JP2018050151A - Image coding device, image coding method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve or maintain coding image quality for a photographing mode assumed to include a large number of gradation images.SOLUTION: A coding part 105 codes an image output from an imaging part 101. An intra-smoothing processing determination part 104, when photographing mode information from a photographing mode setting part 102 indicates a photographing mode that is highly likely to include a large number of gradation images, supplies a signal to enable linear interpolation of reference pixels at the boundary of coding blocks in an in-screen prediction mode. The coding part 105 enables linear interpolation of the reference pixels at the boundary of coding blocks in the in-screen prediction mode according to an output from the intra-smoothing processing determination part 104.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image encoding device, an image encoding method, and a computer program, and more particularly, to an image encoding device that uses intra prediction, an image encoding method, and a computer program.

  2. Description of the Related Art Conventionally, a digital video camera is well known as a camera-integrated moving image recording apparatus that compresses and records moving image data obtained by taking a moving image of a subject.

  As the moving image compression method, MPEG2 method and H.264 which can be compressed at a high compression rate using inter-frame motion prediction. The H.264 system is generally used. In recent years, the HEVC method (ISO / IEC 23008-2) that can be compressed with high efficiency using a more complicated prediction method has been used.

  In the HEVC system, H.264 is used. Various improvements have been adopted to improve the compression efficiency with respect to the H.264 system. As one of them, a technique is known in which a filtering process is performed on a reference pixel adjacent to a coding block in order to increase the coding efficiency by using the correlation between adjacent pixels during the intra prediction process. In particular, in this filter processing, special filter processing for improving visual quality can be applied to a gradation region in which color shading and lightness change little by little depending on conditions.

  With reference to FIG. 8, the necessity of the filtering process for the gradation area will be briefly described. FIG. 8A shows an example of a change in pixel value when there is a block boundary in the gradation area. The horizontal axis represents pixels, and the vertical axis represents luminance values. H. In the H.264 system, compression processing is performed in units of blocks, so that pixels at the block boundary are discontinuous between encoded pixel blocks adjacent to the periphery of the encoding target block. As a result, in a coded image block that employs intra prediction, a predicted image is generated while the pixel values remain discontinuous between reference pixels at the block boundary. Then, as shown in FIG. 8B, a pseudo contour is generated in the predicted image. FIG. 8B shows a state where a pseudo contour is generated in a line connecting from the upper right to the lower left at the center of the encoding target block.

  For such a problem, Patent Document 1 describes a method of generating a predicted value by defining a reference pixel in a wider range than a pixel position defined in the standard. Patent Document 2 describes that gradation detection is performed in units of coding blocks, and the pixel size for intra prediction is set to the minimum size in the standard for an image block determined to be a gradation image.

  Therefore, in the HEVC method, when the absolute value of the difference between the pixel value at both ends of the reference pixel at the adjacent block boundary and the average value is less than a threshold value determined according to the luminance bit depth, the reference pixel is linearly changed. Intra smoothing processing to be interpolated is defined. However, in order to apply this processing, it is necessary to satisfy all of the following three conditions in addition to the difference in pixel values between block boundaries. First, the pixel block size (Transform Unit size: TU size) for frequency conversion is 32 × 32 pixels. Second, the mode value (predModeIntra) of directionality prediction is neither 1 (DC prediction), 10 (horizontal direction prediction), or 26 (vertical direction prediction). Third, the variable strong_intra_smoothing_enabled_flag of the sequence parameter set (hereinafter referred to as “SPS”) is 1.

JP 2008-245088 A JP2011-239365A

  The technique described in the cited document 1 is described in H.C. It is limited to the H.264 system and cannot be applied to a moving picture encoding apparatus that employs the HEVC system.

  The technique described in the cited document 2 is a method that does not depend on the HEVC type intra smoothing process. However, since the processing is performed in units of macroblocks, it is not always possible to increase the encoding efficiency for the entire encoded picture and the entire moving image sequence.

