JP2008252346A - Image encoder and image encoding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to efficiently determine an optimal intra prediction mode without increasing electric power consumption and cost. <P>SOLUTION: In an intra 16×16 prediction, a Cost value is calculated using reference pixel data which have been stored in a prior-to-filter reference frame memory 114 and have been encoded. In an intra 4×4 prediction, for the sake of performing a parallel process, a Cost value is calculated using pixel data of an original image stored in a frame memory 101 to determine the intra prediction mode. As a result, the electric power consumption and the cost are allowed to prevent increasing, so that it is made possible that the intra prediction mode can be efficiently determined. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image encoding device, an image encoding method, a program, and a recording medium, and more particularly to a technique suitable for use in encoding / decoding a moving image by intra prediction.

  In recent years, the digitalization of information related to multimedia has been rapidly progressing, and the demand for higher image quality of video information has increased accordingly. As a specific example, a transition from the conventional SD (standard image quality) of 720 × 480 pixels to HD (high image quality) of 1920 × 1080 pixels is being performed in broadcasting media.

  However, this demand for high image quality causes an increase in digital data at the same time, and a compression encoding technique and a decoding technique that exceed conventional performance are required. In response to these requests, standardization work for an encoding / compression method using an inter-frame prediction method (inter prediction method) using correlation between images in the activities of ITU-T SG16 and ISO / IEC JTC1 / SC29 / WG11 is proceeding. It has been.

  Among these coding and compression systems, H.264 is the coding system that is said to achieve the most efficient coding at present. H.264 / MPEG-4 PART10: AVC (hereinafter referred to as H.264). And H. One of the characteristic techniques introduced in the H.264 method is an intra prediction method that uses the intra-frame correlation and predicts the pixel value in the same frame using the intra-frame pixel value.

  H. In the H.264 intra prediction scheme, a plurality of prediction block sizes / prediction directions are defined (hereinafter referred to as an intra prediction mode). For example, there are four types of prediction directions in intra 16 × 16 prediction that determines a prediction direction based on block data of 16 × 16 pixels. In addition, there are nine types of prediction directions in intra 4 × 4 prediction that determines a prediction direction based on block data of 4 × 4 pixels. The details of the intra prediction mode are disclosed in standards and various technical documents, and thus detailed description thereof is omitted. H. In H.264, highly efficient encoding is realized by selecting the most appropriate one of these intra prediction modes.

  In general, the intra prediction method predicts a processing target pixel block by using information of encoded adjacent pixel blocks. At that time, it is known that a large amount of arithmetic processing is required to determine an optimal intra prediction mode from among a plurality of intra prediction modes. Thus, proposals have been made to reduce the processing related to intra prediction as much as possible. For example, Patent Document 1 proposes a technique for determining a prediction direction by detecting image features using Hadamard transform and selecting an intra prediction mode.

JP 2006-5659 A

  In this way, H.C. The H.264 system has many intra prediction modes, and blocks are further subdivided as compared with the conventional MPEG. Therefore, enormous calculation is required to determine the intra prediction mode. In particular, when performing encoding processing in real time, a very high speed processor is required to perform the encoding processing at a high speed, resulting in a problem that equipment becomes expensive and power consumption increases. was there.

  Therefore, in order to speed up the encoding process, a method of performing the processing of a plurality of blocks in parallel can be considered. However, when processing of a plurality of blocks is performed in parallel, local decoded pixels of the encoded adjacent pixel block necessary for determining the intra prediction mode may not be generated. In this case, since the intra prediction mode cannot be determined until the local decode pixel is generated, there is a problem that the processing efficiency for determining the intra prediction mode is lowered.

  From the above, it has been very difficult to realize a moving picture coding apparatus that can achieve low power consumption and low cost and efficiently determine optimal intra prediction coding. In addition, as described in Patent Document 1, it is effective to provide a circuit for determining the characteristics of an image in the preceding stage of the encoding circuit. However, providing such a determination circuit increases power consumption and costs. There was a problem that it became too large to ignore.

  An object of the present invention is to make it possible to efficiently determine an optimal intra prediction mode without increasing power consumption and cost in view of the above-described problems.

  The image coding apparatus according to the present invention outputs predicted image data to a pixel block constituting an image according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes. An image encoding device that generates and encodes a prediction for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block Intra prediction mode determining means for determining a mode is provided.

  The image coding method according to the present invention provides, for a pixel block constituting an image, predicted image data according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes. An image encoding method for generating and encoding, wherein prediction is performed for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block. It has the intra prediction mode determination process which determines a mode, It is characterized by the above-mentioned.

