JP5872804B2 - Encoding apparatus and encoding method - Google Patents

Description

  The present invention relates to an encoding apparatus and an encoding method.

  Conventionally, various methods have been proposed as image processing methods (see, for example, Patent Documents 1 to 3). For example, Patent Document 1 discloses a technique for executing image processing in units of one pixel by converting image data in a necessary designated range into a raster shape in units of blocks. For example, Patent Document 2 discloses a technique for temporarily stopping the output of a drive pulse while outputting image data for one line. Further, for example, Patent Document 3 discloses a technique for packing a plurality of bits of encoded data as one word for each line or page.

  In image processing, encoding that converts the format of an image based on a predetermined rule is generally performed. As an image encoding system, for example, DPCM (Differential Pulse Code Modulation) is known. This encoding method by DPCM is a method that performs encoding using the feature that pixels in the vicinity often take relatively close pixel values. Therefore, when encoding is performed using DPCM, the image data can be compressed, so that the size of the memory used for recording the image data can be reduced. . For example, when image data is encoded, it is encoded in order from pixel data corresponding to the left end of the screen.

JP 2009-159631 A JP 2001-157122 A JP 07-115548 A

  However, when using DPCM, when encoding pixel data corresponding to the left end of the screen, the pixel data is directly encoded. However, when encoding pixel data other than the pixel data corresponding to the left end of the screen, A difference value between the pixel data and the immediately preceding pixel data is encoded. In this case, there is a problem that it is necessary to decode from the pixel data at the left end of the screen even when acquiring image data constituting a part of the screen.

  Therefore, the present invention can obtain image data constituting a part of the screen without decoding from the pixel data on the left end of the screen while suppressing the size of the memory used for recording the encoded data. It is an object of the present invention to provide a new and improved encoding apparatus and encoding method.

  According to an embodiment of the present invention, a direct encoding unit that directly encodes pixel data, a differential encoding unit that encodes a difference value between pixel data and pixel data before the pixel data, and the direct An encoded data selection unit that selectively outputs the encoded data obtained by the encoding unit or the differential encoding unit, and the encoded data selection unit is configured by the direct encoding unit in each line. An encoding apparatus is provided, which selectively outputs encoded data of a plurality of obtained pixel data.

  According to such a configuration, since encoded data obtained by encoding the difference value can be output, the encoded data is compared with a case where all pixels constituting the image data are directly encoded. The size of the memory used for recording can be reduced. Furthermore, since it is possible to output encoded data obtained by direct encoding, it is possible to acquire image data constituting a part of the screen without decoding from the pixel data at the left end of the screen.

  The encoded data selection unit selects and outputs the encoded data obtained by the direct encoding unit when a predetermined condition is satisfied, and the differential code when the predetermined condition is not satisfied. It is also possible to select and output the encoded data obtained by the conversion unit. According to such a configuration, it is possible to perform direct encoding when a predetermined condition is satisfied, and to encode a difference value when the predetermined condition is not satisfied.

  In addition, the encoded data selection unit selects and outputs the encoded data obtained by the direct encoding unit for the first pixel data and the pixel data each having a predetermined interval in each line. For the pixel data, encoded data obtained by the differential encoding unit may be selected and output. According to such a configuration, since direct encoding is always performed at predetermined intervals, it is possible to more reliably acquire image data constituting a part of the screen without decoding from the pixel data at the left end of the screen. can do.

  The encoded data selection unit may output the encoded data to a memory. According to such a configuration, the size of the memory used for recording the encoded data can be suppressed.

  The difference encoding unit may encode a difference value between the pixel data and the pixel data immediately before the pixel data. According to such a configuration, it is only necessary to store the previous pixel data, so that the circuit scale can be further reduced.

  According to another embodiment of the present invention, the step of directly encoding pixel data, the step of encoding a difference value between pixel data and pixel data before the pixel data, and the direct encoding or Selectively outputting encoded data obtained by encoding the difference value, and selectively outputting encoded data of a plurality of pixel data obtained by the direct encoding unit in each line An encoding method is provided.

  According to such a configuration, since encoded data obtained by encoding the difference value can be output, the encoded data is compared with a case where all pixels constituting the image data are directly encoded. The size of the memory used for recording can be reduced. Furthermore, since it is possible to output encoded data obtained by direct encoding, it is possible to acquire image data constituting a part of the screen without decoding from the pixel data at the left end of the screen.