  In the method employing the HEVC method of intra smoothing, when the variable strong_intra_smoothing_enabled_flag in the SPS is always set to 1, the linear interpolation filter process is applied to all the encoded sequences. In this method, depending on the design of the input image, the resolution of the image may be impaired, and visual characteristics may not necessarily be improved.

  It is an object of the present invention to present an image encoding device, an image encoding method, and a computer program that can apply the HEVC method and that can adaptively determine application of an intra smoothing process according to an input image.

  In order to solve the above problems, an image encoding device according to the present invention is an image encoding device that encodes an imaging unit that captures an image of a subject according to a set shooting mode, and encodes an output image of the imaging unit. Coding means for coding in units of coded blocks, wherein the coding means has a mode for linearly interpolating reference pixels at the coding block boundary in the intra prediction mode; and the coding means performs coding on a block image to be coded. An intra-smoothing process determining unit that determines application of linear interpolation processing of the reference image in the intra-screen prediction mode, wherein a shooting mode set in the imaging unit may include a gradation image more than a predetermined value. And an intra-smoothing process determining means for instructing the encoding means to validate the linear interpolation in the photographing mode. To.

  According to the present invention, since the linear interpolation processing of the reference image in the intra prediction mode is controlled depending on whether or not the shooting mode may include many gradation images, the encoded image quality is maintained or improved by simple processing. it can.

It is a schematic block diagram of Example 1 of the present invention. FIG. 3 is a schematic configuration block diagram of an encoding unit according to the first embodiment. 3 is an operation flowchart according to the first embodiment. It is an example of the encoding data structure of Example 1. FIG. It is an example of a link of the parameter set of Example 1. FIG. 6 is a schematic configuration block diagram of Embodiment 2. FIG. It is a structure and usage example of Example 2. FIG. 6 is an operation flowchart of the second embodiment. It is explanatory drawing of the pseudo contour which generate | occur | produces with a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus in which one embodiment of an image encoding apparatus according to the present invention is introduced. The imaging apparatus illustrated in FIG. 1 includes an imaging unit 101, a shooting mode setting unit 102, an operation unit 103, an intra smoothing process determination unit 104, and an encoding unit 105.

  The imaging unit 101 is an image sensor such as a CCD sensor, an optical system that inputs a subject optical image to the image sensor, and an image processing unit that digitizes an output image signal of the image sensor and outputs it as moving image data in a predetermined video format. Consists of.

  The shooting mode setting unit 102 has a function of setting, in the imaging unit 101, a combination of various camera parameters such as a white balance, a color tone, and a shutter speed, which are determined in advance, according to a user operation by the operation unit 103 and a shooting scene. . The operation unit 103 includes various keys such as a jog dial, a selection key, a determination key, and a mode setting key, and a touch panel.

  The present embodiment has, as one of the shooting modes, a mode suitable for fixed-point shooting of an object at a predetermined fixed interval, for example, a starry sky interval moving image mode, as an imaging device. Hereinafter, although described as the starry sky interval movie mode, the present invention is applied to a predetermined shooting mode in which the imaging device body is fixed and shot, such as night view shooting mode, starry sky mode, time-lapse shooting, time-lapse mode, and time-lapse shooting. Is possible.

  In response to a recording start instruction from the operation unit 103, the shooting mode setting unit 102 notifies the intra smoothing processing determination unit 104 of a shooting mode to be set in the imaging unit 101.

  The intra smoothing processing determination unit 104 determines from the shooting mode information notified from the shooting mode setting unit 102 whether or not the above-described predetermined shooting mode has a possibility that the image to be encoded contains a gradation image more than a predetermined value. . In the case of the predetermined shooting mode, the intra smoothing process determination unit 104 outputs an instruction signal (smoothing activation instruction signal) instructing to enable the intra smoothing process in the intra prediction mode to the encoding unit 105. For example, in the starry sky interval recording mode, since the starry sky is photographed, the input image of the encoding unit 105 includes many gradation images suitable for the intra smoothing process.