  The program of the present invention generates predicted image data for a pixel block constituting an image according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes. A program executed by a computer to perform encoding, and prediction for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block A computer is caused to execute an intra prediction mode determination step for determining a mode.

  The recording medium of the present invention is characterized by recording the program described above.

  According to the present invention, since the prediction mode is determined using the pixel data of the unencoded original image adjacent to the pixel block, the intra prediction mode is determined even if no local decode pixel is generated. be able to. Therefore, the optimal intra prediction mode can be determined efficiently without increasing power consumption and cost. Thereby, an encoding process can be performed at high speed.

(First embodiment)
Hereinafter, a preferred embodiment of an image encoding device according to the present invention will be described in detail with reference to FIGS. 1 to 4 and 7.
FIG. 1 is a block diagram illustrating a functional configuration example of an image encoding device according to the present embodiment.
As illustrated in FIG. 1, the image encoding device 100 includes a frame memory 101, a post-filter reference frame memory 102, a motion prediction unit 103, a motion compensation unit 104, an intra prediction unit 105, and an orthogonal transform unit 106. , And a quantizing unit 107. Furthermore, the image encoding device 100 includes an entropy encoding unit 108, an inverse quantization unit 109, an inverse orthogonal transform unit 110, a switch 111, a subtractor 112, an adder 113, and a pre-filter reference frame memory 114. And a loop filter 115.

  In the above configuration, first, a method for encoding an input image will be described. The frame memory 101 stores input images (original images) in the order of display, and sequentially transmits the encoding target blocks to the motion prediction unit 103, the intra prediction unit 105, and the subtractor 112 in the order of encoding.

  The filtered reference frame memory 102 stores the filtered encoded image as a reference image, and sequentially transmits the reference image data of the encoding target block to the motion prediction unit 103 and the motion compensation unit 104 in the encoding order. . In addition, the pre-filter reference frame memory 114 stores the encoded image before the filtering process as reference image data, and sequentially transmits the reference image data of the encoding target block to the intra prediction unit 105 in the encoding order.

  The subtractor 112 subtracts the predicted image block (predicted image data) transmitted from the switch 111 from the encoding target block transmitted from the frame memory 101, and outputs the image residual data to the orthogonal transform unit 106. A method for generating a predicted image block will be described later. The orthogonal transform unit 106 performs orthogonal transform processing on the image residual data output from the subtractor 112 and transmits transform coefficients to the quantization unit 107.

  The quantization unit 107 quantizes the transform coefficient transmitted from the orthogonal transform unit 106 using a predetermined quantization parameter, and transmits the quantized unit to the entropy coding unit 108 and the inverse quantization unit 109. The entropy encoding unit 108 receives the transform coefficient quantized by the quantization unit 107, performs entropy encoding such as CAVLC and CABAC, and outputs the encoded data.

  Next, a method for generating reference image data using the transform coefficient quantized by the quantization unit 107 will be described. The inverse quantization unit 109 inversely quantizes the transform coefficient quantized by the quantization unit 107. The inverse orthogonal transform unit 110 performs inverse orthogonal transform on the transform coefficient inversely quantized by the inverse quantization unit 109, generates decoded residual data, and transmits the decoded residual data to the adder 113.

  The adder 113 adds the decoded residual data and the predicted image data to generate reference image data, and stores it in the pre-filter reference frame memory 114 as pre-filter reference image data. The reference image data is also transmitted to the loop filter 115. The loop filter 115 filters the reference image data to remove noise, and stores the filtered reference image data in the filtered reference frame memory 102 as filtered reference image data.

  Next, a method for generating predicted image data using the above-described input image data, pre-filter reference image data, and post-filter reference image data will be described. The motion prediction unit 103 uses the coding target block transmitted from the frame memory 101 and the filtered reference image data transmitted from the filtered reference frame memory 102 to move the coding target block in the filtered reference image data. A motion vector representing the quantity is detected. Then, the motion vector detected together with the number of the filtered reference image data is transmitted to the motion compensation unit 104.

  The motion compensation unit 104 uses the motion vector sent from the motion prediction unit 103 to refer to the reference frame image indicated by the number of the filtered reference image data in the filtered reference frame memory 102 to predict each block. Generate image data. Then, the generated predicted image data is transmitted to the switch 111.