  As described above, according to the encoding device and the encoding method of the present invention, the size of the memory used for recording the encoded data is reduced, and the screen can be displayed without decoding from the pixel data at the left end of the screen. Image data constituting a part can be acquired.

It is a figure which shows the data address control at the time of performing DPCM encoding with respect to the input data sequence by the encoding apparatus which concerns on embodiment of this invention. It is a figure which shows the effect in the case of encoding image data with the encoding apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the encoding apparatus and decoding apparatus which concern on embodiment of this invention. It is a figure which shows the operation example of the encoding apparatus which concerns on embodiment of this invention. It is a figure which shows the operation example of the decoding apparatus which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, a noise reduction circuit as a comparative example will be described. In the noise reduction circuit in this comparative example, a DPCM encoder is arranged on the input side of the line memory, and a DPCM decoder is arranged on the output side of the line memory. Thereby, the size of the line memory can be reduced by storing the encoded data compressed in the DPCM format. In such a case, the DPCM encoder directly encodes only the top pixel data (hereinafter also referred to as “pixel value”) of the line, and regarding the subsequent pixel data, the pixel data and the pixel data immediately before the pixel data are encoded. The difference value is encoded.

  Such processing is suitable for a kind of pipeline processing in which the entire screen is sequentially processed in combination with the line memory. However, a part of the image data on the screen is cut out, and the cut out image data is enlarged / reduced. It is not suitable for combination with such processing (for example, trimming / resizer processing). Since the pixel data other than the pixel data corresponding to the left end of the screen is data obtained by encoding the difference value from the previous pixel data, for example, even when only a part of the image data of the screen is desired, it corresponds to the left end of the screen. This is because it is necessary to decode from the pixel data. For this reason, when the noise reduction circuit in the comparative example is used, the processing is limited to the entire screen using the line memory.

  Hereinafter, an encoding apparatus and an encoding method according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows data address control when DPCM encoding is performed on an input data string by the encoding apparatus 10 according to the embodiment of the present invention. In particular, FIG. 1 shows an example in which each input data string is composed of 12-bit pixel data, and each encoded data string is composed of 6-bit pixel data.

<When writing>
Each pixel data constituting the image data is sequentially input as each input data to the encoding apparatus 10 according to the embodiment of the present invention. The image data input to the encoding device 10 may be acquired in any way, for example, may be acquired from a recording medium, or may be acquired from an external device of the encoding device 10. First, the encoding device 10 directly encodes the first pixel data D0 of the input data of each line using 2 clocks (2 data), and stores the encoded pixel data in the memory. To do.

  Subsequently, the encoding apparatus 10 DPCM-encodes the difference value between the next pixel data D1 and the immediately preceding pixel data D0 to 6 bits, and stores the result in the memory as encoded data C1. Subsequently, the encoding apparatus 10 DPCM-encodes the difference value between the next pixel data D2 and the immediately preceding pixel data D1 to 6 bits, and stores the encoded data C2 in the memory. The encoding device 10 repeats the same processing thereafter.

  After that, the encoding device 10 directly encodes other pixel data other than the head constituting the line and stores it in the memory. For example, when the insertion interval of the directly encoded data is set to 8, the encoding device 10 directly encodes the pixel data D8 and stores it in the memory as encoded data. Subsequently, the encoding apparatus 10 DPCM-encodes the difference between the pixel data D9 and the immediately preceding pixel data D8 to 6 bits, and stores the encoded data C9 in the memory. Thereafter, similar processing is repeated to store the encoded data in the memory.

  When DPCM encoding is performed, one address (6 bits) is used for one data transmission. However, when direct encoding is performed, since two addresses (12 bits) are used, direct encoding is performed. Every time the address increases by one, it shifts. The insertion interval of the directly encoded data is not particularly limited. The size of each input data is 12 bits, and the size of each encoded data is 6 bits. However, the size of each input data and the size of the encoded data are not particularly limited.

<When reading>
The decoding device 20 can read image data from the middle of the screen with the insertion interval of the directly encoded data as a delimiter. The decoding device 20 calculates the address of the directly encoded data immediately before from the address of the read data by the equation (1) in FIG. 1, and starts reading from the address. For example, when the decoding device 20 wants to read out the pixel data D11, in Expression (1), “M = 3”, “Adrs_input = 11”, “9 × 1 = 9”, and the reading start address is “9”. That is, it is only necessary to directly read and decode from the encoded data D8.

