JPH088690B2 - 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 a moving image and still image encoding / decoding system that performs multipoint communication with a moving image receiving station and a still image receiving station.

(Prior art) Conventionally, in image communication in a teleconference or the like, moving image communication is performed between moving image communication stations, and still image communication stations are stationary between still image communication stations. Image communication was taking place.

Further, still images are communicated between moving image communication stations by the moving image encoding device and the moving image decoding device in the still image mode.

(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 moving picture communication station and the still picture communication station communicate with the still picture communication station in their respective closed areas, and the communication between the moving picture station and the still picture station is not possible, which is very inconvenient.

In view of the above drawbacks, the 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.

(Means for Solving the Problems) According to the present invention, an image coding apparatus that codes an input image signal by using intra-screen correlation and inter-screen correlation and outputs a moving image output signal and a still image output signal. A sync separator that separates a sync signal from the input image signal and generates a frame pulse indicating the beginning of a frame, a line pulse indicating the beginning of a line, and a vertical sync signal based on the separated sync signal. A first refresh means for generating a first refresh signal for refreshing while moving n lines for each predetermined frame based on the frame pulse and the line pulse; and a still image coding instruction. A write signal generating means for generating a write signal during a predetermined frame in response to the signal, and the line pulse and the vertical synchronizing signal. Line number generating means for generating a line number that moves by n lines for each vertical synchronization section of a frame, and a second refresh signal for instructing intraframe encoding to be performed in the section of the vertical synchronization signal. A second refreshing means, one screen of the input image signal is stored in response to the write signal, the stored image is read from the address corresponding to the line number in the section of the vertical synchronizing signal, and the read image is read. A frame memory for outputting the signal as a still image signal, the input image signal and the still image signal, the vertical synchronizing signal section selects the still image signal, and the section other than the vertical synchronizing signal section receives the still image signal. Redundancy is reduced by using first selecting means for selecting an input image signal and outputting the selected image signal, and the selected image signal and the selected prediction signal. Means for obtaining a reduced prediction error signal, quantization means for quantizing the prediction error signal and outputting a quantized signal, and local decoding using the quantized signal and the selected prediction signal Means for obtaining a signal, first prediction means for generating a first prediction signal from the locally decoded signal using the correlation in the screen, and second prediction means for using the correlation between the screens from the locally decoded signal
Receiving the first refresh signal and the second refresh signal, the second refresh signal is selected in the interval of the vertical sync signal, and the vertical sync signal is generated. A second selecting unit that selects the first refresh signal and outputs the selected refresh signal except the signal section, and receives the first and second prediction signals, and selects the refresh signal The first prediction signal is selected when the refresh line is indicated, and the second prediction signal is selected when the selected refresh signal is a line other than the refresh line. And outputting the selected prediction signal
Selecting means, and a first code converting means for code-converting a signal other than the section of the vertical synchronizing signal in the quantized signal, and outputting the code-converted signal as the moving image output signal, A second code conversion means for code-converting the signal in the section of the vertical synchronization signal and the line number in the quantized signal, and outputting the code-converted signal as the still image output signal; An image encoding device characterized by having is obtained.

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

That is, as shown in FIG. 1, between the moving picture coding apparatus 40, the moving picture decoding apparatus 41 and the still picture decoding apparatus 42, in order to perform multipoint communication, the moving picture coding apparatus 40 and The moving image decoding device 41 is connected by a high speed line 43 for moving images, and the moving image encoding device 40 and the still image decoding device 42 are connected by a low speed line 44 for still images. Then, normal moving image communication is performed between the moving image encoding device 40 and the moving image decoding device 41, and still image communication is performed between the moving image encoding device 40 and the still image decoding device 42. To do. To encode a still image in the moving image encoding device 40, a still image to be transmitted is taken in to 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 line connected to the still image decoding device is much lower than that of the moving image decoding device 41, so that a large amount of data cannot be instantaneously passed.

Therefore, it is necessary for the moving picture coding apparatus to code a still picture little by little and transmit it.

As shown in FIGS. 2 (a), (b), and (c), usually, in moving image coding, periodic image rewriting (refresh) is performed in order to remove an error caused by an error in a transmission path. Are doing. The refresh is performed by intra-frame coding using intra-frame correlation while moving n lines for each predetermined screen, and removes an error generated in the frame memory of the decoder due to a transmission path error, and a new clean The image is written in the frame memory of both the encoder and the decoder. In the areas other than the refresh area, inter-frame coding is performed using the correlation between screens.

