JP2012004898A - Storage device, encoding device, encoding method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage device, an encoding device, an encoding method, and a program capable of reducing an amount of access to a memory, and adjusting a data amount at encoding in a simple structure, and keeping image quality desirable.SOLUTION: A storage device (110) includes: a demultiplexer (114) that inputs two-dimensional image data made up of pixels arranged in a matrix, extracts the image data one line by one line from one direction and sorts the extracted data for one line portion from a certain point in the line into one side of the line or the other side of the line; and first and second memories (115 and 116) each of which stores the data in one side and the other side of the line, respectively. The first memory (115) is a last-in first-out (LIFO) type line memory, and the second memory is a first-in first-out (FIFO) type line memory.

Description

  The present invention relates to a storage device, an encoding device, an encoding method, and a computer program that can reduce the amount of memory access during video processing.

  In signal processing of a display device such as a TV, it has become common to digitally process a video signal in order to improve image quality. In order to perform digital processing of video signals, it is necessary to sample analog signals such as broadcast and video signals and convert them into digital signals. The analog video signal is continuously transmitted, but after sampling, it becomes a set of discrete data. As a display method for a TV or the like, a two-dimensional image cut out at a frame period is continuously transmitted, and the digitized data is handled as a frame-unit image.

  With the recent increase in resolution of video signals, the amount of data per image becomes enormous. Therefore, in order to broadcast using conventional equipment, it is effective to perform some kind of information compression in order to reduce the amount of data. As a compression method, for example, a video compression method such as MPEG is known.

  MPEG and H.264 used for video compression. The technique such as H.264 can perform high compression on the original image, but it requires a difference between the previous and next videos and processing in units of macroblocks such as 16 × 16 (8 × 8). However, there is a tendency that the circuit scale, the amount of memory access, and the like increase, and the demand for hardware increases.

  However, when using functions such as video correction and adjustment, it is necessary to process the video signal without compression, and when using an external memory as it is, it is necessary compared with the case where compression is performed using MPEG or the like. The demand for access is much greater.

  Therefore, a method of compressing using a differential value using DPCM (Differential Pulse Code Modulation) coding is often used. DPCM is a method that predicts the current pixel value from the transmitted pixel value and encodes the difference between the true value and the predicted value, and uses the characteristic of image signals that there is a strong correlation between neighboring pixels. Encoding method.

  DPCM encoding generally belongs to lossless compression, has a low compression rate, and obtains the same or almost the same high-quality image when restoring the image. However, since the compression rate is very low, the amount of data increases, and the advantage of reducing the amount of information to be transmitted decreases. Also, due to the principle of DPCM, if the amount of data after compression is fixed, it is necessary to cut out a portion that cannot be accommodated, and there is a high possibility of irreversible compression in which data cannot be restored.

  In addition, due to the nature of TV scanning, there is no choice but to perform a process of transferring data from the upper left to one line in the right direction and moving to the left end of the next line. For example, when processing such as DPCM encoding is performed in units of lines, a large amount of errors will inevitably appear at the end, leading to degradation of image quality.

  In order to reduce such image quality degradation, for example, in Patent Document 1, encoding is performed preferentially from the center of the screen by expanding the processing direction of DCT conversion from the center of the screen to the left or right or up and down. Therefore, a configuration has been proposed in which distortion due to censoring is not noticeable visually. Further, Patent Document 2 proposes a configuration that includes a plurality of quantization circuits and a plurality of DPCM processing circuits, and switches and uses the optimum one.

JP-A-5-252499 JP 2009-231925 A

  However, in the technique disclosed in Patent Document 1, since the data on the memory is accessed and the data is compressed using DCT conversion or the like, the circuit scale increases and the access amount with the memory further increases. Become. Further, the technique disclosed in Patent Document 2 includes a plurality of quantization circuits, and thus has a problem that the circuit scale increases.

  The present invention has been made in view of such circumstances, and reduces the access amount of the signal processing circuit to the memory, adjusts the data amount at the time of encoding with a simple circuit configuration, and maintains good image quality. An object of the present invention is to provide a storage device, an encoding device, an encoding method, and a computer program.

  The storage device according to the present invention inputs two-dimensional image data composed of pixels arranged in a matrix, extracts the image data line by line in one direction, and extracts the extracted data for one line. A demultiplexer that distributes from one arbitrary point to one side and the other side of the line; and first and second memories that store data distributed to the one side and the other side, respectively, The memory is a LIFO type memory, and the second memory is a FIFO type memory.

