Patent Publication Number: US-9414089-B2

Title: Image processing apparatus and image processing method

Description:
REFERENCE 
     The present application is a continuation application of U.S. patent application Ser. No. 13/888,006 filed on May 6, 2013, which is a continuation application of U.S. patent application Ser. No. 12/792,509 filed on Jun. 2, 2010, which claims priority to and benefit from Japanese Priority Patent Application JP 2009-140368 filed in the Japan Patent Office on Jun. 11, 2009. The entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image processing apparatus and an image processing method, which are suitable for use in, for example, encoding apparatuses operable to encode image data distributed via terrestrial digital broadcasting. 
     2. Description of the Related Art 
     In general, there are widely available image processing apparatuses configured to encode broadcast program content distributed via terrestrial digital broadcasting or the like and to store the encoded content in a disk such as a hard disk or an optical disk. Examples of the image processing apparatuses include a hard disk recorder and a Blu-ray Disc (registered trademark) recorder. 
     Broadcast program content viewed by the audience and information about the broadcast program content (hereinafter referred to as “EPG information”) are distributed via terrestrial digital broadcasting. The EPG information includes the description and keywords of the broadcast program content, broadcast schedules, and genre information indicating the genre of the broadcast program content. 
     One of such image processing apparatuses is configured such that broadcast program content that is stored in the image processing apparatus and that is not reproduced for a certain period of time is stored again at a higher compression ratio (see, for example, Japanese Unexamined Patent Application Publication No. 2009-10603). In this image processing apparatus, a compression ratio and the timing of storage at a compression ratio higher than the compression ratio are selected in accordance with the genre information. 
     SUMMARY OF THE INVENTION 
     Genre information is classified in accordance with the description of broadcast program content. Depending on the broadcast program content, features of image data may change. Thus, an image processing apparatus may more efficiently use genre information to encode image data. 
     Therefore, it is desirable to provide an image processing apparatus and an image processing method which enable improvement in image quality. 
     In an embodiment of the present invention, an image processing apparatus includes a receiving unit configured to receive image data of program content and genre information relating to the program content, a selection unit configured to select a size selection parameter for causing the genre information received by the receiving unit to be reflected in a block size, a determination unit configured to determine a block size in accordance with the size selection parameter selected by the selection unit, the block size being used for orthogonal transformation, and an orthogonal transformation unit configured to perform orthogonal transformation on the image data received by the receiving unit at the block size determined by the determination unit. 
     Thus, the image processing apparatus can cause broadcast program content to be reflected in a block size, thereby appropriately set a block size. 
     In another embodiment of the present invention, an image processing method includes the steps of receiving image data of program content and genre information relating to the program content; selecting a size selection parameter for causing the genre information received in the step of receiving to be reflected in a block size; determining a block size in accordance with the size selection parameter selected in the step of selecting, the block size being used for orthogonal transformation; and performing orthogonal transformation on the image data received in the step of receiving at the block size determined in the step of determining. 
     Thus, in the image processing method, broadcast program content can be reflected in a block size, and therefore a block size can be appropriately set. 
     According to an embodiment of the present invention, broadcast program content can be reflected in a block size, and thus a block size can be appropriately set. Therefore, an image processing apparatus and an image processing method which enable improvement in image quality can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating the configuration of an image processing apparatus; 
         FIG. 2  is a schematic diagram illustrating the configuration of an image encoding unit; 
         FIGS. 3A and 3B  are schematic diagrams depicting variance and texture; 
         FIG. 4  is a schematic diagram describing determination of size selection parameters; 
         FIG. 5  is a schematic diagram illustrating a setting table; 
         FIG. 6  is a flowchart describing a block size setting process procedure; 
         FIG. 7  is a schematic diagram illustrating an additional coefficient table; 
         FIG. 8  is a schematic diagram describing exceptional size selection parameters according to another embodiment; and 
         FIG. 9  is a schematic diagram illustrating an exemplary filter characteristic changing process using time information. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will be described in detail hereinafter with reference to the drawings. The description will be given in the following order:
         1. First Embodiment (Change of DCT Block Size in accordance with Characteristics of Image)   2. Second Embodiment (Use of Other Information)   3. Other Embodiments
 
1. First Embodiment
 
1-1. Configuration of Image Processing Apparatus
       

       FIG. 1  illustrates an image processing apparatus  1 . The image processing apparatus  1  may be a device configured to receive broadcast program content serving as program content and to store the received broadcast program content, such as a hard disk recorder or a personal computer. 
     A digital broadcasting receiving unit  2  may be, for example, an external interface connected to an antenna or a network such as the Internet and configured to receive a broadcast signal S 1  such as a terrestrial digital broadcasting signal. The broadcast signal S 1  may be, for example, a signal encoded according to the Moving Picture Experts Group 2 (MPEG-2) standard. 
     Upon receipt of the broadcast signal Si which represents broadcast program content, the digital broadcasting receiving unit  2  supplies the broadcast signal S 1  to a digital tuner unit  3  as a broadcast signal S 2 . The digital tuner unit  3  decodes the broadcast signal S 2  to generate Electric Program Guide (EPG) information S 3 , image data S 4 , and audio data S 5 , and supplies the EPG information S 3 , the image data S 4 , and the audio data S 5  to, for example, a display apparatus (not illustrated) such as a television apparatus. The EPG information S 3  may include the description and keywords of the broadcast program content, broadcast schedules, broadcast station information, event information, time information, genre information, and other suitable information. 
     Thus, an image based on the image data S 4  is displayed on the display apparatus, and audio based on the audio data S 5  is output. Further, various information in the EPG information S 3  is displayed in response to a request from a user. 
     The digital tuner unit  3  supplies the EPG information S 3  and the image data S 4  to an image encoding unit  4 , and supplies the audio data S 5  to an audio encoding unit  5 . The image encoding unit  4  performs an image encoding process, which will be described below, to encode the image data S 4  in accordance with the H.264/Advanced Video Coding (AVC) scheme to generate a bit stream S 6 , and supplies the bit stream S 6  to a storage unit  6 . 
     The audio encoding unit  5  encodes the audio data S 5  in accordance with a predetermined encoding scheme to generate encoded audio data S 7 , and supplies the encoded audio data S 7  to the storage unit  6 . The storage unit  6  may be, for example, an optical disk such as a hard disk or a Blu-ray Disc (registered trademark), a flash memory, or the like. The storage unit  6  stores the supplied bit stream S 6  and encoded audio data S 7  in association with each other. 
