Vector quantizer

Abstract: A vector quantizer which transmits the input vector of the time when the minimum distortion is larger than the preset distortion threshold value and stores such input vector into the second code book as the new quantizing representative vector for the use in the successive vector quantizing processes. Further, since the first and second code book constitute in the form of tree-structure, calculation for search may be executed at a high speed.

Description: Field of the invention The present invention relates to an image encoding transmission apparatus with motion compensating processing. Prior art In the publication "IEEE Global Telecommunications Conference, 1986, Vol. 1/3, pages 261-265", defining the closest prior art from which the invention proceeds, it is disclosed a vector quantizer performing a new motion vector transmission method, wherein whenever motion vectors and transmitted prediction error signals of previously encoded adjacent blocks are smaller than a pre-determined threshold, the present block's motion vector is forced to zero and is not transmitted to the receiver side. This method reduces the amount of motion vector information in the still picture area. The prediction error signal is first calculated and compared to a threshold on a block by block basis to decide whether the block is significant or not. If the respective block is significant, the first stage vector quantization is carried out. Then the difference between the input and the first stage vector quantization decoder signal is transferred to the second stage vector quantization module. If the difference is greater than another threshold, the second stage vector quantization is carried out on the difference signal, otherwise vector quantization is not carried out at the second vector quantization module. Then the residual error signal of the second stage vector quantization module is transferred to the scala quantization module. In the scala quantization module, if the residual error signal power of the second stage is greater than a third threshold scala quantization, otherwise scala quantization is forced to zero. Finally, all vector quantization and scala quantization decoded signals are added, and the sum of such signals forms the local decoder prediction error signals. These three thresholds are variable to control the encoded information amount. Further, the US patent specification US-A-4 670 851 discloses a vector quantizer in which the vector quantization accuracy depends upon the amount of data to be transmitted. Fig. 1 is a block diagram indicating a configuration of an interframe encoding apparatus of the prior art using an encoding control system, introduced in the Technical Report CS85-3 of IECE Japan, 1986 by Murakami, Itoh and Kamizawa, entitled "Colored Dynamic Video Signal Transmission System for TV Conference". In this figure, 902 designates a subtractor for making subtraction between input video signal series 901 and a preceding frame recovery video signal series 912 and outputting an interframe difference signal series 903. 906 designates an encoding and decoding means (CODEC) for inputting an interframe difference signal series 903 and a block recognition data 905 and outputting an encoding data 907 and an interdecoded frame difference signal series 908. In addition, 909 designates an adder for adding such preceding frame recovery video signal series 912 and inter-decoded frame difference signal 908 and outputting a recovered video signal series 910. 911 designates a frame memory for storing such recovered video signal series 910 as much as one frame. 913 designates a sending buffer for inputting an encoding data 907 to obtain amount of information generated and outputting an encoding control signal 914 and a sending data 915. 916 designates an encoding control means for inputting an encoding control signal 914 and outputting encoding control parameter 917 to a block discrimination means 904. 904 designates a block discrimination means for inputting an encoding control parameter 917 and an interframe difference signal series 903 and outputting a block discrimination data 905. Fig. 2 is an example of structure of the block discrimination means 904 shown in Fig. 1. 1001 designates a threshold value control means for outputting a threshold value Th 1002 corresponding to the encoding control parameter 917 and 1003 designates a block decision means for deciding blocks depending on the threshold value Th 1002. Operation will then be explained. The input video signal series 901 subtracts the preceding frame recovery video signal series 912 with a subtractor 902 and converts it into an interframe difference signal series 902. This interframe difference signal series executes more minute encoding with less encoding error in the same amount of encoding since the total signal power thereof is smaller than the original signal. The interframe difference signal series 903 is encoded and decoded with high performance in the codec 906 in order to obtain the encoded data 907 and inter-decoded frame difference signal series 908. The adder 909 addes the preceding frame recovery video signal series 912 and inter-decoded frame difference signal series 908 to obtain a recovered video signal series 910. This recovered video signal series 910 is stored in the frame memory 911 to give delay of the predetermined frame period and form preceding frame recovery video signal series for the encoding of