JP2003101416A - Image encoding method and image decoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly decode the quantization parameter of a block except for a damaged block when a transmission error occurs, and further to reduce a number of bits of a header part by providing the header part to eliminate necessity to transmit the quantization parameter. SOLUTION: A subtraction unit Sub1 calculates a difference between quantization parameters QP and QP2 and defines the result as a quantization parameter difference DeltaQP1. The quantization parameter QP2 is the same value as a quantization parameter QP0 and encoded as a header encoding signal HdrStr by a header encoding unit HdrEnc. Therefore, the quantization parameter difference DeltaQP1 becomes the difference between the quantization parameter QP which is a quantization parameter of the relevant block, and the quantization parameter QP2 which is a quantization parameter of the header part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a quantization parameter coding method that is strong against a transmission path error without degrading the compression rate when performing coding with quantization on an image signal. An image encoding method, an image decoding method, an image encoding apparatus, an image decoding apparatus, and a recording medium on which a program for implementing the same by software is recorded.

[0002]

2. Description of the Related Art In recent years, in the age of multimedia in which voices, images, and other pixel values are handled in an integrated manner, conventional information media such as newspapers, magazines, televisions, radios, and telephones are transmitted to people. Means have become the subject of multimedia. Generally, multimedia means not only characters but also figures, voices, especially images, etc. are associated with each other at the same time. However, in order to target the above-mentioned conventional information media as multimedia, the information is converted into a digital format. Representation is an essential condition.

However, when the information amount of each of the above information media is estimated as a digital information amount, the amount of information per character is 1 to 2 bytes in the case of characters, whereas that of voice is 64 kbits per second. (Telephone quality), and for moving images, an information amount of 100 Mbits (current television reception quality) or more is required per second, and it is not realistic to handle the enormous amount of information in the digital form as it is in the above information media. For example, videophone is 64kbps ~ 1.5M
Integrated service digital network (IS
Although it has already been put to practical use by DN (Integrated Services Digital Network), it is impossible to send the image of the TV / camera as it is with ISDN.

Therefore, what is needed is an information compression technique. For example, in the case of a videophone, the H.261 and H.263 standards internationally standardized by the ITU (International Telecommunication Union Telecommunication Standardization Sector). The video compression technology of is used.
Moreover, according to the information compression technology of the MPEG-1 standard, it becomes possible to put the image information together with the audio information into a normal music CD (compact disc).

Here, MPEG (Moving Picture Exper)
ts Group) is an international standard for digital compression of moving image signals, and MPEG-1 is a standard for compressing moving image signals up to 1.5 Mbps, that is, information of television signals up to about 1/100. In addition, since the transmission speed for the MPEG-1 standard is mainly limited to about 1.5 Mbps, in MPEG-2 standardized to meet the demand for higher image quality, moving image signals are 2 to 15 Mbps. Is compressed to.

Furthermore, at present, a working group that has been promoting standardization with MPEG-1 and MPEG-2 (ISO / IEC JTC1 / SC29 / WG11)
Has standardized MPEG-4, which has a higher compression rate. M
Initially, PEG-4 not only enables highly efficient encoding at a low bit rate, but also introduces powerful error resilience technology that can reduce subjective image quality degradation even if a transmission path error occurs. .

In MPEG, an image signal is divided into blocks each having a plurality of pixel values, the pixel values are orthogonally transformed in block units, and the orthogonally transformed pixel values are quantized and variable-length coded. Encoding is performed. Quantization is to divide a pixel value component that has been orthogonally transformed by a value called a quantization step, and in decoding, it is an inverse transformation, that is, an operation of multiplying a quantized step by a quantized component. Some dequantization is done. If the quantization step is made coarse, the compression rate is improved but the image quality deterioration due to the compression is increased. Conversely, if the quantization step is made fine, the image quality deterioration due to the compression is reduced but the compression rate is decreased. Therefore, the size of the quantization step is controlled in block units according to the target compression rate and image quality. The quantization parameter representing the quantization step at the time of encoding is stored in the image coded signal together with the quantized component, so that it can be correctly dequantized at the time of decoding. The quantization parameter is a parameter that is almost proportional to the quantization step, and the quantization parameter is multiplied by a weighting value according to the frequency component for roughly quantizing the high-frequency component, which is not noticeably deteriorated. It corresponds to a step.

