JPH088689B2 - Image coding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses a moving picture coding device of a moving picture transmitting station to perform coding of a moving picture and coding of a still picture,
The present invention relates to an image encoding device for performing multipoint communication with a moving image receiving station and a still image receiving station.

(Prior Art) Conventionally, image communication in a teleconference, etc.
The moving image communication station communicates moving images with the moving image communication station, and the still image communication station communicates still images with the still image communication station. Alternatively, still images are communicated between moving image communication stations in the still image mode in the moving image encoding device and moving image decoding device.

(Problems to be Solved by the Invention) However, in image communication in a conventional teleconference or the like, since a moving image coding apparatus and a still image decoding apparatus have different encoding processing methods, a moving image communication station The communication station and the still image communication station communicate with the still image communication station in their respective closed areas, and the communication between the moving image station and the still image station cannot be performed, which is very inconvenient.

Therefore, in view of the above-mentioned drawbacks, a technical problem of the present invention is to provide an image encoding device capable of simultaneously performing multipoint communication between a moving image decoding device and a still image decoding device. is there.

(Means for Solving the Problem) According to the present invention, in an image coding apparatus that uses intra-screen correlation and inter-screen correlation, a means for storing one input image screen and a means for storing the input image and the screen From the output signal of the first selection means, a means for obtaining a signal with reduced redundancy using the output of the first selection means and the third prediction signal, and the correlation between the screens. Means for quantizing the signal with reduced redundancy, wherein the signal with reduced redundancy when used has a value predetermined by a third instruction, and the prediction signal and the quantizing means Means for obtaining a local composite signal using the output, a first predictor for generating a first prediction signal using the intra-picture correlation from the local composite signal, and a second prediction using the inter-picture correlation A signal is generated, and the second instruction is generated by the second instruction. A second predictor capable of storing a prediction signal, a second prediction signal that selects the first prediction signal and the second prediction signal according to a first instruction, and generates the third prediction signal. Selection means,
A code conversion is performed on the output of the quantizing means, and a code conversion is performed on the output of the quantizing means and a first code converting means capable of performing the code conversion by invalidating the input regardless of the input according to the second instruction. A second code conversion means capable of performing code conversion by invalidating all the result prediction errors using the correlation between screens according to the second instruction, and a first control means for performing the first instruction, The second instruction is given to the quantizing means, the second predictor, the first code converting means, and the second code converting means, and the third instruction is given to the quantizing means. An image coding apparatus is provided which is provided with a second control means.

(Summary of the Invention) The invention of the present application enables communication of a still image between a moving image encoding device and a still image decoding device, which has been impossible in the past, and a moving image communication station and a moving image communication station and a still image are transmitted at the same time. Multipoint image communication is performed with the image communication power station.

That is, as shown in FIG. 1, in order to perform multipoint communication between the moving picture coding device 40, the moving picture decoding device 41 and the still picture decoding device 42, the moving picture coding device 40 and the moving picture Connect to the decryption device 41 with a high-speed line 43 for video,
The moving image coding device 40 and the still image decoding device 42 are connected by a low speed line 44 for still images. And the moving picture coding device 40
And the moving picture decoding apparatus 41 perform normal moving picture communication, and the moving picture coding apparatus 40 and the still picture decoding apparatus 42 perform still picture communication. To encode a still image in the moving image encoding device 40, the still image to be transmitted is captured in the moving image encoding device 40, the captured image is encoded little by little, and the encoded data is gradually transferred to the transmission path. Need to be flushed. This is because the transmission rate of the transmission path connected to the still image decoding apparatus 42 is much lower than that of the moving image decoding apparatus 41, so that a large amount of data cannot be sent instantaneously.

Therefore, it is necessary for the moving image encoding device 40 to encode the still images little by little and transmit the encoded still images.

Usually, in encoding a moving image as shown in FIGS. 2A, 2B, and 2C, periodic image rewriting (refreshing) is performed in order to remove an error caused by an error in a transmission path. )
Are doing. Refresh is n for each specified screen
While moving line by line, it is executed by intra-frame coding using intra-frame correlation and removes the error generated in the frame memory of the decoder due to transmission path error, and a new clean image is displayed in both the encoder and the decoder. Write in the frame memory. In the areas other than the refresh area, inter-frame coding is performed by utilizing the correlation between screens.