  The storage device according to the present invention further includes a selection unit that alternately selects the first and second memories, reads the data, and outputs the data to the outside.

  The storage device according to the present invention is characterized in that the demultiplexer distributes the extracted data for one line from the approximate center of the line to the one side and the other side.

  An encoding device according to the present invention is an encoding device that includes the storage device described above and an encoding unit that encodes data stored in the storage device, and the encoding unit includes the storage device. And a DPCM processing unit that performs DPCM processing on the data output from the network, and an entropy encoding unit that entropy encodes the data subjected to DPCM processing.

  The encoding apparatus according to the present invention is characterized in that the entropy encoding unit performs a Huffman encoding process.

  The encoding apparatus according to the present invention is characterized in that the DPCM processing unit performs DPCM processing so as not to exceed a predetermined data amount.

  In the encoding device according to the present invention, the encoding unit performs quantization and encoding for performing quantization and encoding on the data output from the storage device in parallel with the DPCM processing and entropy encoding processing. A code amount determination unit that determines whether or not the amount of code after quantization / encoding exceeds a predetermined value, and the entropy encoding unit or the quantum based on a determination result of the code amount determination unit And a code output unit for selecting and outputting data from the encoding / encoding unit.

  An encoding method according to the present invention is a method for encoding image data in an encoding apparatus having a LIFO type first memory and a FIFO type second memory, wherein the pixels are arranged in a matrix. The data of the two-dimensional image consisting of is input, the image data is extracted line by line in one direction, and the extracted data for one line is extracted from any one point in the line to one side and the other side of the line. The data distributed to the one side and the other side are stored in the first and second memories, respectively, and the data are alternately read from the first and second memories and encoded. .

  A computer program according to the present invention is a computer program for encoding image data in a computer having a LIFO type first memory and a FIFO type second memory, and pixels arranged in a matrix on the computer The data of the two-dimensional image consisting of is input, the image data is extracted line by line in one direction, and the extracted data for one line is extracted from any one point in the line to one side and the other side of the line. A step of storing the data distributed to the one side and the other side in the first and second memories, respectively, and a step of alternately reading and encoding the data from the first and second memories Are executed.

  In the present invention, the storage device includes a LIFO type first memory and a FIFO type second memory. The demultiplexer inputs two-dimensional image data composed of pixels arranged in a matrix, extracts the image data line by line in one direction, and extracts the extracted data for one line in an arbitrary line From one point, the line is distributed to one side and the other side, and stored in the first and second memories, respectively. As a result, the left half of one line stored in the first memory is read from right to left in the reverse order of writing. Further, the right half of one line stored in the second memory is read from left to right as in the order of writing. Therefore, the image data can be accessed from the middle to the left and right ends for each line.

  In the present invention, the selection unit alternately selects the first and second memories, reads the data, and outputs the data to the outside. As a result, the image data is read and output from the middle toward the left and right ends for each line.

  In the present invention, the demultiplexer distributes the input image data for each line from approximately the center to the one side and the other side, and stores them in the first and second memories, respectively. As a result, the image data can be accessed from the center of the screen to the left and right ends for each line. Since encoding is performed preferentially from the center of the screen, even when it is necessary to cut out a portion that cannot be accommodated, an error is present at both the left and right ends of the screen, distortion becomes inconspicuous, and deterioration in image quality is suppressed.

  In the present invention, the encoding unit of the encoding device includes a DPCM processing unit that performs DPCM processing on data output from the storage device, and an entropy encoding unit that entropy encodes the data subjected to DPCM processing. The entropy encoding unit may perform Huffman encoding processing, and the DPCM processing unit may be configured to perform DPCM processing with a predetermined amount of data. As a result, the image data is read out from the middle of each line toward the left and right ends and output to the DPCM processing unit, and even if it is necessary to cut out a portion that cannot be accommodated in the DPCM processing, an error is generated. Located at the left and right ends of the screen, distortion is less noticeable and image quality degradation is suppressed.

  In the present invention, the quantization / encoding unit performs quantization and encoding in parallel with the DPCM process and the entropy encoding process, and the code amount determination unit has a code amount after quantization / encoding of a predetermined code. The code output unit determines whether or not the amount has been exceeded, and the code output unit selects and outputs data from the entropy encoding unit or the quantization / encoding unit based on the determination result. As a result, when there is a possibility that the desired target code amount may be exceeded even if some data is deleted in the DPCM processing, an encoding unit having a higher compression rate is used. Data can be compressed by selecting an appropriate encoding unit according to a desired code amount given in advance.

