JP2000261806A - Coding method, coder, coding and decoding method and coder and decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coder whose power consumption can be reduced. SOLUTION: The coder is provided with coding means 1-4 that encode an input original picture signal (a) through the use of group of picture GOP structure consisting of three picture frames of I, P and B pictures, a local decode processing section 13 that conduct local decoding processing for coding, and a GOP structure discrimination section 9 that discriminates a GOP structure when the an input original picture signal (a) is encoded, allows the local decode processing section 13 to conduct local decode processing while the image frame of the I or P picture is encoded on the basis of the discrimination result and to come to a pause while the image frame of the B picture is coded as its control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intra-coded picture (intra-coded picture: I picture) and an inter-coded picture (predictive-coded picture: P).
Picture), frame interpolation coding frame (bidirectio
GOP (group of pictu) composed of three image frames of nally predictive-coded picture: B picture
res) The present invention relates to an apparatus and a method for performing image coding using a structure. Further, the present invention relates to an encoding / decoding device and an encoding / decoding method capable of performing such image encoding.

[0002]

2. Description of the Related Art One of systems for performing high-efficiency encoding of image signals is described below.
One is a method using a GOP structure in which I, B, and P pictures are periodically inserted. FIG. 4 shows a schematic configuration of a conventional encoding device employing this method.

[0003] The encoding apparatus shown in FIG.
It comprises a DCT transformer 102, a quantizer 103, a variable length encoder 104, an inverse quantizer 105, an inverse DCT transformer 106, an adder 107, and a frame memory 108.

A subtractor 101 receives an input original image signal (a) as one input, a prediction signal (f) output from the frame memory 108 as another input, and receives the input original image signal (a).
Is subtracted from the prediction signal (f) to generate a prediction error signal (g), which is output to the DCT converter 102.

The DCT converter 102 performs a DCT transform on the prediction error signal (g) input from the subtractor 101, and
The CT transform coefficient (h) is output to the quantizer 103. The quantizer 103 converts the DC input from the DCT
The T-transform coefficient (h) is subjected to quantization processing to reduce the amount of irreversible information, and the quantization coefficient (b) obtained by the processing is converted to a variable-length encoder 104 and an inverse quantizer 105
Output to each of.

[0006] The variable length encoder 104 includes a quantizer 103.
The variable-length coding process is performed on the quantized coefficient (b) input from, to generate an output stream (c). This output stream (c) is sent out on the transmission path and received by the decoding device on the receiving side.

The inverse quantizer 105 performs an inverse quantization process on the quantization coefficient (b) input from the quantizer 103, and
A CT transform coefficient (j) is generated, and this is transformed into an inverse DCT
06. The inverse DCT transformer 106 performs inverse DCT on the DCT transform coefficient (j) input from the inverse quantizer 105.
The conversion is performed to generate a prediction error signal (k), which is output to the adder 107.

[0008] The adder 107 receives the prediction error signal (k) input from the inverse DCT converter 106 and the frame memory 10
A reproduction image (m) is generated by performing an addition process with the prediction signal (f) which is the output of No. 8 and output to the frame memory 108. The frame memory 108 generates a prediction signal (f) based on the reproduced image (m) input from the adder 107, and subtracts the prediction signal (f) from the subtractor 101 and the adder 10
7 respectively.

In the above-described coding apparatus, coding is performed adaptively according to each of I, B, and P pictures. In particular,
In an I picture, after an original image signal is DCT-transformed for each block, DCT transform coefficients are quantized, and the quantized value is subjected to variable-length coding. In the P picture, an inter-frame prediction error signal between the already coded I picture and the P picture is generated, and the prediction error signal is
After the CT conversion operation, the data is quantized and subjected to variable length coding. For B pictures, the encoded I picture or P picture
The picture is used for prediction, the obtained prediction signal is subjected to DCT transform operation for each block, and then quantized and variable-length coded.

Next, the configuration of a decoding device that receives and decodes the output stream transmitted from the above-described coding device will be briefly described. FIG. 5 shows a schematic configuration of the decoding apparatus.

The decoding apparatus shown in FIG. 5 comprises a variable length decoder 201, an inverse quantizer 202, an inverse DCT transformer 203, an adder 204, a smoother 205, and a frame memory 206.

