WO2012126627A1

WO2012126627A1 - Classifications in cascaded filtering

Info

Publication number: WO2012126627A1
Application number: PCT/EP2012/001263
Authority: WO
Inventors: Matthias Narroschke; Semih Esenlik; Thomas Wedi; Virginie Drugeon
Original assignee: Panasonic Corporation
Priority date: 2011-03-22
Filing date: 2012-03-22
Publication date: 2012-09-27

Abstract

The present invention relates to image processing which is conducted in subsequent image processing steps requiring classification of pixels, which may be advantageously applied for encoding and decoding of image or video signal. In particular, the present invention relates to performing an efficient classification in subsequent image processing steps. This is achieved by determining values that serve as a basis for classifying pixels in order to judge whether or not and/or which processing is applied, and then applying the same values as a basis in the subsequent processing step.

Description

DESCRIPTION

CLASSIFICATIONS IN CASCADED FILTERING

The present invention relates to the filtering of images. In particular, the present invention relates to an efficient approach for filtering an image area when multiple successive filtering stages are performed.

BACKGROUND OF THE INVENTION

At present, the majority of standardized video coding algorithms are based on hybrid video coding. Hybrid video coding methods typically combine several different lossless and lossy compression schemes in order to achieve the desired compression gain. Hybrid video coding is also the basis for ITU-T standards (H.26x standards such as H.261 , H.263) as well as ISO/IEC standards (MPEG-X standards such as PEG-1 , MPEG-2, and MPEG-4). The most recent and advanced video coding standard is currently the standard denoted as H.264/MPEG-4 advanced video coding (AVC) which is a result of standardization efforts by joint video team (JVT), a joint team of ITU-T and ISO/IEC MPEG groups. This codec is being further developed by Joint Collaborative Team on Video Coding (JCT-VC) under a name High-Efficiency Video Coding (HEVC), aiming, in particular at improvements of efficiency regarding the high-resolution video coding.

A video signal input to an encoder is a sequence of images called frames, each frame being a two-dimensional matrix of pixels. All the above-mentioned standards based on hybrid video coding include subdividing each individual video frame into smaller blocks consisting of a plurality of pixels. The size of the blocks may vary, for instance, in accordance with the content of the image. The way of coding may be typically varied on a per block basis. The largest possible size for such a block, for instance in HEVC, is 64 x 64 pixels. It is then called the largest coding unit (LCU). In H.264/MPEG-4 AVC, a macroblock (usually denoting a block of 16 x 16 pixels) was the basic image element, for which the encoding is performed, with a possibility to further divide it in smaller subblocks to which some of the coding/decoding steps were applied.

Typically, the encoding steps of a hybrid video coding include a spatial and/or a temporal prediction. Accordingly, each block to be encoded is first predicted using either the blocks in its spatial neighborhood or blocks from its temporal neighborhood, i.e. from previously encoded video frames. A block of differences between the block to be encoded and its prediction, also called block of prediction residuals, is then calculated. Another encoding step is a transformation of a block of residuals from the spatial (pixel) domain into a frequency domain. The transformation aims at reducing the correlation of the input block. Further encoding step is quantization of the transform coefficients. In this step the actual lossy (irreversible) compression takes place. Usually, the compressed transform coefficient values are further compacted (losslessly compressed) by means of an entropy coding. In addition, side information necessary for reconstruction of the encoded video signal is encoded and provided together with the encoded video signal. This is for example information about the spatial and/or temporal prediction, amount of quantization, etc.

Figure 1 is an example of a typical H.264/MPEG-4 AVC and/or HEVC video encoder 100. A subtracter 105 first determines differences e between a current block to be encoded of an input video image (input signal s) and a corresponding prediction block s, which is used as a prediction of the current block to be encoded. The prediction signal may be obtained by a temporal or by a spatial prediction 180. The type of prediction can be varied on a per frame basis or on a per block basis. Blocks and/or frames predicted using temporal prediction are called "inter"-encoded and blocks and/or frames predicted using spatial prediction are called "intra"-encoded. Prediction signal using temporal prediction is derived from the previously encoded images, which are stored in a memory. The prediction signal using spatial prediction is derived from the values of boundary pixels in the neighboring blocks, which have been previously encoded, decoded, and stored in the memory. The difference e between the input signal and the prediction signal, denoted prediction error or residual, is transformed 1 10 resulting in coefficients, which are quantized 120. Entropy encoder 190 is then applied to the quantized coefficients in order to further reduce the amount of data to be stored and/or transmitted in a lossless way. This is mainly achieved by applying a code with code words of variable length wherein the length of a code word is chosen based on the probability of its occurrence.

Within the video encoder 100, a decoding unit is incorporated for obtaining a decoded (reconstructed) video signal In compliance with the encoding steps, the decoding steps include dequantization and inverse transformation 130. The so obtained prediction error signal e' differs from the original prediction error signal due to the quantization error, called also quantization noise. A reconstructed image signal Ri is then obtained by adding 140 the decoded prediction error signal e' to the prediction signal s. In order to maintain the compatibility between the encoder side and the decoder side, the prediction signal s is obtained based on the encoded and subsequently decoded video signal which is known at both sides the encoder and the decoder. Due to the quantization, quantization noise is superposed to the reconstructed video signal. Due to the block-wise coding, the superposed noise often has blocking characteristics, which result, in particular for strong quantization, in visible block boundaries in the decoded image. Such blocking artifacts have a negative effect upon human visual perception. In order to reduce these artifacts, a deblocking filter 150 is applied to every reconstructed image block. The deblocking filter is applied to the reconstructed signal Ri. For instance, the deblocking filter of H.264/MPEG- 4 AVC has the capability of local adaptation. In the case of a high degree of blocking noise, a strong (narrow-band) low pass filter is applied, whereas for a low degree of blocking noise, a weaker (broad-band) low pass filter is applied. The strength of the low pass filter is determined by the prediction signal s and by the quantized prediction error signal e'. Deblocking filter generally smoothes the block edges leading to an improved subjective quality of the decoded images. Moreover, since the filtered part of an image is used for the motion compensated prediction of further images, the filtering also reduces the prediction errors, and thus enables improvement of coding efficiency.

After a deblocking filter 150, a sample adaptive offset 155 and/or adaptive loop filter 160 may be applied to the image including the already deblocked signal R₂. Whereas the deblocking filter improves the subjective quality, sample adaptive offset (SAO) and ALF aim at improving the pixel-wise fidelity ("objective" quality). In particular, SAO adds an offset in accordance with the immediate neighbourhood of a pixel. The adaptive loop filter (ALF) is used to compensate image distortion caused by the compression. Typically, the adaptive loop filter is a Wiener filter with filter coefficients determined such that the mean square error (MSE) between the reconstructed Ri and source images s is minimized. The coefficients of ALF may be calculated and transmitted on a frame basis. ALF can be applied to the entire frame (image of the video sequence) or to local areas (blocks). An additional side information indicating which areas are to be filtered may be transmitted (block-based, frame-based or quadtree-based).

In order to be decoded, inter-encoded blocks require also storing the previously encoded and subsequently decoded portions of image(s) in the reference frame buffer 170. An inter-encoded block is predicted 180 by employing motion compensated prediction. First, a best-matching block is found for the current block within the previously encoded and decoded video frames by a motion estimator. The best-matching block then becomes a prediction signal and the relative displacement (motion) between the current block and its best match is then signalized as motion data in the form of three-dimensional motion vectors within the side information provided together with the encoded video data. The three dimensions consist of two spatial dimensions and one temporal dimension. In order to optimize the prediction accuracy, motion vectors may be determined with a spatial sub-pixel resolution e.g. half pixel or quarter pixel resolution. A motion vector with spatial sub-pixel resolution may point to a spatial position within an already decoded frame where no real pixel value is available, i.e. a sub-pixel position. Hence, spatial interpolation of such pixel values is needed in order to perform motion compensated prediction. This may be achieved by an interpolation filter (in Figure 1 integrated within Prediction block 180).

For both, the intra- and the inter-encoding modes, the differences e between the current input signal and the prediction signal are transformed 1 10 and quantized 120, resulting in the quantized coefficients. Generally, an orthogonal transformation such as a two-dimensional discrete cosine transformation (DCT) or an integer version thereof is employed since it reduces the correlation of the natural video images efficiently. After the transformation, lower frequency components are usually more important for image quality then high frequency components so that more bits can be spent for coding the low frequency components than the high frequency components. In the entropy coder, the two-dimensional matrix of quantized coefficients is converted into a one-dimensional array. Typically, this conversion is performed by a so-called zig-zag scanning, which starts with the DC-coefficient in the upper left corner of the two- dimensional array and scans the two-dimensional array in a predetermined sequence ending with an AC coefficient in the lower right corner. As the energy is typically concentrated in the left upper part of the two-dimensional matrix of coefficients, corresponding to the lower frequencies, the zig-zag scanning results in an array where usually the last values are zero. This allows for efficient encoding using run-length codes as a part of/before the actual entropy coding.