  According to the present invention, the image data can be accessed from the middle to the left and right ends for each line, the amount of access to the memory is suppressed without increasing the circuit configuration, and deterioration is displayed on the screen. Can be distributed to the left and right of the image to improve the image quality.

1 is a block diagram illustrating a configuration of a video processing apparatus according to Embodiment 1. FIG. 3 is a block diagram illustrating a configuration of a compression unit of the video processing device according to Embodiment 1. FIG. 3 is an explanatory diagram schematically showing a configuration of first and second line memories according to Embodiment 1. FIG. 6 is a block diagram illustrating a configuration of a video processing apparatus according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of a compression unit of a video processing device according to Embodiment 2. FIG. It is a block diagram which shows the structure of the modification of the compression part which concerns on this invention.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
In the following embodiments, a television receiver having a television reception function will be described as a video processing apparatus according to the present invention.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a video processing apparatus 1 according to the first embodiment. The video processing apparatus 1 includes an analog receiver 2, a digital receiver 3, a video processing unit 4 that is connected to the analog receiver 2 and the digital receiver 3, and that inputs a video signal including images and sounds. , And an external memory 5 connected to the video processing unit 4.

  The analog receiver 2 is for receiving an analog video signal. The analog receiver 2 is a tuner for selecting a desired radio wave from many radio waves and receiving an analog broadcast, a connection terminal for receiving a playback signal from a video playback device such as a VTR (Video Tape Recorder), etc. It is comprised including.

  The digital receiver 3 is for receiving a digital video signal. The digital receiver 3 includes a tuner for receiving a digital broadcast, a receiving terminal for receiving a playback signal from the digital video playback device, and the like.

  The video processing unit 4 is connected to the analog receiver 2 and the digital receiver 3 and inputs a video signal including images and sounds. The video processing unit 4 is connected to a display device (not shown) such as an LCD panel for output. Video / audio information input from the analog receiver 2 and the digital receiver 3 is processed by the video processing unit 4 and output to the display device, and is displayed and output by the display device. The video processing unit 4 includes an analog processing unit 10, a compression unit 11, a transport stream (hereinafter referred to as TS) processing unit 12, an MPEG processing unit 13, a first compression / decompression unit 14, an interlace-progressive, The conversion processing unit 15, the second compression / decompression unit 16, the video correction unit 17, the decompression unit 18, the arbiter 19, and the external memory controller 20 are included.

  The analog processing unit 10 inputs an analog video signal from the analog receiver 2. Here, the description will be made assuming that the input signal is an uncompressed analog signal, but the same applies when a compressed signal is input and expanded internally. The analog processing unit 10 converts an input analog signal into a digital signal by analog-digital conversion processing, and an uncompressed digital video signal is obtained. The obtained video signal is subjected to processing such as YC separation processing and color conversion by the analog processing unit 10, and is output to the compression unit 11 together with a request signal for writing to the external memory 5.

  The compression unit 11 is a circuit for compressing an uncompressed video signal to a certain amount of data. The compression unit 11 receives the video signal and the request signal from the analog processing unit 10, compresses the input video signal, and outputs the compressed signal to the arbiter 19 together with the request signal. Details of the compression processing by the compression unit 11 will be described later.

  The arbiter 19 is a circuit that performs an adjustment process that prioritizes any one process when a plurality of processing units try to access the external memory 5 almost simultaneously. The arbiter 19 determines whether or not a request conflict has occurred when an access request to the external memory 5 by a processing unit such as the analog processing unit 10 or the TS processing unit 12 occurs. A process of determining the access right by performing contention control is performed. Further, the arbiter 19 transmits a request from the processing unit to which the access right is given to the external memory controller 20.

  The external memory controller 20 is a circuit that accesses the external memory 5. When the external memory controller 20 receives an access request to the external memory 5 from a processing unit such as the analog processing unit 10 or the TS processing unit 12 transmitted from the arbiter 19, the external memory controller 20 exchanges data with the corresponding processing unit, Data is read from and written to a predetermined address in the memory 5.

