JP4481612B2 - Image decoding apparatus and method - Google Patents

Description

The present invention relates to decrypt apparatus of the moving image, the motion prediction about beauty how Oyo row planted picture decoding device using a particular weighting factor.

  In recent years, the multimedia era has come to handle voice, images, and other contents in an integrated manner, and information such as newspapers, magazines, televisions, radios, and telephones can be obtained or transmitted by a single terminal. It has become like this. In general, multimedia refers to not only characters but also figures, sounds, especially images that are associated with each other. It is indispensable to express in digital form.

  However, when the information amount of each information medium is estimated as a digital information amount, the information amount per character is 1 to 2 bytes in the case of characters, whereas 64 Kbits per second (phone quality) in the case of voice. In addition, since a moving image requires an information amount of 100 Mbits (current television reception quality) or more per second, it is not realistic to handle the enormous amount of information in the digital format as it is with the information medium. For example, a video phone has already been put into practical use by an integrated services digital network (ISDN) having a transmission speed of 64 Kbits / s to 1.5 Mbits / s. It is impossible to send.

  Therefore, what is needed is information compression technology. For example, in the case of videophones, the H.261 and H.263 standards that have been internationally standardized by the ITU-T (International Telecommunication Union Telecommunication Standardization Sector) are required. Video compression technology is used. Further, according to the information compression technology of the MPEG-1 standard, it is possible to put image information together with audio information on a normal music CD (compact disc).

  Here, MPEG (Moving Picture Experts Group) is an international standard for moving picture signal compression, and MPEG-1 is up to 1.5 Mbps for moving picture signals, that is, up to about 1 / 100th of information of television signals. It is a standard to compress. In addition, since the transmission rate for the MPEG-1 standard is mainly limited to about 1.5 Mbps, MPEG-2 standardized to meet the demand for higher image quality has 2 video signals. Compressed to 15Mbps. Furthermore, at present, the working group (ISO / IEC JTC1 / SC29 / WG11), which has been standardizing with MPEG-1 and MPEG-2, has achieved a compression ratio that exceeds MPEG-1 and MPEG-2, and further, on a per-object basis. MPEG-4 that enables encoding, decoding, and operation and that realizes new functions necessary in the multimedia era has been standardized (see, for example, Non-Patent Document 1). MPEG-4 not only enables efficient coding at a low bit rate, but also introduces a powerful error resilience technique that can reduce image quality degradation even if a transmission path error occurs. In ISO / IEC and ITU, MPEG-4 AVC / ITU H.264 is a next-generation image encoding method. H.264 standardization is being promoted jointly.

  In general, in encoding of moving images, the amount of information is compressed by reducing redundancy in the time direction and the spatial direction. Therefore, in inter-screen predictive coding for the purpose of reducing temporal redundancy, motion detection and prediction image creation are performed in block units with reference to the front or rear picture, and the obtained prediction image and code are obtained. Encoding is performed on the difference value from the current picture. Here, a picture is a term representing a single screen, which means a frame in a progressive image and a frame or field in an interlaced image. Here, an interlaced image is an image in which one frame is composed of two fields having different times. In interlaced image encoding and decoding processing, one frame may be processed as a frame, processed as two fields, or processed as a frame structure or a field structure for each block in the frame. it can.

FIG. 19 is a diagram illustrating an example of picture types and reference relationships. In FIG. 19, a hatched picture is a picture stored in the memory because it is referred to by other pictures. An arrow in FIG. 19 indicates a direction from the referenced picture to the reference picture. Also, the arrangement of pictures is shown in display order.
I0 (Picture 0) is an intra-picture coded picture (I picture) and is a picture that is coded independently of other pictures (that is, without referring to other pictures). P4 (Picture 4) and P7 (Picture 7) are forward predictive coded pictures (P pictures), which are predictively coded by referring to I pictures or other P pictures located in the past in time. It is a picture. B1 to B3 (Picture 1 to Picture 3), B5 (Picture 5), and B6 (Picture 6) are bi-directional predictive coded pictures (B pictures), and refer to other pictures that are temporally located before and after. This is a picture that is predictively encoded.

  FIG. 20 is a diagram illustrating another example of picture types and reference relationships. FIG. 20 is different from FIG. 19 in that the temporal position of the picture referred to by the B picture is not necessarily limited to the picture located before and after in time. For example, in the case of B5 (Picture 5), any two pictures of I0 (Picture 0), P3 (Picture 3), and P6 (Picture 6) can be referred to. That is, it is possible to refer to I0 and P3 located in the past in time. Such a reference method has already been recognized in the MPEG-4 AVC / H.264 draft standard as of September 2001. As a result, the range for selecting a more appropriate predicted image is broadened compared to the conventional case, and the compression rate can be improved.

  FIG. 21 is a diagram illustrating an example of a stream structure of image data. As shown in FIG. 21, the stream is composed of a common information area such as a header and a GOP (Group Of Picture) area. The GOP area is composed of a common information area such as a header and a plurality of picture areas. The picture area is composed of a common information area such as a header and a plurality of slice data areas. The slice data area includes a common information area such as a header and a plurality of macro block data areas.

In the picture common information area, a weight coefficient for performing weighted prediction described later is described according to the reference picture.
In addition, when the stream is transmitted not by a continuous bit stream but by a packet or the like which is a unit of chopped data, the header part and the data part other than the header may be separated and transmitted separately. In that case, the header part and the data part do not become one bit stream as shown in FIG. However, in the case of a packet, even if the transmission order of the header part and the data part is not continuous, only the header part corresponding to the corresponding data part is transmitted in another packet, and it becomes one bit stream. Even if not, the concept is the same as the case of the bit stream described in FIG.

Next, the weighted prediction process in the conventional image encoding method will be described.
FIG. 22 is a schematic diagram when the weighted prediction process is performed in units of frames.
As shown in FIG. 22A, when referring to one frame, the pixel value Q of the predicted image corresponding to the current encoding target block is the reference target block in the i-th frame (Frame i) to be referred to. Can be calculated by a weighted prediction equation as shown in the following equation (1). Also, as shown in FIG. 22B, when referring to two frames, the pixel value Q of the predicted image is the reference target block in the i-th and j-th frames (Frame i and Frame j) to be referenced. If the pixel values are P0 and P1, they can be calculated by a weighted prediction formula as shown in the following formula (2).
Q = (P0 × W0 + D) / W2 (1)
Q = (P0 × W0 + P1 × W1 + D) / W2 (2)
Here, W0 and W1 are weighting factors, D is a bias component (DC component), and W2 is a normalization factor.