  On the other hand, the intra prediction unit 105 functions as an intra prediction mode determination unit, and performs intra prediction using an encoding target block transmitted from the frame memory 101 and original image data around the encoding target block. Then, an appropriate intra prediction mode is selected to generate predicted image data. As described above, the peripheral pixels of the encoding target block are not encoded by using the peripheral pixel data of the encoding target block of the original image, instead of using the peripheral pixels of the encoding target block which has already been encoded. However, the intra prediction mode can be determined. Thereby, the encoding process can be speeded up.

  The switch 111 selects appropriate predicted image data from the predicted image data transmitted from the motion compensation unit 104 or the intra prediction unit 105 and transmits the selected predicted image data to the subtractor 112. Note that, as a method of selecting appropriate prediction image data, for example, a method of selecting an image with a small sum of absolute values of image residuals between an encoding target block and reference image data can be cited. Any selection method may be used.

Next, a method of generating predicted image data in an intra prediction mode that can be selected by the intra prediction unit 105 will be described with reference to FIG.
First, a method of generating predicted image data in an intra prediction mode that can be selected by intra 16 × 16 prediction will be described. Here, it is assumed that the pixel data belonging to the encoding target block is P (x, y). Here, x and y indicate the position in the row direction and the column direction of the matrix pixel data constituting the block, and are integers from 0 to 15. Further, pixel data adjacent to the encoding target block in the vertical direction or the horizontal direction are set to P (x, −1) and P (−1, y), respectively. It should be noted that adjacent pixel data is determined as “unavailable” when it belongs to a different picture or different slice from the encoding target block.

[Prediction mode 0]
The prediction mode 0 is a mode in which vertical (vertical) prediction is performed, and is applied when P (x, −1) is “available”. In this case, in the vertical (vertical) prediction, the pixel data Pred (x, y) of the predicted image data PI is generated using the following equation (1).

[Prediction mode 1]
The prediction mode 1 is a mode for performing horizontal prediction, and is applied when P (−1, y) is “available”. In this case, in horizontal (horizontal) prediction, pixel data Pred (x, y) of the predicted image data PI is generated using the following equation (2).

[Prediction mode 2]
Prediction mode 2 is a mode in which DC prediction is performed. In intra 16 × 16 prediction, pixel data Pred (x, y) of predicted image data PI is generated as described below. First, when all of P (x, −1) and P (−1, y) are “available”, the pixel data Pred (x, y) of the predicted image data PI is used for intra 16 × 16 prediction. Is generated using the following equation (3).

（ここで、「＞＞Ｘ」（Ｘ：自然数）とは、２^Xで割って小数点以下を切り捨てるという意味である。以下も同様。）

(Here, “>> X” (X: natural number) means to divide by 2 ^X and round down the decimal point. The same shall apply hereinafter.)

  When P (x, −1) is unavailable, the pixel data Pred (x, y) of the predicted image data PI is generated using the following equation (4).

  On the other hand, when P (−1, y) is unavailable, the pixel data Pred (x, y) of the predicted image data PI is generated using the following equation (5).

  Furthermore, when P (x, −1) and P (−1, y) are all unavailable, “128” is used as the pixel data Pred (x, y) of the predicted image data PI.

[Prediction mode 3]
The prediction mode 3 is a mode for performing plane prediction, and is applied when all of P (x, −1) and P (−1, y) are “available”. In this case, in the plane prediction, the pixel data Pred (x, y) of the predicted image data PI is generated using the formula shown in the following formula 6.

  Next, a method for generating predicted image data in a prediction mode that can be selected by intra 4 × 4 prediction will be described with reference to FIG. FIG. 4 is a diagram illustrating a positional relationship between pixel data a to p belonging to a 4 × 4 block that is an encoding process target of intra 4 × 4 prediction and pixel data A to M belonging to the periphery of the block data. . Predicted image data PI is generated based on the predicted values of the pixel data a to p. The pixel data A to M are determined to be “unavailable” when they belong to a different picture or a different slice from the encoding target block.

[Prediction mode 0]
The prediction mode 0 is a mode in which vertical (vertical) prediction is performed, and is applied when all of the pixel data A to D illustrated in FIG. 4 are “available”. In this case, the vertical prediction generates the prediction values of the pixel data a to p of the encoding target block using the pixel data A to D as follows.
a, e, i, m: A,
b, f, j, n: B,
c, g, k, o: C,
d, h, l, p: D

[Prediction mode 1]
The prediction mode 1 is a mode for performing horizontal prediction, and is applied when all of the pixel data I to L shown in FIG. 4 are “available”. In this case, the horizontal prediction generates prediction values of the pixel data a to p of the encoding target block using the pixel data I to L as follows.
a, b, c, d: I,
e, f, g, h: J,
i, j, k, l: K,
m, n, o, p: L

[Prediction mode 2]
The prediction mode 2 is a mode for performing DC prediction. When all of the pixel data A to D and I to L shown in FIG. 4 are “available”, the pixel data a to p of the encoding target block are changed. The predicted value is generated by the following equation 7 using the pixel data A to D and I to L.