next frame. Meanwhile, the encoding data 907 is once stored in the sending buffer 913 and is then transmitted as the sending data 915. Moreover, the sending buffer 913 obtains a total sum of the amount of codes as much as one frame as the encoding control signal 914 (amount of information generated) and then supplies it to the encoding control means 916. With such amount of information generated 914 and instruction from external circuit, the encoding control means 916 adaptively controls the encoding control parameters 917 to be used in the block discrimination means 904 for each frame on the basis of the encoding rate which is uniquely selected and an encoding mode signal such as quality of recovered signal. Since the block discrimination means 904 decides the block of the frame as a whole with the threshold value Th corresponding to the encoding control parameter 917, the threshold value Th 1002 is output from the threshold value control means 1001, allowing comparison between Th and data value in the block decision means 1003 depending on the following formula and thereby determining the block discrimination data 905. Data value ≦ Th ν = 0, invalid block > Th ν = 1, valid block For the valid block, a data value corresponding to the block is output as the encoded data 907 along with the block discrimination data ν905, while for the invalid block, a data value corresponding to the block is considered as 0 and only the block discrimination data ν905 is output as the encoded data 907. The encoding control system used in the interframe encoding apparatus of the prior art is executed as described previously, there rises a problem that if the block discrimination threshold values are all lowered in unit of frame in the same degree when an input image becomes stationary image, the number of valid blocks in unit of one frame increases, and amount of information generated becomes extremely large. Still further, Fig. 3 is a block diagram of the image encoding transmission apparatus disclosed in the "Adaptive Quality Control in Dynamic Encoding" by Atsuya Itoh (draft of Image Encoding Symposium, June 3, 1986). As shown in the same figure, the image encoding transmission apparatus is comprised of a preprocessing means (A), a motion compensating means (B), a vector quantizing encoding means (C) and a vector quantizing decoding means (D). The processing means (A) comprises an A/D converter 1101 for generating a pixel signal 1201 through analog/digital conversion (hereinafter referred to as A/D conversion) by reading the video signal for each frame and a block divider 1102 for grouping the adjacent pixels on the image into blocks each of which is composed of the predetermined number of pixels and generating the image vector signal 1202 consisting of pixel signal 1201 group for each block. Moreover, the motion compensating means (B) comprises a frame memory 1103 for storing the decoded recovery signal 1212 of preceding frame and a motion compensating processing means 1204 for producing a plurality of reference blocks 1203 with reference to the current block position from the decoded recovery signal 1212 of the preceding frame stored in the frame memory 1103 and outputting, by searching, the reference block 1204a which is most approximated to the image vector signal 1202 and movement position information 1204b. The vector quantizing encoding means (C) comprises a subtractor 1105 for obtaining difference between the image vector signal 1202 and selected reference block 1204a by subtraction and outputting a difference vector signal 1205, a valid/invalid block discriminating means 1106 for calculating an evaluation value which indicates magnitude of the difference vector signal 1205, executing comparison between the evaluation value and threshold value, and appreciating the block discrimination information as the invalid information under the decision that the image vector signal 1202 is identical to the reference block 1204a when the evaluated value is within the range of threshold value or the block decision information as the valid information considering it as the block to be transmitted when the evaluated value is out of the range of threshold value, a vector quantizing encoding means 1107 for vector-quantizing and encoding only the difference vector 1205 decided as the valid information in the valid/invalid block discriminating means 1106 to output the encoded vector signal 1207 and a variable length encoding means 1108 for encoding, in variable length, the encoded vector signal 1207 and movement location information 1204b through the multiplexing. A multiplex encoded data 1208 output from the variable length encoding means 1108 is output to the communication line through the send buffer 1109. The vector quantizing decoding means (D) comprises a vector quantizing decoding means 1110 for outputting a decoded vector signal 1210 by decoding the encoded vector signal 1207 and an adder 1111 for adding the decoded vector signal 1210 and searched reference block 1204a to output the decoded reproducing vector signal 1211. A space filter 1112 executes the smoothing process of the decoded reproducing signal 1211. Next, operations of image encoding transmission apparatus of the prior art will be explained. First, the dynamic video signal 1200 of the first frame is input to the A/D converter, then converted to the pixel signal 1201 and input to the block divider 1102. The block divider 1102 produces the video vector signal 