     Thus, an encoded version of the broadcast program content is stored in the storage unit  6 . In response to a request from a user, the image processing apparatus  1  reads the broadcast program content stored in the storage unit  6 , decodes the read broadcast program content using a decoding unit (not illustrated), and reproduces the image data S 4  and the audio data S 5 . The decoding unit supplies the image data S 4  and the audio data S 5  to the display apparatus. Consequently, an image based on the image data S 4  is displayed on the display apparatus, and audio based on the audio data S 5  is output to the display apparatus. 
     1-2. Configuration of Image Encoding Unit 
     Referring to  FIG. 2 , when the EPG information S 3  and the image data S 4  are supplied to the image encoding unit  4  from the digital tuner unit  3  via an input terminal  10 , the EPG information S 3  is supplied to an EPG information obtaining unit  31  and the image data S 4  is supplied to a screen rearrangement buffer  11 . 
     The screen rearrangement buffer  11  rearranges the image data S 4  in accordance with the Group Of Picture (GOP) structure in the image data S 4 , and supplies the rearranged image data S 4  to a variance calculation unit  12 . The variance calculation unit  12  calculates a variance value MB_Var of each macroblock, and supplies the variance value MB_Var to a block size setting unit  34 . The variance calculation unit  12  supplies the supplied image data S 4  to an arithmetic unit  13 , a motion estimation/compensation unit  14 , and an intra-prediction unit  15 . 
     When the image data S 4  is to be inter-encoded, the arithmetic unit  13  subtracts a predicted value L 5 , which is supplied from the motion estimation/compensation unit  14 , from the image data S 4 , and supplies the difference therebetween to an orthogonal transformation unit  17  as difference data D 1 . When the image data S 4  is to be intra-encoded, the arithmetic unit  13  subtracts a predicted value L 5 , which is supplied from the intra-prediction unit  15 , from the image data S 4 , and supplies the difference therebetween to the orthogonal transformation unit  17  as difference data D 1 . 
     The orthogonal transformation unit  17  performs orthogonal transformation on the difference data D 1  by performing a Discrete Cosine Transform (DCT) process, and supplies a DCT coefficient D 2  to a quantization unit  18 . 
     The quantization unit  18  quantizes the DCT coefficient D 2  using a quantization parameter QP determined under the control of a rate control unit  19 , and supplies a quantized coefficient D 3  to a dequantization unit  23  and a lossless encoding unit  20 . The lossless encoding unit  20  performs lossless encoding of the quantized coefficient D 3  in accordance with entropy encoding such as Context-based Adaptive Variable Length Code (CAVLC) and Context Adaptive Binary Arithmetic Coding (CABAC), and supplies lossless encoded data D 5  to a storage buffer  21 . 
     The lossless encoding unit  20  obtains information about intra-encoding and inter-encoding from the motion estimation/compensation unit  14  and the intra-prediction unit  15 , and sets the obtained information in header information of the lossless encoded data D 5 . 
     The storage buffer  21  stores the lossless encoded data D 5 , and also outputs the lossless encoded data D 5  as the bit stream S 6  at a predetermined transmission speed. The rate control unit  19  monitors the storage buffer  21 , and determines the quantization parameter QP so that an amount of encoding generated for the lossless encoded data D 5  can approach a certain amount of encoding in certain units of control (such as in units of frames or GOPs). 
     The dequantization unit  23  dequantizes the quantized coefficient D 3  to generate a reproduced DCT coefficient L 1 , and supplies the reproduced DCT coefficient L 1  to an inverse orthogonal transformation unit  24 . The inverse orthogonal transformation unit  24  performs inverse orthogonal transformation on the reproduced DCT coefficient L 1  to generate reproduced difference data L 2 , and supplies the reproduced difference data L 2  to an arithmetic unit  25 . 
     The arithmetic unit  25  sums the predicted value L 5  supplied from the motion estimation/compensation unit  14  or the intra-prediction unit  15  and the reproduced difference data L 2  to generate local decoded images L 3  of blocks to be processed, and supplies the local decoded images L 3  to a deblock filter  26  and a frame memory  27 . 
     The deblock filter  26  executes a deblock filtering process on the blocks to be processed, and supplies results to the frame memory  27 . Thus, deblock-filtered local decoded images L 4  are stored in the frame memory  27 . 
     The frame memory  27  supplies a local decoded image L 4  corresponding to a reference block among the deblock-filtered local decoded images L 4  to the motion estimation/compensation unit  14  or the intra-prediction unit  15 . The motion estimation/compensation unit  14  performs motion estimation on the image data S 4  by referring to the local decoded image L 4  to generate a predicted value L 5  for the blocks to be processed, and supplies the predicted value L 5  to the arithmetic units  13  and  25 . The intra-prediction unit  15  performs intra-prediction on the image data S 4  by referring to the local decoded images L 4  to generate a predicted value L 5  for the blocks to be processed, and supplies the predicted value L 5  to the arithmetic units  13  and  25 . 
     Accordingly, the image encoding unit  4  is configured to encode the image data S 4  and to generate the bit stream S 6 . 
     1-3. Block Size Setting Process 
     Next, a block size setting process will be described. 
     In the MPEG-2 scheme, DCT processing is performed using DCT blocks of 8×8 pixels. In the AVC/H.264 scheme, in contrast, DCT blocks of 4×4 pixels are employed in order to reduce mosquito noise or block noise. It is commonly understood that encoding efficiency can be reduced by DCT processing using DCT blocks of 4×4 pixels. 
     In the AVC/H.264 scheme, Fidelity Range Extension (FRExt), which was standardized as a profile for high-definition video in February 2005, enables switching between DCT blocks of 8×8 pixels and DCT blocks of 4×4 pixels on a macroblock-by-macroblock basis. The standardization of AVC/H.264 FRExt makes it possible to reduce mosquito noise or block noise without reducing encoding efficiency as much as possible. 
     Specifically, the image encoding unit  4  selects DCT blocks of 4×4 pixels or DCT blocks of 8×8 pixels on the basis of the variance value MB_Var of pixel values (for example, luminance values) in a macroblock in consideration of balance between noise reduction and encoding efficiency. 
     That is, when the variance value MB_Var is larger than a size selection threshold DCT_TH, the complexity of the image is high and the occurrence probability of noise is high. Thus, the image encoding unit  4  prioritizes noise reduction and selects DCT blocks of 4×4 pixels. 
     For the image data S 4  for which the variance value MB_Var is less than or equal to the size selection threshold DCT_TH and for which mosquito noise or block noise is less likely to occur, the image encoding unit  4  prioritizes encoding efficiency and selects DCT blocks of 8×8 pixels. 
     Therefore, the image encoding unit  4  can reduce mosquito noise or block noise without reducing encoding efficiency as much as possible. 