A variable-length decoder 201 performs variable-length decoding on an input stream (d) of a high-efficiency coded image input from a transmission line to reproduce a received quantization coefficient (i). To the inverse quantizer 202. Inverse quantizer 2
02 performs an inverse quantization process on the received quantization coefficient (i) input from the variable length decoder 201 to generate a reproduced DCT transform coefficient (j), and outputs this to the inverse DCT transformer 203.

The inverse DCT transformer 203 has a function of the inverse quantizer 20.
Inverse DCT to the reproduced DCT transform coefficient (j)
The conversion is performed to generate a reproduction prediction error signal (k), which is output to the adder 204. The adder 204 performs a process of adding the reproduction prediction error signal (k) input from the inverse DCT converter 203 and the prediction signal (n) output from the frame memory 206 to generate a reproduction image (m). This is output to the smoother 205 and the frame memory 206, respectively.

The smoother 205 smoothes the frame rate of the reproduced image signal (m) to obtain an output decoded image (e). The frame memory 206 includes the adder 204
, Generates a prediction signal (n) based on the reproduced image (m) input from, and outputs it to the adder 204 (feedback input).

[0015]

As described above, I,
G composed of three image frames of B and P pictures
In image encoding using the OP structure, encoding is performed adaptively according to each of I, B, and P pictures. In this case, in the B picture, the coded I picture or P picture is used for prediction and is coded, but the image frame of the B picture is not directly used for prediction.

In the above-described conventional encoding apparatus, a B picture frame that is not used for prediction is dequantized by a dequantizer 105, an inverse DCT transformer 106, an adder 107,
Useless processing such as decoding processing is performed in a local decoding (local decoding) unit including the frame memory 108, which is disadvantageous in terms of power saving.

An object of the present invention is to solve the above problems and to provide an encoding device and an encoding method capable of reducing power consumption. It is still another object of the present invention to provide an encoding / decoding device and an encoding / decoding method which improve the efficiency of encoding / decoding processing by applying the encoding.

[0018]

In order to achieve the above object, an encoding apparatus according to the present invention uses an input original image signal by using a GOP structure composed of three image frames of I picture, P picture and B picture. Encoding means for performing local encoding, local decoding processing means for performing local decoding for the encoding, and determining a GOP structure when the input original image signal is encoded, based on the determination result. The local decoding processing means performs local decoding while the I-picture or P-picture image frame is encoded, and suspends the local decoding processing means while the B-picture image frame is encoded. And a GOP structure determining means for performing control as described above.

The encoding method according to the present invention is an encoding method for encoding an input original image signal using a GOP structure composed of three image frames of I picture, P picture and B picture. A GOP structure when an image signal is encoded is determined, and based on the determination result, when an I-picture or a P-picture image frame is encoded, a local decoding process for the encoding is performed. In encoding a picture frame of a picture, the local decoding process is not performed.

An encoding / decoding apparatus according to the present invention comprises: encoding means for encoding an input original image signal using a GOP structure composed of three image frames of an I picture, a P picture, and a B picture; Local decoding processing means for performing local decoding processing for encoding, performing local decoding processing on an image signal having a predetermined encoding structure received from a communication partner to obtain a reproduced image,
A GOP structure when the input original image signal is encoded is determined. Based on the determination result, while an I-picture or a P-picture image frame is encoded, the local decoding processing unit performs encoding. And a GOP structure determining means for causing the local decoding processing means to perform a local decoding process for obtaining a reproduced image while an image frame of a B picture is encoded. I do.

In the above case, the GOP structure determining means includes:
If there is no received image to be reproduced while the image frame of the B picture is being encoded, the local decoding processing unit may be configured to pause.

According to the encoding / decoding method of the present invention, an input original image signal is encoded by using a GOP structure composed of three image frames of an I picture, a P picture, and a B picture, and a communication destination. An encoding / decoding method for decoding a received image signal having a predetermined encoding structure and sharing a local decoding processing unit for performing the encoding and decoding, wherein the input original image is A GOP structure at the time of encoding a signal is determined. Based on the determination result, while an I-picture or a P-picture image frame is encoded, the local decoding processing means performs local decoding processing for encoding. And B
While the picture frame of the picture is encoded, the local decoding processing means performs a local decoding process for decoding.