Although the quantization parameter can be changed on a block-by-block basis, if the quantization parameter is changed greatly for each block in the same frame encoding, the image quality deterioration of the part quantized with a large quantization parameter is visually obtrusive. Therefore, in general, the degree of change in the quantization parameter for each block is often small. As a result, as a method of encoding the quantization parameter, the method of encoding the difference value of the quantization parameter between adjacent blocks is MPEG-4.
Has been adopted by.

FIG. 8 is a block diagram of the image decoding apparatus of the present invention. Image signal Vin is a blocking unit Blk
In the ing process, the blocks are grouped into blocks each consisting of several pixels to form a blocked signal Blk, and the blocked signal Blk is subjected to frequency conversion such as DCT in a transform coding unit Trans to become a transformed value signal Coef. Quantization unit Q is transformed value signal Coe
Quantize f with a quantization parameter QP and output a quantized value signal QCoef that is a quantum value. It is assumed that the quantization parameter QP is generated by the quantization unit Q so as to have a predetermined compression rate and image quality.

The image signal Vin is a parameter extraction unit Vin
The image parameter Vinfo including information such as image size is extracted by foExt. The image parameter Vinfo notifies the blocking unit Blking and the transform coding unit Trans of information such as the image size necessary for performing the blocking and the frequency conversion, and at the same time, sets the header coded signal HdrStr that is the common information of the image. The header encoding unit HdrEnc is notified to generate.

Switch Se only when the block immediately after the header
l1 is ON, and the quantization parameter QP is the quantization parameter
The header encoding unit HdrEnc is notified as QP0.
The header encoding unit HdrEnc encodes the common information of the image such as the image parameter Vinfo and the quantization parameter QP0 at the bit position subsequent to the synchronization signal to generate the header encoded signal HdrStr.
And

On the other hand, the quantization parameter QP1 delayed by one block by the delay unit Delay0 (that is, the quantization parameter of the block before the block having the quantization parameter QP)
And the difference value of the quantization parameter QP is calculated in the subtraction unit Sub0, and is notified to the block unit coding unit BlkEnc as the quantization parameter difference DeltaQP0. The block unit coding unit BlkEnc codes the quantized value signal QCoef and generates a block coded signal BlkStr to which the quantization parameter difference DeltaQP0 is added as information of the block. The multiplexing unit Mux is a block coded signal BlkStr.
And the header coded signal HdrStr are multiplexed, and the image coded signal is
Generate and output Str0.

FIG. 9 shows a stream structure of a conventional image coded signal. The image coded signal Str0 is the header coded signal Hd
It is composed of rStr and block coded signal BlkStr. Multiple header coded signals HdrStr can be inserted in the image coded signal, but the header coded signal HdrStr at the beginning of the frame needs to include a special signal required only at the beginning of the frame. Frame header coded signal FrmH
drStr and packet header coded signal VPHdr in the middle of frame
There are 2 types of Str. A group of blocks corresponding to positions separated by the header encoded signal is called a packet.

The frame header coded signal FrmHdrStr includes a sync signal Sync, an image size signal FrmSize, and a frame quantization parameter signal FrmQP. Image size signal Frm
Size indicates the number of horizontal / vertical pixels of the image, or the number of horizontal and vertical blocks forming one frame of the image. The frame quantization parameter signal FrmQP represents the quantization parameter QP of the first block of the frame.

The packet header coded signal VPHdrStr includes a sync signal Sync and a packet quantization parameter signal VPQP. The packet quantization parameter signal VPQP represents the quantization parameter QP of the first block of the packet.

The block coded signal BlkStr is a block quantization parameter signal indicating the quantization parameter of each block.
Block quantization parameter signal Blk containing BlkQP
QP is a bit string representing the quantization parameter difference DeltaQP0 in FIG.

FIG. 10 is a block diagram of a conventional image decoding apparatus. In the figure, the same numbers are assigned to the devices and the signals having the same meanings as in the block diagram of the conventional image coding apparatus of FIG. 8, and the description thereof will be omitted.