The H.264/MPEG-4 H.264/MPEG-4 AVC as well as HEVC includes two functional layers, a Video Coding Layer (VCL) and a Network Abstraction Layer (NAL). The VCL provides the encoding functionality as briefly described above. The NAL encapsulates information elements into standardized units called NAL units according to their further application such as transmission over a channel or storing in storage. The information elements are, for instance, the encoded prediction error signal or other information necessary for the decoding of the video signal such as type of prediction, quantization parameter, motion vectors, etc. There are VCL NAL units containing the compressed video data and the related information, as well as non- VCL units encapsulating additional data such as parameter set relating to an entire video sequence, or a Supplemental Enhancement Information (SEI) providing additional information that can be used to improve the decoding performance. Figure 2 illustrates an example decoder 200 according to the H.264/MPEG-4 AVC or HEVC video coding standard. The encoded video signal (input signal to the decoder) first passes to entropy decoder 290, which decodes the quantized coefficients, the information elements necessary for decoding such as motion data, mode of prediction etc. The quantized coefficients are inversely scanned in order to obtain a two-dimensional matrix, which is then fed to inverse quantization and inverse transformation 230. After inverse quantization and inverse transformation 230, a decoded (quantized) prediction error signal e' is obtained, which corresponds to the differences obtained by subtracting the prediction signal from the signal input to the encoder in the case no quantization noise is introduced and no error occurred.

The prediction signal is obtained from either a temporal or a spatial prediction 280. The decoded information elements usually further include the information necessary for the prediction such as prediction type in the case of intra-prediction and motion data in the case of motion compensated prediction. The quantized prediction error signal in the spatial domain is then added with an adder 240 to the prediction signal obtained either from the motion compensated prediction or intra-frame prediction 280. The reconstructed image may be passed through a deblocking filter 250, sample adaptive offset processing 255, and an adaptive loop filter 260 and the resulting decoded signal FU is stored in the memory 270 to be applied for temporal or spatial prediction of the following blocks/images.

State of the art hybrid video coders and decoders, as described above, apply several processing steps, e.g. deblocking, adaptive offset, adaptive loop filter in order to optimize image quality of video images. All of these processing steps correspond to a filtering operation in order to improve subjective or objective image quality. In general, these filtering steps are performed one after the other, as the filtered result serves as an input for the subsequent filtering step. For instance, the sample adaptive offset and/or adaptive loop filter is in general applied after the deblocking filtering. In order to judge, whether or not and/or which filtering processing is applied in the individual steps, a classification is performed. Generally one or more of these filtering steps apply a pixel or block based classification by assigning a classification value which corresponds to a classification category to each pixel or a block. The classification values may be obtained by calculations and/or by applying a categorization based on pixel information of the image. Based on the obtained classification values, the samples are classified into classification categories by assigning the classification values. The classification categories determine the type of processing or more specifically the type of filtering in the case of, for instance, deblocking filtering, adaptive offset filtering and adaptive loop filtering. Figure 3 shows a general processing flow of two subsequent processing steps. Each step firstly calculates, or in general determines, pixel classification values, then classifies pixels according to the calculated classification values and modifies the pixels accordingly. Modifying may or may not include a filtering process depending on the classification. In particular, Fig. 3 shows two subsequent steps, steps 310 and 320, which perform independent calculations of classification values, corresponding to the steps 31 1 and 321 , respectively, which are included in the steps 310 and 320. Based on the respective calculated classification values, the corresponding classification and processing decisions are conducted in steps 312 and 322.

The two processing steps shown in Fig. 3 may be corresponding to a sample adaptive offset filtering and a subsequent adaptive loop filtering. Figure 4 illustrate an example of a sample adaptive offset (SAO) processing according to the JTC-VC document JCTVC-D122, being an input to the 4th meeting in Daegu, KR, 20-28 January, 2011 and also according to the JTC-VC document JCTVC-E049 being an input to the 5th meeting in Geneva, 16-23 March, 201 1. In general, sample adaptive offset may be seen as a kind of filtering of zero-th order. One of adaptive offset methods is called edge offset (EO). It classifies all pixels of a partition or an image area into multiple categories by comparing them with neighboring pixels and compensates the average offset according to each category. The basic concept of EO is to categorize a pixel into a category out of different categories according to their immediate neighborhood and to apply to the pixel a category-dependent offset accordingly. In particular, Figure 4 shows six different example patterns 401 , 402, 403, 404, 405, and 406 corresponding to a pixel "c" and pixels in its neighborhood, which are employed for categorization. Four of the patterns, namely 401 to 404, are one-dimensional patterns and two of them, namely 405 and 406 are two dimensional patterns. Shaded squares in the patterns illustrate those samples in the neighborhood of pixel "c", which are considered when categorizing pixel "c". Tables 410 and 450 show examples of how such categorization may be performed. The example originating from Table 410 shows five categories to which pixel "c" may belong to when considering one of the one-dimensional patterns (masks) 401 to 404, in particular when considering the samples in the shaded (in Figure 4) positions relative to sample "c". For instance, pixel "c" belongs to category 1 when it is smaller than both neighboring pixels of a one-dimensional pattern such as one of 401 to 404. Table 450 shows rules for categorizing pixel "c" according to a two-dimensional pattern such as 405 or 406. These example patterns take four samples neighboring to "c" into account. After having determined a pattern per region, each pixel in a region is categorized into a number of categories (number of categories depending on the selected pixel classification pattern) and an offset value is calculated for each category. The offset value may be the average difference between original and decoded samples. Therefore it may act to correct discrepancy between the original and decoded samples. The determined offset may then be signaled per category within the bitstream. In the above described generalized scheme of processing in Figure 3, the categorization of each pixel may correspond to the calculation of the classification values in step 31 1. The assignment of the same classification values for each pixel in order to classify pixels for modification/processing may correspond to step 312 in Figure 3.

If an image signal is processed by sample adaptive offset filtering, the subsequent processing step may be adaptive loop filtering. An example for an adaptive loop filter, which selects a filter on a block basis, is described in the JCTVC document JCTVC-E323, being an input to the 5th meeting in Geneva, CH, 16-23 March, 2011. As opposed to the HM 2.0 reference model, which classifies each pixel into 16 different categories using a Laplacian based activity metric, the document proposes a metric for a block of pixels. In particular, the metric for filtering decision is based on an averaged Laplacian based activity metric and additional directional information. For this, the Laplacian based activity metric for each pixel is averaged for each 4x4 block, which is illustrated in Figure 5, where block 520 corresponds to block 510 when averaging the value of each pixel in block 510. Thus, each 4x4 block, and in the case of Figure 5 block 520, has one common Laplacian activity value. The additional directional information is computed using a one dimensional activity metric for the block. Depending on the vertical/horizontal activity for each block, it is decided which directional information the 4x4 block contains. With the direction information and the above-mentioned common Laplacian activity value, a final activity metrics for the 4x4 block is determined as a linear combination of direction information and the common Laplacian activity value. This final activity value may represent one classification value for the pixels of a block. This may correspond to step 321 in Figure 3. The assignment of one common classification value to each pixel of the 4x4 block may represent the classification process, which may correspond to step 322 in Figure 3. Based on this classification an encoding or decoding algorithm as in HM2.0, where each pixel is assigned with an individual classification value, is applied to derive filter coefficients for adaptive loop filtering.

However, performing individual calculations of classification values in each step out of subsequent processing steps in order to perform classification requires a high amount of computational operations. SUMMARY OF THE INVENTION

In view of the above existing processing approaches, the present invention aims to provide an efficient classification approach for subsequent processing steps in image processing in order to reduce computational expenses.

It is the particular approach of the present invention to calculate classification values based on the pixels of a first image signal for classification and subsequent processing resulting in a second image signal. Moreover, the second image signal is classified based on the same calculated classification values for processing the second image signal.

According to an aspect of the present invention, a method for processing an image area composed of pixels by subsequent steps is provided, the method comprising the steps of calculating classification values based on a first image signal of pixels corresponding to the image area, classifying the pixels of the first image signal according to a first classification rule based on the calculated classification values, processing the first image signal of the pixels in accordance with the result of the step of classifying the pixels resulting in a second image signal, classifying pixels of the second image signal according to a second classification rule based on the calculated classification values, and processing the second image signal in accordance with the result of the step of classifying the pixels of the second image signal.

According to another aspect of the present invention, an apparatus for processing of an image area composed of pixels is provided, the apparatus comprising a calculation unit configured to calculate classification values based on a first image signal of pixels corresponding to the image area, a first classification unit configured to classify the pixels of the first image signal according to a first classification rule based on the calculated classification values, a first processing unit configured to process the first image signal of the pixels in accordance with the result provided by the first classification unit resulting in a second image signal, a second classification unit configured to classify pixels of the second image signal according to a second classification rule based on the calculated classification values, and a second processing unit configured to process the second image signal in accordance with the result provided by the second classification unit.

