JP3205839B2 - Image coding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to an image encoding device used for a videophone / videoconference system and capable of encoding a moving image and a still image with high efficiency.

[0002]

[Prior art]

As shown in FIG. 14, a conventional videophone / videoconference system includes a microphone 102 and a speaker 104 connected to an audio codec 100, a still image input device 112 and a display 12 as shown in FIG.
4 and the video camera
122 and the display 124 are connected to the video codec 120. The audio codec 100, the still image codec 110, and the moving image codec 120 are completely independently connected to the transmission control unit 130, respectively. The transmission control unit 130 also determines the allocation of the transmission capacity of each of the codecs 100, 110, and 120, and performs multiplexing on the transmission path.

[0003] A moving image is composed of several dozen frames called frames per second. For example, in the NTSC system used for television broadcasting in Japan, there are 30 frames per second.

[0004] As main types of high-efficiency coding methods for image signals, there are inter-frame coding and intra-frame coding. The inter-frame coding is based on extracting a change amount of an image signal between frames preceding and succeeding in the time direction, and is effective for compressing an information amount of a moving image. On the other hand, intra-frame encoding is used for compressing the information amount of a still image. However, each frame of a moving image can be regarded as a still image and applied to a moving image.

Conventionally, high-efficiency coding of still images has been based on intra-frame coding, and high-efficiency coding of moving images has been based on intra-frame coding, inter-frame coding, or a combination thereof. However, the device configurations of the still image codec and the moving image codec are independent of each other.

The above is discussed, for example, in the Journal of the Institute of Television Engineers of Japan, Vol. 39, No. 10, (1985), pp. 912-919.

[0007]

[Problems to be solved by the invention]

In the above prior art, the function of encoding a moving image and the function of encoding a still image are completely separated, and the function of decoding a moving image and the function of decoding a still image are also completely separated. For this reason, the device capacity increases and
There is a problem that the device price increases.

[0008] An object of the present invention is to provide an image encoding apparatus including a transform encoding unit that can be used in common for a function of encoding a moving image and a function of encoding a still image.

[0009]

[Means for Solving the Problems]

In order to achieve the above object, the image encoding device according to the present invention is configured such that an operation instruction from an operator is transmitted, and a switch that outputs an operation signal, and a still image or a moving image that is input based on the operation signal. A coding control unit having a coding parameter control unit for generating a selection signal for selecting a frame and an inter-frame / intra-frame switching signal for switching between inter-frame coding or intra-frame coding; A moving image input device that inputs a moving image and outputs a moving image signal, and a selector that selects the input still image or the moving image according to the selection signal. An image input unit, a discrete cosine transform unit for a still image signal or a moving image signal selected by the selector, based on the inter-frame / intra-frame switching signal; Inter-frame / intra-frame encoding unit for performing inter-frame encoding or intra-frame encoding by one transform encoding unit using a DCT (DCT) method, and intra-frame encoding by the inter-frame / intra-frame encoding unit Entropy encoder for intra-frame encoding for entropy encoding the encoded image signal, and entropy encoding for inter-frame encoding for entropy encoding the image signal inter-frame encoded by the inter-frame / intra-frame encoder. And a still image / moving image compression / encoding unit having an entropy encoding unit, and transmitting a moving image signal and / or a still image signal from the entropy encoding unit of the still image / moving image compression / encoding unit. A transmission encoding unit for transmitting to the channel, and a frame memory (F) of the still / moving image compression encoding unit.
M) is characterized in that the image decoding device is refreshed by a refresh request (DR) generated when switching from a still image to a moving image.

[0010]

[Action]

The still / moving image compression / encoding unit performs inter-frame coding or intra-frame coding. However, the still-image / moving image compression / coding unit operates still and moving image coding. Image coding is also possible.

In the still / moving image decompression decoding unit, inter-frame decoding or intra-frame decoding is performed. However, since still-image decoding alone functions, still image decoding can be performed together with moving image decoding. .

[0012]

【Example】

Next, an embodiment of an image encoding apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of an image encoding / decoding system. The image encoding unit 1 includes a still image input device 1202, a moving image input device 1204, a still / moving image compression encoding unit 302, an encoding control unit 303, a transmission encoding unit 304,
It comprises a storage unit 26 and a switch 24. Image decoding unit 5
Are a transmission decoding unit 305, a decoding control unit 306,
It comprises a moving image decompression decoding unit 307, a still image output device 6804, a moving image output device 6806, a storage unit 58, and a switch 56.
The transmission encoding unit 304 and the transmission decoding unit 305 are connected by a transmission path 310.