  Further, when all of the pixel data A to D shown in FIG. 4 are unavailable, the predicted values of the pixel data a to p of the encoding target block are expressed by the following formula 8 using the pixel data I to L. Generate by expression.

  On the other hand, when all of the pixel data I to L shown in FIG. 4 are unavailable, the predicted values of the pixel data a to p of the encoding target block are expressed by the following Equation 9 using the pixel data A to D. Generate by expression.

  Furthermore, when all of the pixel data A to D and I to L illustrated in FIG. 4 are unavailable, the predicted value “128” of the pixel data a to p of the encoding target block is used.

[Prediction mode 3]
The prediction mode 3 is a mode for performing Diagonal_Down_Left prediction, and is applied when all of the pixel data A to D and I to M shown in FIG. 4 are “available”. In this case, the Diagonal_Down_Left prediction generates prediction values of the pixel data a to p of the encoding target block using the pixel data A to D and I to M according to the following equation (10).

[Prediction mode 4]
The prediction mode 4 is a mode for performing Diagonal_Down_Right prediction, and is applied when all of the pixel data A to D and I to M shown in FIG. 4 are “available”. In this case, the prediction values of the pixel data a to p of the encoding target block are generated by the following equation 11 using the pixel data A to D and I to M.

[Prediction mode 5]
The prediction mode 5 is a mode in which Diagonal_Vertical_Right prediction is performed, and is applied when all of the pixel data A to D and I to M shown in FIG. 4 are “available”. In this case, the prediction values of the pixel data a to p of the encoding target block are generated by the following equation 12 using the pixel data A to D and I to M.

[Prediction mode 6]
The prediction mode 6 is a mode in which Horizontal_Down prediction is performed, and is applied when all of the pixel data A to D and I to M illustrated in FIG. 4 are “available”. In this case, the prediction values of the pixel data a to p of the encoding target block are generated using the pixel data A to D and I to M according to the following equation (13).

[Prediction mode 7]
The prediction mode 7 is a mode for performing Vertical_Left prediction, and is applied when all of the pixel data A to D and I to M illustrated in FIG. 4 are “available”. In this case, the prediction values of the pixel data a to p of the encoding target block are generated using the pixel data A to D and I to M according to the following equation (14).

[Prediction mode 8]
The prediction mode 8 is a mode for performing Horizontal_Up prediction, and is applied when all of the pixel data A to D and I to M shown in FIG. 4 are “available”. In this case, the prediction values of the pixel data a to p of the encoding target block are generated by the following equation 17 using the pixel data A to D and I to M.

  In intra 16 × 16 prediction, prediction mode 1 is a mode having high correlation (weighting) in the horizontal direction, and prediction mode 0 is a mode having high correlation (weighting) in the vertical direction. Further, prediction modes 2 and 3 are modes in which weighting in the horizontal direction and the vertical direction is hardly performed.

  In intra 4 × 4 prediction, prediction modes 1, 6, and 8 are modes with high correlation (weighting) in the horizontal direction, and prediction modes 0, 5, and 7 have high correlation in the vertical direction. This is a mode with (weighting). The prediction modes 2, 3, and 4 are modes in which weighting in the horizontal direction and the vertical direction is hardly performed.

  Hereinafter, with respect to the process of determining the intra prediction mode, the block diagram shown in FIG. 2, the flowchart shown in FIG. 3, and the diagram for explaining the order of intra prediction of 4 × 4 block data in the macroblock shown in FIG. The description will be given with reference. In the present embodiment, the processing of 4 × 4 block data is realized by parallel processing.

FIG. 2 is a block diagram illustrating a detailed functional configuration example of the intra prediction unit 105 according to the present embodiment.
As shown in FIG. 2, the intra prediction unit 105 includes an intra 16 × 16 prediction unit 201, an intra 4 × 4 prediction unit 202, an intra prediction mode setting unit 203, and an intra 16 × 16 mode-specific cost storage unit 204. It has. Further, the intra prediction unit 105 includes an intra 4 × 4 mode-specific cost storage unit 205, an intra 16 × 16 best mode determination unit 206, an intra 4 × 4 best mode determination unit 207, and a best intra prediction mode determination unit 208. It has. The “cost (Cost value)” means a so-called evaluation value obtained by calculation.