The above and other objects and features of the present invention will become more apparent from the following description and preferred embodiments given in conjunction with the accompanying drawings in which: is a block diagram illustrating an example of a state of the art hybrid coder; is a block diagram illustrating an example of a state of the art hybrid decoder; is a schematic drawing illustrating two subsequent processing steps of a state of the art encoder/decoder; is a schematic drawing illustrating the categorization of pixels for sample adaptive offset filtering according to JCTVC-D122; is a schematic drawing illustrating the categorization of pixels for adaptive loop filtering according to JCTVC-E323; is a schematic drawing illustrating two subsequent processing steps according to the present invention; is a schematic drawing illustrating two subsequent processing steps according to an embodiment of the present invention; is a schematic drawing illustrating two subsequent processing steps according to an embodiment of the present invention; is a block diagram illustrating an example of a hybrid coder according to the present invention; is a schematic drawing illustrating an overall configuration of a content providing system for implementing content distribution services; is a schematic drawing illustrating an overall configuration of a digital broadcasting system; is a block diagram illustrating an example of a configuration of a television; is a block diagram illustrating an example of a configuration of an information reproducing/recording unit that reads and writes information from or on a recording medium that is an optical disk; is a schematic drawing showing an example of a configuration of a recording medium that is an optical disk; Figure 15A is a schematic drawing illustrating an example of a cellular phone;

Figure 15B is a block diagram showing an example of a configuration of the cellular phone;

Figure 16 is a schematic drawing showing a structure of multiplexed data;

Figure 17 is a drawing schematically illustrating how each of the streams is multiplexed in multiplexed data;

Figure 18 is a schematic drawing illustrating how a video stream is stored in a stream of

PES packets in more detail;

Figure 19 is a schematic drawing showing a structure of TS packets and source packets in the multiplexed data;

Figure 20 is a schematic drawing showing a data structure of a PMT;

Figure 21 is a schematic drawing showing an internal structure of multiplexed data information;

Figure 22 is a schematic drawing showing an internal structure of stream attribute information;

Figure 23 is a schematic drawing showing steps for identifying video data;

Figure 24 is a schematic block diagram illustrating an example of a configuration of an integrated circuit for implementing the video coding method and the video decoding method according to each of embodiments;

Figure 25 is a schematic drawing showing a configuration for switching between driving frequencies;

Figure 26 is a schematic drawing showing steps for identifying video data and switching between driving frequencies;

Figure 27 is a schematic drawing showing an example of a look-up table in which the standards of video data are associated with the driving frequencies;

Figure 28A is a schematic drawing showing an example of a configuration for sharing a module of a signal processing unit; Figure 28B is a schematic drawing showing another example of a configuration for sharing a module of a signal processing unit;

DETAILED DESCRIPTION

The problem underlying the present invention is based on the observation that the currently employed approaches for performing subsequent processing steps, such as subsequent filtering, lead to rather high computational expenses.

In order to provide a more efficient processing approach, according to the present invention, the values that serve as a basis for classifying pixels in order to judge whether or not and/or which processing is applied, are calculated for one processing step and are reused in the subsequent processing step.

A processing step includes the input of an image signal which may, for example, be an image area or an image block composed of pixels. Further, the processing step includes the classification of the pixels of the input image signal. Finally, the input image signal is processed, for example filtered, in accordance with the classification of the input image signal. In order to classify an input image signal, classification values are assigned to pixels of the input image signal. Therefore, a processing step also includes determining classification values. A classification value may be a calculated value based on pixel values of the input signal. In particular, the classification value may be calculated as a specific metric. As an alternative, a pixel may be categorized and a classification value may be determined by means of a comparison of the pixel value with its neighboring pixel values. Further, a classification value may be understood as a value out of a fixed number of values, where each value corresponds to a classification category. In order to assign the classification values to the pixels of the input image signal, a classification rule needs to be applied. In particular, the classification rule defines how the calculated classification values are to be distributed to the pixels of the image area. For instance, a classification value calculated for each pixel can be simply assigned as the pixel classification. In other words, the pixel class may equal the calculated classification value. As an alternative, a functional relation of the calculated classification values may be assigned to the pixels, such as, for instance, an average of the classification values for a block. If each pixel or the pixel block is classified, it is judged based on the classification whether or not and/or which processing is applied to the pixel or the pixel block. The processing steps may be, for example, deblocking filtering, sample adaptive offset filtering or adaptive loop filtering. For instance, it may be decided if a filter is applied or not, and if it is decided to apply a filter, it is decided which type of filter will be applied in accordance with the classification of the pixels or the block of an input image signal.

As mentioned above, the general approach of the present invention is to only calculate the classification values once in order to apply them for subsequent processing steps. Figure 6 illustrates the general approach of the present invention. A flow chart for the two subsequent processing steps 610 and 620 is shown. The input image signal S' is used for calculating the pixel classification values in step 611. These classification values are then further used in order to classify the pixels of the input image signal S' in step 612. Further, in the same step, the classification is applied in a pixel modification process, which is, for instance a filtering process. Step 612 then provides a processed image S". Depending on the classification of the input image signal, the input image signal can be modified or not. The output image S" of the first step 610 is further processed in the subsequent step 620. Therefore the output image signal S" is provided to step 622, where a classification of the pixels is conducted. The classification of the pixels of image signal S" is performed according to the classification values which are provided from step 611. Thus, no classification values are calculated in step 620. According to the classification carried out in step 622, the image signal S" is processed resulting in an output image S"\ According to the present invention, the calculated classification values of a first processing step are reused in a second processing step for classification. Accordingly, the classification values calculated in the first step are stored and provided for the classification of the pixels in the second step. Hence, the method of the present invention achieves a reduction of the computational operations as classification values are only computed once.

According to an embodiment of the present invention, the first processing step 610 in Figure 6 may correspond to adaptive offset filtering and the second subsequent processing step 620 in may correspond to adaptive loop filtering. Figure 7 is a schematic drawing illustrating the two subsequent processing steps according to the embodiment of the present invention. The first processing step includes the steps 71 1 and 712. In step 711 in Figure 7, the pixel classification values are calculated based on the input signal S'. In particular, the specific calculation of the classification values is based on an approach as in the JCTVC-D122 document. Box 730 in Figure 7 illustrates the categorization of a pixel according to JCTVC-D122, as described above in the background section. In brief, the pixel marked with "c" is categorized in a category from 0 to 4 depending on its pixel value and the two neighboring pixel values in the case of a one dimensional pattern as indicated in the upper part of box 730. Similarly, pixel "c" is categorized in a category from 0 to 6 depending on its pixel value in comparison with the surrounding neighboring pixel values in the case of a two dimensional pattern as illustrated in the lower part of box 730. Thus, the calculation of classification values for a pixel is based on a comparison of the pixel value of the pixel with the pixel values of the neighboring pixels. In particular, the neighboring pixels may be the nearest neighboring pixels. Further, in step 712, the calculated classification values are applied for classifying the pixels of the input image signal S'. The classification process may be conducted by assigning at least one classification value to pixels of the input image signal. In particular, at least one calculated classification value may be assigned to each pixel of the input image signal. In other, words the calculated classification values calculated for each pixel are assigned to the corresponding pixel. According to the classification, the adaptive offset filtering may be conducted and the filtered image signal S" is obtained. This may be similar to the adaptive offset filtering processing as described in document JCTVC-D122. Subsequently, the adaptive offset processed image S" is further processed in the subsequent step, which corresponds to step 722 and may correspond to adaptive loop filtering. In step 722, the pixels of the adaptive offset processed image S" are classified. The classification is conducted in accordance with the classification values which are calculated in step 711 and handed over to step 722. In this particular embodiment, the classification in step 722 is performed by assigning the same classification value to the pixels of the image signal as was assigned to the corresponding pixels of the first input image in step 712. Based on this classification, adaptive loop filtering may be conducted. The filtering processing decision may be similar as pixel based approach of the HM 2.0 reference model or it may be similar to the one indicated in document JCTVC-E323.

According to another embodiment of the present invention, a common classification value for the pixels of a second image signal in the second or subsequent step, which may again correspond to the adaptive offset filtered image, may be assigned based on the calculated classification values of the first image signal of the first processing step. Further, the common classification value may be based on all calculated classification values of the pixels of the first image signal. Furthermore, the common classification value may be an average of all classification values of the pixel of the first image signal. Figure 8 is a schematic drawing illustrating two subsequent processing steps according to this embodiment of the present invention. In particular, the two subsequent steps may again correspond to adaptive offset filtering and a subsequent adaptive loop filtering. The first processing step includes the steps 81 1 and 812. In particular, Figure 8 shows, similar to Figure 7, a calculation of pixel classification values of an input image S' based on the approach as in JCTVC-D122. The calculation of the pixel classification values is conducted in step 811. The specific calculation of classification values is illustrated in box 820, which corresponds to box 720 in Figure 7. Further, in step 812, the pixel classification is conducted, wherein the pixel class equals to calculated classification value. Further, based on the classification, a pixel modification process is applied, which in this case may correspond to an adaptive offset filtering, which may be similar to the process as described as in JCTVC-D122. A processed image signal S" is obtained. Subsequently, in the second processing step is conducted. The adaptive offset filtered image signal S" is classified in step 822. Here, the classification is conducted on a block basis. In particular, the pixel classification values which are calculated in step 81 1 and handed over to step 822 are averaged and applied as a common classification value to each pixel in the block. This is illustrated in box 840. In box 840, the left handed matrix corresponds to the matrix of the classification values calculated in step 81 1 and the right handed matrix corresponds to a common classification value assigned to each pixel of the image signal S". According to the classification, the image signal S" is processed. As a common classification is applied on a block basis, a common processing is also applied on a block basis. The adaptive loop filtering in the second processing step may be conducted similarly to the processing as described in document JCTVC-E323.