Therefore, the still image is encoded by the moving image encoding apparatus of the present invention by using the refresh mode and by encoding every n lines in the intra-frame code in the vertical synchronization section,
The area other than refresh is not encoded. By adding a line number to the encoded still image signal and sending it to the still image decoder, generation of excessive information on each screen is suppressed. In this way, by encoding little by little and transmitting, a large amount of information is prevented from being generated instantaneously.

When encoding a still image, a frame memory 43 for storing a still image is prepared in front of the moving image encoding device 44 as shown in FIG. 3, and the still image to be transmitted is written to the frame memory 43. Put in. Then, the input of the video encoding device 44 is
The output of the still image frame memory 43 is selected only in the vertical synchronization section, and n lines are encoded for each vertical synchronization of the frame determined in the refresh mode. Therefore, a moving image can be coded except during the vertical synchronization period, and moving image communication and still image communication can be performed at the same time.

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 10 and an intra-frame predictor 9, for normal coding and refreshing. The predictors 9 and 10 are switched by. Also, the refresh signal for moving images and the refresh signal for still images are switched by the vertical synchronizing signal. In coding a moving image, the output of the inter-frame predictor 9 having a high coding efficiency is selected as a normal prediction signal, and the difference from the previous screen is coded. When refreshing is performed, the output of the intra-frame predictor 9 is selected as a prediction signal only during that period (n lines), and intra-frame coding is executed. At this time, since the intra-frame predictor 9 uses the value of the previous pixel in the screen of the input signal or the value of the neighboring pixel as the prediction signal, it is correct without being affected by the previous screen in which errors due to transmission path errors are accumulated. The contents of the frame memory 10 can be gradually updated with images.

When encoding a still image, intraframe encoding is performed using the vertical synchronization section. From the input frame memory 1 in which still images are stored, a still image signal is read every n lines according to the line number given from the refresh circuit 2 for each vertical synchronization section of a predetermined frame,
Intra-frame coding is performed. Then, in the next encoded frame, the signal of the next n lines is read and encoded. For each frame determined in this way, encoding is performed gradually while moving n lines. A line number given from the still image refresh circuit 2 is added to the encoded data at this time, and the code converter 2 converts the line number into an efficient code such as a Huffman code. Then, matching with the speed of the transmission line is taken, data is sent little by little over a low speed line for still images.

As shown in FIG. 5, the receiving side still image decoding device has a frame memory 52 after the intra-frame decoder 51, and the signal decoded by the intra-frame decoder 51 is converted by the inverse code converter 50. By writing every n lines to the address of the frame memory 52 designated by the line number subjected to the inverse code conversion, the area of the decoded image is gradually expanded and one still image can be formed.

Since the encoded data is invalid in the vertical synchronization section in the encoding of the moving image, the decoder of the moving image may be a normal one.

(Embodiment) FIG. 6 is a block diagram showing an embodiment of the encoding apparatus of the present invention. An embodiment of the encoding device of the present invention will be described in detail below with reference to the figure.

The input image signal is sent via the line 100 to the frame memory 1,
It is supplied to the sync separator 2 and the switch 5. The frame memory 1 writes the input image signal when the write signal supplied from the refresh circuit 4 via the line 91 instructs writing, and stores the screen. Further, the frame memory 1 reads the still image data at the address corresponding to the line number designated via the line 90 from the refresh circuit 4 in the section of the vertical synchronizing signal given from the sync separator 2. The sync separator 2 separates the sync signal from the input moving image signal supplied via the line 100, and based on the separated sync signal, a frame pulse indicating the beginning of the frame, a line pulse indicating the beginning of the line, and Generates a vertical sync signal. The frame pulse generated by the sync separator 2 is
It is supplied to the refresh circuit 3 via the line 23. The line pulse generated by the sync separator 2 is supplied to the refresh circuit 3 and the refresh circuit 4 via the line 24. Further, the vertical sync signal generated by the sync separator 2 is
It is supplied to the frame memory 1, the refresh circuit 4, the switch 5, the switch 11, the frame memory 10, the code converter 13 and the code converter 14 via the line 21. Refresh circuit 3
Generates a refresh signal for refreshing while moving by n lines for each predetermined frame based on the frame pulse and line pulse supplied from the sync separator 2. The refresh signal generated by the refresh circuit 3 is supplied to the switch 11. The refresh circuit 4 receives a still image instruction signal for instructing encoding of a still image supplied via the line 400, generates a write signal for one frame, and supplies the write signal to the frame memory 1 via the line 41.