  The encoding unit 105 compresses and encodes the moving image data output from the imaging unit 101 by the HEVC method while referring to the notification signal from the intra-smoothing process determination unit 104, and the obtained code data is a predetermined bit stream. Output in format.

  FIG. 2 shows a schematic block diagram of the encoding unit 105. The encoding unit 105 stores the moving image data from the imaging unit 101 in the frame memory 201 in units of frames. In addition, the frame memory 201 stores reference image data used in motion prediction processing.

  The intra prediction unit 202 reads the image data of the encoding target block from the frame image data stored in the frame memory 201, and calculates correlations with a plurality of intra prediction images generated from the reference pixel data around the encoding target block. To do. The intra prediction unit 202 also receives the output signal of the intra smoothing process determination unit 104. When the smoothing activation instruction signal is input from the intra-smoothing process determination unit 104, the intra-prediction unit 202 validates the linear interpolation process for the reference pixel at the coding block boundary in the generation of the predicted image for intra prediction. The intra prediction unit 202 selects an intra prediction method having the highest correlation and notifies the intra / inter determination unit 204 of the intra prediction method.

  The inter prediction unit 203 performs pattern matching between pixel data in units of encoding blocks between the original image data of the encoding target block stored in the frame memory 201 and the encoded image data, and obtains a motion vector. calculate. The inter prediction unit 203 supplies the calculated motion vector to the intra / inter determination unit 204.

  The intra / inter determination unit 204 determines a prediction mode to be applied based on the output results of the intra prediction unit 202 and the inter prediction unit 203, and outputs the prediction mode to the predicted image generation unit 205. For example, the intra / inter determination unit 204 generates a prediction image for the encoding target image block according to the output of the intra prediction unit 202, and calculates a prediction error between the prediction image and the encoding target block image. The intra / inter determination unit 204 also generates a prediction image from the reference image according to the motion vector obtained by the inter prediction unit 203, and calculates a prediction error between the prediction image and the encoding target block image. Then, the intra / inter determination unit 204 compares both prediction errors, and sets the smaller prediction method as a prediction mode to be applied to encoding. In the case where the intra prediction unit 202 and / or the inter prediction unit 203 are executing up to the calculation of the prediction error, the intra / inter determination unit 204 calculates a prediction error that is insufficient, compares them, and applies a prediction mode to be applied. Can be determined.

  The predicted image generation unit 205 generates a predicted image according to the prediction mode determined by the intra / inter determination unit 204. The predicted image generation unit 205 also receives the output signal of the intra smoothing process determination unit 104. When the intra-smoothing process determination unit 104 outputs the smoothing validation instruction signal, the encoding target image is a gradation image as described above. In the case of a gradation image, the prediction image generation unit 205 should apply the three conditions that the intra prediction mode, the TU size is 32 × 32 pixels, and the directionality prediction mode value is neither 1, 10, nor 26. It is determined whether or not the encoding condition is satisfied. When these three conditions are satisfied, the predicted image generation unit 205 generates a predicted image from the reference pixels subjected to the linear interpolation process.

  The subtracter 214 subtracts the predicted image from the predicted image generation unit 205 from the image data to be encoded from the frame memory 201. The difference image data generated by the subtraction in the subtracter 214 is input to the integer conversion unit 206. The integer conversion unit 206 converts the difference image data from the subtracter 214 into a spatial frequency domain in units of encoded blocks. The integer conversion of the integer conversion unit 206 is an example of frequency conversion.

  The quantization unit 207 calculates a quantization coefficient based on the target code amount, and quantizes the spatial frequency domain coefficient data output from the integer transform unit 206. The quantized coefficient data is input to the entropy encoding unit 208 and the inverse quantization unit 210.