The image coded signal Str0 is a separation unit DeMux.
Block encoded signal BlkStr and header encoded signal HdrStr
Is separated into The header coded signal HdrStr is decoded by the header decoding unit HdrDec and the image parameter Vinfo and the quantization parameter QP0 are output. The block coded signal BlkStr is decoded by the block unit decoding unit BlkDec, and the quantized value signal QCoef and the quantization parameter difference DeltaQP0 are output.

In the block immediately after the header, the switch Sel2 selects the quantization parameter QP0 as the quantization parameter QP1. Since the quantization parameter immediately after the header is encoded in the header encoded signal HdrStr, the quantization parameter difference DeltaQP0 is usually 0. Therefore, the addition unit A
Quantization parameter QP1 and quantization parameter difference Delt at dd0
The value of the quantization parameter QP obtained as a result of adding aQP0 is the same as the value of the quantization parameter QP0. Therefore,
It is clear that the conventional image coding apparatus of FIG. 8 can be correctly decoded to the same value as the quantization parameter QP of the block diagram. The quantization parameter QP is notified to the inverse quantization unit IQ, is temporarily stored in the delay unit Delay2, and is used for decoding the quantization parameter of the next block.

For blocks other than immediately after the header, switch
The output of the delay unit Delay2 is selected by Sel2 and becomes the quantization parameter QP1. That is, since the quantization parameter QP1 is the quantization parameter of the previous block, the addition unit Ad
Quantization parameter QP1 and quantization parameter difference Delta at d0
The value of the quantization parameter QP obtained as a result of adding QP0 can be correctly decoded to the same value as the quantization parameter QP of the block diagram in the conventional image coding apparatus of FIG. The quantization parameter QP is notified to the inverse quantization unit IQ, is temporarily stored in the delay unit Delay2, and is used for decoding the quantization parameter of the next block.

The inverse quantization unit IQ is a quantization parameter QP
To dequantize the quantized value signal QCoef and output the dequantized value signal DeCoef. That is, the inverse quantization unit IQ performs the inverse operation of the quantization unit Q of the block diagram in the conventional image coding apparatus of FIG.

The transform decoding unit InvTrans transform-decodes the inverse quantized value signal DeCoef to obtain the inverse transformed value signal DeBlk. That is, the transform decoding unit InvTrans performs the reverse operation of the transform coding unit Trans of the block diagram in the conventional image coding apparatus of FIG. The image parameter required for conversion and decoding is acquired from the image parameter Vinfo.

The deblocking unit DeBlking block-integrates the inverse transform value signal DeBlk to obtain a decoded image signal Vout. That is, the deblocking unit DeBlking performs the inverse operation of the transform coding unit Trans of the block diagram in the conventional image coding apparatus of FIG. Image parameters required for block integration are acquired from the image parameter Vinfo.

In actual image coding and image decoding, the quantization parameter is usually changed in units of several blocks called macroblocks. However, since a macro block is also considered as one form of a block that is a collection of pixels, the term block is used as a concept including a macro block in this specification.

[0025]

In the conventional image coding apparatus and the conventional image decoding apparatus as described above, since the difference value of the quantization parameter is coded, there is the influence of the transmission path error. When the quantization parameter of the block cannot be correctly decoded, the quantization parameters of all subsequent blocks of the frame cannot be correctly decoded.

Therefore, a header coded signal including a synchronization signal
By directly encoding the quantization parameter value in the frame quantization parameter signal FrmQP or the packet quantization parameter signal VPQP in HdrStr, the block immediately after the header encoded signal HdrStr is quantized even if a transmission path error occurs. The parameters can be decrypted correctly.

However, all header encoded signals Hd
If the value of the quantization parameter is directly encoded with rStr, a large number of bits are required for the header coded signal HdrStr, and if a large number of header coded signal HdrStr is inserted to improve error resilience, the compression rate drops sharply. There is a problem to do.

[0028]

In order to solve this problem, a first invention is an image coding method for coding an image signal by using quantization to generate an image coded signal,
When the quantization parameter representing the quantization step used in the encoding is stored in the header part and the image data part of the image coded signal, the quantization parameter stored in the image data part is arranged in the header part. This is an image coding method that is a difference value from a quantization parameter.