  Next, the process of selecting the intra prediction mode in the configuration described above will be described with reference to the flowchart of FIG. In the present embodiment, intra 16 × 16 prediction with a small number of blocks selects an intra prediction mode in order, and intra 4 × 4 prediction with a large number of blocks is processed in two in parallel in order to speed up the processing. Shall be performed.

  The intra prediction mode setting unit 203 sequentially sets the four types of prediction modes for the intra 16 × 16 prediction unit 201. Further, the nine types of prediction modes are set in order for the intra 4 × 4 prediction unit 202. Then, the pre-filter reference frame memory 114 outside the intra prediction unit 105 is instructed to transmit reference image data required in the set intra prediction mode to the intra 16 × 16 prediction unit 201. In addition, it instructs the intra 4 × 4 prediction unit 202 to transmit reference image data required in the intra prediction mode set in the frame memory 101 outside the intra prediction unit 105 (step S301).

  In this way, for 4 × 4 block data in which the peripheral block of the encoding target block may not be encoded, the reference image data is used as the reference image data instead of the encoded peripheral pixel. Use original image data. Therefore, the intra prediction mode can be determined even if the surrounding pixels of the block to be encoded are not encoded, and the encoding process can be speeded up.

  The intra 16 × 16 prediction unit 201 uses the reference image data transmitted from the pre-filter reference frame memory 114 to generate each prediction block data by the method described above. Further, the intra 4 × 4 prediction unit 202 uses the reference image data transmitted from the frame memory 101 to generate each prediction block data by the method described above.

  Next, the prediction error (Cost value) in the prediction mode set using the encoding target data transmitted from the frame memory 101 outside the intra prediction unit 105 and the header data added by the entropy encoding unit 108. ) Is calculated using the following equation (18). Then, the intra 16 × 16 prediction unit 201 transmits the cost value by prediction size and the prediction mode at that time to the cost storage unit 204 by intra 16 × 16 mode. Also, the intra 4 × 4 prediction unit 202 transmits the cost value for each predicted size and the prediction mode at that time to the cost storage unit 205 for each intra 4 × 4 mode (step S302).

In the equation shown in Equation 16, “n” uses a value of “16” or “4” depending on whether it is intra 16 × 16 prediction or intra 4 × 4 prediction. Org (i, j) is the pixel value at the pixel position (i, j) when the upper left of the encoding target data is (0,0) and the lower right is (n, n), Pred (mode, i , j) is also the pixel value of the pixel position (i, j) of the predicted image data. SAD ₀ (mode) represents the number of bits of the header data, and QP ₀ is a coefficient that associates the quantization parameter QP with the quantization scale actually used for quantization.

  Next, in step S303, the intra prediction mode setting unit 203 determines whether or not computation has been performed in all modes. As a result of the determination, if there is a mode in which no calculation is performed, the process proceeds to step S304, and the intra prediction mode setting unit 203 sets a prediction mode different from the selected prediction mode. Then, it returns to step S302 and the intra 16x16 prediction part 201 or the intra 4x4 prediction part 202 repeats a process.

  On the other hand, as a result of the determination in step S303, when the prediction error calculation is performed for all prediction modes, the intra 16 × 16 mode-specific cost storage unit 204 sets the stored prediction mode and cost value to the intra 16 × 16. This is transmitted to the best mode determination unit 206. The intra 4 × 4 mode-specific cost storage unit 205 transmits the stored prediction mode and cost value to the intra 4 × 4 best mode determination unit 207. Then, each of the intra 16 × 16 best mode determination unit 206 and the intra 4 × 4 best mode determination unit 207 selects a prediction mode with the smallest Cost value from the transmitted prediction modes as the best mode for each predicted size. Then, the selected best mode by prediction size is transmitted to the best intra prediction mode determination unit 208 together with the Cost value (step S305).

  Next, the best intra prediction mode determination unit 208 adds the Cost value transmitted from the intra 4 × 4 best mode determination unit 207 until the block size reaches 16 × 16 (that is, 16 × 16/4 × 4 = Add 16 times). Then, the Cost value transmitted from the intra 16 × 16 best mode determining unit 206 is compared with the sum of the 16 Cost values transmitted from the intra 4 × 4 best mode determining unit 207. Then, the mode of the prediction size with a small value is determined as the final intra prediction mode (step S306), and the process ends.