Further, the present invention may be implemented as an apparatus for image processing. An apparatus for processing of an image area composed of pixels according to the present invention comprises a calculation unit configured to calculate classification values based on a first image signal of pixels corresponding to the image area, a first classification unit configured to classify the pixels of the first image signal according to a first classification rule based on the calculated classification values, a first processing unit configured to process the first image signal of the pixels in accordance with the result provided by the first classification unit resulting in a second image signal, a second classification unit configured to classify pixels of the second image signal according to a second classification rule based on the calculated classification values, and a second processing unit configured to process the second image signal in accordance with the result provided by the second classification unit.

The apparatus may further comprise a storage unit configured to store the calculated classification values of the pixels of the first image signal, wherein the storage unit is further configured to provide the calculated classification values to the second classification unit.

The first classification unit may be configured to assign at least one classification value to pixels of the first image signal, and the second classification unit may be configured to assign at least one classification value to the pixels of the second image signal. Furthermore the first classification unit may be configured to assign a classification value to each pixel of the first image signal. The calculation unit may be configured to calculate the classification value for a pixel based on a comparison of the pixel value of the pixel with the pixel values of the neighboring pixels. The neigboring pixels may be the nearest neighboring pixels.

The second classification unit may be configured to assign the same classification value assigned to a pixel of the first image signal as the classification value for a corresponding pixel of the second image signal. Further, the second classification unit may alternatively be configured to assign a common classification value for pixels of the second image signal. The common classification value may be based on all calculated classification values of the pixels of the first image signal. Furthermore, the common classification value may be an average of all calculated classification values of the pixels of the first image signal.

According to an embodiment of the present invention the calculation unit, the first classifying unit and the first processing unit may be comprised in an adaptive offset filter and the second classifying unit and the second processing unit may be comprised in an adaptive loop filter. Further, the apparatus for image processing may be implemented in an encoder or decoder. An encoder 900 according to the present invention is shown in Figure 9. Here, the adaptive offset processing unit 955 and the adaptive loop filter 960 correspond to an apparatus for processing an image area according to the present invention.

All embodiments of the present invention as described above can be combined.

The processing described in each of embodiments can be simply implemented in an independent computer system, by recording, in a recording medium, a program for implementing the configurations of the video coding method and the video decoding method described in each of embodiments. The recording media may be any recording media as long as the program can be recorded, such as a magnetic disk, an optical disk, a magnetic optical disk, an IC card, and a semiconductor memory.

Hereinafter, the applications to the video coding method and the video decoding method described in each of embodiments and systems using thereof will be described.

Figure 10 illustrates an overall configuration of a content providing system ex100 for implementing content distribution services. The area for providing communication services is divided into cells of desired size, and base stations ex106, ex107, ex108, ex109, and ex110 which are fixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as a computer ex1 1 1 , a personal digital assistant (PDA) ex112, a camera ex113, a cellular phone ex1 14 and a game machine ex115, via the Internet ex101 , an Internet service provider ex102, a telephone network ex104, as well as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is not limited to the configuration shown in Figure 10, and a combination in which any of the elements are connected is acceptable. In addition, each device may be directly connected to the telephone network ex104, rather than via the base stations ex106 to ex1 10 which are the fixed wireless stations. Furthermore, the devices may be interconnected to each other via a short distance wireless communication and others.

The camera ex1 13, such as a digital video camera, is capable of capturing video. A camera ex116, such as a digital video camera, is capable of capturing both still images and video. Furthermore, the cellular phone ex1 14 may be the one that meets any of the standards such as Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA), Wideband-Code Division Multiple Access (W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access (HSPA). Alternatively, the cellular phone ex1 14 may be a Personal Handyphone System (PHS).

In the content providing system ex100, a streaming server ex103 is connected to the camera ex113 and others via the telephone network ex104 and the base station ex109, which enables distribution of images of a live show and others. In such a distribution, a content (for example, video of a music live show) captured by the user using the camera ex113 is coded as described above in each of embodiments, and the coded content is transmitted to the streaming server ex103. On the other hand, the streaming server ex103 carries out stream distribution of the transmitted content data to the clients upon their requests. The clients include the computer ex111 , the PDA ex112, the camera ex1 13, the cellular phone ex1 14, and the game machine ex115 that are capable of decoding the above-mentioned coded data. Each of the devices that have received the distributed data decodes and reproduces the coded data.

The captured data may be coded by the camera ex113 or the streaming server ex103 that transmits the data, or the coding processes may be shared between the camera ex1 13 and the streaming server ex103. Similarly, the distributed data may be decoded by the clients or the streaming server ex103, or the decoding processes may be shared between the clients and the streaming server ex103. Furthermore, the data of the still images and video captured by not only the camera ex113 but also the camera ex1 16 may be transmitted to the streaming server ex103 through the computer ex11 1. The coding processes may be performed by the camera ex1 16, the computer ex111 , or the streaming server ex103, or shared among them. Furthermore, the coding and decoding processes may be performed by an LSI ex500 generally included in each of the computer ex11 1 and the devices. The LSI ex500 may be configured of a single chip or a plurality of chips. Software for coding and decoding video may be integrated into some type of a recording medium (such as a CD-ROM, a flexible disk, and a hard disk) that is readable by the computer ex1 11 and others, and the coding and decoding processes may be performed using the software. Furthermore, when the cellular phone ex1 14 is equipped with a camera, the image data obtained by the camera may be transmitted. The video data is data coded by the LSI ex500 included in the cellular phone ex1 14.

Furthermore, the streaming server ex103 may be composed of servers and computers, and may decentralize data and process the decentralized data, record, or distribute data.

As described above, the clients may receive and reproduce the coded data in the content providing system ex100. In other words, the clients can receive and decode information transmitted by the user, and reproduce the decoded data in real time in the content providing system ex100, so that the user who does not have any particular right and equipment can implement personal broadcasting.

Aside from the example of the content providing system ex100, at least one of the video coding apparatus and the video decoding apparatus described in each of embodiments may be implemented in a digital broadcasting system ex200 illustrated in Figure 11. More specifically, a broadcast station ex201 communicates or transmits, via radio waves to a broadcast satellite ex202, multiplexed data obtained by multiplexing audio data and others onto video data. The video data is data coded by the video coding method described in each of embodiments. Upon receipt of the multiplexed data, the broadcast satellite ex202 transmits radio waves for broadcasting. Then, a home-use antenna ex204 with a satellite broadcast reception function receives the radio waves.

Next, a device such as a television (receiver) ex300 and a set top box (STB) ex217 decodes the received multiplexed data, and reproduces the decoded data.

Furthermore, a reader/recorder ex218 (i) reads and decodes the multiplexed data recorded on a recording media ex215, such as a DVD and a BD, or (i) codes video signals in the recording medium ex215, and in some cases, writes data obtained by multiplexing an audio signal on the coded data. The reader/recorder ex218 can include the video decoding apparatus or the video coding apparatus as shown in each of embodiments. In this case, the reproduced video signals are displayed on the monitor ex219, and can be reproduced by another device or system using the recording medium ex215 on which the multiplexed data is recorded. It is also possible to implement the video decoding apparatus in the set top box ex217 connected to the cable ex203 for a cable television or to the antenna ex204 for satellite and/or terrestrial broadcasting, so as to display the video signals on the monitor ex219 of the television ex300. The video decoding apparatus may be implemented not in the set top box but in the television ex300.

Figure 12 illustrates the television (receiver) ex300 that uses the video coding method and the video decoding method described in each of embodiments. The television ex300 includes: a tuner ex301 that obtains or provides multiplexed data obtained by multiplexing audio data onto video data, through the antenna ex204 or the cable ex203, etc. that receives a broadcast; a modulation/demodulation unit ex302 that demodulates the received multiplexed data or modulates data into multiplexed data to be supplied outside; and a multiplexing/demultiplexing unit ex303 that demultiplexes the modulated multiplexed data into video data and audio data, or multiplexes video data and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306 including an audio signal processing unit ex304 and a video signal processing unit ex305 that decode audio data and video data and code audio data and video data, respectively; and an output unit ex309 including a speaker ex307 that provides the decoded audio signal, and a display unit ex308 that displays the decoded video signal, such as a display. Furthermore, the television ex300 includes an interface unit ex317 including an operation input unit ex312 that receives an input of a user operation. Furthermore, the television ex300 includes a control unit ex310 that controls overall each constituent element of the television ex300, and a power supply circuit unit ex31 1 that supplies power to each of the elements. Other than the operation input unit ex312, the interface unit ex317 may include: a bridge ex313 that is connected to an external device, such as the reader/recorder ex218; a slot unit ex314 for enabling attachment of the recording medium ex216, such as an SD card; a driver ex315 to be connected to an external recording medium, such as a hard disk; and a modem ex316 to be connected to a telephone network. Here, the recording medium ex216 can electrically record information using a non-volatile/volatile semiconductor memory element for storage. The constituent elements of the television ex300 are connected to each other through a synchronous bus.

