JP2002016910A - Device and method for encoding image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, when a bit rate is narrowed down, a quantizing step becomes rough and block distortion increases, resulting in a visual feeling of physical disorder. SOLUTION: An image encoding device is provided with an area dividing section 3 which divides the image of original image data S1 into a plurality of areas, a pre-filter 1 which pre-processes the data S1, an encoding section 10 which encodes the data S1 pre-processed by means of the pre-filter 1, and a filter control section 4 which controls the characteristics of the pre-filter 1 at every area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding apparatus and an image encoding method for encoding original image data with high efficiency.

2. Description of the Related Art Conventionally, techniques in such a field include:
MPEG-2 Tes specified in ISO / IEC JTC1 / SC29 / WG11 / N0400
An image coding device shown in t Model 5 is known.

FIG. 7 is a block diagram showing a configuration of an image encoding device 50. In the figure, reference numeral 51 denotes a subtractor that calculates a difference between original image data and image data that has been encoded and decoded in the past, and 52 denotes a DCT (orthogonal transform) that converts the difference data calculated by the subtractor 51 into frequency domain information. vessel),
53, a quantization unit for quantizing the data orthogonally transformed by the DCT 52; 54, a VLC (variable length encoder) for removing the redundancy of the quantized data; 55, a variable length code generated by the VLC 54 at a certain rate; A buffer for smoothing the data and sending it out to the transmission path, 56 is an inverse quantizer for inversely quantizing the data quantized by the quantizer 53, and 57 is an inverse transform for the data inversely quantized by the inverse quantizer 56. The inverse DCT 58 is an adder for adding the data inversely transformed by the inverse DCT 57 and the decoded data n frames before (hereinafter, the adder 58).
Is referred to as local decoded data).

Further, reference numeral 59 denotes a frame memory in a loop for storing the local decoded data added by the adder 58, and reference numeral 60 designates a change in an image as motion vector information based on the original image data and the local decoded data. Motion compensator for controlling reading of frame memory 59 by
Reference numeral 1 denotes a quantization control unit which controls a quantization step and determines a bit rate and an encoded image quality. Reference numeral 62 denotes an activity (8 × 8 pixels of a luminance signal in a frame or a field; It is an activity calculation unit that calculates the value obtained by subtracting the average value of the 64 values from the value (integrated value).

In the case of Main-Profile, which is a general encoding method in the MPEG-2 standard, image signals are rearranged from a display order to an encoding order before encoding (omitted in the drawing), and an I picture ( Encoding is performed according to the picture types of the intra-frame prediction), the P-picture (forward prediction), and the B-picture (pre / post / complementary prediction). These operations are described in a large number of documents, including the Journal of the Institute of Television Engineers of Japan, Vol. 49, No. 4, pp. 435-466 (1995). As a method for controlling the rate, (1) the amount of target information generated in the screen, (2) the feedback control based on the buffer storage amount, and (3) the quantization step is controlled by the activity of the original image data.

FIG. 8 is a block diagram showing a configuration of a conventional image encoding device 70 disclosed in Japanese Patent Application Laid-Open No. 07-107462. In the figure, reference numeral 71 denotes H. described above. Encoding unit represented by 26X or MPEG, 7
Reference numeral 2 denotes a filter unit; 73, an adaptive control circuit for controlling the transfer characteristics of the filter; and 74, a pre-filter control unit for generating a control signal correlated with the amount of information generated in the encoding unit 71. In the image encoding device 70, a filter transfer coefficient calculated from local data of an image detected by the adaptive control circuit 73 is controlled based on the information amount generated by the encoding unit 71.

[0006] Another conventional technique is disclosed in Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 107462, JP-A-6-6784, JP-A-4-306094, JP-A-3-256484, and JP-A-63-304679 are known.