A second aspect of the present invention is an image decoding method for decoding an image coded signal obtained by coding an image signal using quantization, wherein the image data section is used when decoding the image coded signal. The quantization parameter representing the quantization step used in the decoding of is the addition value of the quantization parameter stored in the header part of the image coded signal and the quantization parameter difference value stored in the image data part. Is the image decoding method.

In the present invention having the above configuration, the difference value between the quantization parameter of the block and the quantization parameter encoded in the header portion is encoded. Therefore,
If the quantization parameter coded in the header can be correctly decoded, the quantization parameters of other blocks can be correctly decoded even if the quantization parameter of the block with the transmission path error cannot be correctly decoded. become.

When a plurality of header parts are present in a stream forming one frame, if at least two header parts transmit the same quantization parameter value, even if one header is damaged, the other header part will be transmitted. The quantization parameter of the header can be correctly decoded. That is, conventionally, the difference value between the quantization parameter of the immediately preceding block and the quantization parameter of the block was encoded, but in the present invention, it is not the difference value between the quantization parameter of the immediately preceding block and the quantum of the header part. Since it is a difference value from the quantization parameter, even if the quantization parameter of some blocks is damaged by a transmission error, the quantization parameters of other blocks can be correctly decoded.

Further, if the same quantization parameter is transmitted in all the header parts, it is not necessary to transmit the quantization parameter in all the header parts, so that the compression rate is the same as that of the conventional image coding method and image. Obviously it is higher than the decoding method. The larger the number of header parts, the larger the number of bits that can be reduced. Further, the higher the compression rate, the greater the ratio of the number of bits in the header part to the total number of bits. Therefore, the present invention is more effective as the compression rate is higher.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 7.

(Embodiment 1) FIG. 1 is a block diagram of an image coding apparatus of the present invention. In FIG.
Units that perform the same operations and signals that have the same operations as those in the block diagram of the conventional image coding apparatus in FIG. That is, the blocking unit Blkin
The operations of g, the transform coding unit Trans, the quantization unit Q, the block unit coding unit BlkEnc, the parameter extraction unit VinfoExt, the header coding unit HdrEnc, and the multiplexing unit Mux are the same. The difference is that the quantization parameter difference DeltaQP0 is coded by the block unit coding unit BlkEnc in the block diagram of the conventional image coding apparatus of FIG. 8, whereas the block diagram of the image coding apparatus of the present invention of FIG. It is to encode the quantization parameter difference DeltaQP1.

The procedure for generating the quantization parameter difference DeltaQP1 will be described below. The switch Sel5 is turned on at the beginning of the frame and stores the first quantization parameter QP0 of the frame in the memory unit Mem1. The quantization parameter QP0 is stored in the memory unit Mem1 and is immediately output as the quantization parameter QP2.
The subtraction unit Sub1 calculates the difference between the quantization parameter QP and the quantization parameter QP2 and calculates the quantization parameter difference DeltaQP
Set to 1. The quantization parameter QP2 is the quantization parameter QP0
And has the same value as, and is encoded as a header encoded signal HdrStr by the header encoding unit HdrEnc. Therefore, the quantization parameter difference DeltaQP1 is the difference between the quantization parameter QP which is the quantization parameter of the block and the quantization parameter QP2 which is the quantization parameter of the header part.

As described above, the quantization parameter difference DeltaQ which is the difference value between the quantization parameter QP2 transmitted in the header part and the quantization parameter QP of the block.
By encoding as P1, it is possible to decode the quantization parameter for each block, and even if some blocks are damaged by a transmission error, the quantization parameters of other blocks can be correctly decoded.

FIG. 2 shows a stream configuration diagram of the image coded signal Str1 coded by the block diagram in the image coding apparatus of the present invention in FIG. The difference between the stream structure of the image coded signal of the present invention in FIG. 2 and the stream structure of the conventional image coded signal in FIG. 9 is that the packet header coded signal VPHdrS
The quantization parameter arranged in tr is the packet quantization parameter signal VPQP in the stream structure of the conventional image coded signal of FIG. 9, but is the frame quantization in the stream structure of the image coded signal of the present invention of FIG. Parameter signal Fr
mQP. In this way, when the quantization parameter exists in the header part, all the quantization parameters are encoded as the same quantization parameter value.