FIG. 23 is a schematic diagram when the weighted prediction process is performed in field units.
As shown in FIG. 23A, when referring to one frame (that is, two fields), the pixel values Qa and Qb of the prediction image corresponding to the current encoding target block are the i-th reference to be referred to. Assuming that the pixel values of the reference target block in each of the fields 2 × i + 1, 2 × i constituting the frame (Frame i) are P0a and P0b, the weighted prediction equations shown in the following equations (3) and (4) are used. Can be calculated. Also, as shown in FIG. 23B, when referring to two frames, the pixel values Qa and Qb of the predicted image constitute the i-th and j-th frames (Frame i and Frame j) to be referred to. Assuming that the pixel values P0a, P0b, P1a, and P1b of the reference target blocks in the fields 2 × i + 1, 2 × i, 2 × j + 1, and 2 × j are respectively weighted as shown in the following equations (5) and (6) It can be calculated by a prediction formula.
Qa = (P0a × W0a + Da) / W2a (3)
Qb = (P0b × W0b + Db) / W2b (4)
Qa = (P0a * W0a + P1a * W1a + Da) / W2a (5)
Qb = (P0b × W0b + P1b × W1b + Db) / W2b (6)
Here, W0a, W0b, W1a, and W1b are weighting factors, Da and Db are bias components, and W2 is a normalization factor.

  FIG. 24 is a block diagram showing a functional configuration of a conventional image encoding device 100. As shown in FIG. The image encoding device 100 is a device that performs compression encoding (for example, variable length encoding) of an input image signal Vin and outputs an image encoded signal Str that is a bit stream converted by the compression encoding. Motion detection unit ME, motion compensation unit MC, subtraction unit Sub, orthogonal transform unit T, quantization unit Q, inverse quantization unit IQ, inverse orthogonal transform unit IT, addition unit Add, picture memory PicMem, switch SW and A variable length coding unit VLC is provided.

  The image signal Vin is input to the subtraction unit Sub and the motion detection unit ME. The subtraction unit Sub calculates a difference value between the input image signal Vin and the predicted image and outputs the difference value to the orthogonal transform unit T. The orthogonal transform unit T converts the difference value into a frequency coefficient and outputs it to the quantization unit Q. The quantization unit Q quantizes the input frequency coefficient and outputs the quantized value to the variable length coding unit VLC.

  The inverse quantization unit IQ inversely quantizes the quantized value to restore the frequency coefficient, and outputs the frequency coefficient to the inverse orthogonal transform unit IT. The inverse orthogonal transform unit IT performs inverse frequency conversion from the frequency coefficient to the pixel difference value, and outputs the result to the addition unit Add. The addition unit Add adds the pixel difference value and the predicted image output from the motion compensation unit MC to obtain a decoded image. The switch SW is turned “ON” when an instruction to store the decoded image is given, and the decoded image is stored in the picture memory PicMem.

  On the other hand, the motion detection unit ME to which the image signal Vin is inputted in units of macroblocks searches the decoded image stored in the picture memory PicMem as a search target and detects the position by detecting the image region closest to the input image signal. Is determined. The motion vector is detected in units of blocks obtained by further dividing the macroblock. At this time, since a plurality of pictures can be used as reference pictures, an identification number (picture number Index) for designating a picture to be referenced is required for each block. A reference picture can be specified by taking correspondence with the picture number of each picture in the picture memory PicMem by the picture number Index.

  The motion compensation unit MC uses the motion vector detected by the above processing and the picture number Index to extract an image area necessary for predictive image generation from the decoded image stored in the picture memory PicMem. The motion compensation unit MC performs a pixel value conversion process such as an interpolation process by weighted prediction using a weighting coefficient associated with the picture number Index on the pixel values of the obtained image region, thereby obtaining a final predicted image. Is identified.

FIG. 25 is a block diagram showing an outline of a functional configuration of the variable length coding unit VLC in the conventional image coding apparatus 100 of FIG. The variable length coding unit VLC includes an MV coding unit 101, a quantized value coding unit 102, a weight coefficient coding unit 103, an index coding unit 104, an AFF identification information coding unit 105, and a multiplexing unit 106. Yes.
The MV encoding unit 101 encodes the motion vector, and the quantized value encoding unit 102 encodes the quantized value Qcoef. Further, the weight coefficient encoding unit 103 encodes the weight coefficient Weight, and the index encoding unit 104 encodes the picture number Index. The AFF identification information encoding unit 105 encodes the AFF identification signal AFF (the AFF identification signal AFF will be described later). The multiplexing unit 106 multiplexes each encoded signal output from the MV encoding unit 101, the quantized value encoding unit 102, the weighting coefficient encoding unit 103, the index encoding unit 104, and the AFF identification information encoding unit 105. And an image encoded signal Str is output.

FIG. 26 is a block diagram showing a functional configuration of a conventional image decoding apparatus 200.
The image decoding apparatus 200 is an apparatus capable of decoding the image encoded signal Str encoded by the image encoding apparatus 100, and includes a variable length decoding unit VLD, a motion compensation unit MC, an addition unit Add, a picture. A memory PicMem, an inverse quantization unit IQ, and an inverse orthogonal transform unit IT are provided.

  When the encoded image signal Str is input, the variable length decoding unit VLD separates the encoded motion difference vector MV, the index representing the picture number, and the weighting factor Weight from the input encoded image signal Str. To the motion compensation unit MC. Further, the variable decoding unit VLD decodes the encoded quantized value Qcoef included in the input image encoded signal Str and outputs it to the inverse quantization unit IQ.

  The motion compensation unit MC uses the motion vector output from the variable length decoding unit VLD and the picture number Index to extract an image area necessary for predictive image generation from the decoded image stored in the picture memory PicMem. Using the weight coefficient Weight for the obtained image, a predicted image is generated by performing pixel value conversion processing such as interpolation processing by weighted prediction.

  The inverse quantization unit IQ inversely quantizes the quantized value to restore the frequency coefficient, and outputs the frequency coefficient to the inverse orthogonal transform unit IT. The inverse orthogonal transform unit IT performs inverse frequency conversion from the frequency coefficient to the pixel difference value, and outputs the result to the addition unit Add. The addition unit Add adds the pixel difference value and the predicted image output from the motion compensation unit MC to obtain a decoded image. This decoded image is stored in the picture memory PicMem when used for reference in subsequent inter-screen prediction. The decoded image is output to the outside as a decoded image signal Vout.