In the above case, if there is no received image to be reproduced while the image frame of the B picture is being encoded, the local decoding processing means may be paused.

(Operation) In the coding apparatus and the coding method of the present invention as described above, the local decoding processing means is in a halt state while a B-picture image frame is coded, so that power consumption is correspondingly reduced. Is less.

In the encoding / decoding device and the encoding / decoding method of the present invention, during the encoding of a B picture that does not require local decoding, instead of the local decoding for the frame of the B picture, A local decoding process for reproducing the received image is performed.
Further, when there is no received image to be reproduced during the encoding of the B picture, the local decoding processing means is suspended, so that the power consumption is reduced accordingly.

[0026]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an encoding apparatus according to an embodiment of the present invention. This encoding device includes a subtractor 1, a DCT
A converter 2, a quantizer 3, a variable length encoder 4, an inverse quantizer 5, an inverse DCT converter 6, an adder 7, a frame memory 8,
It comprises a GOP structure judging unit 9. Note that the subtracter 1 and the DCT
The transformer 2, the quantizer 3, the variable length encoder 4, the inverse quantizer 5, the inverse DCT transformer 6, the adder 7, and the frame memory 8 all have the same configuration as that shown in FIG. Since the connection relationship and the operation of each component are the same, the description of these components will be omitted here.

The GOP structure determining section 9 determines the GOP structure when the input original image signal (a) is encoded, and
While an image frame of a picture or a P picture is encoded, the inverse quantizer 5, the inverse DCT transformer 6, the adder 7,
The local decoding unit 13 including the frame memory 8 is set in an operable state, and the local decoding unit is controlled so as to be paused while an image frame of a B picture is encoded. Here, the encoding of the image frame means the subtractor 1,
This means encoding in the DCT transformer 2 and the quantizer 3.

In the coding apparatus of the present embodiment configured as described above, similarly to the coding apparatus shown in FIG. 4 described above, the coding of the image frame is appropriately applied in accordance with each of the I, B, and P pictures. 4 is different from that in FIG. 4 in that the operation state of the local decoding unit 13 is controlled by the GOP structure determination unit 9 as follows.

Here, the GOP structure "I, B,
P, B, P,. . . , I, B, P,. . . (In the case of a GOP structure, the first frame to be coded is always an I picture.)

Based on the determined GOP structure, the GOP structure determining unit 9 sets the local decoding unit in an operable state while the first input I-picture frame is encoded, and sets the local decoding unit to a local state regarding the I-picture frame. Perform decoding processing. Since the local decoding process is not required while the frame of the subsequently input B picture is encoded, the GOP structure determining unit 9 suspends the local decoding unit 13. While a frame of a subsequently input P picture is encoded, the GOP structure determination unit 9
The local decoding unit 13 is made operable to perform a local decoding process on a frame of a P picture. In this way, the GOP structure determination unit 9 controls the operation of the local decoding unit 13 according to the GOP structure of the input original image signal (a).

According to the encoding operation of the encoding apparatus of the present embodiment, while the image frame of the B picture is encoded as described above, the local decoding unit is in the sleep state, and accordingly, the power consumption is reduced. Will be reduced.

Next, a description will be given of an encoding / decoding apparatus provided with the above-described encoding apparatus, which can be used efficiently by sharing the local decoding section between the encoding section and the decoding section.

FIG. 2 is a block diagram showing an embodiment of the encoding / decoding apparatus of the present invention. This encoding / decoding device has a configuration in which the local decoding unit of the encoding device shown in FIG. 1 is shared on the decoding side, and includes an encoding frame memory 8a and a decoding frame memory 8b as frame memories. In addition, a variable length decoder 10, a smoother 11,
It has selectors 12a to 12c. In FIG. 3, buffers provided at the output stage of the variable length encoder 4 and the input stage of the variable length decoder 10 are omitted.

The subtractor 1 receives the input original image signal (a) as one input, the prediction signal (f) output from the encoding frame memory 8a as the other input, and receives the input original image signal (a) from the input original image signal (a). The prediction signal (f) is subtracted to generate a prediction error signal (g), which is output to the DCT converter 2.