First, the configuration in which the television ex300 decodes multiplexed data obtained from outside through the antenna ex204 and others and reproduces the decoded data will be described. In the television ex300, upon a user operation through a remote controller ex220 and others, the multiplexing/demultiplexing unit ex303 demultiplexes the multiplexed data demodulated by the modulation/demodulation unit ex302, under control of the control unit ex310 including a CPU. Furthermore, the audio signal processing unit ex304 decodes the demultiplexed audio data, and the video signal processing unit ex305 decodes the demultiplexed video data, using the decoding method described in each of embodiments, in the television ex300. The output unit ex309 provides the decoded video signal and audio signal outside, respectively. When the output unit ex309 provides the video signal and the audio signal, the signals may be temporarily stored in buffers ex318 and ex319, and others so that the signals are reproduced in synchronization with each other. Furthermore, the television ex300 may read multiplexed data not through a broadcast and others but from the recording media ex215 and ex216, such as a magnetic disk, an optical disk, and a SD card. Next, a configuration in which the television ex300 codes an audio signal and a video signal, and transmits the data outside or writes the data on a recording medium will be described. In the television ex300, upon a user operation through the remote controller ex220 and others, the audio signal processing unit ex304 codes an audio signal, and the video signal processing unit ex305 codes a video signal, under control of the control unit ex310 using the coding method described in each of embodiments. The multiplexing/demultiplexing unit ex303 multiplexes the coded video signal and audio signal, and provides the resulting signal outside. When the multiplexing/demultiplexing unit ex303 multiplexes the video signal and the audio signal, the signals may be temporarily stored in the buffers ex320 and ex321 , and others so that the signals are reproduced in synchronization with each other. Here, the buffers ex318, ex319, ex320, and ex321 may be plural as illustrated, or at least one buffer may be shared in the television ex300. Furthermore, data may be stored in a buffer so that the system overflow and underflow may be avoided between the modulation/demodulation unit ex302 and the multiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration for receiving an AV input from a microphone or a camera other than the configuration for obtaining audio and video data from a broadcast or a recording medium, and may code the obtained data. Although the television ex300 can code, multiplex, and provide outside data in the description, it may be capable of only receiving, decoding, and providing outside data but not the coding, multiplexing, and providing outside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexed data from or on a recording medium, one of the television ex300 and the reader/recorder ex218 may decode or code the multiplexed data, and the television ex300 and the reader/recorder ex218 may share the decoding or coding. As an example, Figure 13 illustrates a configuration of an information reproducing/recording unit ex400 when data is read or written from or on an optical disk. The information reproducing/recording unit ex400 includes constituent elements ex401 , ex402, ex403, ex404, ex405, ex406, and ex407 to be described hereinafter. The optical head ex401 irradiates a laser spot in a recording surface of the recording medium ex215 that is an optical disk to write information, and detects reflected light from the recording surface of the recording medium ex215 to read the information. The modulation recording unit ex402 electrically drives a semiconductor laser included in the optical head ex401 , and modulates the laser light according to recorded data. The reproduction demodulating unit ex403 amplifies a reproduction signal obtained by electrically detecting the reflected light from the recording surface using a photo detector included in the optical head ex401 , and demodulates the reproduction signal by separating a signal component recorded on the recording medium ex215 to reproduce the necessary information. The buffer ex404 temporarily holds the information to be recorded on the recording medium ex215 and the information reproduced from the recording medium ex215. The disk motor ex405 rotates the recording medium ex215. The servo control unit ex406 moves the optical head ex401 to a predetermined information track while controlling the rotation drive of the disk motor ex405 so as to follow the laser spot. The system control unit ex407 controls overall the information reproducing/recording unit ex400. The reading and writing processes can be implemented by the system control unit ex407 using various information stored in the buffer ex404 and generating and adding new information as necessary, and by the modulation recording unit ex402, the reproduction demodulating unit ex403, and the servo control unit ex406 that record and reproduce information through the optical head ex401 while being operated in a coordinated manner. The system control unit ex407 includes, for example, a microprocessor, and executes processing by causing a computer to execute a program for read and write.

Although the optical head ex401 irradiates a laser spot in the description, it may perform high- density recording using near field light.

Figure 14 illustrates the recording medium ex215 that is the optical disk. On the recording surface of the recording medium ex215, guide grooves are spirally formed, and an information track ex230 records, in advance, address information indicating an absolute position on the disk according to change in a shape of the guide grooves. The address information includes information for determining positions of recording blocks ex231 that are a unit for recording data. Reproducing the information track ex230 and reading the address information in an apparatus that records and reproduces data can lead to determination of the positions of the recording blocks. Furthermore, the recording medium ex215 includes a data recording area ex233, an inner circumference area ex232, and an outer circumference area ex234. The data recording area ex233 is an area for use in recording the user data. The inner circumference area ex232 and the outer circumference area ex234 that are inside and outside of the data recording area ex233, respectively are for specific use except for recording the user data. The information reproducing/recording unit 400 reads and writes coded audio, coded video data, or multiplexed data obtained by multiplexing the coded audio and video data, from and on the data recording area ex233 of the recording medium ex215.

Although an optical disk having a layer, such as a DVD and a BD is described as an example in the description, the optical disk is not limited to such, and may be an optical disk having a multilayer structure and capable of being recorded on a part other than the surface. Furthermore, the optical disk may have a structure for multidimensional recording/reproduction, such as recording of information using light of colors with different wavelengths in the same portion of the optical disk and for recording information having different layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data from the satellite ex202 and others, and reproduce video on a display device such as a car navigation system ex211 set in the car ex210, in the digital broadcasting system ex200. Here, a configuration of the car navigation system ex21 1 will be a configuration, for example, including a GPS receiving unit from the configuration illustrated in Figure 12. The same will be true for the configuration of the computer ex1 11 , the cellular phone ex1 14, and others.

Figure 15A illustrates the cellular phone ex1 14 that uses the video coding method and the video decoding method described in embodiments. The cellular phone ex1 14 includes: an antenna ex350 for transmitting and receiving radio waves through the base station ex1 10; a camera unit ex365 capable of capturing moving and still images; and a display unit ex358 such as a liquid crystal display for displaying the data such as decoded video captured by the camera unit ex365 or received by the antenna ex350. The cellular phone ex114 further includes: a main body unit including an operation key unit ex366; an audio output unit ex357 such as a speaker for output of audio; an audio input unit ex356 such as a microphone for input of audio; a memory unit ex367 for storing captured video or still pictures, recorded audio, coded or decoded data of the received video, the still pictures, e-mails, or others; and a slot unit ex364 that is an interface unit for a recording medium that stores data in the same manner as the memory unit ex367. Next, an example of a configuration of the cellular phone ex1 14 will be described with reference to Figure 15B. In the cellular phone ex1 14, a main control unit ex360 designed to control overall each unit of the main body including the display unit ex358 as well as the operation key unit ex366 is connected mutually, via a synchronous bus ex370, to a power supply circuit unit ex361 , an operation input control unit ex362, a video signal processing unit ex355, a camera interface unit ex363, a liquid crystal display (LCD) control unit ex359, a modulation/demodulation unit ex352, a multiplexing/demultiplexing unit ex353, an audio signal processing unit ex354, the slot unit ex364, and the memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation, the power supply circuit unit ex361 supplies the respective units with power from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354 converts the audio signals collected by the audio input unit ex356 in voice conversation mode into digital audio signals under the control of the main control unit ex360 including a CPU, ROM, and RAM. Then, the modulation/demodulation unit ex352 performs spread spectrum processing on the digital audio signals, and the transmitting and receiving unit ex351 performs digital-to-analog conversion and frequency conversion on the data, so as to transmit the resulting data via the antenna ex350.

Also, in the cellular phone ex114, the transmitting and receiving unit ex351 amplifies the data received by the antenna ex350 in voice conversation mode and performs frequency conversion and the analog-to-digital conversion on the data. Then, the modulation/demodulation unit ex352 performs inverse spread spectrum processing on the data, and the audio signal processing unit ex354 converts it into analog audio signals, so as to output them via the audio output unit ex356.

Furthermore, when an e-mail in data communication mode is transmitted, text data of the e-mail inputted by operating the operation key unit ex366 and others of the main body is sent out to the main control unit ex360 via the operation input control unit ex362. The main control unit ex360 causes the modulation/demodulation unit ex352 to perform spread spectrum processing on the text data, and the transmitting and receiving unit ex351 performs the digital-to-analog conversion and the frequency conversion on the resulting data to transmit the data to the base station ex110 via the antenna ex350. When an e-mail is received, processing that is approximately inverse to the processing for transmitting an e-mail is performed on the received data, and the resulting data is provided to the display unit ex358. When video, still images, or video and audio in data communication mode is or are transmitted, the video signal processing unit ex355 compresses and codes video signals supplied from the camera unit ex365 using the video coding method shown in each of embodiments, and transmits the coded video data to the multiplexing/demultiplexing unit ex353. In contrast, during when the camera unit ex365 captures video, still images, and others, the audio signal processing unit ex354 codes audio signals collected by the audio input unit ex356, and transmits the coded audio data to the multiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded video data supplied from the video signal processing unit ex355 and the coded audio data supplied from the audio signal processing unit ex354, using a predetermined method.