By the way, MPEG-
The motion-compensated inter-frame coding method represented by SD2 is SD
This is a system conceived mainly for digital broadcasting, transmission, and storage media from TV to HDTV. In particular, in BS / terrestrial digital broadcasting, HDTV is mainly used and a considerably low bit rate (20 Mbps or less) is assumed (for example, The Institute of Image Information and Television Engineers Vol.53, No11, pp1456-1459 (1
999)). The conventional MPEG-2 and the above-described conventional image encoding device 50 are basic control models, and the image quality cannot be said to be sufficient by themselves. Therefore, various quantization control methods have been devised in addition to the above. At present, when an HDTV signal is compression-coded based on the MPEG-2 standard, a bit rate that satisfies broadcast quality is set to 22 Mbps or more according to an evaluation method defined by ITU-R (see the above-mentioned document, Video Information Media). Journal Vol.5
3, No11, pp 1456-1459 (1999)).

Further, according to this document, it is understood that in order to realize SFN (Single Frequency Network) in digital terrestrial broadcasting, it is necessary to further reduce the bit rate (increase the video compression ratio). It is a well-known fact that if the bit rate is reduced under the conventional control, the quantization step is inevitably coarsened, block distortion is increased, and a sense of visual discomfort occurs.

Further, the above-described conventional image encoding apparatus 70
Uses only the peripheral analysis data of the pixel to be filtered,
Since the processing of the filter unit 72 is performed, the compression efficiency does not always increase. In particular, when the compression ratio is greatly increased, the band is limited even for visually important parts, and visual impairment is caused. There was a problem that there was a possibility that it might be.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and uses an image coding apparatus and an image coding apparatus capable of obtaining a coded image having a high compression ratio and excellent visual quality by utilizing the visual characteristics of human beings more than before. It is an object to provide an encoding method.

[0010]

According to the present invention, there is provided an image coding apparatus comprising: an area dividing section for dividing a screen of original image data into a plurality of areas; a prefilter for preprocessing the original image data; It is characterized by comprising an encoding unit that encodes the processed original image data, and a filter control unit that controls the characteristics of the pre-filter for each area.

Here, the area dividing section preferably divides the screen of the original image data into a central area and a peripheral area.

It is preferable that the image processing apparatus further includes an image analysis unit that analyzes the type of the subject from the original image data, and the filter control unit controls the characteristics of the pre-filter based on the subject information analyzed by the image analysis unit.

Further, the image analysis unit detects the fineness level of the image based on a variance value and / or an average value of at least one of the luminance signal and the color difference signal for each small block, and detects an object based on the fineness level. Is preferably specified.

It is preferable that the image processing apparatus further includes an image analyzing section for analyzing the type of the subject from the original image data, and the area dividing section shifts the central area based on the subject information analyzed by the image analyzing section.

An image encoding apparatus according to the present invention comprises: an area dividing section for dividing a screen of original image data into a plurality of areas; an encoding parameter calculating section for calculating an encoding parameter for each area; An encoding unit for encoding original image data by switching parameters.

Here, it is preferable that the area dividing section divides the screen of the original image data into a central area and a peripheral area.

Preferably, the image processing apparatus further comprises an image analysis section for analyzing the type of the subject from the original image data, and the coding parameter calculation section calculates the coding parameter based on the subject information analyzed by the image analysis section.

Further, the image analysis unit detects the fineness level of the image based on the variance value and / or the average value of at least one of the luminance signal and the color difference signal for each small block, and detects the object based on the fineness level. Is preferably specified.

It is preferable that the image analysis unit detects a subject within a predetermined level range with respect to the primary color based on the average value of the color difference signal for each small block, and specifies the type of the subject from the detected value.

Further, it is preferable that the image processing apparatus further comprises an image analyzing section for analyzing the type of the subject from the original image data, and the area dividing section shifts the central area based on the subject information analyzed by the image analyzing section.

Preferably, the area dividing section divides the screen of the original image data into a plurality of areas based on the quantization step information of the encoding section.

According to the image encoding method of the present invention, in the method of encoding the original image data after preprocessing the original image data by a pre-filter, the screen of the original image data is divided into a plurality of regions, and each region is divided into a plurality of regions. By switching the filter characteristics,
It is characterized in that the original image data is pre-processed.