FIG. 27 is a block diagram showing an outline of a functional configuration of the variable length decoding unit VLD in the conventional image decoding apparatus 200 of FIG.
The variable length decoding unit VLD includes a separation unit 201, an MV decoding unit 202, a quantized value decoding unit 203, a weight coefficient decoding unit 204, an index decoding unit 205, and an AFF identification information decoding unit 206. .

  When the encoded image signal Str is input to the variable length decoding unit VLD, the separating unit 201 separates the input encoded image signal Str and converts the encoded motion difference vector MV into the MV decoding unit 202. In addition, the coded quantized value Qcoef is decoded by the quantized value decoding unit 203, the coded weighting factor Weight is given by the weighting factor decoding unit 204, and the coded picture number Index is index-decoded. The encoded AFF identification signal AFF (hereinafter abbreviated as “AFF”) is output to the unit 205 to the AFF identification information decoding unit 206, respectively.

The MV decoding unit 202 decodes the encoded difference vector and outputs a motion vector MV.
Similarly, the quantized value decoding unit 203 represents the quantized value, the weight coefficient decoding unit 204 represents the weight coefficient Weight, the index decoding unit 205 represents the picture number Index, and the AFF identification information decoding unit 206 represents AFF. Decrypt and output.
ISO (International Organization for Standardization) MPEG-1, MPEG-2, MPEG-4 standards

However, in the conventional weighted predictive coding, coding is performed on a picture-by-picture basis, but it is assumed that a block is always coded / decoded for the same picture (one of a frame or a field). Therefore, only one set of weighting factors is encoded / decoded in a picture.
For this reason, although there is a possibility that the efficiency of motion prediction may be improved by switching between fields and frames in units of blocks, conventionally, only one weight coefficient can be sent in units of pictures. Even if the frames are switched, the prediction efficiency is poor and the compression rate cannot be improved.

Therefore, in the present invention it has been made in view of the above problems, even in the case of switching the field and frame on a block-by-block basis, suitably provide a capable images decoding method in associating a weighting factor The purpose is to do.

To achieve the above object, the image decoding apparatus according to the present invention is an image decoding apparatus for decoding coded Picture included in the encoded signal in block units, the picture is in the frame If the picture is coded so that it is adaptively switched between frame decoding and field decoding of the blocks constituting the picture, the coding included in the coded signal When the block constituting the picture is frame-encoded , the variable-length decoding unit that decodes the frame weighting coefficient that has been decoded and generates a field weighting coefficient from the decoded frame weighting coefficient , by using the pixel value and the decoded frame weighting factor of the reference frame block refers to generate a prediction image, wherein the block is a field If it is Goka generates a prediction image by using the pixel value and the generated field weighting factor of the reference field that the block references, using a motion compensation unit, a prediction image the generated And an adder for decoding the picture .

As a result, the image decoding apparatus according to the present invention generates the field weight coefficient from the frame weight coefficient even when the frame / field switching is performed in units of blocks and the field weight coefficient is not received. The frame / field switching can be adaptively performed and the transmission efficiency can be improved .

In order to achieve the above object, an image decrypted method according to the present invention is an image decoding method for decoding a coded Picture included in the encoded signal in block units, the picture Is included in the encoded signal if the picture is encoded so as to adaptively switch between frame decoding and field decoding of the blocks constituting the picture. Decoding a coded frame weighting factor, generating a field weighting factor from the decoded frame weighting factor, and if the block constituting the picture is frame coded, the block is using pixel values of the reference frame and reference and the decoded frame weighting factor to generate a prediction image, wherein the block is field marks If it is of includes the step of generating a predictive image using a field weighting factor the generated pixel value of the reference field the block referenced by using the prediction image the generated, the picture And a step of decoding .

In order to achieve the above object, the present invention can also be implemented as a program that includes all of the steps of the picture decoding how the above. The program is not only stored in a ROM or the like provided in an apparatus capable of realizing the above method, but can also be distributed via a recording medium such as a CD-ROM or a transmission medium such as a communication network.

According to the image coding method and the image decoding method according to the present invention, field / frame switching can be realized in units of blocks, prediction efficiency can be improved, and the compression rate can be improved.
Further, according to the image coding method and the image decoding method according to the present invention, the frame weight coefficient is generated from the field weight coefficient and the field weight coefficient is generated from the frame weight coefficient. It is possible to omit one of the transmissions and improve transmission efficiency. Therefore, its practical value is high.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
The functional configuration of the image coding apparatus that implements the image coding method according to the present embodiment is the same as that of the conventional image coding apparatus 100 described above, except for the variable-length coding unit VLC. Also, the functional configuration of the image decoding apparatus that implements the image decoding method according to the present embodiment is the same as that of the conventional image decoding apparatus 200 described above, except for the variable-length decoding unit VLD.

For this reason, hereinafter, the variable length coding unit VLC and the variable length decoding unit VLD different from the conventional ones will be mainly described.
FIG. 1 is a block diagram showing an outline of a functional configuration of the variable length coding unit VLC in the present embodiment. As shown in FIG. 1, the variable length coding unit VLC includes an MV coding unit 101, a quantized value coding unit 102, a field weight coefficient coding unit 11, a frame weight coefficient coding unit 12, and an index coding unit. 104, a weighting factor mode determination unit 13, an AFF identification information encoding unit 105, switches 14 and 15, and a multiplexing unit 106. In the following description, the same functional configuration as that of the conventional variable length coding unit VLC is denoted by the same reference numeral, and the description thereof is omitted.

The switches 14 and 15 determine whether the input destination of the weighting factor Weight is the field weighting factor encoding unit 11 or the frame weighting factor encoding unit 12 based on the determination result of the weighting factor mode determination unit 13. , ON / OFF control is performed.
The field weight coefficient encoding unit 11 encodes the input weight coefficient Weight as a field weight coefficient. The frame weight coefficient encoding unit 12 encodes the input weight coefficient Weight as a frame weight coefficient.

The weighting factor mode determination unit 13 performs field / frame determination based on the AFF value and the weighting factor Weight value, and notifies the switches 14 and 15 and the multiplexing unit 106 of the determination result.
FIG. 2 is a block diagram showing an outline of a functional configuration of the variable length decoding unit VLD in the present embodiment. As shown in FIG. 2, the variable length decoding unit VLD includes a separation unit 21, an MV decoding unit 202, a quantized value decoding unit 203, a field weight coefficient decoding unit 22, a frame weight coefficient decoding unit 23, A weight coefficient generation unit 24, an index decoding unit 205, an AFF identification information decoding unit 206, and switches 26 to 28 are provided. In the following description, the same functional configuration as that of the conventional variable length decoding unit VLD is denoted by the same reference numeral, and the description thereof is omitted.