     However, the variance value MB_Var may not necessarily fully represent the occurrence probability of mosquito noise or block noise. For example, as illustrated in  FIGS. 3A and 3B , the occurrence probability of mosquito noise or block noise may differ even when the total number of luminance values that appear is the same.  FIG. 3A  illustrates a low-frequency image in which mosquito noise or block noise is less likely to occur.  FIG. 3B , on the other hand, illustrates a high-frequency image in which mosquito noise or block noise is likely to occur. 
     Further, an image with a large amount of motion tends to include mosquito noise or block noise because a large amount of encoding for the difference data D 1  is likely to occur and a large quantization parameter QP is used. However, it is difficult to recognize this tendency from the variance value MB_Var. 
     As described above, broadcast program content and EPG information are distributed via terrestrial digital broadcasting. The EPG information includes, in addition to broadcast schedule information and information indicating the description of the broadcast program content, genre information about the genre into which the broadcast program content is classified in accordance with the description the broadcast program content. 
     The genre information may indicate the features of the image data S 4  for each broadcast program content. Thus, the image encoding unit  4  according to the present embodiment is configured to change the size selection threshold DCT_TH in accordance with the genre information, thereby switching between the priority of noise reduction or the priority of encoding efficiency in accordance with the description of the broadcast program content. 
     Specifically, the image encoding unit  4  prioritizes noise reduction for broadcast program content having textures (pictures) in which noise is likely to occur, and preferentially uses DCT blocks of 4×4 pixels. The image encoding unit  4  prioritizes encoding efficiency for broadcast program content having textures in which noise is less likely to occur, and preferentially uses DCT blocks of 8×8 pixels. 
     The image encoding unit  4  prioritizes noise reduction for genre information for which noise is likely to occur and for which the amount of motion is large, and preferentially uses DCT blocks of 4×4 pixels. The image encoding unit  4  prioritizes encoding efficiency for genre information for which noise is less likely to occur and for which the amount of motion is small, and preferentially uses DCT blocks of 8×8 pixels. 
     It is commonly understood that the use of DCT blocks of 8×8 pixels allows an increase in quality of gradation. The image encoding unit  4  prioritizes image quality for broadcast program content indicated by genre information for which the importance of gradation is high, and preferentially uses DCT blocks of 8×8 pixels. 
     As described above, the image encoding unit  4  selects DCT blocks of 4×4 pixels when the variance value MB_Var is larger than the size selection threshold DCT_TH, and selects DCT blocks of 8×8 pixels when the variance value MB_Var is less than or equal to the size selection threshold DCT_TH. 
     When preferentially using DCT blocks of 4×4 pixels, the image encoding unit  4  adds a negative offset OF (for example, “−1000”) to the default value (for example, “2000”) of the size selection threshold DCT_TH. Thus, the size selection threshold DCT_TH is reduced, and the image encoding unit  4  allows more frequent selection of DCT blocks of 4×4 pixels. 
     When preferentially using DCT blocks of 8×8 pixels, the image encoding unit  4  adds a positive offset OF (for example, “+1000”) to the default value (for example, “2000”) of the size selection threshold DCT_TH. Thus, the size selection threshold DCT_TH is increased, and the image encoding unit  4  allows more frequent selection of DCT blocks of 8×8 pixels. 
       FIG. 4  illustrates genre information and a list of size selection parameters associated with the genre information. In terrestrial digital broadcasting, broadcast program content is classified into 12 genres (called primary-classification genres). In the present embodiment, in accordance with the rule described above, 4×4-priority elements that represent the priority of DCT blocks of 4×4 pixels are given scores, and the respective offsets OF are determined in accordance with total scores. In the present embodiment, “texture”, “motion”, and “gradation” are provided as 4×4-priority elements. The higher the score, the higher the priority of noise reduction. In this case, DCT blocks of 4×4 pixels are prioritized. 
     Specifically, the 4×4-priority element “texture” represents the degree to which noise is likely to occur in accordance with the picture. The higher the occurrence probability of noise, the higher the score. A genre to which broadcast program content with a large amount of “motion” belongs has a high score because noise is likely to occur. The 4×4-priority element “gradation” represents the importance of gradation in the input image data S 4 . The higher the importance of gradation, the lower the score. This is because it is desirable that DCT blocks of 8×8 pixels be preferentially used. 
     The highest scores of the individual 4×4-priority elements are different (represented by bracketed numbers). That is, noise-priority elements are weighted in accordance with their importance. 
     When the total score obtained by summing the values of the respective 4×4-priority elements is high, noise reduction rather than encoding efficiency is prioritized, that is, DCT blocks of 4×4 pixels are more preferentially used. When the total score is low, on the other hand, encoding efficiency rather than noise reduction is prioritized, that is, DCT blocks of 8×8 pixels are more preferentially used. 
     In the present embodiment, an intermediate value may be taken when the total score is “11”. When the total score is in the range of “10” to “12”, the size selection parameter “default” may be selected, and the offset OF may be set to “0”. When the total score is greater than or equal to “13”, the size selection parameter “4×4 preferential” may be selected, and the offset OF may be set to “−1000”. When the total score is less than or equal to “9”, the size selection parameter “8×8 preferential” may be selected, and the offset OF may be set to “+1000”. 
     Specifically, a news/news report genre includes images of various textures, such as images captured in studios and images captured outdoors such as in sites of events. Thus, the news/news report genre is evaluated as having an element “texture” of “4”, which is an intermediate value. The news/news report genre further includes images with a large amount of motion such as sports and almost still images such as images of a newscaster reporting news, and is thus also evaluated as having an element “motion” of “4”, which is an intermediate value. The news/news report genre has no importance on gradation, and is thus evaluated as having an element “gradation” of “3”, which is an intermediate value. Consequently, the total score is “11”, the size selection parameter “default” is selected, and the offset OF is set to “0”. 
     A sports genre does not exhibit noticeable features, and is thus evaluated as having an element “texture” of “4”, which is an intermediate value. Because of the significance of quick movements, the sports genre is evaluated as having an element “motion” of “7”, which is the maximum value. Since gradation is not so important, the sports genre is evaluated as having an element “gradation” of “3”, which is an intermediate value. Consequently, the total score is “14”, the size selection parameter “4×4 preferential” is selected, and the offset OF is set to “−1000”. 
     Like the news/news report genre, an entertainment &amp; gossip genre is evaluated as having elements “texture”, “motion”, and “gradation” of “4”, “4”, and “3”, respectively, which are intermediate values because of supply of various kinds of image data S 4 . In the entertainment &amp; gossip genre, consequently, the total score is “11”, the size selection parameter “default” is selected, and the offset OF is set to “0”. 