Here, an example of parallel processing will be described with reference to FIG.
Values “0” to “15” given to the respective blocks shown in FIG. 7 indicate the order in which the intra prediction processing is performed. Here, “0”, “2”, “4”, “6”, “8”, “10”, “12”, “14” are defined as pixel blocks belonging to the first group, and “1”. , “3”, “5”, “7”, “9”, “11”, “13”, “15” are defined as pixel blocks belonging to the second group. In the present embodiment, intra prediction processing is performed in parallel between the first group and the second group.

  That is, the pixel block “0” belonging to the first group and the pixel block “1” belonging to the second group are simultaneously subjected to intra prediction processing in the first stage of the parallel processing. Similarly, the pixel block “2” and the pixel block “3” are processed in parallel in the second stage, and then the pixel block “4” and the pixel block “5” are processed in parallel in the third stage. After the first, the pixel block “6”, the pixel block “7”,... Are processed.

  Here, the encoding of the peripheral blocks of the pixel block belonging to the first group is performed at least one stage before the pixel block. Therefore, the surrounding pixel data is already decoded pixel data that has already been encoded at the timing of starting the processing of the pixel blocks belonging to the first group.

  For example, consider intra prediction encoding of the “6” th pixel block shown in FIG. Pixel data belonging to pixel blocks “1”, “3”, “4”, and “5” are selected as the peripheral pixel data, but each has three levels than the pixel block selected “6”. Encoding processing is performed two steps and one step before. Therefore, it is possible to perform intra prediction mode determination using encoded pixel data.

  On the other hand, some of the peripheral blocks of the pixel blocks belonging to the second group are encoded simultaneously with the pixel blocks. Accordingly, there is a case where peripheral pixel data corresponding to the pixel block belonging to the second group is not encoded at the timing of starting the processing of the pixel block belonging to the second group.

  For example, consider encoding the “3” th pixel block selected in FIG. As the peripheral pixel data, pixel data belonging to pixel blocks “0”, “1”, and “2” are selected. In this case, the encoding process is started for the “2” pixel block simultaneously with the “3” pixel block selected. Therefore, the intra prediction mode that uses the encoded peripheral pixel data because the “2” pixel block is not encoded at the timing of determining the intra prediction mode of the “3” selected pixel block. A decision cannot be made.

  However, in this embodiment, since the intra prediction mode is determined using the original image data of the peripheral pixels of the encoding target block as described above, parallel processing can be performed when determining the intra prediction mode. The encoding process can be speeded up.

  In this embodiment, 16 × 16 intra prediction and 4 × 4 intra prediction have been described as examples. However, the present invention can be applied to prediction of other block sizes, for example, 8 × 8 intra prediction. In that case, the 8 × 8 intra prediction may be sequentially processed in the same manner as the 16 × 16 intra prediction, or may be parallelized like the 4 × 4 intra prediction, and the original image data may be used depending on the case. In this case, parallel processing is performed for an 8 × 8 size or smaller.

(Second Embodiment)
Next, another embodiment of the image coding apparatus according to the present invention will be described in detail with reference to the block diagram shown in FIG. 5, the flowchart shown in FIG. 6, and FIG. However, the image coding apparatus 500 according to the present embodiment illustrated in FIG. 5 has substantially the same configuration as that of the first embodiment, but is different in that it includes a peripheral pixel coding presence / absence determining unit 501. Further, the intra prediction unit 105 according to the present embodiment has the same configuration as that of the first embodiment, but is different from the first embodiment in that the prediction image is switched according to the presence / absence of encoding of surrounding pixels. Note that the operations of the components other than the intra prediction unit 105 and the surrounding pixel encoding presence / absence determination unit 501 are the same as those in the first embodiment, and thus description thereof is omitted.

FIG. 6 is a flowchart illustrating an example of a processing procedure for determining an intra prediction mode in the present embodiment.
The peripheral pixel encoding presence / absence determination unit 501 functions as a determination unit, and the 4 × 4 block defined in the first embodiment is illustrated in FIG. 7 based on the address of the 4 × 4 block in the encoding target macroblock. It is determined whether it belongs to the first group or the second group. That is, it is determined whether or not the pixel data is not decoded. If it belongs to the first group, it instructs the intra prediction unit 105 to receive reference image data from the pre-filter reference frame memory 114. If it belongs to the second group, it instructs the intra prediction unit 105 to receive reference image data from the frame memory 101 (step S601).