  The TS processing unit 12 is connected to the digital receiver 3 and inputs a TS signal that is a digital broadcast signal. Here, the TS signal will be described assuming a stream compressed by MPEG and scrambled. The TS processing unit 12 performs processing such as descrambling on the received signal, converts it into stream data in a format that can be MPEG-decoded, and then outputs it to the arbiter 19 together with a request signal for writing to the external memory 5. Since the data processed by the TS processing unit 12 is compressed stream data and is not an image as it is, when the data output from the TS processing unit 12 is written to the external memory 5, it passes through a compression circuit. There is no need.

  The MPEG processing unit 13 reads the stream data descrambled by the TS processing unit 12 from the external memory 5 and performs MPEG decoding processing. The decrypted data is compressed by the first compression / decompression unit 14 and written to the external memory 5 via the arbiter 19 and the external memory controller 20.

  Each frame of MPEG stream data has three types, I frame, P frame, and B frame, depending on whether or not the blocks in the frame refer to the blocks in the previous and subsequent frames at the time of encoding / decoding. To do. In order to perform the MPEG decoding process, not only the reading of the stream data but also an image decoded in the past and written in the external memory 5 is read as a reference frame. Therefore, the first compression / decompression unit 14 is arranged at the subsequent stage of the MPEG processing unit 13. The data decoded by the MPEG processing unit 13 is compressed by the first compression / decompression unit 14 and written to the external memory 5 via the arbiter 19 and the external memory controller 20. On the other hand, when the reference frame is read out, the compressed data is read out from the external memory 5, decompressed by the first compression / decompression unit 14, and returned to the video frame.

  The IP conversion processing unit 15 is a circuit that converts an interlace signal transmitted by analog or digital broadcasting into a progressive signal that can be displayed on a display device such as an LCD panel. For moving images, there are a method called interlace and a method called progressive. In the former, one screen (frame) is divided into two fields for display, and the first field and the second field are alternated. In this case, the alternately upper field is called the top field, and the lower field is called the bottom field, and there is a time difference of half the frame period between the fields. That is, when the frame period is 1/30 seconds, the field period is 1/60 seconds. In order to perform IP conversion, the IP conversion processing unit 15 calls the data of the current field, calls the data of the past and future fields, and creates the signal of the missing part from the relationship, thereby making the progressive Convert to signal. The converted signal is compressed by the second compression / decompression unit 16 and written to the external memory 5 via the arbiter 19 and the external memory controller 20. On the other hand, when calling the data of the past and future fields, the compressed data is read out from the external memory 5, decompressed by the second compression / decompression unit 16, and inputted to the IP conversion processing unit 15.

  The video correction unit 17 is a circuit that performs various processes such as brightness adjustment, color adjustment, and contour correction in order to improve the quality of the video. Specifically, a request is issued to the arbiter 19 in order to read out necessary data from the external memory 5 in accordance with the output destination timing of the video processing unit 4. The read data is expanded by the expansion unit 18 and sent to the video correction unit 17. The video processing unit 17 performs various processes such as brightness adjustment, color adjustment, and contour correction on the received data, and then outputs the data to a display device such as an LCD panel via an output terminal.

  In the first embodiment, the first and second compression / expansion units 14 and 16 each include a compression unit and an expansion unit. When an uncompressed video signal is written to the external memory 5, compression processing is performed by any one of the compression unit 11, the compression unit of the first compression / decompression unit 14, and the compression unit of the second compression / decompression unit 16. On the other hand, when the video data is called from the external memory 5, the compressed data is read from the external memory 5, and the decompression unit of the first compression / decompression unit 14, the decompression unit of the second compression / decompression unit 16, and decompression It is stretched by any one of the sections 18. Compression of the compression unit 11, the compression unit of the first compression / decompression unit 14, and the compression unit of the second compression / decompression unit 16 so that the data compressed by any one of the compression units can be expanded by any one expansion unit. The parts are configured similarly. The decompression unit of the first compression / decompression unit 14, the decompression unit of the second compression / decompression unit 16, and the decompression unit 18 are configured in the same manner, and have a circuit configuration symmetrical to each compression unit. Hereinafter, the configuration of the compression unit according to the first embodiment will be described in detail using the compression unit 11 as an example.

  FIG. 2 is a block diagram showing a configuration of the compression unit 11 according to the first embodiment. As shown in FIG. 2, the compression unit 11 stores the input data in the first buffer memory 110 that temporarily stores the data, the timing control unit 111 that controls the data read / write timing, and the first buffer memory 110. A compression processing unit 112 that encodes and compresses the encoded data, and a second buffer memory 113 that temporarily stores the encoded data.