<Interval trade-off>
If the insertion interval of the directly encoded data is reduced, unnecessary encoded data does not have to be decoded, so that data can be efficiently read from the middle of the screen. For example, when the 122th data is acquired, if the insertion interval of the directly encoded data is 64, it must be read from the directly encoded data at the 64th address, and 60 clocks are waited until the desired data is obtained. There is a need.

  On the other hand, when the insertion interval of the directly encoded data is 8, it is only necessary to read from the 120th directly encoded data, so that data can be obtained only by waiting for 4 clocks. In this case, the waiting time until the desired data is obtained can be reduced to 6.7%. In addition, since unnecessary data is read and DPCM decoding is not performed, power consumption is reduced. However, since direct encoding uses data for two DPCM codes, if the insertion interval of the directly encoded data is reduced, the compression efficiency is lowered and the memory size is increased.

<Effect>
FIG. 2 is a diagram illustrating an effect when image data is encoded by the encoding device 10 according to the embodiment of the present invention. In particular, FIG. 2 shows an example in which the encoding apparatus 10 performs DPCM encoding of image data of 2048 pixels in the horizontal direction from 12 bits to 6 bits.

  In 12-bit to 6-bit DPCM encoding, the memory size is theoretically reduced by up to 50%. When the insertion interval of the directly encoded data is 64, the required memory size is reduced by 49.3% compared to the case where all are directly encoded, and is close to 50%. On the other hand, when the insertion interval of the directly encoded data is 8, although the reduction width is slightly reduced, the required memory size is reduced by 43.8% compared to the case where all are directly encoded. Therefore, even if the encoding device 10 has an insertion interval of directly encoded data of 8, it can be said that the utility value is sufficiently high.

<Configuration>
FIG. 3 is a diagram showing a configuration of the encoding device 10 and the decoding device 20 according to the embodiment of the present invention. Here, in particular, a case where a 12-bit input signal is compressed to 6 bits by DPCM encoding will be described as an example. Since the top pixel data of the input data should be directly encoded, the top pixel data 12 bits are divided into 2 clocks and sent to the subsequent stage as 6 bits × 2. Direct encoding on the pixel data is performed by the direct encoding unit 110.

  For the next pixel data, a difference value between the pixel data and the pixel data encoded immediately before is encoded from 12 bits to 6 bits by the DPCM encoding unit 120. The DPCM encoding unit 120 assigns a code to a relatively small difference value finely and a relatively large difference value coarsely using human visual characteristics.

  Here, since errors during DPCM encoding are canceled each time direct encoding is performed, it is assumed that errors are canceled relatively frequently when the insertion interval of direct encoded data is relatively small. The However, when the directly encoded data insertion interval is relatively large, errors are likely to accumulate. In such a case, the encoding apparatus 10 may perform 6-bit to 12-bit decoding on the encoded data, and DPCM encode the difference value between the reproduced data and the input data. As a result, accumulation of errors during DPCM encoding can be prevented.

  In SW1 (130), the insertion interval of direct encoded data is input as a parameter. SW1 (130) switches between direct encoding and DPCM code in accordance with the insertion interval of direct encoded data. Then, the encoded data is written to the Memory 140. In the example shown in FIG. 3, the insertion interval of the directly encoded data is given to SW1 (130) and SW2 (180) from the outside, but the insertion interval of the directly encoded data is, for example, the encoding device 10 and You may memorize | store in the memory | storage part which each of the decoding apparatus 20 has.

  In reading from the Memory 140, first, the position of read data is designated by the user. The designation by the user is made, for example, by an operation given to the input device by the user. The address calculation unit 150 calculates the read start address by the equation (1) in FIG. 1 using the insertion interval of the directly encoded data as a parameter. The encoded data written in the Memory 140 is decoded by the direct decoding unit 160 or the DPCM decoding unit 170. Since the beginning of reading is always directly encoded pixel data, the direct decoding unit 160 directly decodes and reproduces the data. Then, from the next data, the DPCM decoding unit 170 obtains data by adding the immediately preceding reproduction value to the difference value obtained by DPCM decoding the data.

  SW2 (180) receives the insertion interval of the directly encoded data as a parameter, and SW2 (180) switches between the directly decoded data and the DPCM decoded data in accordance with the directly encoded data insertion interval and passes it to the subsequent stage. . The trimming / resizer 190 performs trimming and resizing on the image data output from the SW2 (180).