In addition, the refresh circuit 4 generates a line number that moves by n lines for each vertical synchronization section of the determined frame in accordance with the line pulse and the vertical synchronization signal supplied from the synchronization separator 2, and the line number is transmitted through the line 90. It is supplied to the memory 1 and the code converter 14. Further, the refresh circuit 4 generates a selection signal for performing intra-frame coding in the vertical synchronization section and supplies it to the switch 11. The switch 5 selects an input signal according to the vertical sync signal supplied from the sync separator 2. When the vertical sync signal indicates the vertical sync interval, the output signal of the frame memory 1 is selected to encode the still image, and the vertical sync signal indicates that the vertical sync signal is outside the vertical sync interval. Occasionally, a moving image is encoded, so an input signal supplied via the line 100 is selected. The output signal of the switch 5 is the subtractor 6
Is supplied to. The subtractor 6 subtracts the signal supplied from the switch 5 from the prediction signal supplied from the switch 12 to obtain a prediction error signal. The output signal of the subtractor 6 is supplied to the quantizer 7. The quantizer 7 quantizes the prediction error signal supplied from the subtractor 6. The output signal of the quantizer 7 is supplied to the adder 8, the code converter 13 and the code converter 14. The adder 8 adds the quantized prediction error signal supplied from the quantizer 7 and the prediction signal supplied from the switch 12 to obtain a locally decoded signal. Adder 8
The locally decoded signal obtained in step 3 is supplied to the intra-frame predictor 9 and the frame memory 10. In-frame predictor 9
Of the locally decoded signal supplied from the adder 8 generates an intra-frame prediction signal using the values of the pixels near the pixel to be encoded from now on, for example, the pixel of the previous pixel or the previous line, Supply to the switch 12. Frame memory
Reference numeral 10 indicates that the locally decoded signal supplied from the adder 8 is delayed by one frame time to obtain an inter-frame prediction signal, but the vertical sync signal supplied from the sync separator 2 is in the vertical sync section. At this time, the still image is encoded, so that the writing of the locally decoded signal is stopped. Frame memory 10
The inter-frame prediction signal output from is supplied to the switch 12. When the refresh signal supplied from the switch 11 indicates a refresh line, the switch 12 selects the output of the intra-frame predictor 9 and indicates that the refresh signal is a line other than the refresh line. Sometimes, the output of the frame memory 10 is selected. The prediction signal output from the switch 12 is supplied to the subtractor 6 and the adder 8. The switch 11 is a sync separator 2
The refresh signal is switched in accordance with the vertical synchronizing signal supplied from. In the vertical synchronization section, a still image is encoded so that the refresh signal of the refresh circuit 4 is selected. In the case other than the vertical synchronization section, since the moving image is encoded, the refresh signal of the refresh circuit 3 is selected. . The refresh signal output from the switch 11 is supplied to the switch 12.

The code converter 13 performs code conversion on the quantized prediction error signal supplied from the quantizer 7, and the vertical sync signal supplied from the sync separator 2 is a vertical sync section. When it indicates that the still image is being encoded, the code conversion is stopped and the invalid code is output. The output signal of the code converter 13 is matched with the speed of the transmission line, and is sent to the moving image decoder via the transmission line as a moving image output signal. The code converter 14 performs code conversion on the quantized prediction error signal supplied from the quantizer 7 in units of n lines, and the vertical sync signal supplied from the sync separator 2 is vertical. The code conversion is performed only when it indicates that it is a synchronization section, and the code conversion is stopped except in the vertical synchronization section. At this time, the line number supplied from the refresh circuit 4 is also code-converted and added to the still image signal code-converted. The output signal of the code converter 14 is matched with the speed of the transmission line, and is sent to the still image decoder via the transmission line as a still image output.