  The first buffer memory 110 includes a demultiplexer 114 that distributes data sent from the analog processing unit 10 according to a signal from the timing control unit 111, and two line memories 115 and 116 that store the distributed data. (First and second line memories 115 and 116) and a selector 117 that selects data from the two line memories 115 and 116 in accordance with signals from the timing control unit 111.

  Data sent from the analog processing unit 10 is distributed by the demultiplexer 114 according to the signal from the timing control unit 111. Specifically, the demultiplexer 114 inputs image data from the analog processing unit 10 according to the scanning direction of the TV broadcast, takes in the image data line by line, and stores the data for one line at the center of the screen. To the left and right halves. The demultiplexer 114 stores the distributed data in the first and second line memories 115 and 116, respectively.

  FIG. 3 is an explanatory diagram schematically showing the configuration of the first and second line memories 115 and 116 according to the first embodiment. As shown in FIG. 3, it is assumed that a buffer memory for one line is constituted by two line memories of first and second line memories 115 and 116. The first line memory 115 treats the last written data as a LIFO (Last In First Out) type memory that outputs first, and the second line memory 116 reads out the first written data first (FIFO ( Treated as First In First Out) type memory. The data of the left half and the right half of one line distributed by the demultiplexer 114 are stored in the first and second line memories 115 and 116, respectively.

  The selector 117 reads out the data stored in the first and second line memories 115 and 116 in a predetermined unit according to the timing control signal from the timing control unit 111 and sends the data to the compression processing unit 112. In the present embodiment, the selector 117 performs reading from the first line memory 115 and reading from the second line memory 116 in parallel. That is, the selector 117 alternately reads out data stored in the first and second line memories 115 and 116 in a predetermined unit according to the timing control signal. As described above, since the first line memory 115 is a LIFO type memory and the second line memory 116 is a FIFO type memory, the last written data is read from the first line memory 115 first. That is, the left half of one line stored in the first line memory 115 is read from right to left in the reverse order of writing. In addition, the first written data is read first from the second line memory 116, that is, the right half of one line stored in the second line memory 116 is the left as in the order of writing. To the right. As a result, the image data input from the analog processing unit 10 can be accessed from the center of the screen to the left and right ends for each line.

  The compression processing unit 112 includes a DPCM processing unit 118 that performs differential pulse code modulation (DPCM) processing on input data, and an entropy encoding unit 119 that entropy encodes the output of the DPCM processing unit 118. Is provided.

  The DPCM processing unit 118 inputs data stored in the first and second line memories 115 and 116 via the selector 117, and performs DPCM processing on the input data for each line. In the present embodiment, the DPCM processing unit 118 performs DPCM processing with a predetermined target data amount. The DPCM processing unit 118 performs DPCM processing on the input data and monitors whether the obtained data amount exceeds the target data amount. When it is determined that the obtained data amount exceeds the target data amount, the DPCM processing unit 118 does not encode the portion that cannot be accommodated, and treats it as, for example, the same pixel value as the previous pixel. Thus, the amount of data obtained and output by the DPCM processing is adjusted so as to become the target data amount.

  In the present embodiment, image data is input from the selector 117 to the DPCM processing unit 118 from the center of the screen to the left and right edges for each line, and is processed in order by the DPCM processing unit 118. As a result, encoding is performed preferentially from the center of the screen, so even if it is necessary to cut out the parts that do not fit, there are errors at the left and right ends of the screen, distortion is not noticeable, and image quality deterioration is suppressed. It is done.

  The entropy encoding unit 119 performs entropy encoding on the output data of the DPCM processing unit 118. Entropy coding is a process of efficiently coding data by assigning codes having different lengths based on the appearance probability of each pixel value of each pixel. Specific examples include Huffman codes and arithmetic codes. In this embodiment, Huffman coding is performed as entropy coding.

  The data output from the entropy encoding unit 119 is temporarily stored in the second buffer memory 113. Similar to the second line memory 116, the second buffer memory 113 treats the first written data as a FIFO type memory that reads first. The data stored in the second buffer memory 113 is output to the arbiter 19 in synchronization with the request signal. Thus, code data is output from the compression unit 11 in accordance with a desired code amount given in advance.