The DCT transformer 2 performs a DCT transform on the prediction error signal (g) input from the subtractor 1 and outputs a DCT transform coefficient (h) to the quantizer 3. The quantizer 3 has D
The DCT transform coefficient (h) input from the CT transformer 2 is subjected to quantization processing to reduce the amount of irreversible information, and the quantization coefficient (b) obtained by the processing is sent to the variable-length encoder 4. The output is output to the inverse quantizer 5 via the selector 12a.

The variable length encoder 4 performs a variable length encoding process on the quantized coefficient (b) input from the quantizer 3 to generate an output stream (c). This output stream (c) is sent out on the transmission path and received by the encoding / decoding device of the transmission destination.

The variable-length decoder 10 performs variable-length decoding on an input stream (d) of a high-efficiency coded image input via a transmission path from a source coding / decoding device, and performs reception quantization. The coefficient (i) is reproduced and output to the inverse quantizer 5 via the selector 12a.

Based on the IPB signal (O) input from the GOP structure determining section 9, the selector 12a
The output of the quantizer 3 is selected to indicate encoding of a picture or a P picture, and the output of the variable length decoder 10 is selected to indicate encoding of a B picture.

The inverse quantizer 5 performs an inverse quantization process on the quantization coefficient (b) or the reception quantization coefficient (i) selected by the selector 12a to generate a reproduced DCT transform coefficient (j). This is output to the inverse DCT converter 6.

The inverse DCT transformer 6 performs an inverse DCT transform on the reproduced DCT transform coefficient (j) input from the inverse quantizer 5 to generate a reproduced prediction error signal (k).
Output to The adder 7 performs an addition process on the reproduction prediction error signal (k) input from the inverse DCT converter 6 and the selection prediction signal (l) output from the selector 12b to generate a reproduction image (m). This is output to the selector 12c.

Based on the IPB signal (O) input from the GOP structure determination section 9, the selector 12c
The input reproduced image (m) is output to the encoding frame memory 8a when indicating the encoding of the picture or the P picture, and the input reproduced image (m) is indicated when the encoding is performed on the B picture. The data is output to each of the decoding frame memory 8b and the smoothing unit 11. The smoother 11 smoothes the frame rate of the reproduced image signal (m) input via the selector 12c to obtain an output decoded image (e).

The encoding frame memory 8a generates a prediction signal (f) based on the reproduced image (m) input via the selector 12c, outputs the prediction signal (f) to the subtractor 1, and outputs the prediction signal (f) via the selector 12b. Output to the adder 7. The decoding frame memory 8b generates a prediction signal (n) based on the reproduced image (m) input via the selector 12c, and outputs this to the adder 7 via the selector 12b.

Based on the IPB signal (O) input from the GOP structure determination section 9, the selector 12b
When the encoding of a picture or a P picture is indicated, the output of the encoding frame memory 8a is selected, and when the encoding of a B picture is indicated, the output of the decoding frame memory 8b is selected.

The GOP structure judging section 9 judges the GOP structure of the input original image signal (a) and, based on the judgment result,
An IPB signal (o) indicating whether encoding is for an I picture, a P picture, or a B picture is generated, and this is output to each of the selectors 12a to 12c. Further, the GOP structure determination unit 9 generates a pause signal (p) at the time of encoding a B picture and when no input stream is input, and outputs the pause signal (p) to the inverse quantum , And output to each of the encoding frame memory 8a, the decoding frame memory 8b, the selectors 12a to 12c, and the smoothing unit 11 to pause.

Next, the operation of the encoding / decoding device will be described.

Also in the encoding of the encoding / decoding device of the present embodiment, the encoding of the frame is performed adaptively according to each of the I, B, and P pictures. Here, for an input original image signal (a) in which image frames are input in time series, a GOP structure “I, B,
B, P, B, B, P, B, B, P, B, B, I,
B,. . . "Will be described as an example.

The GOP structure judging section 9 outputs an IPB signal (o) indicating that the I picture is to be encoded while the frame of the I picture to be input first is encoded based on the determined GOP structure. Output to the selectors 12a to 12c. In response to the IPB signal (o), the selector 12a selects the output of the quantizer 3, the selector 12b selects the output of the encoding frame memory 8a, and the selector 12c selects the encoding frame memory 8a as the output destination. Is selected. This enables a local decoding process for generating a prediction signal (f) when encoding an I picture.