  The separation unit 21 separates the input encoded image signal Str, the encoded motion vector MV to the MV decoding unit 202, and the encoded quantized value Qcoef to the quantized value decoding unit 203. The encoded weight coefficient Weight is sent to the field weight coefficient decoding unit 22 or the frame weight coefficient decoding unit 23 and the weight coefficient generation unit 24, and the encoded picture number Index is sent to the index decoding unit 205. The encoded AFFs are output to the AFF identification information decoding unit 206, respectively.

The field weight coefficient decoding unit 22 decodes the input weight coefficient Weight as a field weight coefficient. The frame weight coefficient decoding unit 23 decodes the input weight coefficient Weight as a frame weight coefficient.
The weight coefficient generation unit 24 generates a field weight coefficient from the frame weight coefficient as necessary. For example, when switching between frames / fields in units of blocks, the field weighting coefficient is not encoded, and therefore it is necessary to generate a field weighting coefficient from the frame weighting coefficient.

  FIG. 3 is a diagram showing an example of the data structure of the picture area in the present embodiment. FIG. 3A shows an example of a detailed data structure of “header” in the common information area in the picture area. In the example of FIG. 3A, “header” has “picture frame coding information” indicating whether a picture is a frame unit or a field unit. When “picture frame coding information” is “1”, it further has a flag indicating whether or not to switch the field and the frame in units of blocks called “AFF”. For example, when “AFF” is “1”, it indicates that a field and a frame are switched in units of blocks. As shown in FIG. 21A, when “AFF” is “1”, all of “field weight coefficient” and “frame weight coefficient” are transmitted. The “field weighting factor” includes “first field weighting factor” and “second field weighting factor”.

  When “picture frame encoding information” is “0”, the picture is encoded in units of fields, and the field and frame cannot be switched in units of blocks. Therefore, as shown in FIG. 3B, there is no “AFF”, and only the “field weight coefficient” is transmitted as the “picture weight coefficient”. FIG. 3C shows a case where “picture frame coding information” is “1” and “AFF” is “0”, and the field and the frame cannot be switched in units of blocks. Accordingly, only the “frame weight coefficient” is transmitted as the “picture weight coefficient”.

FIG. 4 shows the flow of the encoding process related to the weighting coefficient in the variable length decoding unit VLD when the “picture frame encoding information” is “1” and the picture is encoded in units of frames in the present embodiment. It is a flowchart.
First, when the value of “AFF” is “1” and frame / field switching is performed in units of blocks (S10: Yes), an AFF indicating “switched in units of blocks” is encoded (S13). The weighting factor and the field weighting factor are encoded (S14, S15).

  On the other hand, when the value of “AFF” is “0” and frame / field switching is not performed in block units (S10: No), the value “0” of “AFF” indicating “no switching in block units” is set. Encode (S11), and encode the weighting coefficient of the picture (S12).

(Modification)
FIG. 5 is a diagram showing an example of the data structure of the picture area in the modification of the present embodiment. FIG. 5A shows an example of a detailed data structure of “header” in the common information area in the picture area. In the example of FIG. 5A, “header” has “picture frame coding information” indicating whether a picture is a frame unit or a field unit. For example, when the “picture frame coding information” is “1” (that is, the picture is in units of frames), it further has a flag indicating whether to switch the field and the frame in units of blocks, “AFF”. ing. For example, when “AFF” is “1”, it indicates that a field and a frame are switched in units of blocks. As shown in FIG. 5A, when “AFF” is “1”, “frame weight coefficient” is transmitted, and “frame weight coefficient” is diverted. To do.

  When “picture frame coding information” is “0”, this means that a picture is coded in units of fields. In this case, frame / field switching is not performed in units of blocks. Therefore, as shown in FIG. 5B, when there is no “AFF”, it means that only “field weight coefficient” is transmitted as “picture weight coefficient”. FIG. 5C shows a case where “picture frame coding information” is “1” and “AFF” is “0”, and frame / field switching is not performed in units of blocks, and is always coded in frames. . Accordingly, only the “frame weight coefficient” is transmitted as the “picture weight coefficient”.

FIG. 6 shows an encoding process related to a weighting coefficient in the variable-length encoding unit VLC when “picture frame encoding information” is “1” and a picture is encoded in units of frames in the modification of the present embodiment. It is a flowchart which shows a flow.
First, when the value of “AFF” is “1” and frame / field switching is performed in block units (S10: Yes), “AFF” indicating “switching in block units” is encoded (S13). The frame weighting coefficient is encoded (S15).

  On the other hand, when the value of “AFF” is “0” and frame / field switching is not performed in block units (S10: No), the value “0” of “AFF” indicating “no switching in block units” is set. Encoding is performed (S11), and one of “field weighting coefficient” and “frame weighting coefficient” that matches the coding unit of the block is encoded as “picture weighting coefficient” based on the picture frame encoding information ( S12).

FIG. 7 shows a flow of decoding processing relating to the weighting coefficient when “picture frame coding information” in the variable length decoding unit VLD in FIG. 2 is “1” and a picture is coded in units of frames. It is a flowchart. FIG. 7 is a flowchart relating to a decoding process corresponding to the encoding process of FIG.
First, the variable length decoding unit VLD decodes “AFF” (S20). As a result, when the value of “AFF” is “1” and indicates that the frame / field switching is performed in block units (S21: Yes), the frame weighting coefficient is decoded (S23), and the frame weighting is performed. Based on the coefficient (for example, diverting the frame weight coefficient), a field weight coefficient is generated (S24).

On the other hand, when the value of “AFF” is “0” and indicates that the frame / field switching is not performed in units of blocks (S21: No), “field weight coefficient” or “picture weight coefficient” Any one of the “field weight coefficients” is decoded (S22).
As described above, by using the image coding method and the image decoding method according to the present embodiment, field / frame switching is realized in units of blocks, the prediction efficiency is improved, and the compression rate is finally improved. It becomes possible to make it. Further, even if the “field weighting factor” is not encoded, the “length weighting factor” is generated from the “frame weighting factor” in the variable length decoding unit VLD, so that the field / unit in the block unit is not affected. It is possible to switch frames.

(Embodiment 2)
In this embodiment, an example in which the data structure of the picture area in Embodiment 1 is different will be described.