  The entropy encoding unit 208 entropy encodes the quantized coefficient data from the quantization unit 207. For example, in the case of inter prediction, the entropy encoding unit 208 compresses information on a vector value used in motion prediction using a bias in the appearance probability of bit data such as a CABAC (context adaptive arithmetic coding) method. The entropy encoding unit 208 supplies the encoded data after compression to the bit stream generation unit 213.

  The bit stream generation unit 213 adds header information including parameters necessary for decoding to the encoded data from the entropy encoding unit 208, and outputs the data in a predetermined streaming format. Parameters necessary for the decoding process include, for example, an SPS and a picture parameter set (hereinafter referred to as “PPS”). The bit stream generation unit 213 also associates the picture to which the intra smoothing process is applied in the encoded image so as to refer to a header having a strong_intra_smoothing_enabled_flag field value of 1 in the SPS. What are the details of the method of associating the SPS and PPS headers for the coded picture to which the intra-smoothing process is applied, and the relationship between the data structure of the bit stream? It will be described later. The output of the bit stream generation unit 213 is recorded on a recording medium (not shown) such as a memory card or a hard disk.

  The code amount control unit 209 obtains the code amount of the encoded data output from the entropy encoding unit 208, calculates the target code amount per picture based on the bit rate and the buffer model, and Feedback control of the quantization factor.

  The part related to the local decoding process will be described. The inverse quantization unit 210 performs inverse quantization by multiplying the quantized coefficient data from the quantization unit 207 by a quantization coefficient. Thereby, the coefficient data is reconstructed. The inverse integer transform unit 211 performs inverse integer transform of the coefficient data output from the inverse quantization unit 210 into pixel data. The adder 215 adds the predicted image data from the predicted image generation unit 205 to the output of the inverse integer conversion unit 211. Thereby, the image data is restored. The output image data of the adder 215 is supplied to the predicted image generation unit 205 and the loop filter 212 as reference image data.

  The loop filter 212 performs filter processing to reduce the coding distortion generated at the block boundary on the output image data of the adder 215 and stores the filter image in the frame memory 201.

  Some or all of the functions of the shooting mode setting unit 102, the intra smoothing process determination unit 104, and the encoding unit 105 can be realized by a computer program that runs on a computer.

  FIG. 3 shows a flowchart of the encoding process of the present embodiment. The process shown in FIG. 3 is executed by the shooting mode setting unit 102, the intra smoothing process determination unit 104, and the encoding unit 105. The processing shown in FIG. 3 can also be realized by a computer program that can be executed on a computer. The shooting mode setting unit 102 (or a CPU (not shown) that controls the whole) inputs a new frame image data from the imaging unit 101 to the encoding unit 105 or sets a preset operation state check. The process shown in FIG. 3 is executed.

  In step S <b> 301, the shooting mode setting unit 102 determines whether the recording start state is triggered by a user operation or the like on the operation unit 103. If it is not in the recording start state (FALSE in S301), the flow shown in FIG. If it is in the recording start state (TRUE in S301), the process proceeds to S302.

  In step S <b> 302, the intra smoothing processing determination unit 104 acquires shooting mode information indicating the shooting mode currently set in the imaging unit 101 from the shooting mode setting unit 102. In step S <b> 303, the intra smoothing processing determination unit 104 determines whether the shooting mode of the imaging unit 101 is the starry sky interval mode based on the shooting mode information from the shooting mode setting unit 102. When the set shooting mode is the starry sky interval mode (TRUE in S303), the intra smoothing process determining unit 104 outputs an intra smoothing process enabling signal (ON or HIGH) to the encoding unit 105, and the process proceeds to S304. To do. When it is not the starlit sky interval mode (FALSE in S303), the intra smoothing process determination unit 104 turns off or lowers the intra smoothing process enable signal to the encoding unit 105, and proceeds to S306.