In the first embodiment, in the header portion, the first quantization parameter of the frame, quantization parameter QP0
However, the predetermined value of the quantization parameter (average value of the quantization parameter of the frame) may be transmitted in the header part. In that case, the predetermined value of the quantization parameter is recorded in the memory unit Mem1.

(Embodiment 2) FIG. 3 is a block diagram of an image decoding apparatus of the present invention, in which an image encoded signal Str1 encoded by the block diagram of the image encoding apparatus of the present invention of FIG. 1 is decoded. To do. In FIG. 3, FIG.
Units having the same operation and signals having the same operation as those in the block diagram of the conventional image decoding apparatus of No. 0 are given the same symbols, and the description thereof will be omitted. That is, the separation unit DeMux, the block unit decoding unit BlkDec, the inverse quantization unit IQ,
Transform decoding unit InvTrans, deblocking unit De
The operations of Blking and the header decoding unit HdrDec are the same. The difference is that the block unit decoding unit BlkDec extracts the quantization parameter difference DeltaQP0 in the block diagram of the conventional image encoding apparatus of FIG.
In the block diagram of the image decoding apparatus according to the present invention, the quantization parameter difference DeltaQP1 is extracted.

The procedure for decoding the quantization parameter QP from the quantization parameter difference DeltaQP1 will be described below. Quantization parameter QP extracted by header decoding unit HdrDec
0 is stored in the memory unit Mem2 and is immediately output as the quantization parameter QP2. Addition unit Add
1 becomes the quantization parameter QP by adding the quantization parameter QP2 and the quantization parameter difference DeltaQP1 for each block.

As described above, the quantization parameter difference DeltaQP1 does not depend on the quantization parameters of other blocks.
Since the quantization parameter QP can be decoded from, the image can be decoded by correctly decoding the quantization parameters of other blocks that are not damaged even if the block is damaged by a transmission error.

(Third Embodiment) FIG. 4 is a block diagram of an image coding apparatus according to the present invention. In FIG. 4, FIG.
Units that perform the same operations and signals that have the same operations as in the block diagram of the image coding apparatus of the present invention are denoted by the same symbols, and description thereof will be omitted. That is, the blocking unit Blkin
The operations of g, the transform coding unit Trans, the quantization unit Q, the block unit coding unit BlkEnc, the parameter extraction unit VinfoExt, the header coding unit HdrEnc, the multiplexing unit Mux, the switch Sel1, the memory unit Mem1, and the subtraction unit Sub1 are the same. Is.

In the block diagram of the image coding apparatus of the present invention shown in FIG. 4, the quantization parameter is not always transmitted in the header portion, and the quantization parameter is transmitted only in some headers. In the header part where the quantization parameter should be transmitted, the switch Sel3 is turned on and the quantization parameter QP
0 is the header coding unit Hd as the quantization parameter QP3
rEnc is notified. The switch Sel3 is turned off in the header portion that does not transmit the quantization parameter, and the quantization parameter is not transmitted in the header portion.

FIG. 5 shows a stream configuration diagram of the image coded signal Str2 coded by the block diagram in the image coding apparatus of the present invention of FIG. The difference between the stream structure of the image coded signal of the present invention in FIG. 5 and the stream structure of the conventional image coded signal in FIG. 9 is that the packet header coded signal VPHdrS
The quantization parameter arranged in tr is the packet quantization parameter signal VPQP in the stream structure of the conventional image coded signal of FIG. 9, but is omitted in the stream structure of the image coded signal of the present invention of FIG. That is. In this way, even in the stream in which the quantization parameter is omitted in the header part, the fact that the quantization parameters transmitted in the header part are all the same quantization parameter value is used, and the quantization parameter values extracted from other header parts are used. Can be used to decode the quantization parameter.

In the third embodiment, in the header part, the first quantization parameter of the frame, quantization parameter QP0
However, the predetermined value of the quantization parameter (average value of the quantization parameter of the frame) may be transmitted in the header part. In that case, the predetermined value of the quantization parameter is recorded in the memory unit Mem1.