Therefore, in the still image encoding by the moving image encoding apparatus of the present invention, the refresh mode is used to encode every n lines by the intra-frame encoding, and the data other than the refresh is invalid by the inter-frame encoding. Encoding is performed by substituting a code indicating that there is such information, and generation of excessive information for each screen is suppressed. By encoding and transmitting the data little by little in this manner, a large amount of information is prevented from being generated instantaneously.

In encoding a still image, as shown in FIG. 3, a frame memory 43 for storing a still image is used as a moving image encoding device.
Prepare in front of 44 and write the still image to be sent to the frame memory 43. The input of the moving picture coding device 44 selects the output of the still picture frame memory 43, and codes n lines for each screen defined in the refresh mode.

The moving picture coding apparatus of the present invention has a structure as shown in FIG. 4, and has two predictors, an inter-frame predictor 45 and an intra-frame predictor 46, for normal coding and refreshing. Switch predictors 45 and 46 with. In normal encoding, the output of the inter-frame predictor 45 with good encoding efficiency is selected as the prediction signal, and the difference from the previous screen is encoded. When refreshing is performed, the output of the intra-frame predictor 46 is selected as a prediction signal only during that period (n lines),
Performs intraframe coding. At this time, since the intra-frame predictor 46 uses the value of the previous pixel in the screen of the input signal or the value of the neighboring pixel, the correct image is obtained without being affected by the previous screen in which errors due to transmission path errors are accumulated. The contents of the frame memory can be updated. When encoding a still image, the area other than the refresh line in the screen, that is, the area encoded using interframe prediction, receives all the encoded data after replacing it with invalid data between frames. Send to the side. That is, the effective data on the screen is only the refresh line, and it is possible to suppress the generation of a large amount of information instantaneously. The coded data at this time is converted into an efficient code such as a Huffman code by the second code converter 48, the speed of the transmission line is matched, and the data is gradually transferred over a low speed line for still images. send. At this time, the moving image coding apparatus stores the inter-frame prediction signal immediately before the coding of the still image is stored in the inter-frame predictor 45, and while performing the coding of the still image, If the output of the code converter 47 of No. 1 is replaced with invalid data, the moving picture decoding apparatus can freeze the picture immediately before the coding of the still picture.

Alternatively, the signal supplied from the still image frame memory may be used as an input signal to the moving image coding apparatus, and the coding may be performed as if a normal moving image signal was input.

Then, as the moving picture coding device, when restarting the coding of the moving picture, by using the prediction signal stored in the inter-frame predictor 45, a new intra-screen correlation is newly used for the entire screen. It is possible to perform efficient moving picture coding using the correlation between screens immediately after the coding of a still picture is completed without refreshing by intra-frame coding. Even in the moving picture decoding device, like the moving picture coding device, without refreshing the entire screen,
Interframe decoding can be performed immediately.

If the still picture decoding apparatus on the receiving side has a feedback loop as shown in FIG. 5, the signal sent from the moving picture coding apparatus can be correctly decoded. The decoding signal selection switch selects the output of the intraframe decoder 49 when the intraframe coding is executed, outputs the data as the output of the still picture decoding device, and stores it in the frame memory. The output of the interframe decoder 50 is selected in the area where the interframe coding is executed. By doing this, for example, at time t in FIG.
At the time t + 1, the inter-frame coding is performed on the area refreshed in step S1, and the refresh line moves to the next area. However, the area where inter-frame coding is performed becomes invalid data when the coded data is encoded. Since the data is replaced, the data refreshed and stored in the frame memory becomes the output of the interframe decoder 50 as it is even after performing the interframe decoding, and the refreshed data stored in the frame memory is retained again. . By repeating this operation, the area to be refreshed is moved, and the area of the refreshed new image is gradually expanded to become one still image.