<Operation>
FIG. 4 is a diagram illustrating an operation example of the encoding device 10 according to the embodiment of the present invention. As shown in FIG. 4, the direct encoding unit 110 acquires the top pixel data (step S11), and directly encodes the acquired top pixel data (step S12). The encoded data obtained by the direct encoding is output to the Memory 140 (Step S13). The Memory 140 accumulates the output encoded data.

  The direct encoding unit 110 acquires the next pixel data (step S21), and directly encodes the next pixel data (step S22). Further, the DPCM encoding unit 120 encodes a difference value between the pixel data and the pixel data immediately before the pixel data (step S23). SW1 (130) selects encoded data from the encoded data obtained by the encoding by the direct encoding unit 110 and the encoded data obtained by the encoding by the DPCM encoding unit 120 (step S24). ).

  For example, SW1 (130) selects encoded data obtained by encoding by the direct encoding unit 110 when a predetermined condition is satisfied, and by the DPCM encoding unit 120 when the predetermined condition is not satisfied. Encoded data obtained by encoding can be selected. The predetermined condition is not particularly limited, but corresponds to the insertion interval of the directly encoded data in the above example. That is, SW1 (130) selects the encoded data obtained by the encoding by the direct encoding unit 110 at every predetermined interval, and the encoded data obtained by the encoding by the DPCM encoding unit 120 in the meantime. Can be selected.

  SW1 (130) outputs the selected encoded data to Memory 140 (step S25). The Memory 140 accumulates the output encoded data. If the encoding is not finished (“No” in step S26), the process returns to step S21. If the encoding is finished (“Yes” in step S26), the encoding is finished. Encoding ends when, for example, encoding of the entire image data is completed.

  FIG. 5 is a diagram illustrating an operation example of the decoding device 20 according to the embodiment of the present invention. As shown in FIG. 5, the direct decoding unit 160 acquires the first encoded data (step S31), and directly decodes the acquired first encoded data (step S32). The pixel data obtained by the direct decoding is output to the trimming / resizer 190 (step S33). Note that the first encoded data here is, for example, encoded data at the read start address calculated from the read data address by the equation (1) in FIG. In this way, the decoding device 20 can acquire image data constituting a part of the screen without decoding from the pixel data at the left end of the screen.

  The direct decoding unit 160 acquires the next encoded data (step S41), and directly decodes the next encoded data (step S42). Further, the DPCM decoding unit 170 adds the difference value obtained by decoding the encoded data to the pixel data immediately before the encoded data (step S43). SW2 (180) selects pixel data from the pixel data obtained by decoding by the direct decoding unit 160 and the pixel data obtained by decoding by the DPCM decoding unit 170 (step S44). As described above, the SW2 (180) can select the pixel data according to the insertion interval of the directly encoded data, for example.

  The SW2 (180) outputs the selected pixel data to the trimming / resizer 190 (step S45). The trimming / resizer 190 performs trimming processing and resizing on the output pixel data. If the decoding is not finished (“No” in step S46), the process returns to step S41, and if the decoding is finished (“Yes” in step S46), the decoding is finished. Decoding ends when, for example, decoding of the entire image data is completed.

  As described above, according to the noise reduction circuit in the comparative example, the use efficiency of the line memory can be improved (for example, doubled) while suppressing the visual image quality deterioration. However, when the noise reduction circuit in the comparative example is used, the image data cannot be read from the middle of the screen, so that the scene where the circuit can be applied is limited to the combination with the pipeline processing of the full screen.

  According to the embodiment of the present invention, since image data can be read even from the middle of the screen, it is possible to improve the use efficiency of the memory in combination with wider image processing such as trimming and resizing. In the noise reduction circuit in the comparative example, only the pixel data at the left end of the screen can decode the input data without deterioration. In the embodiment of the present invention, since direct encoding is performed at predetermined intervals in the screen, image quality degradation is always canceled at predetermined pixels. Therefore, according to the embodiment of the present invention, there is an effect that it is easy to obtain more stable image quality.