     A drama genre has various types of dramas including, for example, dramas with a comparatively small amount of motion, such as romance dramas, and dramas with a large amount of motion, such as action dramas and sports dramas. Further, because of having no noticeable features in textures and no importance on gradation, the drama genre, like the news/news report genre, is evaluated as having elements “texture”, “motion”, and “gradation” of “4”, “4”, and “3”, respectively, which are intermediate values. In the drama genre, consequently, the total score is “11”, the size selection parameter “default” is selected, and the offset OF is set to “0”. 
     Because of the large amount of camera work, flash lighting, blinking illumination, etc., a music genre is evaluated as having an element “motion” of “7”, which is a large value. Because of having no noticeable features in textures and no importance on gradation, the music genre is evaluated as having elements “texture” and “gradation” of “4” and “3”, respectively, which are intermediate values. In the music genre, consequently, the total score is “14”, the size selection parameter “4×4 preferential” is selected, and the offset OF is set to “−1000”. 
     Because of having a comparatively large amount of motion of performers in, for example, an action game and a large amount of camera work, a variety genre is evaluated as having an element “motion” of “6”. Because of having no noticeable features in textures and no importance on gradation, the variety genre is evaluated as having elements “texture” and “gradation” of, “4” and “3”, respectively, which are intermediate values. In the variety genre, consequently, the total score is “13”, the size selection parameter “4×4 preferential” is selected, and the offset OF is set to “−1000”. 
     Like the drama genre, a movie genre has various types of movies including movies with a comparatively small amount of motion, such as romance movies, and movies with a large amount of motion, such as action movies and sports movies. Like the drama genre, because of having no noticeable features in textures, like the news/news report genre and the drama genre, the movie genre is evaluated as having elements “motion” and “texture” of “4” and “4”, respectively, which are intermediate values. Because of having a high importance of gradation, the movie genre is evaluated as having an element “gradation” of “1”, which is the lowest value. In the movie genre, consequently, the total score is “9”, the size selection parameter “8×8 preferential” is selected, and the offset OF is set to “+1000”. 
     An animation/SFX genre has a large number of line drawings, and may be an animation-SFX combined genre. Animations predominantly contain line drawings with rapid changes in color tone, and have a feature that block noise or mosquito noise is likely to occur due to the rapid changes in color. In contrast, SFX is live action, and involves a small amount of camera work and a small amount of motion, which are greatly different features from those of animations. In the present embodiment, improvement in the quality of animation is prioritized, and a size selection parameter is selected based on the animation. The animation/SFX genre is evaluated as having an element “texture” of “7”, which is the largest value, and elements “motion” and “gradation” of, “4” and “3”, respectively, which are intermediate values. In the animation/SFX genre, consequently, the total score is “14”, the size selection parameter “4×4 preferential” is selected, and the offset OF is set to “−1000”. 
     A documentary/education genre generally includes scenes with slow changes in color, such as nature, landscape, and other scenes. Thus, the documentary/education genre is evaluated as having an element texture of “1”. Further, since photography of landscapes and the like rather than photography of humans (performers) is dominant, the amount of motion is small. Thus, the documentary/education genre is evaluated as having an element “motion” of “3”. Because of having images of many landscapes, the documentary/education genre has comparatively high importance on gradation in scenes such as sunset, sky, and other scenes, and is evaluated as having an element “gradation” of “2”. In the documentary/education genre, the total score is “6”, the size selection parameter “8×8 preferential” is selected, and the offset OF is set to “+1000”. 
     A theater/stage genre has various performances including those with a comparatively small amount of motion, such as Rakugo or Japanese comedy stages, and those with a large amount of motion and a large amount of camera work, such as dance and ballet shows. Thus, the theater/stage genre is evaluated as having elements “texture”, “motion”, and “gradation” of “4”, “4”, and “3”, respectively, which are intermediate values. In the theater/stage genre, consequently, the total score is “11”, the size selection parameter “default” is selected, and the offset OF is set to “0”. 
     A hobby/education genre generally includes programs with a comparatively small amount of motion, such as gardening programs, Go-playing programs, and Shogi or Japanese chess playing programs, and many demonstrations are performed with still images. Further, in general, comparatively simple pictures may also be used. Thus, the hobby/education genre is evaluated as having an element “motion” of “2”, an element “texture” of “3”, which is a value slightly smaller than an intermediate value, and an element “gradation” of “3”, which is an intermediate value. In the hobby/education genre, consequently, the total score is “8”, the size selection parameter “8×8 preferential” is selected, and the offset OF is set to “+1000”. 
     A welfare genre has various programs including programs with a small amount of motion, such as programs reporting welfare problems, and programs with a large amount of motion, such as historical programs with text broadcasting. Thus, like the news/news report genre and the drama genre, the welfare genre is evaluated as having elements “texture”, “motion”, and “gradation” of “4”, “4”, and “3”, respectively, which are intermediate values. In the welfare genre, consequently, the total score is “11”, the size selection parameter “default” is selected, and the offset OF is set to “0”. 
     Specifically, upon receipt of the EPG information S 3  supplied from the digital tuner unit  3  ( FIG. 1 ), the EPG information obtaining unit  31  ( FIG. 2 ) of the image encoding unit  4  supplies the EPG information S 3  to a genre information obtaining unit  32 . The genre information obtaining unit  32  extracts genre information corresponding to broadcast program content to be recorded from the EPG information S 3 , and supplies the genre information to a parameter determination unit  33 . 
     The parameter determination unit  33  stores a setting table in which genre information is associated with size selection thresholds DTD_TH. In  FIG. 5 , the default size selection threshold DCT_TH is “2000”, by way of example. That is, when a size selection threshold DTC_TH corresponding to genre information is selected, a value obtained by automatically adding the offset OF corresponding to the size selection parameter to the default size selection threshold DCT_TH is selected. When the size selection threshold DTD_TH corresponding to the genre information is selected, the parameter determination unit  33  supplies the size selection threshold DTC_TH to the block size setting unit  34 . 
     The variance value MB_Var of each macroblock is supplied to the block size setting unit  34  from the variance calculation unit  12 . The block size setting unit  34  compares the variance value MB_Var with the size selection threshold DTC_TH. 
     When the variance value MB_Var is larger than the size selection threshold DTD_TH, the block size setting unit  34  selects DCT blocks of 4×4 pixels, and supplies a size signal indicating the selection of DCT blocks of 4×4 pixels to the orthogonal transformation unit  17 . When the variance value MB_Var is less than or equal to the size selection threshold DTD_TH, the block size setting unit  34  selects DCT blocks of 8×8 pixels, and supplies a signal indicating the selection of DCT blocks of 8×8 pixels to the orthogonal transformation unit  17 . 
     The orthogonal transformation unit  17  executes DCT processing on the difference data D 1  at the block size indicated by the size signal supplied from the block size setting unit  34 . 