FIG. 2 is a block diagram showing the configuration of the image encoding / decoding system of FIG. 1 in more detail. The image input unit 12 collectively represents a still image input device 1202 and a moving image input device 1204. The inter-frame / intra-frame encoder 14 and the entropy encoder 16 include a still / moving image compression encoder 30.
2 shows, the coding parameter control unit 20 and the control unit 22
1 shows an encoding control unit 303, and the moving image transmission encoding unit 18 and the still image transmission encoding unit 28 show a transmission encoding unit 304.

The still image transmission decoding unit 52 and the moving image transmission decoding unit 62 indicate a transmission decoding unit 305, the control unit 54 and the encoding parameter control unit 60 indicate a decoding control unit 306, Entropy decoding unit 64 and inter-frame / intra-frame decoding unit 66
Indicates a still image / moving image decompression decoding unit 307. The image output unit 68 collectively represents the still image output device 6804 and the moving image output device 6806.

Next, the image encoding unit 1 will be described. The image input unit 12
An image signal specified by the input device instruction signal input from the line 1010 is output to the line 1002. The inter-frame / intra-frame encoding unit 14 performs inter-frame / intra-frame encoding on the image signal from the line 1002 according to the inter-frame / intra-frame switching signal input from the line 1012, and The inner-coded image signal is output to a line 1004.

The entropy coding unit 16 generates an inter-frame / intra-frame switching signal from the line 1014 and a moving image coding system switching signal from the line 1015 to output an inter-frame / frame
Entropy-encoding the intra-coded image signal, outputting the entropy-encoded moving image to a line 1006,
The entropy-coded still image is output on line 1008.

The moving image transmission encoding unit 18 receives the entropy-encoded moving image signal from the line 1006, performs transmission encoding along with the encoding parameter from the line 1016, and outputs the encoded signal to the transmission line 1050.

The control unit 22 temporarily stores the entropy-encoded still image signal from the line 1008 in the storage unit 26 via the line 1020 according to the operation signal input from the operator switch 24 via the line 1022, Output to line 1024. The still image signal that has been entropy-encoded and once stored in the storage unit 26 is
When there is a transmission instruction from 24, it is output to the line 1024 via the line 1020 and the control unit 22.

The control unit 22 responds to the transmission instruction from the line 1022 and
A coding control signal for instructing a still image coding process, an intra-frame / inter-frame coding process, and an input device selection process is transmitted through a line 10.
Output to 18.

The coding parameter control unit 20 obtains an input device instruction signal on the basis of the coding control signal from the control unit 22 and outputs it on a line 1010, and obtains an inter-frame / intra-frame switching signal on a line 101
2, 1014, and outputs on line 1015 a moving image coding system switching signal indicating whether the moving image is to be inter-frame encoded or intra-frame encoded.

The still image transmission encoding unit 28 receives the entropy-encoded still image signal from the line 1024, performs transmission encoding, and
Output to the transmission path 1052.

Next, the image decoding unit 5 will be described. Still image transmission decoding section 52 outputs a still image signal input from transmission path 1052 to line 1102.

The control unit 54 temporarily stores the still image signal from the line 1102 in the storage unit 58 by the line 1106 or outputs the still image signal to the line 1110 according to the operation signal input by the line 1104 from the switch 56 for the operator. The still image signal once stored in the storage unit 58 is transmitted to the line 1106 and the control unit 54 in response to a decoding instruction from the switch 56.
Output to line 1110.

The control unit 54 responds to the operation signal from the line 1104
A decoding control signal for instructing a still image decoding process, an intra-frame / inter-frame decoding process, and an output device selection process is transmitted on line 11.
Output to 08.

The moving image transmission decoding unit 62 receives the moving image signal from the transmission path 1050, and after transmitting and decoding, converts the coding parameter into a line.
1112, and outputs the entropy-encoded video signal to a line 1120.