  FIG. 8 is a diagram illustrating a data structure example of a picture area in the present embodiment. FIG. 8 is a diagram illustrating a detailed data structure of “header” in the common information area in the picture area. In the present embodiment, a structure example of “header” in the case where “picture frame coding information” is “1” and a picture is coded in units of frames and the field weighting factor can be omitted will be described.

As shown in FIGS. 8A and 8B, “header” has “Field coefficient presence / absence information” in addition to “AFF”. The “Field coefficient presence / absence information” is a flag indicating whether there is a field weight coefficient. For example, “1” is set when there is a field weight coefficient, and “0” is set when the field weight coefficient is omitted.
FIG. 8A shows an example in which “1” is set in “AFF” and “1” is set in the “Field coefficient presence / absence information”, and the field weighting coefficient is also transmitted. The “field weighting coefficient” includes the “first field weighting coefficient” and the “second field weighting coefficient” as in the case of the first embodiment.

FIG. 8B shows an example in which “1” is set in “AFF” and “0” is set in “Field coefficient presence / absence information”.
FIG. 8C is an example in which “0” is set in “AFF”, so that switching between fields and frames is not performed in units of blocks.
FIG. 9 is a flowchart showing a flow of an encoding process related to a weighting coefficient in the variable length encoding unit VLC in the present embodiment.

First, when the value of “AFF” is “1” and frame / field switching is performed in block units (S10: Yes), “AFF” indicating that there is switching in block units is encoded (S31). ).
Further, it is determined whether or not the field weighting factor can be generated from the frame weighting factor (S32). If possible, the information indicating that the field weighting factor is generated and the frame weighting factor are encoded (S36, S37). . If the field weighting factor is not generated from the frame weighting factor, information indicating whether there is a field weighting factor, a frame weighting factor, and a field weighting factor are encoded (S33 to S35).

On the other hand, when the value of “AFF” is “0” and frame / field switching is not performed in units of blocks (S10: No), the process is the same as the flowchart of FIG. 6 (S11, S12).
FIG. 10 is a flowchart showing the flow of the decoding process related to the weighting factor in the variable length decoding unit VLD of FIG. FIG. 10 is a flowchart relating to a decoding process corresponding to the encoding process of FIG.

  First, the variable length decoding unit VLD decodes “AFF” (S20), and the value of “AFF” is “1”, indicating that frame / field switching is performed in units of blocks. (S21: Yes), the information indicating the presence / absence of the field weight coefficient is decoded (S41).

  Next, it is determined whether or not there is a field weighting factor (S42). If there is no field weighting factor, the frame weighting factor is decoded (S45), and a field weighting factor is generated from the frame weighting factor (S46). If there is a field weighting factor, the frame weighting factor and the field weighting factor are decoded (S43, S44).

On the other hand, when the value of “AFF” is “0” and indicates that the frame / field switching is not performed in block units (S21: No), the picture weight coefficient is decoded (S22).
As described above, field / frame switching is realized in units of blocks by using the image encoding method and the image decoding method according to the present embodiment. Furthermore, even if the field weighting factor is omitted, it can be generated from the frame weighting factor.

(Embodiment 3)
In the present embodiment, an example in which the data structure of the picture area in the first embodiment is different will be described.

  FIG. 11 is a diagram illustrating a data structure example of a picture area in the present embodiment. FIG. 11 is a diagram showing a detailed data structure of “header” in the case where “picture frame coding information” is “1” and a picture is coded on a frame basis in the common information area in the picture area. It is. In the present embodiment, a structure example of “header” in the case where the frame weighting factor can be omitted will be described.

As shown in FIGS. 11A and 11B, “header” has “Frame coefficient presence / absence information” in addition to “AFF”. This “Frame coefficient presence / absence information” is a flag indicating whether or not there is a frame weight coefficient. For example, “1” is set when there is a frame weight coefficient, and “0” is set when the frame weight coefficient is omitted.
FIG. 11A shows an example in which “1” is set in “AFF” and “1” is set in the “Frame coefficient presence / absence information”, and a case where a frame weight coefficient is also transmitted is shown. FIG. 11B is an example in which “1” is set in “AFF” and “0” is set in “Frame coefficient presence / absence information”. FIG. 11C is an example in which “0” is set in “AFF”, so that switching between fields and frames is not performed in units of blocks.

FIG. 12 is a flowchart showing the flow of the encoding process related to the weighting factor in the variable length encoding unit VLC in the present embodiment.
First, when the value of “AFF” is “1” and frame / field switching is performed in block units (S10: Yes), “AFF” indicating that there is switching in block units is encoded (S51). ).

  Further, it is determined whether or not the frame weighting coefficient is generated from the field weighting coefficient (S52), and when it is generated, the information indicating that the frame weighting coefficient is generated and the field weighting coefficient are encoded (S56, S57). . When the frame weighting coefficient is not generated from the field weighting coefficient (S52: No), the information indicating whether there is a frame weighting coefficient, the field weighting coefficient, and the frame weighting coefficient are encoded (S53 to S55).

On the other hand, when the value of “AFF” is “0” and frame / field switching is not performed in units of blocks (S10: No), the same encoding as in the flowchart of FIG. 6 is performed (S11, S12).
FIG. 13 is a flowchart showing the flow of decoding processing relating to the weighting factor in the variable length decoding unit VLD of FIG. FIG. 13 is a flowchart relating to a decoding process corresponding to the flow of the encoding process of FIG.

First, the variable length decoding unit VLD decodes “AFF” (S20), and the value of “AFF” is “1”, indicating that frame / field switching is performed in units of blocks. (S21: Yes), the information indicating the presence / absence of the frame weight coefficient is decoded (S61).
Next, it is determined whether or not there is a frame weight coefficient (S62). If there is no frame weight coefficient (S62: Yes), the field weight coefficient is decoded (S65), and a frame weight coefficient is generated from the field weight coefficient. (S66). If there is a frame weight coefficient (S62: No), the field weight coefficient and the frame weight coefficient are decoded (S63, S64).

On the other hand, when the value of “AFF” is “0” and indicates that the frame / field switching is not performed in block units (S21: No), the picture weight coefficient is decoded (S22).
As described above, field / frame switching is realized in units of blocks by using the image encoding method and the image decoding method according to the present embodiment. Furthermore, even if the frame weighting factor is omitted, it can be generated from the field weighting factor.

(Embodiment 4)
Furthermore, the program for realizing the image encoding method and the image decoding method shown in each of the above embodiments is recorded in a storage medium such as a flexible disk, thereby showing in each of the above embodiments. Processing can be easily performed in an independent computer system.