If the still picture decoding apparatus has a feedback loop as described above, the still picture can be transmitted using the refresh mode of the moving picture coding apparatus.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

-First Embodiment- FIG. 6 is a block diagram showing the configuration of an encoding apparatus according to the first embodiment of the present invention. Input image signal is line 100
It is supplied to the frame memory 1, the sync separator 2 and the switch 5 via. The frame memory 1 writes the input image signal when the writing signal supplied from the control circuit 4 via the line 41 indicates writing, and stores the screen. The sync separator 2 separates synchronization from the input moving image signal supplied via the line 100, and generates a frame pulse indicating the beginning of a frame and a line pulse indicating the beginning of a line based on the separated synchronization signal. , Refresh circuit 3 and control circuit 4. The refresh circuit 3 generates a refresh control signal for refreshing while moving by n lines for each predetermined frame based on the frame pulse and the line pulse supplied from the sync separator 2. The refresh control signal generated by the refresh circuit 3 is supplied to the control circuit 4, the switch 11, the code converter 12, and the code converter 13. The control circuit 4 generates a write signal for one frame time when the still image signal supplied via the line 400 is instructing to encode the still image, and outputs the write signal via the line 41 to the frame memory. Supply to 1. Further, the control circuit 4 generates a control signal for executing the encoding of the still image when the still image signal supplied via the line 400 indicates the encoding of the still image, and the line 450 is connected. Via switch 5, frame memory 1
0, to the code converter 12 and the code converter 13. Further, the control circuit 4 confirms that the still image signal supplied via the line 400 instructs the encoding of the still image, and the refresh control signal supplied from the refresh circuit 3 is a line other than refresh. At this time, the quantizer 7 is supplied with a stop signal for stopping the quantization and setting it as invalid data.

The switch 5 selects the input moving image signal supplied via the line 100 when the control signal supplied from the control circuit 4 via the line 450 indicates the encoding of the moving image, and the control signal is selected. Indicates still image encoding,
Select the output of frame memory 1. The output signal of the switch 5 is supplied to the subtractor 6. The subtractor 6 subtracts the signal supplied from the switch 5 from the prediction signal supplied from the switch 11 to obtain a prediction error signal. The output signal of the subtractor 6 is supplied to the quantizer 7. Quantizer 7
Stops the quantization and outputs invalid data when the stop signal supplied from the control circuit 4 indicates the stop. When the stop signal indicates not stopped,
The prediction error signal supplied from the subtractor 6 is quantized.

That is, while still image coding is being performed, normal quantization is performed in the area in which intra-frame coding is performed, and data in the area in which inter-frame coding is performed is made invalid by invalidating the data between frames. The amount of information generated by encoding is only the refresh line that has been intra-frame encoded. As described above, when the still image is being encoded, the generation of excessive information is suppressed by gradually and gradually encoding. The output signal of the quantizer 7 is supplied to the adder 8, the code converter 12, and the code converter 13.
The adder 8 adds the quantized prediction error signal supplied from the quantizer 7 and the prediction signal supplied from the switch 11 to obtain a locally decoded signal. The locally decoded signal obtained by the adder 8 is supplied to the intra-frame predictor 9 and the frame memory 10. The intra-frame predictor 9 uses the values of the pixels in the vicinity of the pixel to be encoded from the locally decoded signal supplied from the adder 8 such as the previous pixel or the previous line to predict the intra-frame prediction. A signal is generated and supplied to the switch 11. The frame memory 10 delays the locally decoded signal supplied from the adder 8 by one frame when the control signal supplied from the control circuit 4 indicates the coding of a moving image, and obtains an inter-frame prediction signal. , When the control signal indicates still image encoding,
The writing of the locally decoded signal supplied from the adder 8 is stopped, and the signal of the previous frame is held. Frame memory 10
The inter-frame prediction signal output from is supplied to the switch 11. When the refresh control signal supplied from the refresh circuit 3 indicates that the refresh line is a refresh line, the switch 11 selects the output of the intra-frame predictor 9 and confirms that the refresh control signal is a line other than the refresh line. When it is shown, the output of the frame memory 10 is selected. The prediction signal output from the switch 11 is supplied to the subtractor 6 and the adder 8.