  By performing such a determination, the encoded peripheral pixel data is selected as the reference image data when the peripheral block of the encoding target block is encoded, and the peripheral pixel when it is not encoded. The pixel data of the original image can be selected. Therefore, it is possible to determine an intra prediction mode with better encoding efficiency than that of the first embodiment, and it is possible to maintain high speed encoding processing.

  In the present embodiment, the presence / absence of encoding of peripheral pixel data is determined by roughly dividing the first group and the second group. However, when the “3” selected block shown in FIG. 7 is encoded, the neighboring pixel data belonging to the “2” block is not encoded, but “0” and “1” The peripheral pixel data belonging to the pixel block has already been encoded. In this case, encoded pixel data is used for the peripheral pixel data belonging to the “0” and “1” pixel blocks, and original image data is used for the peripheral pixel data belonging to the “2” pixel block. A determination may be made to achieve higher encoding efficiency.

  Next, the intra prediction mode setting unit 203 in the intra prediction unit 105 sequentially sets the four types of prediction modes for the intra 16 × 16 prediction unit 201. Further, the nine types of prediction modes are set in order for the intra 4 × 4 prediction unit 202. Then, it instructs the intra 16 × 16 prediction unit 201 to transmit reference image data required in the intra prediction mode set in the pre-filter reference frame memory 114. Also, reference image data necessary for the intra prediction mode set for the frame memory 101 or the pre-filter reference frame memory 114 instructed by the surrounding pixel encoding presence / absence determination unit 501 is transmitted to the intra 4 × 4 prediction unit 202. (Step S602). In addition, since the process after the following step S302 is the same as that of 1st Embodiment, description is abbreviate | omitted.

  In the present embodiment, 16 × 16 intra prediction and 4 × 4 intra prediction have been described as examples. However, the present invention can also be applied to prediction of other block sizes, for example, 8 × 8 intra prediction. At that time, the 8 × 8 intra prediction may be sequentially processed in the same manner as the 16 × 16 intra prediction, or is parallelized like the 4 × 4 intra prediction, and the original image data is used or encoded depending on the case. Whether to use peripheral pixel data may be selected.

  As described above, in this embodiment, the prediction mode is determined using pixel data of an unencoded original image adjacent to the pixel block. Thereby, it is possible to efficiently determine the intra prediction mode without increasing the power consumption and the cost. Therefore, the encoding process can be performed at high speed.

(Other embodiments according to the present invention)
Each means constituting the image encoding apparatus and each step of the image encoding method in the embodiment of the present invention described above can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium (storage medium) recording (storing) the program are included in the present invention.

  In addition, the present invention can be implemented as, for example, a system, apparatus, method, program, or recording medium (storage medium). Specifically, the present invention may be applied to a system including a plurality of devices. It may also be applied to an apparatus consisting of a single device.

  The present invention includes a case where a software program for realizing the functions of the above-described embodiments (in the embodiment, a program corresponding to the flowcharts shown in FIGS. 3 and 6) is supplied directly or remotely to a system or apparatus. . This includes the case where the system or the computer of the apparatus is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Examples of the recording medium (storage medium) for supplying the program include a flexible disk, a hard disk, an optical disk, and a magneto-optical disk. Further, there are MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R) and the like.

  As another program supply method, there is a method of connecting to a homepage on the Internet using a browser of a client computer. Further, the computer program itself of the present invention or a compressed file including an automatic installation function can be downloaded from the homepage by downloading it to a recording medium (storage medium) such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  As another method, the program of the present invention is encrypted, stored in a recording medium such as a CD-ROM, distributed to users, and encrypted from a homepage via the Internet to users who have cleared predetermined conditions. Download the key information to be solved. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. Furthermore, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.

  Furthermore, as another method, a program read from a recording medium (storage medium) is first written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of the program, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

It is a block diagram which shows the function structural example of the image coding apparatus in the 1st Embodiment of this invention. It is a block diagram which shows the detailed structural example of the intra estimation part of the image coding apparatus in the 1st Embodiment of this invention. In the 1st Embodiment of this invention, it is a flowchart which shows an example of the process sequence which determines intra prediction mode. It is a figure which shows a 4 * 4 block, peripheral pixel data, and positional relationship. It is a block diagram which shows the function structural example of the image coding apparatus in the 2nd Embodiment of this invention. It is a flowchart which shows an example of the process sequence which determines intra prediction mode in the 2nd Embodiment of this invention. In the 1st Embodiment of this invention, it is a figure which shows the order which carries out intra prediction of the 4x4 block in a macroblock.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image coding apparatus 101 Frame memory 102 Reference frame memory after filter 103 Motion prediction part 104 Motion compensation part 105 Intra prediction part 106 Orthogonal transformation part 107 Quantization part 108 Entropy encoding part 109 Inverse quantization part 110 Inverse orthogonal transformation part 111 Switch 112 Subtractor 113 Adder 114 Pre-filter reference frame memory 115 Loop filter