According to the image encoding method of the present invention, in a method of encoding original image data, a screen of the original image data is divided into a plurality of regions, and encoding parameters are switched for each region to encode the original image data. It is characterized in that

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image encoding apparatus and an image encoding method according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a configuration of an image encoding device according to the present embodiment. In FIG. 1, reference numeral 1 denotes a pre-filter for performing pre-processing such as band limitation and noise removal on the original image data S1, reference numeral 2 denotes an image analysis unit for analyzing the original image data S1 to identify the type of a subject, and reference numeral 3 denotes an image. An area information generation section (area division section) that divides a screen (frame) of the original image data S1 into a plurality of areas using the feature information S2 output from the analysis section 2.

Reference numeral 4 denotes a filter controller for switching the transfer function and type of the prefilter 1 based on the area information S3 output from the area information generator 3, and 5 denotes area information S4 output from the area information generator 3. A weight parameter calculating unit (coding parameter calculating unit) for calculating a parameter for determining a quantization step based on the encoding unit 10 for coding the original image data S1 preprocessed by the pre-filter 1; Is a quantization step storage unit for storing quantization steps used in the encoding unit 10.

When the original image data S1 is input to the encoding unit 10, the encoding unit 10 scans from a scan in the screen order (hereinafter referred to as raster scan) to a scan in a block obtained by dividing the screen into a plurality of small blocks. (Hereinafter referred to as “block scan”), the original image data S1 is encoded. Although the scan conversion block is omitted, when the pre-filter 1 is applied, depending on the type of the filter, there are a type that is performed by raster scan and a type that is performed by block scan. Shall not be mentioned.

Further, a subtractor 11 calculates a difference between the original image data S1 and the previously encoded and decoded image data.
Reference numeral 12 denotes a DCT (orthogonal transformer) for converting the difference data calculated by the subtractor 11 into frequency domain information, and reference numeral 13 denotes a DCT.
A quantization unit for quantizing the data orthogonally transformed in 12;
Reference numeral 4 denotes a VLC (Variable Length Encoder) for removing the redundancy of the quantized data, 15 a buffer for smoothing the variable length code generated by the VLC 14 at a certain rate and sending it out to a transmission path, and 16 a quantization unit 13 Is an inverse quantization unit that inversely quantizes the data quantized by.

Reference numeral 17 denotes an inverse DCT for inversely transforming the data inversely quantized by the inverse quantization unit 16, and reference numeral 18 denotes an inverse DCT 17
The adder 1 adds the data inversely transformed by the above and the decoded data n frames before to output local decoded data S5.
Reference numeral 9 denotes a frame memory in a loop for storing the local decoded data S5 added by the adder 18, and reference numeral 20 denotes original image data S1.
A change in an image is used as motion vector information based on the local decoded data S5 and the motion compensation unit that controls reading of the in-loop frame memory 19 based on the motion vector.
Reference numeral 1 denotes a quantization control unit that controls a quantization step and determines a bit rate and an encoded image quality.

Next, the operation will be described. First, an overall schematic operation will be described with reference to FIG. The original image data S1 includes a luminance signal and a color difference signal (Pb, Pr or C
b, Cr). The original image data S1 is input to the pre-filter 1, and filtering suitable for encoding is performed. Prefilter 1
The filter control unit 4 controls the transfer function of the filter and the type of the filter.

Original image data S that has passed through the prefilter 1
1 is input to the encoding unit 10 and an encoding process is performed.
The encoding unit 10 first converts the original image data S1 into a subtractor 11
The difference between the original image data S1 and the image data stored in the in-loop frame memory 19 is obtained. This difference data is input to the DCT 12 and is converted into frequency domain information. Further, the data converted into the information in the frequency domain is input to the quantization unit 13, and a quantization process is performed under the control of the quantization control unit 21. The quantized data has its redundancy removed by the VLC 14, smoothed at a predetermined bit rate by the buffer 15, and sent to the transmission path.