     Accordingly, the image encoding unit  4  evaluates the 4×4-priority elements indicating the priority of DCT blocks of 4×4 pixels in accordance with the occurrence probability of noise in the image data S 4 , which is contained for each genre of broadcast program content. The image encoding unit  4  causes the evaluation of the 4×4-priority elements to be reflected in the block size in the DCT processing. 
     Therefore, the image encoding unit  4  can cause not only the variance value MB_Var of the image data S 4  but also the occurrence probability of noise, which may not necessarily be recognized from the variance value MB_Var, to be reflected in the block size of the DCT blocks. Thus, the image encoding unit  4  can set a block size suitable for the image data S 4 , and can increase the image quality of the bit stream S 6 . 
     The series of encoding and block size setting processes described above can be executed by hardware or software. When the series of encoding and the block size setting processes are implemented by software, the image encoding unit  4  is formed in a virtual manner in a central processing unit (CPU) and a random access memory (RAM). Then, when a block size setting program stored in a read-only memory (ROM) is developed on the RAM, the encoding process is executed. 
     1-4. Block Size Setting Process Routine 
     A block size setting process routine RT 1  executed in accordance with a block size setting process program will now be described with reference to a flowchart of  FIG. 6 . 
     The image encoding unit  4  starts the block size setting process routine RT 1 . When the EPG information S 3  and the image data S 4  are supplied in step SP 1 , the image encoding unit  4  proceeds to step SP 2 . 
     In step SP 2 , the image encoding unit  4  obtains genre information from the EPG information S 3 . Then, the image encoding unit  4  proceeds to step SP 3 . 
     In step S 3 , the image encoding unit  4  selects a size selection parameter corresponding to the genre information. When the size selection parameter “4×4 preferential” is selected, the image encoding unit  4  proceeds to step SP 4 . When the size selection parameter “default” is selected, the image encoding unit  4  proceeds to step SP 5 . When the size selection parameter “8×8 preferential” is selected, the image encoding unit  4  proceeds to step SP 6 . In the first embodiment, the size selection threshold DCT_TH corresponding to a size selection parameter is selected, thus allowing the size selection parameter to be selected indirectly. 
     In step SP 4 , the image encoding unit  4  sets the size selection threshold DCT_TH to “1000”. Then, the image encoding unit  4  proceeds to step SP 7 . 
     In step SP 5 , the image encoding unit  4  sets the size selection threshold DCT_TH to “2000”. Then, the image encoding unit  4  proceeds to step SP 7 . 
     In step SP 6 , the image encoding unit  4  sets the size selection threshold DCT_TH to “3000”. Then, the image encoding unit  4  proceeds to step SP 7 . 
     In step SP 7 , the image encoding unit  4  compares the size selection threshold DCT_TH set in any of steps SP 4  to SP 6  with the variance value MB_Var of the macroblock to determine a block size. Then, the image encoding unit  4  proceeds to step SP 8 . 
     In step SP 8 , the image encoding unit  4  executes DCT processing on the difference data D 1  at the block size determined in step SP 7 . Then, the image encoding unit  4  proceeds to an end step, and the process ends. 
     1-5. Operation And Advantageous Effects 
     In the above configuration, the image encoding unit  4  in the image processing apparatus  1  receives image data S 4  of broadcast program content serving as program content and genre information regarding the broadcast program content, and selects a size selection parameter for causing the genre information to be reflected in the block size. The image encoding unit  4  selects the size selection threshold DCT_TH corresponding to the size selection parameter, thereby determining a block size used for orthogonal transformation based on the size selection parameter. The image encoding unit  4  performs orthogonal transformation on the difference data D 1 , which is data to be processed based on the image data S 4 , at the determined block size. 
     Therefore, the image encoding unit  4  can cause the features of the image data S 4 , which correspond to the description of the broadcast program content indicated by the genre information, to be reflected in the determined block size. Thus, DCT processing serving as orthogonal transformation can be executed using an appropriate block size. 
     The image encoding unit  4  compares an index value indicating a feature of a pixel value of the image data S 4  with the block selection threshold DHC_TH selected in accordance with the size selection parameter, and selects a block size used for DCT transformation, thus causing the genre information to be reflected in the block size. 
     Thus, the image encoding unit  4  can cause not only the features of the image data S 4  in accordance with the description of the broadcast program content but also the features of the pixel values to be reflected in the determined block size. That is, the image encoding unit  4  can cause the features of pixel values that can be recognized by the analysis of the image data S 4  to be reflected in the determination of a block size, and can further cause the features of the image data S 4  that may not necessarily be recognized by the analysis of the image data S 4  and that correspond to the description of the broadcast program content to be reflected in the determination of a block size. Consequently, the image encoding unit  4  can more appropriately select a block size. 
     The image encoding unit  4  employs a variance value MB_Var that represents the variance of each macroblock, which is the unit of encoding, as a feature of pixel values. 
     Accordingly, the image encoding unit  4  can cause the occurrence probability of noise that can be recognized by the analysis of the image data S 4  to be reflected in the determination of a block size. Thus, a more appropriate block size can be selected. 
     The image encoding unit  4  determines a block size from a predetermined first block size of DCT blocks of 4×4 pixels and a second block size of DCT blocks of 8×8 pixels larger than the first block size of DCT blocks of 4×4 pixels. When noise reduction is to be prioritized, the image encoding unit  4  reduces the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 4×4 pixels as the block size used for DCT transformation. When encoding efficiency is to be prioritized, the image encoding unit  4  increases the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 8×8 pixels as the block size used for DCT transformation. 
     Therefore, when it is not necessary to reduce noise, the image encoding unit  4  prioritizes encoding efficiency to preferentially use DCT blocks of 8×8 pixels, and can thus increase encoding efficiency without reducing image quality. 
     When gradation is to be emphasized, the image encoding unit  4  increases the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 8×8 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase quality of gradation in broadcast program content having scenes with a high importance of gradation, such as movies. 
     When the genre information indicates the sports genre, the image encoding unit  4  reduces the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 4×4 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase image quality with high priority on noise reduction in broadcast program content belonging in the sports genre in which the amount of motion is large and in which the occurrence probability of noise is high. 
     When the genre information indicates the animation/SFX genre, the image encoding unit  4  reduces the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 4×4 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase image quality with high priority on noise reduction in broadcast program content belonging to the animation genre in which the use of line drawings is dominant and in which the occurrence probability of noise is high. 
     When the genre information indicates the music genre, the image encoding unit  4  reduces the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 4×4 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase image quality with high priority on noise reduction in broadcast program content belonging to the music genre in which the amount of motion is large because of the use of flash lighting and illumination. 