  In S304, the encoding unit 105 encodes the input frame image data by enabling the intra-smoothing process according to the output of the intra-smoothing process determining unit 104 (intra-smoothing process enable signal = high). In step S <b> 305, the bit stream generation unit 213 generates a bit stream that associates an SPS with a strong_intra_smoothing_enabled_flag set to 1 and a slice header for the encoded picture data.

  In step S <b> 306, the encoding unit 105 compresses and encodes the frame image data with the intra smoothing process disabled according to the output of the intra smoothing process determination unit 104 (intra smoothing process enable signal = low). In step S307, the bit stream generation unit 213 generates a bit stream for the encoded picture data by associating the SPS with strong_intra_smoothing_enabled_flag set to 0 and the slice header.

  The structure of the bit stream data output from the bit stream generation unit 213 will be described. FIG. 4A shows an example of a bit stream structure when the intra smoothing process is enabled in steps S305 and S307, and FIG. 4B shows a reference relationship of parameter sets.

  As shown in FIG. 4A, the HEVC encoded bitstream uses the H.264 standard. As in the H.264 system, a data structure in which a plurality of access units (hereinafter referred to as “AU”) are consecutive in decoding order is employed. Each AU consists of encoded data that can be decoded on a screen-by-screen basis. The AU includes an access unit delimiter (AUD) indicating a start position, a video parameter set (VPS) having various parameters necessary for decoding, and a plurality of NAL units called SPS or PPS. Data encoded in actual macroblock units is stored as slice data for each picture following the header parameter.

  Both the header information called SPS and the header information called PPS can be changed during the stream according to the standard. For example, parameters such as a quantization matrix and deblocking filter strength can be reloaded in AU units according to the pattern. In order to realize this function, at the stream output timing, the encoded slice data and the header information necessary for decoding the encoded slice data are associated by the identifier (ID) included in each header information. .

  FIG. 4B shows a reference relationship between VPS, SPS, PPS, and slice data. The VPS has vps_video_parameter_set_id for identifying the VPS. The SPS has sps_video_parameter_set_id with the ID of the VPS referred to by the SPS, and sps_seq_parameter_set_id for identifying the SPS. Similarly, the PPS has pps_seq_parameter_set_id with the ID of the SPS referred to by the PPS, and pps_pic_parameter_set_id for identifying the PPS. The slice header contains a PPS ID referenced by the slice and slice_pic_parameter_set_id. Based on the links of the identification information, as shown in the reference relationship indicated by arrows in FIG. 4B, the header information having the same ID is associated from the slice data to PPS, from PPS to SPS, and from SPS to VPS. Thereby, a different header can be referred for each AU.

  In the example shown in FIG. 4B, the shooting mode of the input image corresponding to slice 0 and slice 1 is other than the starry sky interval mode, and the portion corresponding to slice 2 is an image of the starry sky interval mode. As a result, these slices 0 and 1 are configured to refer to SPS0 having a strong_intra_smoothing_enabled_flag value of 0. For slice 2, SPS2 having strong_intra_smoothing_enabled_flag value of 1 is referred to. Thereby, at the time of decoding of slice 2, it is possible to generate a predicted image using smoothing processing and obtain a reproduced image without block boundary distortion.

  The setting of whether to enable or disable the intra smoothing process performed in steps S305 and S307 may be performed after preparing SPS having a corresponding flag value after the encoded slice data is generated.

  As described above, in the first embodiment, the validity / invalidity of the intra smoothing process can be switched in units of slices. Since the validity / invalidity of the intra-smoothing process is uniquely determined by the shooting mode at the start of recording, the validity / invalidity of the intra-smoothing process can be determined quickly and easily.

  A description will be given of a second embodiment in which shooting state acquisition means for detecting whether or not fixed-point shooting is in a fixed installation is provided, and in the case of fixed installation, the intra smoothing process is validated.