The data quantized by the quantization unit 13 is also input to the inverse quantization unit 16 and is inversely quantized. The inversely quantized data is inversely transformed by the inverse DCT 17 and added by the adder 18 to the encoded data of n frames before. Adder 18
Are output to the in-loop frame memory 19 and the motion compensation unit 20, respectively. The motion compensator 20 controls the reading of the in-loop frame memory 19 based on the local decoded data S5 input from the adder 18 and the original image data S1 passed through the prefilter 1.

The original image data S1 is also input to the image analysis unit 2, and extracts an approximate image by comparing it with a database (not shown) of the subject based on the visual characteristics. The feature information S2 obtained by this extraction and the quantization step distribution information S9 output from the quantization step storage unit 6 are given to the area information generator 3, and the area information generator 3 uses the information S2 and S9. Then, the area information S4 is generated.
The area information S4 generated by the area information generator 3 is sent to the weight parameter calculator 5. Weight parameter calculator 5
Then, in addition to the area information S4 from the area information generating unit 3,
Based on the difference data S7 from the encoding unit 10, the quantization control unit 21 generates a weight parameter for determining a quantization step.

In the quantization unit 10, the difference data S7, which is the result of the subtraction by the subtractor 11, is used as the weight parameter calculation unit 5.
However, the output data from the DCT 12 may be provided, or the output data from the motion compensation unit 20 may be provided.

In the area information generating section 3, the original image data S1
The screen is divided into a plurality of areas by inputting a synchronizing signal S8 such as a frame pulse or a line pulse synchronized with. FIG. 2 shows an example of area division. As shown in the figure, the area information generating unit 3 sequentially superposes a plurality of concentric circles (ellipses) having different radii from the center to the area A, the area B, and the area C.
The screen is divided into three areas. Note that a rectangle or a square may be used instead of a circle.

The reason for such division is as follows. That is, in general, when shooting a subject with a camera,
The main subject is predominantly centered on the screen, but this is because the viewer's gaze tends to concentrate on the center of the screen. Therefore, the coding efficiency is increased by changing the characteristics of the pre-filter 1 and / or the weight parameter (coding parameter) of the quantization control unit 21 between the central region where the line of sight is concentrated and the peripheral region where the line of sight is not so concentrated. Can be improved.

When changing the characteristics of the pre-filter 1, the characteristics of the pre-filter 1 are weakest in the area A located at the center of the screen (reference value fc). In a region B slightly distant from the center of the screen, the characteristics of the pre-filter 1 are set to be about 1.2 times fc (1.2 × fc). In the region C farthest from the center of the screen, the characteristics of the pre-filter 1 are set to be about 1.5 times fc (1.5 × fc).

On the other hand, when changing the weight parameter of the quantization control unit 21, the weight parameter is set to be weakest in the area A located at the center of the screen (reference value Qc). In the area B slightly away from the center of the screen, the strength of the weight parameter is Q
It is set to about 1.2 times c (1.2 × Qc). In the region C farthest from the center of the screen, the strength of the weight parameter is set to about 1.5 times Qc (1.5 × Qc).

The area information generating section 3 divides the screen into a plurality of elliptical shapes having different sizes as shown in FIG. 2, and a weight parameter calculating section for reflecting the area information S4 indicating the area in the quantization control. Notify 5 The area information S4 is 3
Bits (eight types) are assumed, but the number of bits is not limited. In FIG. 2, the screen of the original image data S1 is divided into areas A, B, and C, and A: 000 (binary),
The area information S4 is allocated such as B: 001, C: 010.

On the other hand, in the image analysis section 2, the original image data S
From 1, an object which is visually conspicuous locally is specified. Specifically, the variance (σγ) and the average (Pmean) of the luminance signal (Pb) and the chrominance signal (Pr) of the m × n small block are obtained, and the variance obtained in advance from various images is obtained. Is compared with the average value, and the type of the partial subject is specified. The variance value (σγ) and the average value (Pmean) are calculated by the following formulas.