     When the genre information indicates the variety genre, the image encoding unit  4  reduces the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 4×4 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase image quality with high priority on noise reduction in broadcast program content belonging to the variety genre in which the amount of motion is large and in which the occurrence probability of noise is high. 
     When the genre information indicates the documentary/education genre, the image encoding unit  4  increases the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 8×8 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase encoding efficiency while maintaining image quality in broadcast program content belonging to the documentary/education genre in which a large number of low-frequency images are included and in which the occurrence probability of noise is low. 
     When the genre information indicates the hobby/education genre, the image encoding unit  4  increases the block selection threshold DCT_TH, thereby preferentially using the size of DCT blocks of 8×8 pixels as the block size used for DCT transformation. 
     Thus, the image encoding unit  4  can increase encoding efficiency while maintaining image quality in broadcast program content belonging to the hobby/education genre in which the amount of motion is small and in which the occurrence probability of noise is low. 
     The image encoding unit  4  encodes image data in accordance with the H.264/AVC scheme. The orthogonal transformation unit  17  uses the difference data D 1 , which represents the difference between pixel values, as image data to be subjected to DCT processing, and executes DCT processing as orthogonal transformation. 
     Thus, the image encoding unit  4  can encode the image data S 4  of the broadcast program content at a high compression ratio. 
     The image encoding unit  4  evaluates which of noise reduction and encoding efficiency to prioritize on the basis of a plurality of 4×4-priority elements serving as priority elements each of which represents the occurrence probability of noise of the image data S 4 . The 4×4-priority elements are weighted with individual values. 
     Thus, the image encoding unit  4  can appropriately evaluate the occurrence probability of noise on the basis of a plurality of factors while taking the importance of the plurality of factors into account. 
     With the above configuration, the image encoding unit  4  selects a size selection parameter to be reflected in the block size using the features of the image data S 4  in accordance with the description of the broadcast program content indicated by the genre information. The image encoding unit  4  causes the size selection parameter to be reflected in the block size used for DCT processing. 
     Thus, the image encoding unit  4  can cause broadcast program content, which may not necessarily be recognized only by the analysis of the image data S 4 , to be reflected in the block size, and can appropriately determine the priority of noise reduction or encoding efficiency. According to an embodiment of the present invention, therefore, an image processing apparatus and an image processing method which enable increase in image quality can be achieved. 
     2—Second Embodiment 
     2-1. Block Size Setting Process Using Information Other than Genre Information 
     In a second embodiment, portions corresponding to those of the first embodiment illustrated in  FIGS. 1 to 6  are represented by the same reference numerals, and descriptions thereof will be omitted. The second embodiment is different from the first embodiment in that a block size is changed using not only genre information but also information other than the genre information included in the EPG information S 3 . 
     The EPG information S 3  includes, in addition to genre information, broadcast station information indicating the broadcast station that distributes the broadcast program content, event information that describes the broadcast program content, and other suitable information. 
     The broadcast program content is generally captured and edited in a distributor, that is, a broadcast station, and tends to have different levels of noise included in the image data S 4 , due to the difference in equipment or technique used, depending on the broadcast station. Encoding efficiency may be prioritized for image data S 4  based on a broadcast signal Si distributed from a broadcast station that tends to distribute broadcast program content having less noise. Conversely, noise reduction may be prioritized for image data S 4  based on a broadcast signal S 1  distributed from a broadcast station that tends to distribute broadcast program content having much noise. 
     Therefore, an image encoding unit (not illustrated in the figures) according to the second embodiment (hereinafter referred to as an “image encoding unit  104 ”) is configured to cause broadcast station information to be reflected in a size selection parameter. 
     Event information directly represents the broadcast program content. For example, when the event information includes text such as “live broadcasting”, “on-the-spot broadcasting”, or “live video”, at least a main portion in the broadcast program content is possibly broadcast live. 
     In general, recorded broadcast program content may be distributed with noise reduced in advance by certain image processing. Live broadcast content, on the other hand, usually contains more noise because of insufficient time to perform such modifications. Thus, broadcast program content that is mainly broadcast live has a high occurrence probability of noise, and it is desirable that noise reduction be prioritized. 
     Further, when event information corresponding to broadcast program content belonging to genres other than the sports genre, such as the movie genre, the drama genre, and the hobby/education genre, contains the name of a sport, at least a main part of the broadcast program content may possibly contain a scene of the sport. In this case, the occurrence probability of noise is high, and it is desirable that noise reduction be prioritized. 
     When the event information about broadcast program content belonging to the documentary/education genre includes the geographic name of a place with a great nature spot or a historic building or includes a word indicating a place with a great nature spot or a historic building, at least a main part of the broadcast program content may possibly contain a scene of the great nature spot or historic building. Examples of the geographic name of a place with a great nature spot or a historic building include “the Grand Canyon” and “the Great Barrier Reef”, and examples of the word indicating a place with a great nature spot or a historic building include “coral reef”, “beech virgin forest”, “jungle”, “world heritage”, and “ancient city”. Such broadcast program content has low occurrence probability of noise, and it is desirable that encoding efficiency be prioritized. 
     Thus, when the event information includes such keywords representing visual features of image data S 4  (hereinafter referred to as “feature keywords”), the image encoding unit  104  causes the feature keywords to be reflected in the size selection parameter. 
     When the EPG information S 3  is supplied from the EPG information obtaining unit  31 , a genre information obtaining unit (not illustrated in the figures) corresponding to the genre information obtaining unit  32  (hereinafter referred to as a “genre information obtaining unit  132 ”) extracts genre information and broadcast station information corresponding to the broadcast program content that is currently being recorded from the EPG information S 3 , and supplies the extracted genre information and broadcast station information to a parameter determination unit (not illustrated in the figures) corresponding to the parameter determination unit  33  (hereinafter referred to as a “parameter determination unit  133 ”). 
     The genre information obtaining unit  132  stores a list of feature keywords representing visual features of the image data S 4 . The genre information obtaining unit  132  searches for a feature keyword from the event information corresponding to the broadcast program content that is currently being recorded within the EPG information S 3 . When the event information includes the feature keyword, the genre information obtaining unit  132  supplies the feature keyword to the parameter determination unit  133  together with the genre information and the broadcast station information. 
     The parameter determination unit  133  stores a score table in which total scores are associated with genre information instead of using a setting table in which size selection thresholds DCT_TH ( FIG. 5 ) are associated with genre information. Further, the parameter determination unit  133  stores an additional coefficient table in which, as illustrated in  FIG. 7 , broadcast station information, feature keywords, and additional coefficients are associated with one another. 