  FIG. 5 is a block diagram illustrating a schematic configuration of an imaging apparatus that employs the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals. An acceleration sensor 511, a GPS sensor 512, a tripod contact detection unit 513, and a shooting state acquisition unit 514 are added to the first embodiment, and it is determined by these elements whether the imaging apparatus main body is fixedly installed. The intra smoothing process determination unit 504 controls validity / invalidity of the intra smoothing process of the encoding unit 105 according to the output of the shooting state acquisition unit 514 in addition to the shooting mode information from the shooting mode setting unit 102.

  The acceleration sensor 511 is a small accelerometer created using MEMS (Micro Electro Mechanical Systems) technology, and has a function of measuring the gravitational acceleration of the earth and detecting the tilt of the imaging device. The acceleration sensor 511 outputs the acquired acceleration information to the shooting state acquisition unit 514.

  The GPS sensor 512 has a function of receiving radio waves from a GPS (Global Positioning System) satellite and accurately determining where the imaging device is on the earth. The GPS sensor 512 outputs the acquired three-dimensional position coordinate information (latitude, longitude, altitude) to the imaging state acquisition unit 514.

  The tripod contact detection unit 513 serves as a tripod attachment / detachment detection means for attaching a tripod or a monopod to a tripod mounting screw hole (see FIG. 6A) provided on the bottom surface of the imaging apparatus (FIGS. 6B and 6C). (See Fig. 4). When the tripod contact detection unit 513 detects the tripod attachment, the tripod contact detection unit 513 outputs a detection signal to the imaging state acquisition unit 514. FIG. 7A shows a bottom view of the imaging apparatus shown in FIG. FIG.7 (b) shows the front view of the state which attached the tripod, FIG.7 (c) shows the front view of the state which attached the monopod.

  The imaging state acquisition unit 514 determines whether or not the imaging device is in a fixed installation state according to the outputs of the acceleration sensor 511, the GPS sensor 512, and the tripod contact detection unit 513, and the determination result is sent to the intra smoothing processing determination unit 504. Supply. For example, when no acceleration is generated in any spatial axis direction as the output value of the acceleration sensor 511, the imaging state acquisition unit 514 determines that it is in a fixed installation state. If there is no difference in the position information acquired by the output value of the GPS sensor 512 a plurality of times at a predetermined time interval, the shooting state acquisition unit 514 determines that the fixed installation state is set. Further, when the output value of the tripod contact detection unit 513 indicates that a tripod (or a monopod) is attached, the photographing state acquisition unit 514 determines that the fixed installation state is present.

  Note that the acceleration sensor 511, the GPS sensor 512, and the tripod contact detection unit 513 are examples of means necessary for determining the fixed installation state in order to determine whether or not the fixed installation state is set. Any one or more may be provided. In addition, the user may notify the intra-moothing process determination unit 504 of the fixed installation state via the shooting mode setting unit 102 by a menu operation.

  FIG. 7 shows an operation flowchart of the second embodiment shown in FIG. With reference to FIG. 7, the intra smoothing process determination process using the installation state determination in the second embodiment will be described.

  Since the processes of steps S701, S702, and S703 are the same as the processes of steps S301, S302, and S303, respectively, description thereof is omitted. When it is the starry sky interval mode (TRUE in S703), the process proceeds to S704. If it is not the starry sky interval mode (FALSE in S703), the intra smoothing process determination unit 504 turns off or lowers the intra smoothing process enable signal to the encoding unit 105, and proceeds to S708.

  In step S <b> 704, the intra smoothing processing determination unit 504 acquires the installation state and installation posture information of the imaging apparatus from the imaging state acquisition unit 514. In step S <b> 705, the intra smoothing process determination unit 504 determines whether or not it is in a fixed installation state suitable for a fixed shooting state, that is, a situation in which image data including a gradation image suitable for the intra smoothing process is recorded for a long time. When in the fixed installation state (TRUE in S705), the intra smoothing process determining unit 104 outputs the intra smoothing process enabling signal (ON or high) to the encoding unit 105, and the process proceeds to S706. If it is not in the fixed installation state (FALSE in S705), the intra smoothing processing determination unit 504 turns off or lowers the intra smoothing processing enabling signal to the encoding unit 105, and proceeds to S708.