[0040]

(Equation 1)

Here, as shown in FIG.
For example, in the case of a lawn or a fine grass, for example, since the luminance variance value is relatively high and the image is determined to be a green image from the color difference average value, various images in which the variance value and the average value are calculated in advance are used. The most similar image is extracted from.
By this extraction, it is found that the small block 25 is a subject that is strict in encoding. The subject information S11 obtained by the image analysis unit 2 is given to the weight parameter calculation unit 5, and the weight parameter calculation unit 5 outputs the subject information S11.
The encoding parameter is calculated based on

Since the quantization control unit 21 controls the quantization step given to the quantization unit 13 using this encoding parameter, a small block 25 having an image of a lawn or a fine plant is small. It is quantized in a quantization step. As a result, even when an image such as lawn or fine vegetation is present in a part of the screen, the part can be quantized with the optimal quantization step, so that a code of visually superior quality with less flickering can be obtained. To obtain an image.

The subject information S6 obtained by the image analysis unit 2 is also supplied to the filter control unit 4, and the filter control unit 4 switches the transfer function of the pre-filter 1 or the type of filter based on the subject information S6. . As a result, the small block 25 having the image of the lawn or the fine grass is filtered with the optimal filter characteristics, and thus a coded image with little flicker and excellent visual quality can be obtained.

Further, based on the average value of each of the luminance signal (Pb) and the color difference signal (Pr) obtained by the image analysis unit 2, a subject (for example, a subject that is within a predetermined level range with respect to the primary colors and is easily visible). Red, etc.) and may be used as the subject identification information. In this case, the image analysis unit 2 compares the average / variance value data of the subject, which is held in advance, with the same data calculated from the original image data S1, and determines the result having the smallest difference value as the subject information S11 as the weight parameter calculation unit 5. Notify. The weight parameter calculation unit 5 calculates an encoding parameter based on the subject information S11, and the quantization control unit 21 controls a quantization step given to the quantization unit 13 using the encoding parameter. As a result, a subject having a color close to the primary color in which the viewer's line of sight tends to concentrate is quantized in a small quantization step, so that a coded image with visually excellent quality can be obtained.

Next, the filter control section 4 and the prefilter 1 will be described. In FIG. 4, reference numerals 30 to 32 denote transfer function units for each filter; 33, a filter selection determination table for selecting a filter characteristic from the area information S3 and the subject information S6; 34, a spatial band limiting filter unit for limiting a spatial frequency band; Is a time integration filter unit, and 36 is a noise reduction filter unit for performing median filtering and removal of isolated points.

The region information S3 and the subject information S6 are input to the filter selection decision table 33. The filter selection decision table 33 uses the filter units 34, 35, and 36 based on the region information S3 and the subject information S6.
Are controlled corresponding to the transfer function units 30, 31, 32, respectively. Each of the transfer function units 30, 31, and 32 includes a selector for selecting a desired transfer function from a plurality of transfer functions (parameters for determining the strength of the filter). Function part 30, 31, 3
2 to adjust the filter characteristics based on the transfer function given by Note that the transfer function includes filter-through.

Here, since the viewer's line of sight is most concentrated at the center of the screen, as shown in FIG. 2, for the area A located at the center of the screen, each filter unit 34,
The control for 35 and 36 is weakened, and the control is increased as it goes to region B and region C. For example, for the spatial band limiting filter unit 34, the band limitation is made through or weak in the region A, and the band limitation is increased in the order of the region B and the region C. The same control may be applied to the noise reduction filter unit 36. However, if ideal noise reduction can be realized, each area may be uniformly controlled.

On the other hand, for the subject information S6 specified by the image analysis unit 2, the filter selection determination table 33 adaptively controls according to the information generation amount of the information generation amount information S12 provided from the buffer 15. Basically, if the amount of information per picture is lower than the average rate, the filter is loosened, and if the amount of information is higher than the average rate, the filter is strengthened. The above-mentioned area information S3
May be combined with to control each of the filter units 34, 35, 36.