     The parameter determination unit  133  selects a total score corresponding to the genre information in accordance with the score table. The parameter determination unit  133  further selects an additional coefficient corresponding to the broadcast station information and feature keyword supplied from the genre information obtaining unit  132  in accordance with the additional coefficient table. 
     When the genre information indicates the sports genre, the total score has been determined on the assumption that scenes of sports are included, and the score table does not apply. When the name of a sport is supplied, the parameter determination unit  133  checks the genre information, and selects an additional coefficient only when the genre information does not indicate the sports genre. 
     For the name of a nature spot, similarly, when the geographic name of a place with a great nature spot or a historic building or a word indicating a place with a great nature spot or a historic building is supplied, the parameter determination unit  133  checks the genre information, and selects an additional coefficient only when the genre information does not indicate the documentary/education genre. 
     The parameter determination unit  133  multiplies the selected total score by the corresponding additional coefficient, and calculates a resulting multiplied score. For example, the genre information indicates the documentary/education genre, the broadcast station information indicates content “H”, and the feature keyword “live broadcasting” is supplied. In this case, the total score “6” is multiplied by “0.9” for the content “H” and “1.2” for the feature keyword “live broadcasting”. Consequently, the multiplied score is given by 6×0.9×1.2=6.48. Further, when no feature keywords are supplied, the parameter determination unit  133  multiplies the total score corresponding to the genre information only by the additional coefficient corresponding to the broadcast station information. 
     The parameter determination unit  133  has five levels of offsets OF, namely, “−2000”, “−1000”, “0”, “+1000”, and “+2000”, and selects one offset OF in accordance with the resulting score. In the present embodiment, the offsets OF represent numerical values of size selection parameters. 
     The parameter determination unit  133  selects the offset OF “−2000” when the multiplied score is “less than 7.0”. The parameter determination unit  133  selects the offset OF “−1000” when the multiplied score is “greater than or equal to 7.0 and less than or equal to 10.0”. The parameter determination unit  133  selects the offset OF “0” when the multiplied score is “greater than or equal to 10.0 and less than or equal to 13.0”. The parameter determination unit  133  selects the offset OF “+1000” when the multiplied score is “greater than 13.0 and less than 15.0”. parameter determination unit  133  selects the offset OF “+2000” when the multiplied score is “greater than or equal to 15.0”. 
     The parameter determination unit  133  supplies the selected offset OF to a block size setting unit (not illustrated in the figures) corresponding to the block size setting unit  34  (hereinafter referred to as a “block size setting unit  134 ”). The block size setting unit  134  adds the supplied offset OF to the default value “2000”, thereby calculating the size selection threshold DCT_TH. The block size setting unit  134  compares the size selection threshold DCT_TH with the variance value MB_Var supplied from the variance calculation unit  12 . 
     Accordingly, the image encoding unit  104  calculates a multiplied score, thereby determining a priority of noise reduction and maintenance of resolution in the image data S 4  using, in addition to genre information, broadcast station information and feature keywords. 
     Thus, the image encoding unit  104  can determine a priority of noise reduction and encoding efficiency using the occurrence probability of noise in the image data S 4 , which may not necessarily be recognized from only genre information, and can more appropriately select a block size. 
     2-2. Operation and Advantageous Effects 
     In the above configuration, the image encoding unit  104  receives event information that describes broadcast program content included in the EPG information S 3 . When the event information includes a feature keyword indicating the occurrence probability of noise in image data, the image encoding unit  104  causes the feature keyword to be reflected in the determination of a block size. 
     Thus, the image encoding unit  104  can determine a block size using a feature keyword that directly represents the broadcast program content, and can therefore more appropriately set a block size. 
     The image encoding unit  104  receives broadcast station information indicating the broadcast station that has distributed the broadcast program content, and causes the broadcast station information indicating the broadcast station that has distributed the broadcast program content to be reflected in the determination of a block size. 
     Thus, the image encoding unit  104  can cause the occurrence probability of noise for each broadcast station to be reflected in the determination of a block size, and can therefore more appropriately set a block size. 
     The image encoding unit  104  determines a size selection threshold DCT_TH in accordance with the primary-classification genre to which the broadcast program content belongs. When the sub-classification genre to which the broadcast program content belongs is exceptional for the occurrence probability of noise indicated by the primary-classification genre, the image encoding unit  104  causes the exceptional sub-classification genre to be reflected in the determination of a block size regardless of the size selection threshold DCT_TH corresponding to the primary-classification genre. 
     Thus, the image encoding unit  104  can cause the broadcast program content to be appropriately reflected in the determination of a block size, and can more appropriately set a block size. 
     With the above configuration, the image encoding unit  104  causes a feature keyword included in the event information to be reflected in the determination of a block size, thus allowing the occurrence probability of noise in the image data S 4  to be more appropriately reflected in the block size. Consequently, the image encoding unit  104  can appropriately adjust the balance between noise reduction and encoding efficiency, and can increase image quality in the bit stream S 6 . 
     Other Embodiments 
     In the first and second embodiments described above, the image encoding unit determines a size selection parameter in accordance with the primary-classification genre to which broadcast program content belongs, by way of example. The present invention is not to be limited thereto, and, in an embodiment, for example, a size selection parameter may be determined in accordance with the sub-classification genre to which broadcast program content belongs, which is indicated by genre information. In this case, the image encoding unit stores a setting table in which sub-classification genres are associated with size selection parameters, and selects a size selection parameter in accordance with the sub-classification genre. Then, for example, the image encoding unit uses a size selection threshold DCT_TH corresponding to the size selection parameter. 
     Thus, the image encoding unit enables more detailed classification of broadcast program content, and therefore more appropriately select a size selection parameter. 
     The image encoding unit may also have a setting table ( FIG. 8 ) in which exceptional sub-classifications indicating that the sub-classification genre to which broadcast program content belongs is exceptional for the occurrence probability of noise indicated by primary-classification genre to which the broadcast program content belongs are associated with size selection parameters. When the sub-classification genre to which broadcast program content belongs is an exceptional sub-classification genre, the image encoding unit determines a size selection parameter corresponding to the exceptional sub-classification genre as the size selection parameter of the broadcast program content regardless of the size selection parameter corresponding to the primary-classification genre to which broadcast program content belongs. 
     The image encoding unit preferentially uses the block size of 8×8 pixels when the sub-classification genre is “politics &amp; congress/debate &amp; conference” (“news/news report”), “lifestyle/food &amp; cooking/health &amp; medicine” (“entertainment &amp; gossip”), “classics &amp; opera” (“music”), “travel &amp; tour” (“variety”), “SFX” (“animation/SFX”), “historical &amp; travel/interview &amp; discussion” (“documentary/education”), or “comedy &amp; sitcom” (“theater/stage”). The image encoding unit preferentially uses the block size of 4×4 pixels when the sub-classification genre is “animation” (“movie”), “sports” (“documentary/education”), or “dance &amp; ballet” (“theater/stage”). In the above examples, the bracketed words indicate primary-classification genres to which sub-classification genres belong. 