The encoding parameter control unit 60 obtains an intra-frame processing image selection signal based on the decoding control signal from the line 1108 and the encoding parameter from the line 1112 and outputs the same to the line 1114, and outputs an inter-frame / intra-frame switching signal. Is output to line 1116, and
An output device instruction signal is obtained and output on line 1118.

The entropy decoding unit 64 captures a still image signal from the line 1110 or a moving image signal from the line 1120 according to the intra-frame processed image selection signal input via the line 1114,
The entropy-decoded image signal for intra-frame encoding is output on a line 1122, and the entropy-decoded image signal for inter-frame encoding is output on a line 1124.

The inter-frame / intra-frame decoder 66 intra-frame decodes the entropy-decoded image signal from the line 1122, inter-frame decodes the entropy-decoded image signal from the line 1124, and According to the inter-frame / intra-frame switching signal input by
Output to 1126. The image output unit 68 takes in an image signal from the line 1126 and outputs an image according to the output device instruction signal input via the line 1118.

Next, details of the image encoding unit 1 will be described. FIG. 3 is a block diagram showing the image input unit 12 in detail. The image input unit 12 includes the image input devices 1202 and 1204 and the selector 1
It consists of 206. The image input device 1202 is used for inputting a still image, and the image input device 1204 is used for inputting a moving image. Selector
Reference numeral 1206 outputs a moving image or a still image to be encoded to a line 1002 in accordance with the input device instruction signal transmitted from the encoding parameter control unit 20 of FIG.
Note that the number of image input devices is not limited to two, and the number can be increased or decreased as needed.

FIG. 4 is a block diagram showing the inter-frame / intra-frame encoding unit 14 in detail. The inter-frame / intra-frame coding unit 14 includes a pre-processing circuit 1402, a differentiator 1404 for obtaining an inter-frame prediction error signal, a selector 1406, and a transform coding circuit 14.
08, quantizer 1410, representative value circuit 1412, and inverse transform circuit
1414, a selector 1416, and an adder 1418 for performing local decoding processing
And a frame memory 1420 for storing one or more frames of a moving image signal.

When the image signal from the line 1002 is an analog color / luminance composite signal (for example, an NTSC composite signal), the preprocessing circuit 1402 also performs analog-to-digital conversion of the image signal and separates color / luminance signals.

As a conversion method applied to the conversion encoding circuit 1408,
Discrete cosine transform (DCT: Disc) with high compression efficiency for image signals
rete Cosine Transform) is attracting attention. Quantizer 1
Scalar quantization (SQ: Scalar Quant)
Quantization) and Vector Quantization (VQ)
One or both of n) can be applied.

The inter-frame / intra-frame encoding section 14 performs
The redundancy of the image signal is deleted by any one of the coding method using the combination in the frame and the coding method using the intra-frame coding. In the following description, the coding based on the combination between frames / intra-frames is referred to as inter-frame coding.

First, when using intra-frame encoding, the selector 1406 selects an image signal from the pre-processing circuit 1402 according to the inter-frame / intra-frame switching signal input from the line 1012, and the selector 1416 selects Select an input value of zero. The input image signal is
Pre-processing, transform coding, and quantization are performed.
Is output to On the other hand, since a signal value of zero is input from the selector 1416 to the adder 1418, the contents of the frame memory 1420 remain stored.

Next, when using inter-frame coding, the selector 1406 selects the signal from the differentiator 1404 according to the inter-frame / intra-frame switching signal input from the line 1012, and
Selects the signal from the inverse transform circuit 1414. Pre-processing circuit
The difference between the image signal from 1402 and the image signal one frame before read from the frame memory 1420 is calculated by a differentiator 1404.
, And output to the line 1004 via the selector 1406, the transform coding circuit 1408, and the quantizer 1410. In addition, line 10
The signal output to 04 is represented by a representative value circuit 1412 and an inverse conversion circuit 141.
4. The signal is input to the adder 1418 via the selector 1416. Adder
At 1418, the image signal of the previous frame read from the frame memory 1420 and the change between the frames input from the selector 1416 are added and output to the frame memory 1420 as a new image signal.

According to the above configuration, one still image / moving image compression encoding unit 302 sharing the inter-frame encoding and the intra-frame encoding is common.
Can be executed by the inter-frame / intra-frame encoding unit 14. Note that the inter-frame coding is applied only to a moving image, but the intra-frame coding is applicable to both a still image and a moving image.