1202 by blocking the predetermined number of the adjacent pixel signals 1201 on the image and then outputs such signal. Next, the video vector signal 1202 passes directly the subtractor 1105 and is then input to the vector quantizing encoding means 1107. Thereafter, the vector quantizing encoding means 1107 performs the vector quantizing and encoding of the video vector signal 1202 as explained below. A mean value m of the video vector signal 1202 is first calculated. Separation of mean value is carried out on the basis of mean value m and the mean value separating vector is output. The vector most approximated to the mean value separating vector is searched from the code-book storing a plurality of pattern vectors to be output as the encoded vector 1207 of the vector signal 1202. The vector quantized and encoded vector signal 1207 is output to the communication line as the send encoded data 1209a through the send buffer 1009 after it is encoded to the code in variable length. Meanwhile, the encoded vector signal 1207 is input to the vector quantizing encoding means 1110 and then decoded. Thereafter, it passes the adder 1111 and is then written into the frame memory 1103 after the smoothing processing by the space filter 1112. A dynamic video signal 1200 of the second frame is converted to the video vector signal 1202 in the preprocessing circuit (A) and is then output and the video vector signal 1202 is input to the subtractor 1105. Moreover, this vector signal 1202 is input to the motion compensating processing means 1104. On the other hand, a plurality of reference block signals 1203 including the vector signal in the same position as the input block is produced from the decoded reproducing signal 1212 stored in the frame memory 1103 and is then input to the motion compensating processing means 1104. In the motion compensating processing means, distortion between the vector signal 1202 and the reference block signal 1203 is calculated, the reference block which gives minimum distortion is selected and the reference block signal 1204a thereof and movement position information 1204b are output respectively. The subtractor 1105 calculates difference between the vector signal 1202 and reference block signal 1204a to produce the difference vector signal 1205 and then outputs such signal to the vector quantizing encoding means 1107 and valid/invalid block discrimination means 1106. The valid/invalid block discrimination means 1106 makes decision expressed by the following formula. d : evaluated value ε i : difference vector signal element When d ≧ Th, valid When d < Th, invalid In case decision by the valid/invalid block discrimination means 1106 is valid, the difference vector signal 1205 is subject to the vector quantizing and encoding as the information to be sent. Moreover, in case decision by the valid/invalid block discrimination means 1106 is invalid, the selected reference block 1204a is considered as identical to the video vector signal 1202 and only the movement position information 1204b is transmitted. Next, the encoding vector signal 1207 is multiplexed in the variable length encoding means 1108 together with the movement position information 1204b through the variable length encoding, wherein the shorter code is assigned for the signal having high generation probability and the longer code to the signal having low generation probability, and is then output to the send buffer 1109. Meanwhile, the encoded vector signal 1207 is converted to the decoded vector signal 1210 in the vector quantizing decoding means 1110, then added to the reference block signal 1204a in the adder and is converted to the decoded reproducing vector signal 1211. Further, the decoded reproducing vector signal 1211 is subject to the smoothing process in case the movement position information 1204b is large and is then stored in the frame memory 1103. Here, the smoothing process of space filter 1112 is carried out on the basis of the movement position information 1204b obtained by the motion compensation and the control is carried out so that the smoothing process is executed only to the same region, but to the stationary region. With the configuration as described, the video encoding transmission apparatus of the prior art also carries out the smoothing process with a filter to the region to which the encoding with high accuracy has been conducted to produce the decoded image approximated to the input dynamic image signal and on the other hand, is accompanied by a problem as deteriorating quality of decoded image because the smoothing process is not carried out to the stationary region to execute the on-off control of filter with the motion vector information and thereby encoding noise to the roughly encoded region is accumulated. Summary of the Invention The image encoding transmission apparatus of the present invention has been proposed to overcome the problems described and it is therefore an object of the present invention to provide an image encoding transmission apparatus which effectively suppresses encoding noise and realizes local quality control of reproduced image. In order to attain the object described above, the image encoding transmission apparatus of the present invention is defined in the appended claim. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram indicating a configuration of the block discrimination means of the prior art; Fig. 2 is a block diagram indicating a configuration of the interframe encoding apparatus shown in Fig. 1; Fig. 3 is a block diagram indicating a configuration of an image encoding transmission apparatus of the prior art; Fig. 4 is a block diagram of an embodiment suitable for an image encoding transmission apparatus of the present invention; Fig. 5 is a detail block diagram of the vector quantizing encoding means of the embodiment shown in Fig. 4; Fig. 6 is a structure of the code book used for vector quantizing encoding and vector quantizing decoding; Fig. 7 is a block diagram of the vector quantizing decoding means; Fig. 8 is illustration for explaining pixel arrangement of an adaptive type space filter; Fig. 9 a table for explaining an example of smoothing characteristic control of the adaptive type space filter; Fig. 10 is a block diagram of an image encoding transmission apparatus depending on another embodiment of the present invention. An embodiment suitable for an image encoding transmission apparatus of the present invention will be explained with reference to Figs. 4 - 10. Fig. 4 is a block diagram indicating a configuration of an image encoding transmission apparatus depending on the embodiment of the present invention. Moreover, Fig. 5 is a detail block diagram of the vector quantizing encoding means. In these figures, the like elements as those in the prior art of Fig. 1 are given the like numerals and explanation thereof are omitted here. As shown in these figures, the vector quantizing encoding means 1107 comprises a quantizing control means 1107a for controlling quantizing characteristics based on the decision information 1206 output from the valid/invalid block discrimination means 1106 and amount of information 1209b of send data of the preceding frame stored tentatively to the send buffer 1109, a mean value separation means 1107b for calculating a mean value m of the effective difference vector signal 1207a output from the quantizing control means 1107a and separating a mean value of the difference vector signal 1207a, an inner product vector quantizing means 1107c for vector-quantizing the mean value separating vector signal 1207b2 output from the mean value separating means 1107b and a code book 1107d for storing a plurality of pattern vector. Therefore, the quantizing control means 1107a directly outputs the difference vector signal 1205 as effective difference vector signal 1207a when the information describe 1206 is valid and or the zero vector as the effective difference vector 1207a when the information is invalid. The mean value separating means 1107b separates a mean value of the effective difference vector signal 1207 on the basis of the mean value m calculated above. Moreover, the mean value separating means 1107b quantizes the mean value m on the basis of the quantizing characteristic (S1) designated by the quantizing control means 1107a and outputs the mean value quantizing number 1207bl. This circuit then outputs the mean value separating vector 1207b2 output from the mean value separating means 1107b to the internal product vector quantizing means 1107c. Next, the internal product vector quantizing means 1107c selects the pattern vector having the largest internal product by calculation of internal product of the mean value separating vector 1207b2 using a code book 1107d for storing a pattern vector of a plurality of mean value separating and normalizing vectors arranged in the form of tree-structure as shown in Fig. 6. Moreover, the detail block diagrams of the vector quantizing decoding means 1110 is shown in Fig. 7 and the vector quantizing decoding means 1110 comprises a mean value decoding means 1110b for decoding the quantized and decoded mean value m 1207b1 on the basis of the quantization characteristic (S1) output from the quantizing control means 1107a, an amplitude gain decoding means 1110c for decoding the amplitude gain in accordance with the quantization characteristic (S1) and an index decoding means 1110a. Operations of the embodiment will then be explained. The processes up to generation of difference vector signal 1205 are same as the procedures described previously and explanation thereof is eliminated herein. The difference vector signal 1205 obtained by the procedures similar to that of prior art is output to the valid/invalid block discrimination means 1106 and vector quantizing encoding means 1107 as in the case of the prior art. The difference vector 1205 input to the quantizing control means 1107a is subject to adjustment of each element of vector based on the valid/invalid block information 1206. Namely, for the valid block, a value of the difference vector signal 1205 is directly output to the mean value separating means 1107b as the valid difference vector signal 1207a and for the invalid block, the valid difference vector signal 1207a substituting each element with 0 is output. The vector quantizing encoding is not applied to the invalid block and therefore the vector quantizing and encoding of the valid block will be described. The quantizing controlling means 1107a is responsive to the input of amount of information 1209b to be stored in the buffer which is identical to the amount of send information of the preceding frame and periodically outputs, in unit of encoding object block, the quantizing characteristic signal which specifies the quantizing step width based on the amount of information to be stored in the buffer 1209b. The mean value separating means 1107b calculates the mean value m of