  Since the processes in steps S706, S707, S708, and S709 are the same as the processes in S304, S305, S306, and S307, respectively, detailed description thereof is omitted.

  When the imaging apparatus is not in the fixed setting state, it is considered that the possibility that the gradation image is continuously input to the encoding unit is low. Therefore, in this embodiment, the processing load for gradation image determination is reduced by uniformly disabling the intra smoothing process in the fixed setting state regardless of the shooting mode.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (9)

An image encoding device that encodes an imaging unit that images a subject according to a set shooting mode,
Encoding means for encoding an output image of the imaging means in units of encoding blocks, and encoding means having a mode for linearly interpolating reference pixels at the encoding block boundary in the intra prediction mode;
The encoding unit is an intra-smoothing process determining unit that determines application of linear interpolation processing of a reference image in the intra prediction mode to an encoding target block image, and a shooting mode set in the imaging unit is An image encoding apparatus comprising: an intra-smoothing process determining unit that instructs the encoding unit to validate the linear interpolation in a predetermined shooting mode that may include a gradation image more than a predetermined level. .   The image encoding apparatus according to claim 1, wherein the predetermined shooting mode is any one of a night scene shooting mode, a starry sky mode, a starry sky interval mode, and a time lapse mode. Furthermore, it has an imaging state acquisition means for acquiring an installation state of the imaging means,
The intra smoothing determination unit is a predetermined shooting mode in which a shooting mode set in the imaging unit may include a gradation image more than a predetermined value, and the installation state acquired by the shooting state acquisition unit is fixed installation 3. The image encoding apparatus according to claim 1, wherein when the status is indicated, the encoding unit is instructed to enable the linear interpolation. 4.   The image coding apparatus according to claim 3, wherein the photographing state acquisition unit includes one or more of an acceleration sensor, a GPS sensor, and a tripod attachment / detachment detection unit for the imaging unit.   The imaging state acquisition unit notifies the intra-moothing process determination unit of the fixed installation state when the output of the acceleration sensor indicates that no acceleration is generated in any spatial axis direction. The image encoding device according to claim 4.   The imaging state acquisition unit notifies the intra smoothing process determination unit of the fixed installation state when the output of the GPS sensor indicates that there is no difference in position information acquired a plurality of times at predetermined time intervals. The image encoding device according to claim 4, wherein   5. The imaging state acquisition unit notifies the intra-moothing process determination unit of the fixed installation state when the output of the tripod attachment / detachment detection unit indicates mounting of a tripod or a monopod. Image coding apparatus. An image encoding method for encoding an output image of an imaging unit that images a subject according to a set shooting mode,
Intra-smoothing that enables linear interpolation of reference pixels at the coding block boundary in the intra prediction mode when the shooting mode set in the imaging means is a predetermined shooting mode that may include a gradation image more than a predetermined value. A processing decision step;
A coding step for coding the output image of the imaging unit in coding block units, wherein the interpolation is performed by linearly interpolating reference pixels at the boundary of the coding block in the intra prediction mode according to the validation of the linear interpolation; And a coding step. A computer program for encoding imaging means for imaging a subject according to a set shooting mode, the computer comprising:
Encoding means for encoding an output image of the imaging means in units of encoding blocks, and encoding means having a mode for linearly interpolating reference pixels at the encoding block boundary in the intra prediction mode;
The encoding unit is an intra-smoothing process determining unit that determines application of linear interpolation processing of a reference image in the intra prediction mode to an encoding target block image, and a shooting mode set in the imaging unit is A computer program for functioning as an intra-smoothing process determining unit that instructs the encoding unit to validate the linear interpolation in a predetermined shooting mode that may include more than a predetermined gradation image.

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