Next, one embodiment of the still image decoding apparatus of the present invention will be described with reference to FIG. The still image signal encoded by the moving image encoding apparatus of the present invention is supplied from the transmission line to the inverse code converter 50 via the line 500. The inverse sign converter 50 performs inverse sign conversion to obtain a prediction error signal and a line number in units of n lines. The prediction error signal obtained by the inverse code converter 50 is supplied to the intraframe decoder 51 via the line 5051, and the frame number is the frame memory via the line 5052.
Supplied to 52. The intra-frame decoder 51 performs intra-frame decoding by using the value of a pixel in the vicinity of the pixel to be decoded now, for example, the pixel of the previous pixel or the previous line as a prediction signal. At this time, the same prediction function as the intraframe encoder in the encoder is used. In-frame decoder 51 Decoder
The still image signal decoded in 51 is supplied to the frame memory 52. The frame memory 52 is an intra-frame decoder 51
The in-frame decoded signal supplied from the inverse code converter 50
Write to the address specified by the line number supplied from. In this way, the frame memory 52 gradually expands the area of the decoded image by writing the decoded signal to the address designated by the line number n lines at a time, and obtains one still image.

When transform coding such as orthogonal transform is used as the intra-frame predictor and the intra-frame decoder, an orthogonal transformer or the like is inserted between the subtractor 6 and the quantizer 7 of the coding device shown in FIG. At this time, the intra-frame predictor 9 is deleted, and the prediction signal when performing intra-frame coding of the switch 12 is
Make it more than give zero.

 The moving image decoder may be a normal one.

(Effects of the Invention) As described in detail above, by using the image coding device of the present invention, it is possible to simultaneously perform multipoint communication between a moving image decoding device and a still image decoding device. Therefore, the conventional still image communication station is performed in the still image communication station, and the moving image communication station is performed in the closed area of the moving image communication station, so that 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, FIG. 2 (a), (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, FIG. 4 is a block diagram of a moving image coding apparatus according to the present invention, FIG. 5 is a block diagram of an embodiment of a still image decoding apparatus on the receiving side, and FIG. 6 is an encoding according to an embodiment of the present invention. It is a block diagram of an apparatus. In the figure, 1,10,52 …… frame memory, 2 …… sync separator, 3,4 …… refresh memory, 5,11,12 …… switch, 6
…… Subtractor, 7 …… Quantizer, 8 …… Adder, 9 …… Intra-frame predictor, 13, 14 …… Code converter, 50 …… Inverse sign converter, 51
...... In-frame decoder.

Claims (1)

[Claims] 1. An image coding apparatus for coding an input image signal by using intra-screen correlation and inter-screen correlation and outputting a moving image output signal and a still image output signal, wherein the input image signal is synchronized with the input image signal. A signal is separated, and a frame pulse indicating the beginning of a frame based on the separated synchronization signal,
A line pulse indicating the beginning of a line, a sync separator for generating a vertical sync signal, and a first for refreshing while moving by n lines for each predetermined frame based on the frame pulse and the line pulse. First refresh means for generating a refresh signal, write signal generating means for generating a write signal in response to the still image coding instruction signal, and the line pulse and the vertical synchronizing signal. A line number generating means for generating a line number that moves by n lines for each vertical synchronization section of the determined frame, and a second instruction for instructing intra-frame encoding in the section of the vertical synchronization signal. Second to generate the refresh signal of
Refreshing means, the input image signal is stored in one screen in response to the write signal, the stored image is read from an address corresponding to the line number in the section of the vertical synchronizing signal, and the read signal is read. Receiving the input image signal and the still image signal, selecting the still image signal in the section of the vertical synchronization signal, and inputting the input image other than the section of the vertical synchronization signal. First selecting means for selecting a signal and outputting the selected image signal; means for obtaining a prediction error signal with reduced redundancy using the selected image signal and the selected prediction signal; Quantization means for quantizing a prediction error signal and outputting a quantized signal, means for obtaining a locally decoded signal using the quantized signal and the selected prediction signal, and the local decoding First prediction means for generating a first prediction signal using the correlation in the screen from the signal, and a second prediction generating a second prediction signal using the correlation between the screens from the local decoded signal. Means for receiving the first refresh signal and the second refresh signal, selecting the second refresh signal in a section of the vertical synchronizing signal, and the first refresh in a section other than the section of the vertical synchronizing signal. Second selecting means for selecting a signal and outputting the selected refresh signal, and receiving the first and second prediction signals and indicating that the selected refresh signal is a refresh line Selects the first prediction signal, and selects the second prediction signal when the selected refresh signal indicates a line other than a refresh line, Third selection means for outputting the selected prediction signal, and code conversion of the signal other than the section of the vertical synchronization signal in the quantized signal, and the code-converted signal is the moving image output signal. A first code converting means for outputting as a signal, the signal of the section of the vertical synchronizing signal in the quantized signal and the line number are code-converted, and the code-converted signal is output as the still image output signal. And a second code conversion means for outputting as the image coding apparatus.