In the configuration of the compression unit 11 described above, the first and second line memories 115 and 116 each have half the size of one line of image data, and the first and second line memories 115 and 116 are included. One buffer memory 110 has a size corresponding to one line of image data. Further, since the necessary capacity of the second buffer memory 113 is determined by the amount of compressed data, it can be configured with the same amount of memory even when compared with the configuration of the conventional compression circuit.
According to the configuration of the first embodiment, it is possible to suppress the access amount to the memory without increasing the circuit configuration, distribute the deterioration to the left and right of the screen, and improve the image quality.

(Embodiment 2)
FIG. 4 is a block diagram showing the configuration of the video processing device 6 according to the second embodiment. In the following description, the same reference numerals are used for the devices and internal configurations common to the configuration of the first embodiment, and detailed description thereof is omitted.

  The video processing device 6 according to the second embodiment is connected to the analog receiver 2, the digital receiver 3, and the analog receiver 2 and the digital receiver 3, and inputs a video signal including images and sounds. And an external memory 5 connected to the video processing unit 4. The configurations of the analog receiver 2, the digital receiver 3, and the external memory 5 of the second embodiment are basically the same as those of the first embodiment. Hereinafter, the video processing unit 4 will be described in detail.

  The video processing unit 4 includes an analog processing unit 10, a compression unit 21, a TS processing unit 12, an MPEG processing unit 13, a first compression / decompression unit 22, an IP conversion processing unit 15, a second compression / decompression unit 23, a video correction unit 17, The decompression unit 24, the arbiter 19, and the external memory controller 20 are included. The configurations of the analog processing unit 10, TS processing unit 12, MPEG processing unit 13, IP conversion processing unit 15, video correction unit 17, arbiter 19, and external memory controller 20 are basically the same as those in the first embodiment. . Hereinafter, the compression unit 21, the first compression / decompression unit 22, the second compression / decompression unit 23, and the expansion unit 24 will be described in detail.

  In the second embodiment, the first and second compression / decompression units 22 and 23 each include a compression unit and a decompression unit. When an uncompressed video signal is written to the external memory 5, compression processing is performed by any one of the compression unit 21, the compression unit of the first compression / decompression unit 22, and the compression unit of the second compression / decompression unit 23. On the other hand, when the video data is called from the external memory 5, the compressed data is read from the external memory 5, and the decompression unit of the first compression / decompression unit 22, the decompression unit of the second compression / decompression unit 23, and decompression It is expanded by any one of the parts 24. Compression of the compression unit 21, the compression unit of the first compression / decompression unit 22, and the compression of the second compression / decompression unit 23 so that the data compressed by any one of the compression units can be expanded by any one expansion unit The parts are configured similarly. The decompression unit of the first compression / decompression unit 22, the decompression unit of the second compression / decompression unit 23, and the decompression unit 24 are configured in the same manner, and have a circuit configuration symmetrical to each compression unit. Hereinafter, the configuration of the compression unit according to the second embodiment will be described in detail using the compression unit 21 as an example.

  FIG. 5 is a block diagram showing a configuration of the compression unit 21 according to the second embodiment. As shown in FIG. 5, the compression unit 21 stores in the first buffer memory 210 that temporarily stores input data, the timing control unit 211 that controls the timing of data writing and reading, and the first buffer memory 210. A compression processing unit 212 that encodes and compresses the data that is encoded, and a second buffer memory 213 that temporarily stores the encoded data.

  The first buffer memory 210 includes a demultiplexer 214 that distributes data sent from the analog processing unit 10 according to a signal from the timing control unit 211, and first and second line memories that store the distributed data. 215 and 216, and a selector 217 that selects data from the first and second line memories 215 and 216 in accordance with a signal from the timing control unit 211. The configurations of the demultiplexer 214, the first and second line memories 215 and 216, and the selector 217 are basically the same as the demultiplexer 114, the first and second line memories 115 and 116, and the selector 117 of the first embodiment. The detailed description is omitted.

  The compression processing unit 212 includes a DPCM processing unit 218 that performs DPCM processing on input data, an entropy encoding unit 219 that entropy encodes the output of the DPCM processing unit 218, and quantizes the input data And a quantization / encoding unit 220 that performs encoding, and a code amount determination unit 221 that determines whether the code amount of the data encoded by the quantization / encoding unit 220 is within a predetermined target code amount And a code output unit 222 that selects and outputs code data from either the entropy encoding unit 219 or the quantization / encoding unit 220 in accordance with the output of the code amount determination unit 221.