     Thus, the image encoding unit can execute DCT processing on broadcast program content belonging to an exceptional sub-classification genre having a tendency different from the corresponding primary-classification genre at an appropriate block size. 
     Further, in the first embodiment described above, a size selection parameter is selected in accordance with genre information. The present invention is not to be limited thereto, and, in an embodiment, time information indicating the current time may further be received and the time information may be reflected in a block size. For example, in the midnight time zone in which low-quality video is generally distributed, the quality of images tends to be low. Thus, noise reduction may be prioritized and the size of DCT blocks of 4×4 pixels may be preferentially used. 
     Further, as illustrated in  FIG. 9 , when the time indicated by the time information time is within a designated period of time determined in advance (for example, from 5:00 am to 8:59 am), the image encoding unit may preferentially use the size of DCT blocks of 4×4 pixels for a time display area TM where the current time is displayed. In this case, the image encoding unit determines a size selection parameter for an area other than the time display area TM using a method similar to that of the first embodiment. 
     Thus, the image encoding unit can reduce noise in the time display area TM where text information is displayed in a frame image  50 , and can therefore appropriate remove noise that is likely to occur around the text information. This avoids the image encoding unit to give a user an impression of low quality of an entire image because text information is unclear due to noise. 
     Furthermore, in addition to the example illustrated in  FIG. 9 , for example, the size of DCT blocks of 4×4 pixels may be preferentially used for a superimposition area where scenes are superimposed with text in genres of content having a large amount of superimposed text, such as variety shows, or for the entirety of a frame image. 
     Further, in the first and second embodiments described above, the orthogonal transformation unit  17  provides switching between DCT blocks of 4×4 pixels and DCT blocks of 8×8 pixels. The present invention is not to be limited thereto, and there is no limitation on the size of DCT blocks to be switched. For example, DCT blocks of 16×16 pixels or 32×32 pixels may also be used. In addition, three or more sizes may be used as block sizes, and a block size may be selected in accordance with a plurality of selection thresholds. 
     Furthermore, in the first and second embodiments described above, DCT processing is used as orthogonal transformation, by way of example. The present invention is not to be limited thereto, and, in an embodiment, a variety of orthogonal transformation processes such as wavelet transformation may be used. 
     In the first and second embodiments described above, furthermore, the variance value MB_Var is used as an index that represents features of pixels, by way of example. The present invention is not to be limited thereto, and a variety of indices may be used. An index may not necessarily be calculated for each macroblock as the unit of encoding, but may be calculated in units of various sizes, for example, in units of 8×8 pixels or 32×32 pixels. In the embodiments of the present invention, there is no limitation on the default value which may be set to any value. There is no limitation on the number of offsets OF, the values of the offsets OF, and the method for calculating the offsets OF. For example, an offset OF may be calculated by multiplying a total score as a size selection parameter by a predetermined coefficient. 
     Furthermore, in the first and second embodiments described above, the embodiments of the present invention are applied to the distribution of terrestrial digital broadcasting. The present invention is not to be limited thereto, and the embodiments of the present invention may be applied to, for example, various types of program content such as program content stream-distributed via the Internet and program content distributed on-demand. Further, the EPG information S 3  may not necessarily be obtained at the same time as the broadcast signal S 1 , and may be separately obtained via a network such as the Internet. In this case, more detailed genre information can be acquired. A setting table or a score table corresponding to such genre information may be stored, thus enabling a block size to be set in accordance with more detailed classifications. 
     In the first and second embodiments described above, an encoding process is executed in accordance with the AVC/H.264 scheme. The present invention is not to be limited thereto, and the embodiments of the present invention can also be applied to any encoding scheme that uses a filter capable of reducing noise caused by encoding. 
     Furthermore, in the first embodiment described above, a 4×4-priority element is evaluated as a priority element to evaluate the priority of noise reduction, by way of example. The present invention is not to be limited thereto, and the priority of encoding efficiency may be evaluated. Further, there is no limitation on the number of priority elements, and one or more desired priority elements may be used. 
     Further, in the second embodiment described above, a size selection parameter selected in accordance with genre information is multiplied by an additional coefficient selected in accordance with broadcast station information and a feature keyword, by way of example. The present invention is not to be limited thereto, and it is to be understood that either of or both the broadcast station information and the feature keyword may be reflected in the determination of a block size. For example, an additional coefficient selected in accordance with the broadcast station information and the feature keyword may be added. Alternatively, an additional coefficient may be selected in accordance with one of the broadcast station information and the feature keyword. Furthermore, in an embodiment of the present invention, either of or both the broadcast station information and the feature keyword may be reflected in the determination of a block size without using genre information. In this case, a size selection parameter, the size selection threshold DTD_TH corresponding thereto, or the like is selected from a setting table in which one of the broadcast station information and the feature keyword or both are associated with size selection parameters. Alternatively, a size selection threshold DCT_TH illustrated in  FIG. 5  may be selected as a size selection parameter, and may be multiplied by an additional coefficient to determine the selection threshold DCT_TH to be actually used. 
     Furthermore, in the foregoing embodiments, an encoding program, a block size setting program, and the like are stored in advance in a ROM, a hard disk drive, or the like, by way of example. The present invention is not to be limited thereto, and the above programs may be installed into a flash memory or the like from an external storage medium such as a memory stick (which is a registered trademark of Sony Corporation). Further, the block size setting program and the like may be obtained from outside via a wireless local area network (LAN) based on the universal serial bus (USB), Ethernet (registered trademark), Institute of Electrical and Electronics Engineers (IEEE) 802.11a/b/g, or any other suitable standard, and may further be distributed via terrestrial digital television broadcasting or broadcasting satellite (BS) digital television broadcasting. 
     In the embodiments described above, the image encoding unit  4  serving as an encoding apparatus is configured using a receiving unit corresponding to the screen rearrangement buffer  11  and the EPG information obtaining unit  31 , a selection unit and a determination unit corresponding to the parameter determination unit  33 , and an orthogonal transformation unit corresponding to the orthogonal transformation unit  17 . An image processing apparatus according to an embodiment of the present invention may at least include a receiving unit, a selection unit, a determination unit, and an orthogonal transformation unit, and may be configured only using, for example, the image encoding unit  4 . Alternatively, an encoding apparatus according to an embodiment of the present invention may be configured using a receiving unit, a selection unit, a determination unit, and an orthogonal transformation unit, which may have other various configurations. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.