The pre-filter 1 has three types of filters: a spatial filter unit 34, a time integration filter unit 35, and a noise reduction filter unit 36.
Each has a transfer function (a parameter for determining the strength of the filter), and the transfer function is individually controlled by the filter selection determination table 33. It is assumed that the transfer function includes filter-through. As described above, the filter control unit 4 performs control so as to adaptively change the filter characteristics between a visually conspicuous portion and a non-visually visible portion, so that filtering such as band limitation can be effectively performed. Encoding efficiency can be increased.

Next, the operation of the weight parameter calculator 5 will be described. The area parameter S4 from the area information generator 3, the subject information S11 analyzed by the image analyzer 2, and the difference data S7 from the subtractor 11 are input to the weight parameter calculator 5. In the quantization control unit 21, the buffer 1
5 based on the information generation amount information S12 and the activity (not shown in FIG. 1) obtained from the encoded image.
Controls the quantization step. The larger the quantization step, the smaller the amount of code (the amount of information) that occurs, but, on the other hand, the greater the degradation (block distortion) of the image at the time of decoding, which is a visually significant obstacle.

In the conventional activity control, the quantization step is switched by knowing the local fineness level of the screen by the quantization control unit 21 so as to make the deterioration less noticeable. Is high, the quantization step is controlled uniformly, resulting in a large deterioration. In the present embodiment,
Since the visual screen area information and the type of the subject can be specified, the information is converted into a coefficient for the quantization step, the weight parameter calculation unit 5 calculates the weight coefficient S13, and the quantization control unit 21 Have given. As a result, the quantization step is controlled for each area based on the visual screen area information and the type of the subject, so that an encoded image with visually excellent quality can be obtained.

The weight parameter calculating section 5 is also effective in that, in addition to the area information S4 and the subject information S11, difference data S7 to be actually encoded is added as a reference parameter. By multiplying the original quantization step by the weight coefficient S13, the quantization control can be effectively performed in terms of visual and coding efficiency.

Note that the weight parameter calculation unit 5 controls the quantization step of the encoding unit 10 by using the visual area information S4 and the subject information S11 specified by the image analysis. Even if the information is applied not only to the quantization step but also to the multiplication of the high-frequency component of the coefficient of the DCT 12, or to the transfer function of an in-loop filter, an encoded image with visually excellent quality can be obtained.

Next, processing for adaptively shifting each area divided by the area information generating section 3 will be described. The region information generation unit 3 includes the feature information S detected by the image analysis unit 2.
2, and the quantization step distribution information S9 totalized by the quantization step storage unit 6 are input. Feature information S2
Is data indicating a partial fineness level (for example, a variance value or an activity) of the subject as a distribution on the screen.
On the other hand, as shown in FIG.
Is the quantization step S output from the quantization controller 21.
10 (macroblock unit), quantization step storage unit 6
Is the data obtained by accumulating the data in one frame unit and obtaining the distribution in the screen.

Although the area information generating section 3 basically makes the center of the screen the most visually important area as described above, the visual characteristics are not always gathered at the center for all the images. For example, in an image as shown in FIG.
Eyes are always concentrated in the lower half of the screen. Therefore, the divided information is shifted in the horizontal or vertical direction by referring to the feature information S2 analyzed from the original image and the quantization step distribution information S9 determined at the time of actual encoding by the area information generating unit 3. In addition, the center of the area can be corrected to a position where the visual characteristics gather. As a result, it is possible to obtain an encoded image having visually excellent quality.

[0056]

Since the image encoding apparatus and the image encoding method according to the present invention are configured as described above, the following effects can be obtained. That is, since the screen of the original image data is divided into a plurality of regions and the filter characteristics or the quantization steps are switched for each region, the deterioration is hardly noticeable visually, and the information amount can be effectively reduced. Therefore, high-quality images can be transmitted at a low rate.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image encoding device according to the present embodiment.

FIG. 2 is a diagram illustrating an example of area division by an area information generation unit.

FIG. 3 is a diagram showing original image data having a lawn or fine vegetation.

FIG. 4 is a block diagram illustrating a configuration of a filter control unit and a prefilter.