the valid difference vector signal 1207a, quantizes such means value based on the quantizing characteristic signal (S1) and outputs as the mean value quantizing number 1207b1, and also separates the mean value of the valid difference vector on the basis of the means value m and then outputs such mean value as the mean value separating vector 1207b2 to the inner product vector quantizing means 1107c. In the inner product vector quantizing means 1107c, the internal product of the valid difference vector 1207b2 and the pattern vector normalized to a mean value 0 and a magnitude 1 in the code book 1107d is calculated to obtain the index 1207c2 of code vector which gives the maximum internal product and the amplitude gain 1207c1 given by such maximum internal product value in view of the quantization based on the quantizing characteristic signal (S1). Here, the pattern vector is configurated in the form of tree-structure as shown in Fig. 6 for speed-up of operation during search of code vector (quantizing representative vector) giving the maximum inner product in the vector quantization process so that the higher vectors are designed to become the representative vectors of the lower vectors. A procedure to select, in each phase, only one code vector giving the larger internal product with the mean value separating vector 1207b2 from a pair of code vectors is sequentially executed from the highest phase to the lowest phase in order to determine the quantizing representative vector of the lowest phase. In the pattern vectors arranged in the form of binary tree-structure, 0 or 1 is assigned in the direction of branching from respective nodes and a stream of binary number representing a path up to the quantizing representative vector of the lowest stage corresponds to the index 1207c2 of the quantizing representative vector. Moreover, in accordance with a magnitude of amplitude gain obtained, a new index 1207c2 having truncated the lower bits of index 1207c2 is transmitted. Therefore, since accuracy of vector quantization is variably controlled in accordance with magnitude of amplitude gain in the vector quantizing and encoding, the amplitude gain quantizing number 1207c1 may be considered as the encoding accuracy. As described, the encoded vector signal 1207 output from the vector quantizing encoding means 1107 is composed of mean value quantizing number 1207b1, amplitude gain quantizing number 1207c1, index 1207c2, valid/invalid block information 1206 and quantizing characteristic (S1), output to the variable length encoding means 1108, output to the send buffer 1109 after multiplexing with the motion information 1204b and is then output to the communication line as the send information. Operations of vector quantizing encoding means (D) will be explained on the basis of Fig. 7. For the valid block, the mean value quantizing number 1207b, amplitude gain quantizing number 1207c and index 1207c2 in the encoded vector signal 1207 are respectively decoded in the mean value decoding means 1110b, amplitude gain decoding means 1110c and index decoding means 1110a, then decoded to the valid difference vector signal 1207a by the multiplication and addition carried out respectively in the multiplier 1110e and adder 1110f and thereafter output as the decoded signal 1210. Here, the quantizing characteristic signal (S1) which specifies quantization step width is used for the decoding of mean value and amplitude gain. Meanwhile, for the invalid block, the 0 signal 1210g produced from the 0 signal generator 1110g is output from the selector 1110h, decoded into the decoded valid difference vector signal 1207a and output as the decoded vector signal 1210. The decoded vector signal 1210 is added to the reference block 1204a in the adder 1111 and is then output as the decoded reproduction signal 1211. Next, Fig. 8 shows arrangement, on the display screen, of the input signal sample pixels for the bi-dimensional space filter in such a case that such bi-dimensional space filter is used as the an adaptive type space filter and the adaptive space filter will be explained hereunder. Under the condition that the sample value interested to be smoothed and output is designated as X and the adjacent sample pixel values on the bidimensional arrangement for such sample, as A, B, C, D, E, F, G, H sequentially to the right from the left direction, the smoothing process can be executed in accordance with the following formula. X = a 1 X + (a 2 /4)(B + D + E + G) + (a 3 /4)(A + C + F + H) where, (a 1 + a 2 + a 3 = 1) Here, X is the interested pixel sample value smoothed, namely a filter output signal sample value, and a 1 , a 2 , a 3 are smoothing characteristic coefficient for controlling the smoothing characteristic. When the larger the smoothing characteristic coefficient a 1 , the weaker the smoothing effect, and the smaller the coefficient, the stronger the effect. An example of adaptive controlling method of the adaptive type space filter 1122 will be indicated. As an adaptive control parameter of the adaptive type space filter 1122, the movement position information 1204b, an amplitude gain quantizing number 1207c1 which indicates the encoding accuracy of encoding object block during the vector quantizing and encoding and a valid/invalid block information 1206 are respectively input to the adaptive type space filter 1122. In this adaptive type space filter 1122, the filter characteristic is adaptively controlled for each encoding object