  In the above description, an example in which 12-bit pixel data is encoded into 6-bit encoded data has been described. However, the present invention is not limited to this, and even if 10-bit pixel data is encoded into 5-bit encoded data. Alternatively, 14-bit pixel data may be encoded into 7-bit encoded data. Further, although DPCM is used as a compression method, the compression format is not limited, and can be implemented with a small circuit scale, isometric coding, or a method with little deterioration in image quality. Furthermore, although it is easy to control the insertion interval of the directly encoded data to be a power of 2, it is not necessarily limited to this.

  In the embodiment of the present invention, the DPCM encoding unit 120 encodes the difference value between the pixel data to be encoded and the immediately preceding pixel data at the time of DPCM encoding. You may encode the difference value with pixel data. For example, the DPCM encoding unit 120 may encode the difference value between the pixel data to be encoded and the pixel data that is N before (N is an integer of 2 or more). In that case, the difference value may be added to the pixel data that is N times before in the decoding by the DPCM decoding unit 170. Also, the encoding device 10 performs direct encoding from the first pixel data to the Nth pixel data.

  In the embodiment of the present invention, the data encoded by the encoding device 10 is output to the Memory 140, but the output destination of the encoded data is not particularly limited. For example, it may be output to a device other than the Memory 140 (device having a function other than the storage function).

  Further, although the encoding apparatus 10 performs direct encoding every predetermined interval, the direct encoding may not be performed every predetermined interval. For example, the encoding apparatus 10 may analyze image data and determine whether to perform direct encoding according to the analysis result. For example, for an area of image data where it is desired to avoid accumulation of encoding errors, direct encoding may be performed. When it is analyzed that a face appears in the image data, the face is analyzed. You may code directly with respect to an area | region.

  The DPCM encoding unit 120 shown in FIG. 3 can also function as a differential encoding unit. SW1 (130) can also function as an encoded data selection unit. The DPCM decoding unit 170 can also function as a differential decoding unit. Furthermore, SW2 (180) can also function as a decoded data selection unit.

  The difference between the technique described in the above-mentioned document as the prior art document and the technique according to the embodiment of the present invention will be briefly described. After performing the first processing, it is converted into a raster and the second processing is performed. In this regard, it is assumed that the technology does not use the compression encoding according to the embodiment of the present invention, and the technology does not lead to a reduction in the line memory used.

  The technique described in Japanese Patent Laid-Open No. 2001-157122 is a technique for controlling a sensor and a DRAM to perform DRAM access without a line memory. In this respect, the technology does not use the compression coding according to the embodiment of the present invention, and the embodiment of the present invention is different from the technology in that only the input / output control to the memory is not required.

  The technique described in Japanese Patent Laid-Open No. 07-115548 is a technique for adding redundant bits for packing every 16 bits in combination with variable length coding. In this regard, in the embodiment according to the present invention, equal-length encoding is assumed, and it is difficult to combine the technique with a line memory having a fixed size.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Encoding apparatus 20 Decoding apparatus 110 Direct encoding part 120 DPCM encoding part (differential encoding part)
140 Memory
150 Address Calculation Unit 160 Direct Decoding Unit 170 DPCM Decoding Unit (Differential Decoding Unit)
190 Trimming Resizer

Claims (4)

A direct encoding unit that directly encodes pixel data into two clocks ;
A differential encoding unit that encodes a differential value between pixel data and pixel data before the pixel data;
An encoded data selection unit that selectively outputs encoded data obtained by the direct encoding unit or the differential encoding unit;
With
The encoded data selection unit selectively outputs encoded data of a plurality of pixel data obtained by the direct encoding unit in each line, and in each line, the first pixel data and each of the encoded data are a predetermined interval For the pixel data having, select and output the encoded data obtained by the direct encoding unit, for other pixel data, select and output the encoded data obtained by the differential encoding unit, Encoding device. The encoded data selection unit includes:
Outputting the encoded data to a memory;
The encoding device according to claim 1. The differential encoding unit
Encoding a difference value between the pixel data and the pixel data immediately before the pixel data;
The encoding device according to claim 1. Directly encoding pixel data into two clocks ;
Encoding a difference value between pixel data and pixel data before the pixel data;
A step of outputting encoded data obtained by encoding of the direct encoding or the difference value selectively, in each line, the encoded data of a plurality of pixel data more obtained the direct coding Selectively outputting
For each line, for the leading pixel data and pixel data each having a predetermined interval, selecting and outputting the encoded data obtained by the direct encoding; and
For other pixel data, selecting and outputting encoded data obtained by encoding the difference value;
The encoding method characterized by including.

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