(Embodiment 4) FIG. 6 is a block diagram of the image decoding apparatus of the present invention. The image coded signal Str2 encoded by the block diagram of the image encoding apparatus of the present invention of FIG. 4 is decoded. To do. In FIG. 6, FIG.
Units that perform the same operations as those in the block diagram of the image decoding apparatus of the present invention and signals of the same operations are denoted by the same symbols, and description thereof will be omitted. That is, the separation unit DeMux, the block unit decoding unit BlkDec, the inverse quantization unit IQ,
Transform decoding unit InvTrans, deblocking unit De
The operations of Blking and the header decoding unit HdrDec are the same.

The header decoding unit HdrDec extracts the quantization parameter QP3 only when the quantization parameter is transmitted in the header part. Only when the quantization parameter QP3 can be correctly extracted (when there is no transmission line error and the quantization parameter is transmitted in the header part), the switch Sel4 is turned ON and the quantization parameter QP3 is stored as the quantization parameter QP0 in the memory. Unit Mem2 is notified. The memory unit Mem2 stores the quantization parameter QP0 and immediately outputs it as the quantization parameter QP2.
The addition unit Add1 adds the quantization parameter difference DeltaQP1 and the quantization parameter QP2 for each block, and decodes the quantization parameter QP.

As described above, even in the stream in which the quantization parameter is omitted in the header part, the fact that the quantization parameter values transmitted in the header part are all the same quantization parameter value is used to extract from other header parts. The image can be decoded by correctly decoding the quantization parameter using the quantization parameter value.

(Fifth Embodiment) Furthermore, a program for realizing the configuration of the image coding method or the image decoding method shown in each of the above embodiments is recorded in a storage medium such as a floppy (registered trademark) disk. By doing so, it becomes possible to easily carry out the processing shown in each of the above embodiments in an independent computer system.

FIG. 7 is an explanatory diagram of a case where the present invention is carried out by a computer system using a floppy disk storing the image coding method or the image decoding method of the first to second embodiments.

FIG. 7B shows the external appearance, sectional structure, and floppy disk as viewed from the front of the floppy disk, and FIG. 7A shows an example of the physical format of the floppy disk which is the recording medium body. . The floppy disk FD is built in a case F, and a plurality of tracks Tr are formed concentrically from the outer circumference to the inner circumference on the surface of the disk F, and each track is angularly divided into 16 sectors Se. ing. Therefore, in the floppy disk storing the program, the image encoding method and the image decoding method as the program are recorded in the area allocated on the floppy disk FD.

Further, FIG. 7C shows a structure for recording / reproducing the program on / from the floppy disk FD. When the program is recorded on the floppy disk FD, the image encoding method or the image decoding method as the program is written from the computer system Cs via the floppy disk drive. When the image coding method and the image decoding method are constructed in a computer system by a program in a floppy disk, the program is read from the floppy disk by a floppy disk drive and transferred to the computer system.

In the above description, a floppy disk is used as the recording medium, but an optical disk may be used as well. Further, the recording medium is not limited to this, and any recording medium such as an IC card and a ROM cassette that can record the program can be similarly used.

[0054]

As described above, according to the image coding method and the image decoding method according to the present invention, when a transmission error occurs, the quantization parameters other than the block damaged by the transmission error are corrected. Since it can be decoded, it has more error resilience than ever before, that it correctly decodes only the quantization parameter of the block after the header, and it can also realize the header part that does not require the transmission of the quantization parameter. Practical value is high because the number of bits can be reduced and the image compression rate is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an image coding apparatus according to a first embodiment of the present invention.

FIG. 2 is a stream configuration diagram of a coded image signal according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an image decoding device according to a second embodiment of the present invention.

FIG. 4 is a block diagram of an image coding apparatus according to a third embodiment of the present invention.

FIG. 5 is a stream configuration diagram of a coded image signal according to the third embodiment of the present invention.

FIG. 6 is a block diagram of an image decoding device according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a storage medium for storing a program for realizing the image coding method and the image decoding method according to the fifth embodiment of the present invention by a computer system.

FIG. 8 is a block diagram of a conventional image encoding device.