FIG. 5 is a block diagram showing the entropy encoding unit 16 in detail. The entropy coding unit 16 includes an entropy coding circuit 1602 for intra-frame coding and a buffer memory.
1604, a selector 1606, an entropy coding circuit 1608 for inter-frame coding, a selector 1610, and a buffer memory 16
Consists of 12

First, when the inter-frame / intra-frame switching signal from the line 1014 indicates the inside of a frame, the image signal input from the line 1004 is converted to an entropy encoding circuit for intra-frame encoding.
After being entropy-encoded in 1602 and temporarily stored in the buffer memory 1604, as an encoded still image signal,
Output to line 1008. On the other hand, the interframe encoding entropy encoding circuit 1608 encodes the zero signal value selected by the selector 1606. Next, when the inter-frame / intra-frame switching signal from the line 1014 indicates the inter-frame, the inter-frame encoding entropy encoding circuit 1608 is used.
Encodes the image signal input from the line 1004 via the selector 1606.

The selector 1610 selects an image signal according to a moving image coding system switching signal from a line 1015 that indicates whether to encode a moving image by intra-frame encoding or inter-frame encoding. That is, the selector 1610 selects the image signal from the inter-frame encoding entropy encoding circuit 1608 when the moving image is inter-frame encoded, and selects the intra-frame encoding entropy code Circuit 16
Select the image signal from 02. The image signal selected by the selector 1610 and entropy-encoded is temporarily stored in the buffer memory 1612 and then output to the line 1006 as a moving image signal.

As described above, according to the present embodiment, when intra-frame encoding and its entropy encoding are performed on a still image, inter-frame encoding is performed by regarding a signal value of zero as a moving image. And its entropy coding can be continued. Therefore, regardless of the presence or absence of still image coding, the receiving side can obtain continuous entropy codes of moving images.

Next, details of the image decoding unit 5 will be described. FIG. 6 is a block diagram showing the entropy decoding unit 64 in detail. The entropy decoding unit 64 includes a buffer memory 6402, a selector 6404, an entropy decoding circuit 6406 for intra-frame encoding, a buffer memory 6408, and an entropy decoding circuit 6410 for inter-frame encoding.

First, in the case of still image decoding, the selector 6404 selects an image signal input from the line 1110 via the buffer memory 6402 in accordance with the intra-frame processed image selection signal from the line 1114, and outputs the same instruction signal. In the case of decoding an intra-frame encoded moving image, an image signal input from a line 1120 is selected via a buffer memory 6408. The selected image signal is entropy-decoded in the intra-frame encoding entropy decoding circuit 6406, and as the intra-frame decoding image signal,
Output to line 1122. Next, the image signal input from the line 1120 is input to the inter-frame encoding entropy decoding circuit 6410 via the buffer memory 6408, and after being entropy-decoded, a line signal is output as the inter-frame decoding image signal.
Output to 1124.

FIG. 7 is a block diagram showing the inter-frame / intra-frame decoder 66 in detail. The inter-frame / in-frame decoding unit 66 includes a representative value circuit 6600, 6604 and an inverse conversion circuit 6602, 6606.
, An adder 6608, a frame memory 6610, and a selector 6612
And a post-processing circuit 6614.

First, the intra-frame decoding image signal input from the line 1122 passes through the representative value circuit 6600 and the inverse conversion circuit 6602, is intra-frame decoded, and is output to the selector 6612. On the other hand, the inter-frame decoding image signal input from the line 1124 passes through the representative value circuit 6604 and the inverse conversion circuit 6606, and is added by the adder 6608 to the decoded image signal of one frame before output from the frame memory 6610. Are output to the selector 6612 and are also input to the frame memory 6610. Next, the selector
6612 selects an intra-frame decoded image signal or an inter-frame decoded image signal according to the inter-frame / intra-frame switching signal on line 1116. The post-processing circuit 6614 performs post-processing such as noise removal, and outputs the decoded image signal to a line 1126.

FIG. 8 is a block diagram showing the image output unit 68 in detail. The image output unit 68 includes a selector 6802 and an image output device 680.
4,6806. The image output device 6804 is used for outputting a still image, and the image output device 6806 is used for outputting a moving image. Selector 6802 responds to the output device indication signal from line 1118
The image signal input from 1124 is output to the image output device 6804 or
Output to 6806. The number of image output devices is not limited to two, and the number can be increased or decreased as needed.