  The DPCM processing unit 218 inputs data stored in the first and second line memories 215 and 216 via the selector 217, and performs DPCM processing on the input data for each line. Further, the DPCM processing unit 218 may perform DPCM processing with a predetermined target data amount, like the DPCM processing unit 118 according to the first embodiment. In this case, the DPCM processing unit 218 performs DPCM processing on the input data and monitors whether the obtained data amount exceeds the target data amount. If it is determined that the obtained data amount exceeds the target data amount, the DPCM processing unit 218 does not encode the portion that cannot be accommodated, and treats it as a pixel value similar to the previous pixel, for example. Thus, the amount of data obtained by the output DPCM processing is adjusted to the target data amount. In the second embodiment, image data is input from the selector 217 to the DPCM processing unit 218 from the center of the screen to the left and right ends for each line. The image data is processed by the DPCM processing unit 218 from the center of the screen toward the left and right ends for each line. As a result, encoding is performed preferentially from the center of the screen, so even if it is necessary to cut out the parts that do not fit, there are errors at the left and right ends of the screen, distortion is not noticeable, and image quality deterioration is suppressed. It is done.

  The entropy encoding unit 219 performs entropy encoding on the output data of the DPCM processing unit 218. Entropy coding is a process of efficiently coding data by assigning codes having different lengths based on the appearance probability of each pixel value of each pixel. Specific examples include Huffman codes and arithmetic codes. In this embodiment, Huffman coding is performed as entropy coding.

  The quantization / encoding unit 220 performs quantization and encoding processing on the data input from the selector 217 in parallel with the DPCM / entropy encoding processing. As the quantization process, for example, a process of truncating the lower bits of the pixel data so as to become the target code amount is performed, and as the encoding process, information indicating how many bits of the lower bits are truncated is added. Data processed by the quantization / encoding unit 220 is output to the code amount determination unit 221 and the code output unit 222.

  The code amount determination unit 221 determines that the code amount obtained by the quantization / encoding process by the quantization / encoding unit 220 is a predetermined target code amount (for example, 1/2 or 1/3 of the original data amount). It is determined whether or not it is within the set value. When the DPCM processing unit 218 is configured to perform DPCM processing with a predetermined target data amount, the predetermined target code amount related to the quantization / encoding unit 220 is equal to the predetermined target data amount related to the DPCM processing unit 218. It is set to be lower than the target code amount (for example, when the predetermined target code amount related to the DPCM processing unit 218 is set to ½ of the original data amount, the predetermined code amount related to the quantization / encoding unit 220 is set. Is set to 1/3 of the original data amount).

  The code output unit 222 selects and outputs code data from either the entropy encoding unit 219 or the quantization / encoding unit 220 according to the determination of the code amount determination unit 221. Here, the encoding process by the DPCM processing unit 218 and the entropy encoding unit 219 increases the amount of data because the compression rate is low, and the encoding process by the quantization / encoding unit 220 is irreversible with a high compression rate. Since compression is performed, it is assumed that the code amount output from the entropy encoding unit 219 is large and the code amount output from the quantization / encoding unit 220 is small. If the code amount determination unit 221 determines that the code amount obtained by the quantization / encoding process by the quantization / encoding unit 220 is within the predetermined target code amount, the entropy encoding unit The code output unit 222 selects and outputs the code data from the entropy encoding unit 219, assuming that the code amount output from 219 is within a desired amount. On the other hand, when the code amount determination unit 221 determines that the code amount obtained by the quantization / encoding process by the quantization / encoding unit 220 does not fall within the predetermined target code amount, the entropy encoding unit Since the code output from 219 may exceed the desired amount, the code data from the quantization / encoding unit 220 is selected and output.

  Data output from the code output unit 222 is stored in the second buffer memory 213. Similar to the second line memory 216, the second buffer memory 213 handles the first written data as a FIFO-type memory that reads first. The data stored in the second buffer memory 213 is output to the arbiter 19 in synchronization with the request signal. Thus, code data is output from the compression unit 21 according to a desired code amount given in advance.

  In the configuration of the compression unit 21 described above, the first and second line memories 215 and 216 each have half the size of one line of image data, and the first and second line memories 215 and 216 are the first line memories 215 and 216 respectively. One buffer memory 210 has a size corresponding to one line of image data. Further, since the second buffer memory 213 is determined by the amount of compressed data, it can be configured with the same amount of memory as compared with the configuration of the conventional compression circuit.