Claims (14)

An image code that generates and encodes predicted image data according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes for a pixel block constituting the image Device.
Intra prediction mode determination means for determining a prediction mode for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block. An image encoding device. Determining means for determining whether or not the pixel block is adjacent to undecoded pixel data;
If the pixel block is adjacent to undecoded pixel data as a result of the determination by the determination unit, the intra prediction mode determination unit uses the pixel data of the original image adjacent to the pixel block, and The image code according to claim 1, wherein when a pixel block is not adjacent to undecoded pixel data, a prediction mode is determined using decoded pixel data adjacent to the pixel block. Device.   The intra prediction mode determination unit selects whether to use decoded pixel data adjacent to the pixel block or pixel data of an original image adjacent to the pixel block according to the size of the pixel block. The image encoding apparatus according to claim 1, wherein a prediction mode is determined.   When the size of the pixel block is larger than a predetermined size, the intra prediction mode determination unit uses decoded pixel data adjacent to the pixel block, and the size of the block is equal to or smaller than the predetermined size. The image encoding apparatus according to claim 3, wherein a prediction mode is determined using pixel data of an original image adjacent to the pixel block.   Whether the intra-prediction mode determination unit selects whether to use pixel data of an original image adjacent to the pixel block or decoded pixel data adjacent to the pixel block according to the size of the pixel block The image encoding apparatus according to claim 2, wherein:   When the size of the pixel block is larger than a predetermined size, the intra prediction mode determination unit uses decoded pixel data adjacent to the pixel block, and the size of the pixel block is equal to or smaller than the predetermined size. Wherein the prediction mode is determined using the pixel data of the original image adjacent to the pixel block or the decoded pixel data depending on whether or not the pixel data adjacent to the pixel block has been decoded. The image encoding device according to claim 5. An image code that generates and encodes predicted image data according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes for a pixel block constituting the image A method of
An intra prediction mode determining step of determining a prediction mode for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block; Image coding method to be performed. Determining whether the pixel block is adjacent to undecoded pixel data;
In the intra prediction mode determination step, as a result of the determination in the determination step, when the pixel block is adjacent to undecoded pixel data, the pixel data of the original image adjacent to the pixel block is used. 8. The image according to claim 7, wherein when the pixel block is not adjacent to undecoded pixel data, a prediction mode is determined using decoded pixel data adjacent to the pixel block. Encoding method.   In the intra prediction mode determination step, whether to use the decoded pixel data adjacent to the pixel block or the pixel data of the original image adjacent to the pixel block is selected according to the size of the pixel block. 8. The image encoding method according to claim 7, wherein a prediction mode is determined.   In the intra prediction mode determination step, when the size of the pixel block is larger than a predetermined size, decoded pixel data adjacent to the pixel block is used, and the size of the block is equal to or smaller than the predetermined size. 10. The image encoding method according to claim 9, wherein the prediction mode is determined using pixel data of an original image adjacent to the pixel block.   In the intra prediction mode determination step, whether to use pixel data of an original image adjacent to the pixel block or decoded pixel data adjacent to the pixel block is selected according to the size of the pixel block. 9. The image encoding method according to claim 8, wherein presence / absence is determined.   In the intra prediction mode determination step, when the size of the pixel block is larger than a predetermined size, decoded pixel data adjacent to the pixel block is used, and the size of the pixel block is equal to or smaller than the predetermined size. In some cases, depending on whether pixel data adjacent to the pixel block has been decoded, the prediction mode is determined using pixel data of the original image adjacent to the pixel block or decoded pixel data. The image encoding method according to claim 11, wherein For the pixel blocks constituting the image, prediction image data is generated and encoded according to decoded pixel data adjacent to the pixel block and a prediction mode selected from a plurality of prediction modes. A program to be executed by a computer,
Causing a computer to execute an intra prediction mode determination step of determining a prediction mode for encoding from among the plurality of prediction modes using pixel data of an unencoded original image adjacent to the pixel block. A program characterized by   A computer-readable recording medium having the program according to claim 13 recorded thereon.

Images