The code converter 12 uses the quantizer 7 when the control signal supplied from the control circuit 4 indicates the coding of a moving image.
The quantized prediction error signal supplied from the above is code-converted using a highly efficient code such as Huffman code.
When the control signal indicates the encoding of the still image, the code conversion is stopped and the code indicating that the data is invalid is output. Further, the code converter 12 switches between refresh encoding and inter-frame encoding by the refresh control signal supplied from the refresh circuit 3.
The code-converted signal is matched with the speed of the line and becomes the output of the code converter 12. The output signal of the code converter 12 is
It is supplied to the moving picture decoding apparatus via a high speed line. When the control signal supplied from the control circuit 4 indicates the coding of a still image, the code converter 13 sends the quantized prediction error signal supplied from the quantizer 7 to a Huffman code or the like. Code conversion is performed using a code with good efficiency. When the control signal indicates the coding of the moving image, a code indicating that the data is invalid is output. Further, like the code converter 12, it also switches the code. The code-converted signal is matched with the line speed and becomes the output of the code converter 13. The output signal of the code converter 13 is supplied to the still image decoding device via the low speed line.

Next, the still image decoding apparatus will be described with reference to FIG.

The still image encoded in the refresh mode of the moving image encoder is supplied to the code inverse converter 20 via the line 200 from the low speed line for still images. The code reverse converter 20 performs reverse code conversion while matching the line speed and the decoding speed. When the refreshed area is reverse code converted by the intraframe coding, the intraframe decoding is performed via the line 2021. It is supplied to the adder 21, and when the area coded by the inter-frame prediction is subjected to the inverse code conversion, it is supplied to the adder 22 via the line 2022. Further, the code inverse converter 20 detects whether the signal has undergone intra-frame coding or a signal which has undergone inter-frame coding from the code, and the intra-frame decoder 21 and the inter-frame decoder 25 A switching signal for selecting the above is supplied to the switch 24 via the line 2024. The intraframe decoder 21 performs intraframe decoding by using the value of a decoded pixel in the vicinity of the pixel to be decoded, for example, the previous pixel or the previous line as the prediction signal and supplies it to the switch 24. At this time, the same prediction function as that on the transmitting side is used. Adder 22 is a line
The inter-frame signal subjected to the inverse code conversion supplied via 2022 and the inter-frame prediction signal supplied from the frame memory 23 are added to obtain an inter-frame decoded signal. At this time, the signal supplied from the code inverse converter 20 is encoded as invalid data between frames at the time of encoding, so the inter-frame prediction signal supplied from the frame memory 23 is directly output from the adder 22. Become. The interframe decoded signal output from the adder 22 is supplied to the switch 24. The switch 24 selects the output of the intraframe decoder 21 or the adder 22 according to the switching signal supplied via the line 2024. The output signal of the switch 24 is the frame memory 23.
To the output of the still image decoding device. The frame memory 23 delays the signal supplied from the switch 24 by one frame time and supplies it to the adder 22 as an inter-frame prediction signal.

On the other hand, in the case of the moving picture decoding apparatus, a normal moving picture decoding apparatus having the same prediction function as that of the moving picture coding apparatus may be used.

-Second Embodiment- Next, a second embodiment will be described with reference to FIG.

Even when the still image encoding is instructed, the moving image encoding apparatus can regard the signal output from the frame memory 1 as a moving image and continue the normal interframe encoding operation. . That is, in this case, the intraframe coding is applied to the refreshed line and the interframe coding is applied to the other lines, and the same prediction error signal is simultaneously supplied to the code converters 12 and 13. The code converter 12 performs the same operation as in normal moving image coding. The code converter 13 performs the operation during normal still image coding. Further, regardless of the control signal for encoding the still image supplied from the control circuit 4 via the line 450, the writing to the frame memory 10 may be always executed.

By doing this, when the transmission of the still image is completed,
The contents of the frame memories 10 and 23 are both still images supplied from the frame memory 1. Further, the contents of the frame memory of the inter-frame decoding loop in the moving picture decoding device are the same as the contents of the frame memory 1.