FIG. 14 is an explanatory diagram when the image encoding method and the image decoding method of each of the above embodiments are implemented by a computer system using a program recorded on a recording medium such as a flexible disk.
FIG. 14B shows an appearance, a cross-sectional structure, and a flexible disk as viewed from the front of the flexible disk, and FIG. 14A shows an example of a physical format of the flexible disk that is a recording medium body. The flexible disk FD is built in the case F, and on the surface of the disk, a plurality of tracks Tr are formed concentrically from the outer periphery toward the inner periphery, and each track is divided into 16 sectors Se in the angular direction. ing. Therefore, in the flexible disk storing the program, the program is recorded in an area allocated on the flexible disk FD.

  FIG. 14C shows a configuration for recording and reproducing the program on the flexible disk FD. When the program for realizing the image encoding method and the image decoding method is recorded on the flexible disk FD, the program is written from the computer system Cs via the flexible disk drive. When the image encoding method and the image decoding method for realizing the image encoding method and the image decoding method by the program in the flexible disk are constructed in the computer system, the program is read from the flexible disk by the flexible disk drive. Transfer to computer system.

  In the above description, a flexible disk is used as the recording medium, but the same can be done using an optical disk. Further, the recording medium is not limited to this, and any recording medium such as an IC card or a ROM cassette capable of recording a program can be similarly implemented.

(Embodiment 5)
Furthermore, application examples of the image coding method and the image decoding method shown in the above embodiment and a system using the same will be described.

FIG. 15 is a block diagram showing the overall configuration of a content supply system ex100 that implements a content distribution service. A communication service providing area is divided into desired sizes, and base stations ex107 to ex110, which are fixed wireless stations, are installed in each cell.
The content supply system ex100 includes, for example, a computer ex111, a PDA (personal digital assistant) ex112, a camera ex113, a mobile phone ex114, a camera via the Internet ex101, the Internet service provider ex102, the telephone network ex104, and the base stations ex107 to ex110. Each device such as the attached mobile phone ex115 is connected.

However, the content supply system ex100 is not limited to the combination as shown in FIG. 15, and may be connected in combination. Also, each device may be directly connected to the telephone network ex104 without going through the base stations ex107 to ex110 which are fixed wireless stations.
The camera ex113 is a device capable of shooting a moving image such as a digital video camera. The mobile phone is a PDC (Personal Digital Communications) system, a CDMA (Code Division Multiple Access) system, a W-CDMA (Wideband-Code Division Multiple Access) system, or a GSM (Global System for Mobile Communications) system mobile phone, Alternatively, PHS (Personal Handyphone System) or the like may be used.

  In addition, the streaming server ex103 is connected from the camera ex113 through the base station ex109 and the telephone network ex104, and live distribution or the like based on the encoded data transmitted by the user using the camera ex113 becomes possible. The encoded processing of the captured data may be performed by the camera ex113, or may be performed by a server or the like that performs data transmission processing. The moving image data shot by the camera 116 may be transmitted to the streaming server ex103 via the computer ex111. The camera ex116 is a device such as a digital camera that can shoot still images and moving images. In this case, the moving image data may be encoded by the camera ex116 or the computer ex111. The encoding process is performed in the LSI ex117 included in the computer ex111 and the camera ex116. Note that image encoding / decoding software may be incorporated into any storage medium (CD-ROM, flexible disk, hard disk, or the like) that is a recording medium readable by the computer ex111 or the like. Furthermore, you may transmit moving image data with the mobile phone ex115 with a camera. The moving image data at this time is data encoded by the LSI included in the mobile phone ex115.

  In this content supply system ex100, the content (for example, video shot of music live) taken by the user with the camera ex113, camera ex116, etc. is encoded and transmitted to the streaming server ex103 as in the above embodiment. On the other hand, the streaming server ex103 stream-distributes the content data to the requested client. Examples of the client include a computer ex111, a PDA ex112, a camera ex113, a mobile phone ex114, and the like that can decode the encoded data. In this way, the content supply system ex100 can receive and play back the encoded data at the client, and can also receive a private broadcast by receiving, decoding, and playing back at the client in real time. It is a system that becomes possible.

The image encoding device or the image decoding device described in the above embodiments may be used for encoding and decoding of each device constituting this system.
A mobile phone will be described as an example.
FIG. 16 is a diagram illustrating the mobile phone ex115 using the image coding method and the image decoding method described in the above embodiment. The mobile phone ex115 includes an antenna ex201 for transmitting and receiving radio waves to and from the base station ex110, a video from a CCD camera, a camera unit ex203 capable of taking a still image, a video shot by the camera unit ex203, and an antenna ex201. A display unit ex202 such as a liquid crystal display that displays data obtained by decoding received video and the like, a main body unit composed of a group of operation keys ex204, an audio output unit ex208 such as a speaker for audio output, and audio input To store encoded data or decoded data such as a voice input unit ex205 such as a microphone, captured video or still image data, received mail data, video data or still image data, etc. Storage media ex207 and storage media ex207 attached to mobile phone ex115 And a slot portion ex206 to ability. The storage medium ex207 stores a flash memory element, which is a kind of EEPROM (Electrically Erasable and Programmable Read Only Memory), which is a nonvolatile memory that can be electrically rewritten and erased, in a plastic case such as an SD card.

  Further, the cellular phone ex115 will be described with reference to FIG. The cellular phone ex115 controls the main control unit ex311 which is configured to control the respective units of the main body unit including the display unit ex202 and the operation key ex204. The power supply circuit unit ex310, the operation input control unit ex304, and the image encoding Unit ex 312, camera interface unit ex 303, LCD (Liquid Crystal Display) control unit ex 302, image decoding unit ex 309, demultiplexing unit ex 308, recording / reproducing unit ex 307, modulation / demodulation circuit unit ex 306, and audio processing unit ex 305 via the synchronization bus ex 313. Are connected to each other.

When the end of call and the power key are turned on by the user's operation, the power supply circuit unit ex310 starts up the camera-equipped digital cellular phone ex115 in an operable state by supplying power from the battery pack to each unit. .
The mobile phone ex115 converts the voice signal collected by the voice input unit ex205 in the voice call mode into digital voice data by the voice processing unit ex305 based on the control of the main control unit ex311 including a CPU, ROM, RAM, and the like. The modulation / demodulation circuit unit ex306 performs spectrum spread processing, and the transmission / reception circuit unit ex301 performs digital analog conversion processing and frequency conversion processing, and then transmits the result via the antenna ex201. Also, the cellular phone ex115 amplifies the received signal received by the antenna ex201 in the voice call mode, performs frequency conversion processing and analog-digital conversion processing, performs spectrum despreading processing by the modulation / demodulation circuit unit ex306, and performs analog conversion by the voice processing unit ex305. After being converted into an audio signal, it is output via the audio output unit ex208.