Then, the modulation/demodulation unit ex352 performs spread spectrum processing on the multiplexed data, and the transmitting and receiving unit ex351 performs digital-to-analog conversion and frequency conversion on the data so as to transmit the resulting data via the antenna ex350.

When receiving data of a video file which is linked to a Web page and others in data communication mode or when receiving an e-mail with video and/or audio attached, in order to decode the multiplexed data received via the antenna ex350, the multiplexing/demultiplexing unit ex353 demultiplexes the multiplexed data into a video data bit stream and an audio data bit stream, and supplies the video signal processing unit ex355 with the coded video data and the audio signal processing unit ex354 with the coded audio data, through the synchronous bus ex370. The video signal processing unit ex355 decodes the video signal using a video decoding method corresponding to the coding method shown in each of embodiments, and then the display unit ex358 displays, for instance, the video and still images included in the video file linked to the Web page via the LCD control unit ex359. Furthermore, the audio signal processing unit ex354 decodes the audio signal, and the audio output unit ex357 provides the audio.

Furthermore, similarly to the television ex300, a terminal such as the cellular phone ex114 probably have 3 types of implementation configurations including not only (i) a transmitting and receiving terminal including both a coding apparatus and a decoding apparatus, but also (ii) a transmitting terminal including only a coding apparatus and (iii) a receiving terminal including only a decoding apparatus. Although the digital broadcasting system ex200 receives and transmits the multiplexed data obtained by multiplexing audio data onto video data in the description, the multiplexed data may be data obtained by multiplexing not audio data but character data related to video onto video data, and may be not multiplexed data but video data itself.

As such, the video coding method and the video decoding method in each of embodiments can be used in any of the devices and systems described. Thus, the advantages described in each of embodiments can be obtained.

Furthermore, the present invention is not limited to embodiments, and various modifications and revisions are possible without departing from the scope of the present invention.

Video data can be generated by switching, as necessary, between (i) the video coding method or the video coding apparatus shown in each of embodiments and (ii) a video coding method or a video coding apparatus in conformity with a different standard, such as MPEG-2, H.264/AVC, and VC-1.

Here, when a plurality of video data that conforms to the different standards is generated and is then decoded, the decoding methods need to be selected to conform to the different standards. However, since to which standard each of the plurality of the video data to be decoded conform cannot be detected, there is a problem that an appropriate decoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexing audio data and others onto video data has a structure including identification information indicating to which standard the video data conforms. The specific structure of the multiplexed data including the video data generated in the video coding method and by the video coding apparatus shown in each of embodiments will be hereinafter described. The multiplexed data is a digital stream in the MPEG2-Transport Stream format.

Figure 16 illustrates a structure of the multiplexed data. As illustrated in Figure 16, the multiplexed data can be obtained by multiplexing at least one of a video stream, an audio stream, a presentation graphics stream (PG), and an interactive graphics stream. The video stream represents primary video and secondary video of a movie, the audio stream (IG) represents a primary audio part and a secondary audio part to be mixed with the primary audio part, and the presentation graphics stream represents subtitles of the movie. Here, the primary video is normal video to be displayed on a screen, and the secondary video is video to be displayed on a smaller window in the primary video. Furthermore, the interactive graphics stream represents an interactive screen to be generated by arranging the GUI components on a screen. The video stream is coded in the video coding method or by the video coding apparatus shown in each of embodiments, or in a video coding method or by a video coding apparatus in conformity with a conventional standard, such as PEG-2, H.264/AVC, and VC-1. The audio stream is coded in accordance with a standard, such as Dolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. For example, 0x1011 is allocated to the video stream to be used for video of a movie, 0x1100 to 0x1 11 F are allocated to the audio streams, 0x1200 to 0x121 F are allocated to the presentation graphics streams, 0x1400 to 0x141 F are allocated to the interactive graphics streams, 0x1 B00 to 0x1 B1 F are allocated to the video streams to be used for secondary video of the movie, and 0x1 A00 to 0x1 A1 F are allocated to the audio streams to be used for the secondary video to be mixed with the primary audio.

Figure 17 schematically illustrates how data is multiplexed. First, a video stream ex235 composed of video frames and an audio stream ex238 composed of audio frames are transformed into a stream of PES packets ex236 and a stream of PES packets ex239, and further into TS packets ex237 and TS packets ex240, respectively. Similarly, data of a presentation graphics stream ex241 and data of an interactive graphics stream ex244 are transformed into a stream of PES packets ex242 and a stream of PES packets ex245, and further into TS packets ex243 and TS packets ex246, respectively. These TS packets are multiplexed into a stream to obtain multiplexed data ex247.

Figure 18 illustrates how a video stream is stored in a stream of PES packets in more detail. The first bar in Figure 20 shows a video frame stream in a video stream. The second bar shows the stream of PES packets. As indicated by arrows denoted as yy1 , yy2, yy3, and yy4 in Figure 20, the video stream is divided into pictures as I pictures, B pictures, and P pictures each of which is a video presentation unit, and the pictures are stored in a payload of each of the PES packets. Each of the PES packets has a PES header, and the PES header stores a Presentation Time-Stamp (PTS) indicating a display time of the picture, and a Decoding Time-Stamp (DTS) indicating a decoding time of the picture.

Figure 19 illustrates a format of TS packets to be finally written on the multiplexed data. Each of the TS packets is a 188-byte fixed length packet including a 4-byte TS header having information, such as a PID for identifying a stream and a 184-byte TS payload for storing data. The PES packets are divided, and stored in the TS payloads, respectively. When a BD ROM is used, each of the TS packets is given a 4-byte TP_Extra_Header, thus resulting in 192-byte source packets. The source packets are written on the multiplexed data. The TP_Extra_Header stores information such as an Arrival_Time_Stamp (ATS). The ATS shows a transfer start time at which each of the TS packets is to be transferred to a PID filter. The source packets are arranged in the multiplexed data as shown at the bottom of Figure 19. The numbers incrementing from the head of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes not only streams of audio, video, subtitles and others, but also a Program Association Table (PAT), a Program Map Table (PMT), and a Program Clock Reference (PCR). The PAT shows what a PID in a PMT used in the multiplexed data indicates, and a PID of the PAT itself is registered as zero. The PMT stores PIDs of the streams of video, audio, subtitles and others included in the multiplexed data, and attribute information of the streams corresponding to the PIDs. The PMT also has various descriptors relating to the multiplexed data. The descriptors have information such as copy control information showing whether copying of the multiplexed data is permitted or not. The PCR stores STC time information corresponding to an ATS showing when the PCR packet is transferred to a decoder, in order to achieve synchronization between an Arrival Time Clock (ATC) that is a time axis of ATSs, and an System Time Clock (STC) that is a time axis of PTSs and DTSs.

Figure 20 illustrates the data structure of the PMT in detail. A PMT header is disposed at the top of the PMT. The PMT header describes the length of data included in the PMT and others. A plurality of descriptors relating to the multiplexed data is disposed after the PMT header. Information such as the copy control information is described in the descriptors. After the descriptors, a plurality of pieces of stream information relating to the streams included in the multiplexed data is disposed. Each piece of stream information includes stream descriptors each describing information, such as a stream type for identifying a compression codec of a stream, a stream PID, and stream attribute information (such as a frame rate or an aspect ratio). The stream descriptors are equal in number to the number of streams in the multiplexed data.

When the multiplexed data is recorded on a recording medium and others, it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management information of the multiplexed data as shown in Figure 21. The multiplexed data information files are in one to one correspondence with the multiplexed data, and each of the files includes multiplexed data information, stream attribute information, and an entry map. As illustrated in Figure 21 , the multiplexed data includes a system rate, a reproduction start time, and a reproduction end time. The system rate indicates the maximum transfer rate at which a system target decoder to be described later transfers the multiplexed data to a PID filter. The intervals of the ATSs included in the multiplexed data are set to not higher than a system rate. The reproduction start time indicates a PTS in a video frame at the head of the multiplexed data. An interval of one frame is added to a PTS in a video frame at the end of the multiplexed data, and the PTS is set to the reproduction end time.

As shown in Figure 22, a piece of attribute information is registered in the stream attribute information, for each PID of each stream included in the multiplexed data. Each piece of attribute information has different information depending on whether the corresponding stream is a video stream, an audio stream, a presentation graphics stream, or an interactive graphics stream. Each piece of video stream attribute information carries information including what kind of compression codec is used for compressing the video stream, and the resolution, aspect ratio and frame rate of the pieces of picture data that is included in the video stream. Each piece of audio stream attribute information carries information including what kind of compression codec is used for compressing the audio stream, how many channels are included in the audio stream, which language the audio stream supports, and how high the sampling frequency is. The video stream attribute information and the audio stream attribute information are used for initialization of a decoder before the player plays back the information.