FIG. 5 is a diagram showing quantization step distribution information stored in a quantization step storage unit.

FIG. 6 is a diagram illustrating an example in which the area division by the area information generating unit is shifted.

FIG. 7 is a block diagram illustrating a configuration of a conventional image encoding device.

FIG. 8 is a block diagram illustrating a configuration of a conventional image encoding device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Prefilter, 2 ... Image analysis part, 3 ... Region information generation part (region division part), 4 ... Filter control part, 5 ... Weight parameter calculation part (encoding parameter calculation part), 6 ... Quantization step accumulation part , 11: subtractor, 12: DCT (orthogonal transformer), 13: quantizer, 14: VLC (variable length encoder), 15: buffer, 16: inverse quantizer, 17: inverse D
CT, 18 adder, 19 frame memory in loop,
20: motion compensation unit; 21: quantization control unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 KK03 MA23 ME01 NN01 PP14 PP21 SS02 TA01 TA46 TB07 TB08 TC10 TC18 TC43 TD04 UA02 UA11

Claims (13)

[Claims] 1. An area dividing unit that divides a screen of original image data into a plurality of areas; a prefilter that preprocesses the original image data; and a code that encodes the original image data preprocessed by the prefilter. An image coding apparatus, comprising: a coding unit; and a filter control unit configured to control characteristics of the pre-filter for each of the regions. 2. The image encoding apparatus according to claim 1, wherein the area dividing unit divides the screen of the original image data into a central area and a peripheral area. 3. The image processing apparatus according to claim 1, further comprising an image analysis unit configured to analyze a type of a subject from the original image data, wherein the filter control unit controls characteristics of the pre-filter based on subject information analyzed by the image analysis unit. The image encoding device according to claim 1 or 2, wherein: 4. The image analysis unit detects a fineness level of an image based on a variance value and / or an average value of at least one of a luminance signal and a color difference signal for each small block, and detects the fineness level of the image from the fineness level. 4. The image encoding apparatus according to claim 3, wherein the type of the subject is specified. 5. An image analysis unit for analyzing a type of a subject from the original image data, wherein the region dividing unit shifts the region of the central part based on subject information analyzed by the image analysis unit. 3. The image encoding apparatus according to claim 2, wherein: 6. An area dividing section for dividing a screen of original image data into a plurality of areas; an encoding parameter calculating section for calculating an encoding parameter for each area; and switching the encoding parameter for each area. An image encoding apparatus, comprising: an encoding unit that encodes the original image data. 7. The image encoding apparatus according to claim 6, wherein the area dividing unit divides the screen of the original image data into a central area and a peripheral area. 8. An image analysis unit for analyzing a type of a subject from the original image data, wherein the coding parameter calculation unit calculates a coding parameter based on subject information analyzed by the image analysis unit. The image encoding device according to claim 6 or 7, wherein: 9. The image analysis unit detects a fineness level of an image based on a variance value and / or an average value of at least one of a luminance signal and a color difference signal for each small block, and detects the fineness level of the image from the fineness level. 9. The image encoding apparatus according to claim 8, wherein the type of the subject is specified. 10. The image analysis unit detects an object within a predetermined level range with respect to a primary color by an average value of each small block of a color difference signal, and specifies a type of the object based on the detected value. The image encoding device according to claim 8. 11. An image analyzing unit for analyzing a type of a subject from the original image data, wherein the region dividing unit shifts the region of the central part based on subject information analyzed by the image analyzing unit. 8. The image encoding apparatus according to claim 7, wherein: 12. An image encoding method for encoding an original image data after preprocessing the original image data with a prefilter, wherein the screen of the original image data is divided into a plurality of regions, and a filter characteristic of the prefilter is determined for each region. Switch,
An image encoding method, wherein the original image data is pre-processed. 13. An image encoding method for encoding original image data, wherein the original image data screen is divided into a plurality of regions, and encoding parameters are switched for each region to encode the original image data. An image coding method characterized by the above-mentioned.