Next, the operation of the image encoding / decoding device according to the present embodiment will be described. FIG. 9 is a diagram for describing a procedure for encoding / decoding a moving image / still image. In FIG. 9, inter-frame coding for a moving image is used as an example. Video i
From i + 1 frame, from j to j + 5 frame, from k to k + 2
The frame is transmitted via the transmission line 1050 in FIG.
Immediately after the inter-frame coding of the moving image i + 1 frame in which the coding of the moving image is interrupted by the still image coding, a zero signal value is coded as described in FIG. For this reason,
The contents of the frame memory 1420 of the encoding unit and the frame memory 6610 of the decoding unit are both held in the (i + 1) th frame. Even if the encoding of the moving image is interrupted, the still moving image is encoded and decoded. It is possible to proceed to the encoding processing of the next moving image j frame.

On the other hand, after the still image is encoded, it is temporarily stored in the storage unit 26 via the line 1008 in FIG. 2 and transmitted to the image decoding unit, and is read from the storage unit 2 and transmitted. After that, it is stored in the storage unit 58. If a still image needs to be decoded, the still image code is read from storage 58 via line 1110 and decoded. At this time, the moving image i + 4 and i + 5 frames are transmitted at the same time, but are discarded because the image decoding unit is occupied by still image decoding. As a result, the content of the frame memory 1420 of the encoding unit immediately after the completion of the still image decoding is the moving image i + 5, whereas the content of the frame memory 6610 of the decoding unit remains i + 3. As described above, immediately after decoding a still image, a mismatch between frame memories always occurs. Therefore, a refresh request (DR: Demand Refresh) is issued from the image decoding unit to the image encoding unit. The transmission path of this refresh request is not shown in FIG. Upon receiving the refresh request, the image encoding unit performs intra-frame encoding of only k frames of the moving image, and only in this case, writes the contents of the k frames into the frame memory 1420. Then, the image decoding unit that has received the code of the moving image k frame performs intra-frame decoding on this,
Also in this case only, the contents of the k frame are also written in the frame memory 6610, and the contents of the frame memories of the encoding unit and the decoding unit are matched.

Here, how the conventional refresh request is used will be described. FIG. 15 is a diagram for explaining a conventional refresh request procedure. Conventionally, FM (frame memory) parity information is used for detecting mismatch between frame memories in a transmitting unit and a receiving unit. That is, when a transmission error occurs in the encoded data and the FM parity information, an error is detected in an FM parity check that compares the parity obtained from the decoded data in the receiving unit with the transmitted FM parity information, and an error detection signal is output. Is returned to the transmission unit. After resetting the frame memory, the transmitting unit transmits an error detection acknowledgment signal, and upon receiving the signal, the receiving unit resets the frame memory and completes a series of operations.

In contrast to the conventional example described above, in the embodiment of the present invention,
Since it is obvious that frame memory mismatch always occurs as a result of still image decoding, a refresh request is issued without going through an error detection procedure such as a parity check.

FIG. 10 shows another example of encoding / decoding of a moving image / still image.
FIG. 6 is a diagram for explaining one procedure. In FIG. 10, intra-frame encoding for a moving image is used as an example. Video i
From i + 1 frame, from j to j + 5 frame, from k to k + 2
The frame is transmitted via the transmission line 1050 in FIG.
Moving picture i in which moving picture coding is interrupted by still picture coding
Intra-frame decoding immediately after the +1 frame is prohibited until decoding of a valid moving image j frame starts. this is,
This is to prevent the image content of the image output unit from being destroyed by decoding the invalid data in the frame. In order to correctly execute the prohibition of decoding of a moving image using the intra-frame encoding / decoding, a frame identification code described later is used.

On the other hand, as in FIG. 9, after the still image is encoded,
When temporarily stored in the storage unit 26 via the line 1008 in FIG. 2 and transmitted to the image decoding unit, the data is read from the storage unit 26, transmitted, and then accumulated in the storage unit 58. If a still image needs to be decoded, the still image code is read from storage 58 via line 1110 and decoded. At this time, the moving image j + 4 and j + 5 frames are also transmitted at the same time, but are discarded because the image decoding unit is occupied by still image decoding. However, in this procedure, since the moving image is transmitted by intra-frame encoding for each frame, it is not necessary to make a refresh request.