  Further, when an e-mail is transmitted in the data communication mode, text data of the e-mail input by operating the operation key ex204 of the main body is sent to the main control unit ex311 via the operation input control unit ex304. The main control unit ex311 performs spread spectrum processing on the text data in the modulation / demodulation circuit unit ex306, performs digital analog conversion processing and frequency conversion processing in the transmission / reception circuit unit ex301, and then transmits the text data to the base station ex110 via the antenna ex201.

  When transmitting image data in the data communication mode, the image data captured by the camera unit ex203 is supplied to the image encoding unit ex312 via the camera interface unit ex303. When image data is not transmitted, the image data captured by the camera unit ex203 can be directly displayed on the display unit ex202 via the camera interface unit ex303 and the LCD control unit ex302.

  The image encoding unit ex312 has a configuration including the image encoding device described in the present invention, and an encoding method using the image data supplied from the camera unit ex203 in the image encoding device described in the above embodiment. The image data is converted into encoded image data by compression encoding, and is sent to the demultiplexing unit ex308. At the same time, the cellular phone ex115 sends the voice collected by the voice input unit ex205 during imaging by the camera unit ex203 to the demultiplexing unit ex308 via the voice processing unit ex305 as digital voice data.

  The demultiplexing unit ex308 multiplexes the encoded image data supplied from the image encoding unit ex312 and the audio data supplied from the audio processing unit ex305 by a predetermined method, and the multiplexed data obtained as a result is a modulation / demodulation circuit unit Spread spectrum processing is performed in ex306, digital analog conversion processing and frequency conversion processing are performed in the transmission / reception circuit unit ex301, and then transmitted through the antenna ex201.

When receiving data of a moving image file linked to a homepage or the like in the data communication mode, the received signal received from the base station ex110 via the antenna ex201 is subjected to spectrum despreading processing by the modulation / demodulation circuit unit ex306, and the resulting multiplexing is obtained. Data is sent to the demultiplexing unit ex308.
In addition, in order to decode the multiplexed data received via the antenna ex201, the demultiplexing unit ex308 separates the multiplexed data into the encoded image data and the audio data, and transmits the encoded data via the synchronization bus ex313. The encoded image data is supplied to the image decoding unit ex309 and the audio data is supplied to the audio processing unit ex305.

  Next, the image decoding unit ex309 is configured to include the image decoding device described in the present invention, and decodes encoded image data by a decoding method corresponding to the encoding method described in the above embodiment. Thus, the reproduction moving image data is generated and supplied to the display unit ex202 via the LCD control unit ex302, thereby displaying, for example, moving image data included in the moving image file linked to the homepage. At the same time, the audio processing unit ex305 converts the audio data into an analog audio signal, and then supplies the analog audio signal to the audio output unit ex208. Thus, for example, the audio data included in the moving image file linked to the home page is reproduced. The

  It should be noted that the present invention is not limited to the above-described system, and recently, digital broadcasting using satellites and terrestrial waves has become a hot topic. As shown in FIG. Any of the decoding devices can be incorporated. Specifically, in the broadcasting station ex409, a coded bit stream of video information is transmitted to a communication or broadcasting satellite ex410 via radio waves. Receiving this, the broadcasting satellite ex410 transmits a radio wave for broadcasting, and receives the radio wave with a home antenna ex406 having a satellite broadcasting receiving facility, such as a television (receiver) ex401 or a set top box (STB) ex407. The device decodes the encoded bit stream and reproduces it. In addition, the image decoding apparatus described in the above embodiment can also be implemented in the reproduction apparatus ex403 that reads and decodes the encoded bitstream recorded in the storage medium ex402 that is a recording medium. In this case, the reproduced video signal is displayed on the monitor ex404. Further, a configuration in which an image decoding apparatus is mounted in a set-top box ex407 connected to a cable ex405 for cable television or an antenna ex406 for satellite / terrestrial broadcasting, and this is reproduced on a monitor ex408 of the television is also conceivable. At this time, an image encoding device may be incorporated in the television instead of the set top box. It is also possible to receive a signal from the satellite ex410 or the base station ex107 by the car ex412 having the antenna ex411 and reproduce the moving image on a display device such as the car navigation ex413 that the car ex412 has.

  Further, the image signal can be encoded by the image encoding device shown in the above embodiment and recorded on a recording medium. As a specific example, there is a recorder ex420 such as a DVD recorder that records an image signal on a DVD disk ex421 or a disk recorder that records on a hard disk. Further, it can be recorded on the SD card ex422. If the recorder ex420 includes the image decoding device described in the above embodiment, the image signal recorded on the DVD disc ex421 or the SD card ex422 can be reproduced and displayed on the monitor ex408.

The configuration of the car navigation ex 413 is, for example, the configuration shown in FIG. 17 excluding the camera unit ex203 and the camera interface unit ex303, and the same is also considered for the computer ex111, the television (receiver) ex401, and the like. It is done.
In addition to the transmission / reception type terminal having both the encoder and the decoder, the terminal such as the mobile phone ex114 has three mounting formats, that is, a transmitting terminal having only an encoder and a receiving terminal having only a decoder. Can be considered.

As described above, the image encoding method and the image decoding method described in the above embodiment can be used in any of the above-described devices and systems, and thereby the effects described in the above embodiment can be obtained. Obtainable.
Further, the present invention is not limited to the above-described embodiment, and various modifications or corrections can be made without departing from the scope of the present invention.

  The present invention is applicable to an image coding apparatus and an image decoding apparatus that perform motion prediction by switching frames / fields in units of blocks, and methods thereof, and in particular, the image coding that performs motion prediction using a weighting coefficient. Useful for devices.