  With such a configuration, in the second embodiment, the amount of access to the memory can be suppressed without increasing the circuit configuration, and deterioration can be distributed to the left and right of the screen, thereby improving the image quality. Further, if there is a possibility that even if a part of data is deleted in the DPCM process, the desired target code amount may be exceeded, an encoding unit having a higher compression rate is used. Accordingly, it is possible to select an appropriate encoding unit and compress data according to a desired code amount given in advance.

  In the first and second embodiments described above, the compression unit has storage means including the first and second line memories 115 and 116 (215 and 216) and the second buffer memory 113 (213). Furthermore, the timing control unit 111 (211), the demultiplexer 114 (214), the selector 117 (217), and the compression processing unit 112 (212) as hardware other than the storage unit are configured. Is not limited to this. FIG. 6 is a block diagram showing a configuration of a modification of the compression unit according to the present invention. As illustrated in FIG. 6, the compression unit may include a first line memory 315, a second line memory 316, a second buffer memory 313, and a microcomputer 300.

  In this case, the configurations of the first line memory 315, the second line memory 316, and the second buffer memory 313 are basically the same as those in the first or second embodiment. The microcomputer 300 includes a control unit 301, a storage unit 302, and a temporary storage unit 303. The control unit 301 uses a CPU (Central Processing Unit) to read the compression program P stored in the storage unit 302 into the temporary storage unit 303 and execute it, so that the microcomputer 300 of the first or second embodiment is used. The timing control unit 111 (211), the demultiplexer 114 (214), the selector 117 (217), and the compression processing unit 112 (212) function.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

11, 21 Compression unit (encoding device)
110, 210 First buffer memory (storage device)
112, 212 Compression processing unit (encoding unit)
114, 214 Demultiplexer 115, 215, 315 First line memory (first memory)
116, 216, 316 Second line memory (second memory)
117, 217 selector (selection unit)
118, 218 DPCM processing unit 119, 219 Entropy encoding unit 220 Quantization / encoding unit 221 Code amount determination unit 222 Code output unit P Program (computer program)

Claims (9)

Inputs two-dimensional image data consisting of pixels arranged in a matrix, extracts the image data line by line in one direction, and extracts the extracted data for one line from any one point in the line A demultiplexer that distributes between one side and the other side;
A first memory and a second memory for storing data distributed to the one side and the other side, respectively;
The storage device, wherein the first memory is a LIFO type memory, and the second memory is a FIFO type memory. The storage device according to claim 1, further comprising a selection unit that alternately selects the first and second memories, reads data, and outputs the data to the outside. The storage device according to claim 1, wherein the demultiplexer distributes the extracted data for one line from the approximate center of the line to the one side and the other side. The storage device according to any one of claims 1 to 3,
An encoding device including an encoding unit that encodes data stored in the storage device,
The encoding unit includes:
A DPCM processing unit that performs DPCM processing on data output from the storage device;
An entropy encoding unit that entropy encodes data subjected to DPCM processing. The encoding apparatus according to claim 4, wherein the entropy encoding unit performs a Huffman encoding process. The encoding apparatus according to claim 4 or 5, wherein the DPCM processing unit performs DPCM processing so as not to exceed a predetermined data amount. The encoding unit includes:
In parallel with the DPCM process and the entropy encoding process, a quantization / encoding unit that performs quantization and encoding on the data output from the storage device;
A code amount determination unit for determining whether or not the code amount after the quantization / encoding exceeds a predetermined value;
A code output unit that selects and outputs data from the entropy encoding unit or the quantization / encoding unit based on a determination result of the code amount determination unit. The encoding device according to any one of the above. A method of encoding image data in an encoding device having a LIFO type first memory and a FIFO type second memory,
Inputs two-dimensional image data consisting of pixels arranged in a matrix, extracts the image data line by line in one direction, and extracts the extracted data for one line from any one point in the line To one side and the other side,
Storing the data distributed to the one side and the other side in the first and second memories, respectively;
An encoding method, comprising: alternately reading and encoding data from the first and second memories. A computer program for encoding image data in a computer having a LIFO type first memory and a FIFO type second memory,
Input two-dimensional image data consisting of pixels arranged in a matrix to a computer, extract the image data line by line in one direction, and extract the extracted data for one line from any one point in the line Allocating between one side and the other side of the line;
Storing the data distributed to the one side and the other side in the first and second memories, respectively;
And a step of alternately reading and encoding data from the first and second memories.

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