FIG. 9 is a stream configuration diagram of a conventional image coded signal.

FIG. 10 is a block diagram of a conventional image decoding device.

[Explanation of symbols]

Vin video signal Vout Decoded video signal Blking blocking unit DeBlking Deblocking unit Trans transcoding unit InvTrans conversion decoding unit Q quantization unit IQ dequantization unit BlkEnc Block-wise coding unit BlkDec Block-wise decoding unit Mux multiplexing unit DeMux Separation Unit VinfoExt Parameter extraction unit HdrEnc header encoding unit HdrDec header decoding unit Add0, Add1 addition unit Sub0, Sub1 subtraction unit Mem1, Mem2 memory unit Delay0, Delay2 delay unit Sel1, Sel2, Sel3, Sel4, Sel5, Sel6 switches Cs computer system FD floppy disk FDD floppy disk drive

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Claims (12)

[Claims] 1. An image encoding method for producing an image encoded signal by encoding an image signal using quantization, wherein a quantization parameter representing a quantization step used in the encoding is provided in the image encoding. An image coding method in which the quantization parameter stored in the image data portion when stored in the header portion and the image data portion of the signal is a difference value from the quantization parameter arranged in the header portion. 2. The image coding method according to claim 1, wherein all the quantization parameters stored in the image data section are coded by a difference value from the quantization parameters arranged in the header section. 3. The image coding method according to claim 1, wherein all the quantization parameters stored in the header of the same frame have the same quantization parameter value. 4. The image coding method according to claim 1, wherein the quantization parameter is stored only in a part of the header. 5. An image decoding method for decoding an image coded signal in which an image signal is coded using quantization, wherein the image data part is decoded when the image coded signal is decoded. The image decoding, which is a quantization parameter indicating the quantization step to be used, is an addition value of the quantization parameter stored in the header part of the image coded signal and the quantization parameter difference value stored in the image data part. Method. 6. The image decoding method according to claim 5, wherein all the quantization parameters stored in the image data section are decoded by the addition value with the quantization parameter arranged in the header section. 7. The image decoding method according to claim 5, wherein all the quantization parameters stored in the header of the same frame have the same quantization parameter value. 8. The image decoding method according to claim 5, wherein the quantization parameter is decoded from only a part of the header. 9. An image coding apparatus for coding an image signal, comprising: an image coding means for coding an image signal using quantization; and an initial value of a quantization step used in the coding. First quantization parameter encoding means for encoding,
Second quantization parameter coding means for coding the quantization parameter stored in the image data section as a difference value from the initial value of the quantization step; the coded signal generated by the image coding means; An image coding apparatus comprising: a first quantization parameter coding means and a multiplexing means for multiplexing the coded signals generated by the second quantization parameter coding means into an image coded signal. 10. An image decoding apparatus for decoding an image coded signal, wherein the image coded signal is classified into image data, a first quantization parameter signal and a second quantization parameter signal. A first quantization parameter decoding means for decoding an initial value of the quantization step from the first quantization parameter signal, and data extracted from the second quantization parameter signal in the quantization step. The second quantization parameter decoding means for decoding the quantization parameter of the image data part as an addition value to the initial value, and the quantization parameter decoded by the second quantization parameter decoding means are used for the above An image decoding apparatus including image decoding means for decoding image data to form a decoded image signal. 11. A storage medium for storing a program for performing the image encoding method according to claim 1 by a computer, wherein the program encodes an image signal by using quantization and an image code. An image coding method for generating a coded signal, wherein a quantization parameter representing a quantization step used in the coding is stored in the image data part when the header part and the image data part of the image coded signal are stored. A storage medium characterized in that the stored quantization parameter is for performing an image coding method which is a difference value from the quantization parameter arranged in the header section. 12. A storage medium for storing a program for executing the image decoding method according to claim 5 by a computer, wherein the program is an image code obtained by encoding an image signal in a computer. An image decoding method for decoding a coded signal, wherein a quantization parameter representing a quantization step used in decoding of an image data part when decoding the image coded signal is A storage medium for performing an image decoding method, which is an addition value of a quantization parameter stored in a header section and a quantization parameter difference value stored in an image data section.