3 is a block diagram illustrating an outline of a functional configuration of a variable-length coding unit according to Embodiment 1. FIG. 6 is a block diagram illustrating an outline of a functional configuration of a variable-length decoding unit according to Embodiment 1. FIG. (A) is an example of a detailed data structure of “header” in the common information area of the picture area in the first embodiment. (B) is an example when there is no “AFF” and only “field weighting coefficient” is transmitted as “picture weighting coefficient”. (C) is an example in which the field and the frame cannot be switched in units of blocks because “picture frame coding information” is “1” and “AFF” is “0”. 6 is a flowchart showing a flow of an encoding process related to a weighting coefficient in a variable-length decoding unit when “picture frame encoding information” in Embodiment 1 is “1” and a picture is encoded in units of frames. (A) is an example of a detailed data structure of “header” in the common information area of the picture area in the modification of the first embodiment. (B) is an example in which “picture frame coding information” is “0” and there is no “AFF” for field coding at all times, and only “field weighting coefficient” is transmitted as “picture weighting coefficient”. . (C) is an example in which the field and the frame cannot be switched in units of blocks because “picture frame coding information” is “1” and “AFF” is “0”. 7 is a flowchart showing a flow of an encoding process related to a weighting coefficient in a variable-length decoding unit when “picture frame encoding information” is “1” and a picture is encoded in units of frames in a modification of the first embodiment. is there. FIG. 3 is a flowchart showing a flow of a decoding process related to a weighting coefficient when “picture frame coding information” in the variable length decoding unit of FIG. 2 is “1” and a picture is coded in units of frames. (A) is an example of a detailed data structure of “header” in the common information area of the picture area in the second embodiment, “1” is set in “AFF”, and “Field coefficient presence / absence information” is set in “Field coefficient presence / absence information”. In this example, “1” is set. (B) is a diagram similar to (a), in which “1” is set in “AFF” and “0” is set in “Field coefficient presence / absence information”. (C) is an example in which field and frame switching is not performed in units of blocks because “0” is set in “AFF”. 10 is a flowchart showing a flow of an encoding process related to a weighting coefficient in a variable length encoding unit according to the second embodiment. 12 is a flowchart showing a flow of a decoding process related to a weighting coefficient in a variable length decoding unit in the second embodiment. (A) is a figure which shows the example of a data structure of the picture area | region in Embodiment 3, "1" is set to "AFF", and "1" is set to "Frame coefficient presence / absence information". is there. (B) is a diagram similar to (a), in which “1” is set in “AFF” and “0” is set in “Frame coefficient presence / absence information”. (C) is an example in which field and frame switching is not performed in units of blocks because “0” is set in “AFF”. 10 is a flowchart showing a flow of encoding processing relating to a weighting coefficient in a variable length encoding unit according to Embodiment 3. 12 is a flowchart showing a flow of a decoding process related to a weighting coefficient in a variable length decoding unit in the third embodiment. It is explanatory drawing at the time of implementing with the computer system using the program recorded on recording media, such as a flexible disk, the image coding method of the said Embodiment 1, 2, and 3 and an image decoding method. (A) is explanatory drawing which showed the example of the physical format of the flexible disk which is a recording medium main body. (B) is explanatory drawing which showed the external appearance seen from the front of the flexible disk, sectional structure, and a flexible disk. (C) is an explanatory diagram showing a configuration for recording and reproducing the program on the flexible disk FD. It is a block diagram which shows the whole structure of the content supply system which implement | achieves a content delivery service. It is a figure which shows an example of a mobile telephone. It is a block diagram which shows the internal structure of a mobile telephone. It is a block diagram which shows the whole structure of the system for digital broadcasting. It is a figure which shows an example of the kind and reference relationship of a picture. It is a figure which shows the other example of the kind of picture, and a reference relationship. It is a figure which shows an example of the stream structure of image data. (A) is a schematic diagram in the case of performing a weighted prediction process with reference to one frame. (B) is a schematic diagram in the case of performing weighted prediction processing with reference to two frames. (A) is a schematic diagram in the case of performing a weighted prediction process with reference to the 1st or 2nd field corresponding to each. (B) is a schematic diagram in the case of performing a weighted prediction process with reference to two first or second fields corresponding to each. It is a block diagram which shows the function structure of the conventional image coding apparatus. It is a block diagram which shows the outline of a function structure of the variable length coding unit in the conventional image coding apparatus. It is a block diagram which shows the function structure of the conventional image decoding apparatus. It is a block diagram which shows the outline of a function structure of the variable length decoding unit in the conventional image decoding apparatus.

Explanation of symbols

PicMem Picture memory Add Addition unit Sub Subtraction unit ME Motion detection unit MC Motion compensation unit T Orthogonal transform unit IT Inverse orthogonal transform unit Q Quantization unit IQ Inverse quantization unit VLC Variable length coding unit VLD Variable length decoding unit SW Switch Se Sector Cs Computer system FD Flexible disk FDD Flexible disk drive 11 Field weight coefficient encoding unit 12 Frame weight coefficient encoding unit 13 Weight coefficient mode determining unit 14, 15 Switch 21 Separating unit 22 Field weight coefficient decoding unit 23 Frame weight coefficient decoding Conversion unit 24 weight coefficient generation unit 26 to 28 switch 100 image encoding device 101 MV encoding unit 102 quantized value encoding unit 103 weight coefficient encoding unit 104 index Encoding unit 105 AFF identification information encoding unit 106 multiplexing unit 116 camera 200 image decoding device 201 separation unit 202 MV decoding unit 203 quantized value decoding unit 204 weight coefficient decoding unit 205 index decoding unit 206 AFF Identification information decoder

Claims (2)

An image decoding apparatus for decoding coded Picture included in the encoded signal in block units,
When the picture is composed of frames and the picture is coded so as to adaptively switch between frame decoding and field decoding of the blocks constituting the picture, the coded signal A variable length decoding unit that decodes the encoded frame weighting factor included in and generates a field weighting factor from the decoded frame weighting factor;
When a block constituting the picture is frame-encoded, a prediction image is generated using a pixel value of a reference frame referred to by the block and the decoded frame weight coefficient, and the block is a field A motion compensation unit that generates a prediction image using a pixel value of a reference field referred to by the block and the generated field weighting coefficient when encoded ,
Using a prediction image the generated, an adder for decoding the picture,
An image decoding apparatus comprising: An image decoding method for decoding a coded Picture included in the encoded signal in block units,
When the picture is composed of frames and the picture is coded so as to adaptively switch between frame decoding and field decoding of the blocks constituting the picture, the coded signal Decoding the encoded frame weighting factor included in and generating a field weighting factor from the decoded frame weighting factor;
When a block constituting the picture is frame-encoded, a prediction image is generated using a pixel value of a reference frame referred to by the block and the decoded frame weight coefficient, and the block is a field If encoded, generating a predicted image using a pixel value of a reference field referenced by the block and the generated field weighting factor;
A step of using the prediction image the generated, decoding the picture,
An image decoding method comprising:

Images