Next, a description will be given of a frame identification code for correctly executing prohibition of decoding of a moving image during still image coding. Figure
FIG. 11 illustrates a frame identification code. In the figure, the code sequence (A) corresponds to the output signal of the intra-frame encoding entropy encoding circuit 1602 in FIG.
Is an invalid code corresponding to the synchronization period of the NTSC television signal, etc., 560 is an entropy code for one moving image frame, 562 is an entropy code for one moving image frame immediately before the start of still image coding, and 570 is It is an entropy code of a still image. Further, the code sequence (a) is obtained by adding a synchronization identifier to the entropy code of the moving image according to the instruction of the encoding parameter sent to the moving image transmission encoding unit 18 via the line 1016 in FIG. Things. Reference numeral 552 denotes a frame synchronization, 554 denotes a moving image continuous code, 556 denotes a moving image discontinuous code, and 558 denotes a dummy code temporarily packed because there is no moving image code. In the code string (a), whether or not the frame is a moving image frame immediately before the start of still image coding can be easily determined based on whether or not the moving image discontinuous code 556 immediately after the frame synchronization 552. The code string (s) is obtained by adding a header of a business document system / business document exchange format to the still image entropy coding by the control unit in FIG.

FIG. 12 is a diagram showing another embodiment of the frame identification code. In the figure, 565 is a moving image end code, and 564 is a zero padding part. The code example (a) is the same as that shown in FIG. In the code example (b), the entropy code for one frame of the moving image immediately before encoding the still image can be determined by the moving image end code 562. In this case, upon detecting the moving image end code 562, the image decoding unit immediately prohibits subsequent decoding of the moving image code. Also, the code string (c)
Is different from the code sequence (b) in the position of the moving image end code 562, and is located immediately after the frame synchronization 552. In the code sequence (d), no identification code is particularly arranged, and a sufficiently long zero padding is provided after the entropy code 562 for one frame of a moving image immediately before the start of still image coding, with a frame synchronization 552 interposed therebetween. It has been done. In this case, if the image decoding side has a function of regarding a sufficiently long sequence of zeros as a moving image end code, zero padding also plays a role equivalent to the moving image end code.

As described above, the code strings (b), (c),
Although the three code strings of (d) have been described, any code other than the above code examples can be adopted as the code string of the present embodiment as long as one frame immediately before the start of still image coding can be identified.

Here, a conventional code string will be described. FIG.
FIG. 1 is a diagram illustrating an example of a conventional code sequence of a moving image.
In the figure, 700 is frame synchronization, 702 is line synchronization, 704 is an encoding parameter, and 706 is an image code. Line synchronization 702, coding parameter 704, image code 706
Although the detailed description of each is omitted, the most important thing in relation to the present embodiment is that there is no means for classifying one TV frame unit which is united by the frame synchronization 700. Is a point. In the above-described embodiment of the present invention, an identification code for judging one frame of a moving image immediately before encoding a still image is further provided, which is different from the conventional example.

Next, a description will be given of the positioning of a frame identification code for correctly executing the prohibition of decoding of a moving image during still image coding in a seven-layer communication protocol. FIG. 13 is a diagram illustrating a communication protocol of a video conference / video telephone system using a moving image, a still image, and a binary image. In the figure,
210 is the physical layer, 220,221 is the data link layer, 230,231
Is the network layer, 240,241 is the transport layer, 2
50,251 is a session layer, 260 is a presentation layer, 261 is a moving image coding method, 262 is a still image coding method, 263 is a binary image coding method, 270 is an application layer, and 272 is business Document system / Office document exchange format (O
DA / ODIF) and 271 are application programs. The office document system / office document exchange format 272 is a document structure exchange protocol that is being standardized for the purpose of efficiently exchanging digitized documents. Binary images and still images are or are going to be organized into such a document structure. However, for moving images,
Because the position in the document structure is unclear, this protocol example is a different system from ODA / ODIF. That is, the session layer 250, the transport layer 240, the network layer 230, and the data link layer 220 are communication protocols of a moving image system. On the other hand, the session layer 251, the transport layer 241, the network layer 231, and the data link layer 221
This is a communication protocol of the DIF system.