During the encoding of the subsequent B picture, the GOP structure judging unit 9 outputs an IPB signal (o) indicating that the encoding is for the B picture to each of the selectors 12a to 12c. In response to the IPB signal (o), the selector 12a selects the output of the variable length decoder 10, the selector 12b selects the output of the decoding frame memory 8b, and the selector 12c selects the decoding frame as the output destination. The memory 8b is selected. Thus, when encoding a B picture, the local decoding unit 13 'can perform a local decoding process for decoding and reproducing the input stream instead of the local decoding process for the frame of the B picture. Becomes At this time, if the input stream is not input, the GOP structure determination unit 9 converts the pause signal (p) into the inverse quantizer 5, the inverse DCT transformer 6, the adder 7, the code Output to each of the frame memory for decoding 8a, the frame memory for decoding 8b, the selectors 12a to 12c, and the smoothing unit 11. As a result, the local decoding unit 13 'is in a sleep state, and power consumption is reduced.

In the case where the above-mentioned B picture is encoded using the GOP structure of M = 3 where two frames are continuous, the result of the output reproduced image (e) when the input stream (d) is input is As shown in FIG.

As can be seen from the results shown in FIG. 3, when the type of the frame to be encoded of the input original image signal (a) is a B picture, the input stream is decoded and reproduced. When the type of the frame to be coded is an I picture or a P picture (however, except for the I picture to be coded first), the decoding process for the input stream cannot be performed, and the reproduced image (m) Becomes discontinuous. For this reason, in the present embodiment, frame smoothing is performed by performing frame interpolation processing (using the reproduced image of the previous frame) on frames in which the reproduced image (m) is discontinuous. Thereby, the motion reproducibility of the output reproduction image (e) is improved.

In the coding and decoding apparatus described above, a received signal that can be decoded by the local decoding unit 13 'during coding of a B picture is highly efficiently coded by a coding method using a GOP structure or a similar method. Image signal. In the case of the present embodiment, since the local decoding unit 13 can perform a decoding process that is asymmetric to the coding process during the coding, the local decoding unit 13 codes an image having a frame rate of, for example, 30 frames / sec. During transmission, an image signal with a frame rate of 15 frames / sec can be received and decoded. In addition, it is also possible to receive an MPEG1 image while transmitting an MPEG2 image, or to receive an SDTV image while transmitting an HDTV image. Furthermore, a JPEG still image can be received while an MPEG moving image is being transmitted.

In this embodiment, the local decoding unit 1
3 is shared by the encoding unit and the decoding unit, but a local decoding unit may be provided in each of the encoding unit and the decoding unit. In this case, power saving is achieved in the encoding unit as in the encoding device shown in FIG.

[0054]

As described above, according to the encoding of the present invention, the local decoding processing means is stopped during the encoding of the B picture which does not require the local decoding processing. Power consumption can be reduced accordingly.

Further, according to the encoding / decoding of the present invention, the local decoding process for the B picture, which was unnecessary in principle, can be assigned to the process for decoding the received image. It can be performed more efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an encoding device according to the present invention.

FIG. 2 is a block diagram showing an embodiment of the encoding / decoding device of the present invention.

FIG. 3 is a diagram illustrating a relationship between an encoded frame and a reproduced image frame.

FIG. 4 is a block diagram illustrating a schematic configuration of a conventional encoding device.

FIG. 5 is a block diagram illustrating an example of a decoding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Subtractor 2 DCT converter 3 Quantizer 4 Variable length encoder 5 Inverse quantizer 6 Inverse DCT transformer 7 Adder 8 Frame memory 13 Local decoding part

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[Procedure amendment]

[Submission date] March 8, 2000 (200.3.8)

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[Correction target item name] 0018

[Correction method] Change

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[0018]

In order to achieve the above object, an encoding apparatus according to the present invention uses an input original image signal by using a GOP structure composed of three image frames of I picture, P picture and B picture. Encoding means for performing local encoding, local decoding processing means for performing local decoding for the encoding, and determining a GOP structure when the input original image signal is encoded, based on the determination result. The local decoding processing means performs local decoding while the I-picture or P-picture image frame is encoded, and suspends the local decoding processing means while the B-picture image frame is encoded. And a GOP structure determining means for performing control as described above.