The multiplexed data to be used is of a stream type included in the PMT. Furthermore, when the multiplexed data is recorded on a recording medium, the video stream attribute information included in the multiplexed data information is used. More specifically, the video coding method or the video coding apparatus described in each of embodiments includes a step or a unit for allocating unique information indicating video data generated by the video coding method or the video coding apparatus in each of embodiments, to the stream type included in the PMT or the video stream attribute information. With the configuration, the video data generated by the video coding method or the video coding apparatus described in each of embodiments can be distinguished from video data that conforms to another standard.

Furthermore, Figure 23 illustrates steps of the video decoding method. In Step exS100, the stream type included in the PMT or the video stream attribute information is obtained from the multiplexed data. Next, in Step exS101 , it is determined whether or not the stream type or the video stream attribute information indicates that the multiplexed data is generated by the video coding method or the video coding apparatus in each of embodiments. When it is determined that the stream type or the video stream attribute information indicates that the multiplexed data is generated by the video coding method or the video coding apparatus in each of embodiments, in Step exS102, decoding is performed by the video decoding method in each of embodiments. Furthermore, when the stream type or the video stream attribute information indicates conformance to the conventional standards, such as MPEG-2, H.264/AVC, and VC-1 , in Step exS103, decoding is performed by a video decoding method in conformity with the conventional standards.

As such, allocating a new unique value to the stream type or the video stream attribute information enables determination whether or not the video decoding method or the video decoding apparatus that is described in each of embodiments can perform decoding. Even when multiplexed data that conforms to a different standard, an appropriate decoding method or apparatus can be selected. Thus, it becomes possible to decode information without any error. Furthermore, the video coding method or apparatus, or the video decoding method or apparatus can be used in the devices and systems described above.

Each of the video coding method, the video coding apparatus, the video decoding method, and the video decoding apparatus in each of embodiments is typically achieved in the form of an integrated circuit or a Large Scale Integrated (LSI) circuit. As an example of the LSI, Figure 24 illustrates a configuration of the LSI ex500 that is made into one chip. The LSI ex500 includes elements ex501 , ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to be described below, and the elements are connected to each other through a bus ex510. The power supply circuit unit ex505 is activated by supplying each of the elements with power when the power supply circuit unit ex505 is turned on.

For example, when coding is performed, the LSI ex500 receives an AV signal from a microphone ex1 17, a camera ex113, and others through an AV IO ex509 under control of a control unit ex501 including a CPU ex502, a memory controller ex503, a stream controller ex504, and a driving frequency control unit ex512. The received AV signal is temporarily stored in an external memory ex511 , such as an SDRAM. Under control of the control unit ex501 , the stored data is segmented into data portions according to the processing amount and speed to be transmitted to a signal processing unit ex507. Then, the signal processing unit ex507 codes an audio signal and/or a video signal. Here, the coding of the video signal is the coding described in each of embodiments. Furthermore, the signal processing unit ex507 sometimes multiplexes the coded audio data and the coded video data, and a stream IO ex506 provides the multiplexed data outside. The provided multiplexed data is transmitted to the base station ex107, or written on the recording media ex215. When data sets are multiplexed, the data should be temporarily stored in the buffer ex508 so that the data sets are synchronized with each other.

Although the memory ex51 1 is an element outside the LSI ex500, it may be included in the LSI ex500. The buffer ex508 is not limited to one buffer, but may be composed of buffers. Furthermore, the LSI ex500 may be made into one chip or a plurality of chips.

Furthermore, although the control unit ex510 includes the CPU ex502, the memory controller ex503, the stream controller ex504, the driving frequency control unit ex512, the configuration of the control unit ex510 is not limited to such. For example, the signal processing unit ex507 may further include a CPU. Inclusion of another CPU in the signal processing unit ex507 can improve the processing speed. Furthermore, as another example, the CPU ex502 may serve as or be a part of the signal processing unit ex507, and, for example, may include an audio signal processing unit. In such a case, the control unit ex501 includes the signal processing unit ex507 or the CPU ex502 including a part of the signal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and a special circuit or a general purpose processor and so forth can also achieve the integration. Field Programmable Gate Array (FPGA) that can be programmed after manufacturing LSIs or a reconfigurable processor that allows re-configuration of the connection or configuration of an LSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-new technology may replace LSI. The functional blocks can be integrated using such a technology. The possibility is that the present invention is applied to biotechnology.

When video data generated in the video coding method or by the video coding apparatus described in each of embodiments is decoded, compared to when video data that conforms to a conventional standard, such as MPEG-2, H.264/AVC, and VC-1 is decoded, the processing amount probably increases. Thus, the LSI ex500 needs to be set to a driving frequency higher than that of the CPU ex502 to be used when video data in conformity with the conventional standard is decoded. However, when the driving frequency is set higher, there is a problem that the power consumption increases. In order to solve the problem, the video decoding apparatus, such as the television ex300 and the LSI ex500 is configured to determine to which standard the video data conforms, and switch between the driving frequencies according to the determined standard. Figure 25 illustrates a configuration ex800. A driving frequency switching unit ex803 sets a driving frequency to a higher driving frequency when video data is generated by the video coding method or the video coding apparatus described in each of embodiments. Then, the driving frequency switching unit ex803 instructs a decoding processing unit ex801 that executes the video decoding method described in each of embodiments to decode the video data. When the video data conforms to the conventional standard, the driving frequency switching unit ex803 sets a driving frequency to a lower driving frequency than that of the video data generated by the video coding method or the video coding apparatus described in each of embodiments. Then, the driving frequency switching unit ex803 instructs the decoding processing unit ex802 that conforms to the conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includes the CPU ex502 and the driving frequency control unit ex512 in Figure 26. Here, each of the decoding processing unit ex801 that executes the video decoding method described in each of embodiments and the decoding processing unit ex802 that conforms to the conventional standard corresponds to the signal processing unit ex507 in Figure 22. The CPU ex502 determines to which standard the video data conforms. Then, the driving frequency control unit ex512 determines a driving frequency based on a signal from the CPU ex502. Furthermore, the signal processing unit ex507 decodes the video data based on the signal from the CPU ex502. For example, the identification information described is probably used for identifying the video data. The identification information is not limited to the one described above but may be any information as long as the information indicates to which standard the video data conforms. For example, when which standard video data conforms to can be determined based on an external signal for determining that the video data is used for a television or a disk, etc., the determination may be made based on such an external signal. Furthermore, the CPU ex502 selects a driving frequency based on, for example, a look-up table in which the standards of the video data are associated with the driving frequencies as shown in Figure 27. The driving frequency can be selected by storing the look-up table in the buffer ex508 and in an internal memory of an LSI, and with reference to the look-up table by the CPU ex502.

Figure 26 illustrates steps for executing a method. First, in Step exS200, the signal processing unit ex507 obtains identification information from the multiplexed data. Next, in Step exS201 , the CPU ex502 determines whether or not the video data is generated by the coding method and the coding apparatus described in each of embodiments, based on the identification information. When the video data is generated by the video coding method and the video coding apparatus described in each of embodiments, in Step exS202, the CPU ex502 transmits a signal for setting the driving frequency to a higher driving frequency to the driving frequency control unit ex512. Then, the driving frequency control unit ex512 sets the driving frequency to the higher driving frequency. On the other hand, when the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1 , in Step exS203, the CPU ex502 transmits a signal for setting the driving frequency to a lower driving frequency to the driving frequency control unit ex512. Then, the driving frequency control unit ex512 sets the driving frequency to the lower driving frequency than that in the case where the video data is generated by the video coding method and the video coding apparatus described in each of embodiment.

Furthermore, along with the switching of the driving frequencies, the power conservation effect can be improved by changing the voltage to be applied to the LSI ex500 or an apparatus including the LSI ex500. For example, when the driving frequency is set lower, the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set to a voltage lower than that in the case where the driving frequency is set higher.

Furthermore, when the processing amount for decoding is larger, the driving frequency may be set higher, and when the processing amount for decoding is smaller, the driving frequency may be set lower as the method for setting the driving frequency. Thus, the setting method is not limited to the ones described above. For example, when the processing amount for decoding video data in conformity with H.264/AVC is larger than the processing amount for decoding video data generated by the video coding method and the video coding apparatus described in each of embodiments, the driving frequency is probably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limited to the method for setting the driving frequency lower. For example, when the identification information indicates that the video data is generated by the video coding method and the video coding apparatus described in each of embodiments, the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set higher. When the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1 , the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set lower. As another example, when the identification information indicates that the video data is generated by the video coding method and the video coding apparatus described in each of embodiments, the driving of the CPU ex502 does not probably have to be suspended. When the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1 , the driving of the CPU ex502 is probably suspended at a given time because the CPU ex502 has extra processing capacity. Even when the identification information indicates that the video data is generated by the video coding method and the video coding apparatus described in each of embodiments, in the case where the CPU ex502 has extra processing capacity, the driving of the CPU ex502 is probably suspended at a given time. In such a case, the suspending time is probably set shorter than that in the case where when the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switching between the driving frequencies in accordance with the standard to which the video data conforms. Furthermore, when the LSI ex500 or the apparatus including the LSI ex500 is driven using a battery, the battery life can be extended with the power conservation effect.