In the conventional videophone / videoconference system shown in FIG. 14, the still image coding system 262 and the moving image coding system 261 are independent and do not interfere with each other. On the contrary,
In the present embodiment, since both coding methods are integrated and used after switching, mutual interference between the methods always exists. Part 1
One is the provision of a frame identification code to one frame of a moving image code immediately before encoding a still image. This is considered to correspond to notifying the start of still image coding to the moving image coding via the path indicated by the line 268.

[0058]

【The invention's effect】

According to the present invention, a still image can be encoded by sharing a device for encoding a moving image, and a still image can be decoded by sharing a device for decoding a moving image. It is possible to reduce the size of the conference system. Further, since the frame memory is refreshed by the refresh request generated at the time of switching from the still image to the moving image, it is possible to eliminate the mismatch between the frame memories generated at the time of the switching.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image encoding / decoding system including an image encoding device of the present invention.

FIG. 2 is a detailed view of FIG.

FIG. 3 is a detailed diagram of an image input unit.

FIG. 4 is a detailed diagram of an inter-frame / intra-frame encoding unit.

FIG. 5 is a detailed diagram of an entropy encoding unit.

FIG. 6 is a detailed diagram of an entropy decoding unit.

FIG. 7 is a detailed diagram of an inter-frame / intra-frame decoding unit.

FIG. 8 is a detailed diagram of an image output unit.

FIG. 9 is an explanatory diagram showing an operation of an image encoding / decoding system including the image encoding device of the present invention.

FIG. 10 is an explanatory diagram showing the operation of an image encoding / decoding system including the image encoding device of the present invention.

FIG. 11 is an explanatory diagram illustrating a frame identification code.

FIG. 12 is an explanatory diagram illustrating a frame identification code.

FIG. 13 is an explanatory diagram illustrating a communication protocol of an image encoding / decoding system including the image encoding device of the present invention.

FIG. 14 is a configuration diagram of a conventional videophone / videoconference system.

FIG. 15 is an explanatory diagram illustrating a conventional refresh request procedure.

FIG. 16 is an explanatory diagram showing a code example of a conventional moving image.

[Explanation of symbols]

 1 image encoding unit 5 image decoding unit 12 image input unit 1202 still image input device 1204 moving image input device 24,56 switch 26,58 storage unit 302 static Picture / movie compression / encoding section 303 ... Encoding control section 304 ... Transmission coding section 305 ... Transmission decoding section 306 ... Decoding control section 307 ... Still picture / movie decompression decoding section 310 ... Transmission Road 68: Image output unit 6804: Still image output device 6806: Video output device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiko Kaneda 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-60-219882 (JP, A) 65788 (JP, A) JP-A-62-199185 (JP, A) JP-A-63-121372 (JP, A)

Claims (1)

(57) [Claims] A switch for receiving an operation instruction from an operator and outputting an operation signal; a selection signal for selecting an input still image or moving image based on the operation signal; An encoding control unit having an encoding parameter control unit for generating an inter-frame / intra-frame switching signal for switching intra-frame encoding; a still image input device for inputting a still image and outputting a still image signal; An image input unit having a moving image input device that inputs and outputs a moving image signal, and a selector that selects the input still image or the moving image according to the selection signal; and an image input unit that is selected by the selector. A method using a discrete cosine transform (DCT) method for a still image signal or a moving image signal based on the inter-frame / intra-frame switching signal.
An inter-frame / intra-frame encoding unit for performing inter-frame encoding or intra-frame encoding by one transform encoding unit;
An entropy encoder for intra-frame encoding for entropy-encoding an image signal intra-frame encoded by the inter-frame / intra-frame encoder; and an image inter-frame encoded by the inter-frame / intra-frame encoder. A still image / moving image compression encoding unit having an entropy encoding unit for inter-frame encoding for entropy encoding a signal; and the entropy encoding of the still image / moving image compression encoding unit. A transmission encoding unit for transmitting a moving image signal and / or a still image signal from a transmission unit to a transmission path, and a frame memory (FM) of the still / moving image compression encoding unit.
Is an image encoding device characterized by being refreshed by a refresh request (DR) generated when the image decoding device switches from a still image to a moving image.