4 forward transform means, 5 transform coefficient encoding means, 6 transform coefficient decoding means, 7 transform coefficient correction means, 8 inverse transform means, 9, 10 correction means, 11, 12 appearance bit counter, 13 correction value calculation means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Yoshida 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Fumitaka Ono 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd.

Claims (12)

[Claims] 1. An image processing apparatus comprising: conversion means for converting an original image into a plurality of conversion coefficients; and coding means for coding the conversion coefficient converted by the conversion means from its upper bits and outputting a code. Is an image encoding apparatus, wherein, when encoding of a transform coefficient is interrupted up to intermediate bits, information notifying that the encoding is interrupted is added to the code and output. 2. An image processing apparatus comprising: conversion means for converting a conversion coefficient already converted; and coding means for coding the conversion coefficient converted by the conversion means from its upper bits and outputting a code. An image encoding apparatus, wherein when encoding of a transform coefficient is interrupted up to intermediate bits, information for notifying that the encoding has been interrupted is added to the code and output. 3. The image according to claim 1, wherein the conversion means divides the original image or the converted conversion coefficient into a low-frequency component and a high-frequency component by band filtering. Encoding device. 4. The coding means according to claim 1, wherein said coding means adds a first marker code indicating the end of the code and a second marker code indicating the coding termination information to the code sequence and outputs the code sequence. Or the image encoding device according to claim 2. 5. The method according to claim 1, wherein the second marker code is expressed in units of the number of bit planes of the transform coefficient encoded before the transmission is terminated, and this representation is used as position information of the transform coefficient. 5. The image encoding device according to 4. 6. The image encoding apparatus according to claim 4, wherein the second marker code uses, as position information, the number of transform coefficients encoded before transmission is stopped. 7. The method according to claim 1, wherein the second marker code represents the number of transform coefficients encoded before transmission is terminated in units of lines, and the representation is used as position information of the transform coefficients. Item 7. The image encoding device according to Item 6. 8. The method according to claim 1, wherein the second marker code represents the number of transform coefficients encoded before the transmission is terminated in units of rectangular areas, and the representation is used as position information of the transform coefficients. Item 7. The image encoding device according to Item 6. 9. A decoding means for decoding a code, reproducing a transform coefficient, outputting a decoded transform coefficient, and detecting coding cutoff information added to the code, and decoding the coding cutoff information. If the means detects the correction transform coefficient, the correction transform coefficient is estimated by statistical data and corrected, and the corrected transform coefficient is output as a corrected transform coefficient. Inversely transforming the decoded transform coefficients and outputting a reproduced image when the decoding means does not detect the encoded cut-off information. And an image decoding device. 10. The correction means accumulates decoded transform coefficients when the decoding means detects the encoding cutoff information, corrects the decoded transform coefficients based on the accumulated value, and outputs the corrected transform coefficients as corrected transform coefficients. The image decoding apparatus according to claim 9, wherein: 11. A decoding means for decoding a code, reproducing a transform coefficient, outputting a decoded transform coefficient, and detecting coding cut-off information added to the code, and decoding the coding cut-off information. A first correction unit for estimating and correcting the decoding transform coefficient by statistical data when the unit detects the correction coefficient, and outputting the corrected conversion coefficient as a correction conversion coefficient; and If the correction conversion coefficient of the correction means is 0, the correction conversion coefficient of the first correction means is re-corrected to an estimated value obtained by referring to a nearby correction conversion coefficient, and a re-correction conversion coefficient is output. A second correction unit, when the decoding unit detects the encoding cutoff information, performs inverse conversion on the correction conversion coefficient or the re-correction conversion coefficient, and outputs a reproduced image; If the issue of truncation information was not detected by the decoding means performs inverse transform on the decoded transform coefficients, the image decoding apparatus comprising the inverse transform means for outputting the reproduced image. 12. The first correction means, when the decoding means detects the coding cutoff information, accumulates decoded transform coefficients, corrects the decoded transform coefficients based on the accumulated value, and performs correction conversion. The image decoding apparatus according to claim 11, wherein the image is output as a coefficient.