There are cases where a plurality of video data that conforms to different standards, is provided to the devices and systems, such as a television and a mobile phone. In order to enable decoding the plurality of video data that conforms to the different standards, the signal processing unit ex507 of the LSI ex500 needs to conform to the different standards. However, the problems of increase in the scale of the circuit of the LSI ex500 and increase in the cost arise with the individual use of the signal processing units ex507 that conform to the respective standards.

In order to solve the problem, what is conceived is a configuration in which the decoding processing unit for implementing the video decoding method described in each of embodiments and the decoding processing unit that conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1 are partly shared. Ex900 in Figure 28A shows an example of the configuration. For example, the video decoding method described in each of embodiments and the video decoding method that conforms to H.264/AVC have, partly in common, the details of processing, such as entropy coding, inverse quantization, deblocking filtering, and motion compensated prediction. The details of processing to be shared may include use of a decoding processing unit ex902 that conforms to H.264/AVC. In contrast, a dedicated decoding processing unit ex901 is probably used for other processing unique to the present invention. Since the present invention is characterized by application of deblocking filtering, for example, the dedicated decoding processing unit ex901 is used for such filtering. Otherwise, the decoding processing unit is probably shared for one of the entropy decoding, inverse quantization, spatial or motion compensated prediction, or all of the processing. The decoding processing unit for implementing the video decoding method described in each of embodiments may be shared for the processing to be shared, and a dedicated decoding processing unit may be used for processing unique to that of H.264/AVC.

Furthermore, ex1000 in Figure 28B shows another example in that processing is partly shared. This example uses a configuration including a dedicated decoding processing unit ex1001 that supports the processing unique to the present invention, a dedicated decoding processing unit ex1002 that supports the processing unique to another conventional standard, and a decoding processing unit ex1003 that supports processing to be shared between the video decoding method in the present invention and the conventional video decoding method. Here, the dedicated decoding processing units ex1001 and ex1002 are not necessarily specialized for the processing of the present invention and the processing of the conventional standard, respectively, and may be the ones capable of implementing general processing. Furthermore, the configuration can be implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing the cost are possible by sharing the decoding processing unit for the processing to be shared between the video decoding method in the present invention and the video decoding method in conformity with the conventional standard.

Most of the examples have been outlined in relation to an H.264/AVC based video coding system, and the terminology mainly relates to the H.264/AVC terminology. However, this terminology and the description of the various embodiments with respect to H.264/AVC based coding is not intended to limit the principles and ideas of the invention to such systems. Also the detailed explanations of the encoding and decoding in compliance with the H.264/AVC standard are intended to better understand the exemplary embodiments described herein and should not be understood as limiting the invention to the described specific implementations of processes and functions in the video coding. Nevertheless, the improvements proposed herein may be readily applied in the video coding described. Furthermore the concept of the invention may be also readily used in the enhancements of H.264/AVC coding and/or HEVC currently discussed by the JCT-VC.

To summarize, the present invention relates to image processing which is conducted in subsequent image processing steps requiring classification of pixels, which may be advantageously applied for encoding and decoding of image or video signal. In particular, the present invention relates to performing an efficient classification in subsequent image processing steps. This is achieved by determining values that serve as a basis for classifying pixels in order to judge whether or not and/or which processing is applied, and then applying the same values as a basis in the subsequent processing step.

Claims

A method for processing an image area composed of pixels by subsequent steps, the method comprising the steps of: calculating classification values based on a first image signal of pixels

corresponding to the image area, classifying the pixels of the first image signal according to a first classification rule based on the calculated classification values, processing the first image signal of the pixels in accordance with the result of the step of classifying the pixels resulting in a second image signal, classifying pixels of the second image signal according to a second classification rule based on the calculated classification values, and processing the second image signal in accordance with the result of the step of classifying the pixels of the second image signal.

A method according to claim 1 , further comprising the step of: storing the calculated classification values of the pixels of the first image signal, and providing the calculated classification values to the step of classifying pixels of the second image signal.

3. The method according to claim 1 or 2, wherein the step of classifying the pixels according to a first classification rule based on the calculated classification values, comprises the step of: assigning at least one classification value to pixels of the first image signal, and wherein the step of classifying pixels of the second image signal according to a second classification rule based on the calculated classification values comprises the step of: assigning at least one classification value to the pixels of the second image signal.

The method according to any of the claims 2 to 3, wherein in the step of assigning at least one classification value to pixels of the first image signal, a classification value is assigned to the each pixel of the first image signal.

The method according to any of the claims 1 to 4, wherein in the step calculating classification values, the calculation of the classification value for a pixel is based on a comparison of the pixel value of the pixel with the pixel values of the neighboring pixels.

The method according to claim 5, wherein the neighboring pixels are the nearest neighboring pixels.

The method according to any of the claims 4 to 6, wherein in the step of assigning at least one classification value to the pixels of the second image signal, the same classification value assigned to a pixel of the first image signal is assigned as the classification value of a corresponding pixel of the second image signal.

8. The method according to any of the claims 4 to 6, wherein in the step of assigning at least one classification value to the pixels of the second image, a common classification value for the pixels of the second image signal is assigned.

9. The method according to claim 8, wherein the common classification value is based on all calculated classification values of the pixels of the first image signal.

10. The method according to claim 9, wherein the common classification value is an average of all classification values of the pixels of the first image signal.

1 1 . The method according to any of the claims 1 to 10, wherein processing the first image signal corresponds to adaptive offset filtering and processing the second image signal corresponds to adaptive loop filtering.

12. The method according to any of the claims 1 to 1 1 , wherein the image area is an image block composed of pixels.

13. A method for encoding an image area composed of pixels, the method comprising the steps of: compressing and reconstructing the image area, and applying processing to the reconstructed area according to any of the claims 1 to 12.

14. A method for decoding a coded image area composed of pixels, the method comprising the steps of: reconstructing the coded image area, and applying processing according to any of the claims 1 to 12 to the reconstructed image area.

A computer program product comprising a computer-readable medium having computer-readable program code embodied thereon, the program code being adapted to carry out the method according to any of the claims 1 to 12.

16. An apparatus for processing of an image area composed of pixels, the apparatus comprising: a calculation unit configured to calculate classification values based on a first image signal of pixels corresponding to the image area, a first classification unit configured to classify the pixels of the first image signal according to a first classification rule based on the calculated classification values, a first processing unit configured to process the first image signal of the pixels in accordance with the result provided by the first classification unit resulting in a second image signal, a second classification unit configured to classify pixels of the second image signal according to a second classification rule based on the calculated classification values, and a second processing unit configured to process the second image signal in accordance with the result provided by the second classification unit.

17. The apparatus according to claim 16, wherein the apparatus unit further comprises: a storage unit configured to store the calculated classification values of the pixels of the first image signal, wherein the storage unit is further configured to provide the calculated classification values to the second classification unit.

18. The apparatus according to claim 16 or 17, wherein the first classification unit is configured to assign at least one classification value to pixels of the first image signal, and wherein the second classification unit is configured to assign at least one classification value to the pixels of the second image signal.

19. The apparatus according to claim 18, wherein in the first classification unit is configured to assign a classification value to each pixel of the first image signal.

20. The apparatus according to claim 16 or 19, wherein in the calculation unit is

configured to calculate the classification value for a pixel is based on a

comparison of the pixel value of the pixel with the pixel values of the neighboring pixels.

21 . The apparatus according to claim 20, wherein the neigboring pixels are the

nearest neighboring pixels.

22. The apparatus according to any of the claims 18 to 21 , wherein the second classification unit is configured to assign the same classification value assigned to the a pixel of the first image signal as the classification value for a corresponding pixel of the second image signal.

23. The apparatus according to any of the claims 18 to 21 , wherein the second

classification unit is configured to assign a common classification value for pixels of the second image signal.

24. The apparatus according to claim 23, wherein the common classification value is based on all calculated classification values of the pixels of the first image signal.

25. The apparatus according to claim 24, wherein the common classification value is an average of all calculated classification values of the pixels of the first image signal.

26. The apparatus according to any of the claims 16 to 25, wherein the calculation unit, the first classifying unit and the first processing unit are comprised in an adaptive offset filter and wherein the second classifying unit and the second processing unit are comprised in an adaptive loop filter.

27. An apparatus for encoding an image area composed of pixels, the apparatus comprising: an encoder with a decoder for compressing and reconstructing the current area, and an apparatus for processing the reconstructed area according to any of the claims 16 to 26.

An apparatus for decoding a coded image area composed of pixels, the apparatus comprising: a decoder for reconstructing the coded image area, and an apparatus for processing the reconstructed image area according to any of the claims 16 to 26.

29. An integrated circuit for embodying the apparatus according to any of the claims 16 to 26, comprising a memory for storing pixels to be processed.