Claims (1)

Claims 1. An input original image signal is represented by a G composed of three image frames of an I picture, a P picture, and a B picture.
Coding means for performing coding using an OP structure; local decoding processing means for performing local decoding processing for the coding; and determining a GOP structure when the input original image signal is coded. On the basis of the determination result, the local decoding processing means performs local decoding processing while the I-picture or P-picture image frame is being coded, and performs the local decoding processing while the B-picture image frame is being coded. And a GOP structure determining means for controlling so as to suspend the means. 2. An input original image signal is a G signal composed of three image frames of an I picture, a P picture, and a B picture.
In an encoding method for performing encoding using an OP structure, a GOP structure at the time of encoding the input original image signal is determined, and an I-picture or P-picture image frame is encoded based on the determination result. In this case, a local decoding process for the encoding is performed, and the local decoding process is not performed when an image frame of a B picture is encoded. 3. An input original image signal is a G signal composed of three image frames of an I picture, a P picture, and a B picture.
Encoding means for performing encoding using an OP structure; performing local decoding processing for the encoding; and performing local decoding processing on an image signal having a predetermined encoding structure received from a communication partner. A local decoding processing unit for obtaining a reproduced image; and a GOP structure when the input original image signal is encoded. Based on the determination result, while an I-picture or P-picture image frame is encoded, A GOP structure for causing the local decoding processing means to perform local decoding processing for encoding, and for performing local decoding processing for obtaining a reproduced image while the image frame of the B picture is encoded. An encoding / decoding device comprising: a determination unit. 4. The encoding / decoding apparatus according to claim 3, wherein the GOP structure determining unit determines that there is no received image to be reproduced while the image frame of the B picture is encoded.
An encoding / decoding device characterized by being configured to suspend local decoding processing means. 5. The encoding / decoding device according to claim 3, wherein a frame rate of a transmission image encoded by said encoding means and a frame rate of a reception image reproduced by said local decoding processing means. Encoding / decoding apparatus characterized in that: 6. The encoding / decoding device according to claim 3, wherein the image signal encoded by the encoding unit is an MPEG2 signal.
An encoding / decoding device, wherein the received image reproduced by the local decoding processing means is an MPEG1 image. 7. The encoding / decoding device according to claim 3, wherein the image signal encoded by the encoding unit is an MPEG moving image, and the received image reproduced by the local decoding unit is An encoding / decoding device characterized by being a JPEG still image. 8. The encoding / decoding device according to claim 3, wherein the image signal encoded by said encoding means is an HDTV image, and the received image reproduced by said local decoding processing means is an SDTV. An encoding / decoding device characterized by being an image. 9. An input original image signal is a G signal composed of three image frames of an I picture, a P picture, and a B picture.
The encoding is performed using the OP structure, and the image signal having the predetermined encoding structure received from the communication partner is decoded, and the local decoding processing means for performing the encoding and decoding is shared. A GOP structure at the time of encoding the input original image signal, and determining whether or not an I-picture or P-picture image frame is encoded based on the determination result. Causes the local decoding processing means to perform local decoding processing for encoding, and causes the local decoding processing means to perform local decoding processing for decoding while an image frame of a B picture is encoded. Characteristic encoding / decoding method. 10. The encoding / decoding method according to claim 9, wherein when there is no received image to be reproduced while the image frame of the B picture is encoded, the local decoding processing unit is paused. Encoding / decoding method. 12. The encoding / decoding method according to claim 9, wherein a frame rate of a transmitted image to be encoded is different from a frame rate of a received image. 13. The encoding / decoding method according to claim 9, wherein the image signal to be encoded is an MPEG2 image, and the received image is an MPEG1 image. 14. The encoding / decoding method according to claim 9, wherein an image signal to be encoded is an MPEG moving image, and a received image is a JPEG still image. . 15. The encoding / decoding method according to claim 9, wherein an image signal to be encoded is an HDTV image, and a received image is an SDTV image.