-Third Embodiment- Further, the embodiment of Fig. 3 will be described.

In the above description, the prediction method is described as intraframe coding, but this embodiment uses transform coding such as orthogonal transform.

As shown in FIG. 8, the inter-frame prediction error is transformed by the orthogonal exchanger 31, the transform coefficient obtained as a result is quantized by the quantizer 32, and supplied to the code converters 12 and 13, and at the same time, the inverse orthogonal transform is performed. Also supplied to the vessel 33. The inverse orthogonal transformer 33 executes an inverse transformation for the orthogonal transformation in the orthogonal transformer 31. For the switching of the switch 36, the ground side is selected during intra-frame coding, the ground side is selected during inter-frame coding, and the output of the frame memory 35 is selected during inter-frame coding.

(Effects of the Invention) As described in detail above, by using the image encoding device of the present invention, it is possible to simultaneously perform multipoint communication between the image decoding device and the still image decoding device. In the conventional still image communication station, the still image communication station and the moving image communication station are performed in the closed areas of the moving image communication station, and the communication frame can be greatly expanded.

Thus, when the present invention is put to practical use, its effect is extremely large.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a connection relationship with a moving picture coding apparatus for performing multipoint communication between a moving picture decoding apparatus and a still picture decoding apparatus according to the present invention, FIGS. b) and (c) are conceptual diagrams showing refreshing in encoding a moving image according to the present invention, and FIG. 3 is a conceptual diagram when encoding a still image by the moving image encoding device according to the present invention, 4 is a block diagram of a moving picture coding apparatus of the present invention, FIG. 5 is a block diagram of a still picture decoding apparatus on the receiving side, and FIG. 6 is a block of a coding apparatus according to the first embodiment of the present invention. FIG. 7, FIG. 7 is a block diagram of a receiving-side still image decoding apparatus according to the first embodiment of FIG. 6, and FIG. 8 is transform coding for orthogonal exchange etc. according to the third embodiment of the present invention. It is a block diagram when using. 1 ... Frame memory, 2 ... Sync separator, 3 ... Refresh circuit, 4 ... Control circuit, 5,11,24,36 ... Switch, 6,30 ... Subtractor, 7,32 ... Quantum Aromatizer, 8,22,34 ...
... Adder, 9 ... Intra-frame predictor, 10,23, 35 ... Frame memory, 12, 13 ... Code converter, 20 ... Code inverse converter, 21 ... In-frame decoder, 31 ... Orthogonal transformer, 33
…… Inverse orthogonal transformer.

Claims (1)

[Claims] 1. An image coding apparatus using intra-screen correlation and inter-screen correlation, wherein a means (1) for storing an input image and an output signal from the means (1) for storing the input image and the screen. A first selecting means (5) for selecting any of the above, and means (6) for obtaining a signal with reduced redundancy using the output of the first selecting means (5) and the third predicted signal, Means for quantizing the redundancy-reduced signal, wherein the redundancy-reduced signal when using the correlation between screens can be set to a predetermined value according to a third instruction; Means (8) for obtaining a local composite signal using the third prediction signal and the output of the quantizing means (7), and generating a first prediction signal using the intra-picture correlation from the local composite signal. Generate a second prediction signal using the correlation between the first predictor (9) and the screen A second predictor (10) capable of storing the second predicted signal according to the second instruction, the first predicted signal and the second predicted signal are selected by the first instruction. The output of the second selecting means (11) for generating the third prediction signal and the output of the quantizing means (7) is code-converted, and the code conversion is made invalid by the second instruction regardless of the input. The output of the first code conversion means (12) and the quantization means (7) that can be converted is code-converted, and the result prediction error using the correlation between the screens is invalidated by the second instruction and coded. Second code conversion means (13) capable of conversion, first control means (3) for giving the first instruction, the quantization means (7), the second predictor (10). ), The first code conversion means (12),
And a second control means (4) for giving the second instruction to the second code converting means (13) and giving a third instruction to the quantizing means (7). Image encoding device.