block, as shown in Fig. 9, on the basis of a degree of encoding accuracy indicated by the amplitude gain quantizing number 1207cl and the smoothing process is carried out considering the pixels in the encoding object block as the processing unit. However, in case the movement position information 1204b is "0" and the valid/invalid block information 1206 is invalid block in the motion compensating process, it is required to avoid attenuation in the higher frequency range of the stationary region. Therefore, the smoothing process is not carried out for all encoding object blocks in the motion compensating object block. An application example of the adaptive type space filter 1122 in such a case that the vector quantizing and encoding method is employed as the block encoding means has been explained in this embodiment, but the adaptive type filter 1122 can also be applied also to the case introducing the conversion encoding method. In this case, the effect similar to that of the above embodiment can also be obtained by using, as the encoding accuracy information, the encoding length after the conversion coefficient quantizing and encoding of the encoding object block for the adaptive control parameter. In above example, moreover, the adaptive type space filter 1122 is applied to the interframe encoding transmission apparatus, but the similar effect can also be demonstrated also by applying such filter to the frame encoding transmission apparatus. Fig. 10 shows a block diagram of the apparatus where the adaptive type space filter 1122 is applied to the frame encoding transmission apparatus as an example of another embodiment of the present invention. In the case of this embodiment, the block encoding for the valid block is carried out in the frame based on the valid/invalid block information 1206 by the block encoding means 1107. The adder used as the adaptive adder in this embodiment executes, if the input valid/invalid block information 1206 is the valid block, addition of the frame decoding vector signal 1210 and the reference block 1204a is carred out and meanwhile outputs the input reference block 1204a directly as the decoded reproduction signal for the invalid block. Moreover, such adder controls also the adaptive type space filter 1122 in accordance with the encoding accuracy information. This embodiment uses the adaptive type space filter 1122 as the filter comprised within the loop but similar effect can also be attained even in case the adaptive type space filter 1122 is applied to the decoding apparatus in the receiving side.

Claims: An image encoding transmission apparatus with motion compensating processing comprising: a preprocessing means (A) for reading a dynamic image signal for each frame, producing a pixel signal through A/D conversion, forming blocks each of which is formed by the predetermined number of adjacent pixels on the image and generating image vector signal (1202) consisting of pixel signal groups for each block, a motion compensating means (1104) for generating a plurality of reference blocks with reference to the current block unit from a reproduced signal of the previous frame and detecting a motion vector of the image vector signal by searching the reference block which is most approximated to the image vector signal, a vector quantizing encoding means (1107) for compressing and encoding such image vector signal on the basis of the searched reference block and motion vector by utilizing correlation between frames, an output buffer (1109) for sending, frame by frame, the encoded image vector signal to the transmission line (1209a), and a vector quantizing decoding means (1110) for decoding the image vector signal encoded in the vector quantizing encoding means (1107) and generating reproduced signal by adding the vector signal of reference block searched to the obtained decoded vector signal, an encoding accuracy control means (1108) for changing the encoding accuracy of the vector quantizing encoding means during the vector quantizing and encoding in accordance with the amount of information that is to be sent of the encoded image vector signal to be temporarily stored in the output buffer, characterized by further comprising: an adaptive spatial filter (1122) executing the smoothing process of the reproduced signal (1211) by using the pixel values including, at a predetermined ratio, the pixel values approximated to each pixel value of the reproduced signal; smoothing characteristic control means controlling ON/OFF conditions of the smoothing process of the adaptive spatial filter on the basis of the motion vector and enhancing a degree of smoothing operation of the adaptive spatial filter in case the encoding accuracy is low and lowering the degree of smoothing operation in case the encoding accuracy is high.

Inventors: FUKUHARA TAKAHIRO, HASEGAWA YURI, ITOH ATSUSHI, KAMIZAWA KOH, KATO YOSHIAKI, MATSUZAKI KAZUHIRO, MURAKAMI TOKUMICHI, FUKUHARA, TAKAHIRO, HASEGAWA, YURI, ITOH, ATSUSHI, KAMIZAWA, KOH, KATO, YOSHIAKI, MATSUZAKI, KAZUHIRO, MURAKAMI, TOKUMICHI, FUKUHARA, TAKAHIRO, C/O MITSUBUSHI DENKI K.K., HASEGAWA, YURI, C/O MITSUBUSHI DENKI K.K., ITOH, ATSUSHI, C/O MITSUBUSHI DENKI K.K., KAMIZAWA, KOH, C/O MITSUBUSHI DENKI K.K., KATO, YOSHIAKI, C/O MITSUBUSHI DENKI K.K., MATSUZAKI, KAZUHIRO, C/O MITSUBUSHI DENKI K.K., MURAKAMI, TOKUMICHI, C/O MITSUBUSHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1989
Main classification: H04N7
IPC codes: H04N7, G06T9, H03M7