DESCRIPTION
MOVING PICTURE CODING METHOD AND MOVING PICTURE DECODING METHOD
5 Technical Field
The present invention relates to a moving picture coding
method and a moving picture decoding method, and particularly to
a coding method and a decoding method for performing
inter-picture prediction with; reference to previously coded
10 pictures.
Background Art
With development of multimedia applications, it has been
popular to handle integrally all kinds of media information such as
15 video, audio and text. Since digitized images have an enormous
amount of data, image information compression techniques are
absolutely essential for storage and transmission of such
information. It is also important to standardize such compression
.1
techniques for interoperation of compressed image data. There 20 exist international standards for image compression techniques, such as H.261 and H.263 standardized by ITU-T (International Telecommunication Union - Telecommunication Standardization Sector) and MPEG-1, MPEG-2 and MPEG-4 standardized by ISO (International Organization for Standardization). ITU is now 25 working for standardization of H.26L as the latest standard for image coding.
Coding of moving pictures, in general, compresses information amount by reducing redundancy in both temporal and spatial directions. Therefore, in inter-picture prediction coding, 30 which aims at reducing the temporal redundancy, motion of a current picture is estimated on a block-by-block basis with reference to preceding or subsequent pictures so as to generate
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predictive images of the current picture, and then differential values between the obtained predictive images and the current picture are coded.
Here, the term "picture" represents a single sheet of an 5 image, and it represents a frame when used in a context of a progressive image, whereas it represents a frame or a field in a context of an interlaced image. The interlaced image here is a single frame that is made up of two fields having different times respectively. In the process of coding and decoding the interlaced
10 image, a single frame can be handled as a frame, as two fields, or as a frame structure or a field structure on every block in the frame.
The following description will be given assuming that a picture is a frame in a progressive image, but the same description
15 can be given even assuming that a picture is a frame or a field In an interlaced image.
Fig. 35 is a diagram for explaining types of pictures and reference relations between them.
A picture like Picture U, which is /ntra-picture prediction
20 coded without reference to any pictures, is referred to as an I-picture. A picture like Picture PIG, which is /nter-picture prediction coded with reference to one picture, is referred to as a P-picture. And a picture, which can be /nter-picture prediction coded with reference to two pictures at the same time, is referred
25 to as a B-picture. B-pictures, like Pictures B6, B12 and B18, can refer to two pictures located in arbitrary temporal directions. Reference pictures can be specified on a block-by-block basis, on which motion is estimated, and they are discriminated between a first reference picture which is described earlier in a bit stream
30 including the coded pictures and a second reference picture which is described later in the bit stream. However, it is required in order to code and decode above pictures that the reference
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pictures be already coded and decoded. Figs. 36A and 36B show examples of order of pictures in which B-plctures are coded and decoded. Fig. 36A shows a display order of the pictures, and Fig. 36B shows a coding and decoding order reordered from the display 5 order as shown in Fig. 36A. These drawings show that the pictures are reordered so that the pictures which are referred to by Pictures B3 and B6 are previously coded and decoded.
Next, reference indices for specifying reference pictures will be explained with reference to Fig. 37 and Fig. 38. For the sake of
10 simplicity, numbers for identifying actual pictures are referred to as picture numbers, while numbers used for specifying reference pictures for inter-picture prediction are referred to as reference indices. Particularly, indices indicating first reference pictures and second reference pictures are referred to as first reference
15 Indices and second reference indices, respectively. Default values as shown in Fig. 37 are usually assigned to the reference indices In an initial state, but the assignment can be changed according to commands.
Fig. 37 shows the assignment of two reference indices to the
20 picture numbers In the initial state of frame coding, and Fig. 38 shows an assignment of reference indices updated using commands from the assignment as shown In Fig. 37. When there Is a sequence of pictures ordered In coding order, picture numbers are assigned to the pictures stored in a memory in coding order.
25 Commands for assigning the reference Indices to the picture numbers are described in a header of a slice that is the smaller unit of coding than a picture, and thus the assignment can be updated every time one slice Is coded. It Is possible to use a differential value between an original picture number and an updated picture
30 number as the above command and code an arbitrary number of such commands as a command sequence. The first command in the command sequence is applied to a picture number of a current
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picture and indicates a picture number corresponding to a reference index number "0". The second command in the command sequence is applied to the picture number corresponding to the reference index number "0" and indicates a picture number 5 corresponding to a reference index number "1". The third command is applied to the picture number corresponding to the reference index number "1" and indicates a picture number corresponding to a reference index number "2". The same applies to the fourth and the following commands. In the example of the
10 first reference indices in Fig. 38, a command "-2" is given first and thus the reference Index number "0" is assigned to the picture with its number "11" by adding "-2" to the picture number "13" of the current picture. Next, a command " + 1" is given and thus the reference index number "1" is assigned to the picture with its
15 number "12" by adding " + 1" to the picture number "11" corresponding to the reference index number "0". The following picture numbers are assigned to the reference index numbers in the same manner. The same goes for the second reference indices.
20 Fig. 39 is a schematic diagram showing an example of a bit
stream generated as a result of the above-mentioned coding. As shown in this figure, the maximum number of reference indices Max_idxl for the first reference pictures (refl) and the maximum number of reference indices Max_idx2 for the second reference
25 pictures (ref2) are described in the picture common information of the bit stream, and the reference index assignment command sequences idx_cmdl and idx__cmd2 for refl and ref2 are described in the slice header.
A document related to the above conventional technology is
30 ITU-T Rec. H.264 | ISO/IEC 14496-10 AVC Joint Final Committee Draft of Joint Video Specification (2002-8-10) (P.54, 8.3.6.3 Default index orders / P.56, 8.3.6.4 Changing the default index
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orders).
By the way, as a method of coding an interlaced image, frame coding and field coding can be used by switching them per block in one picture. This Is referred to as Macroblock Adaptive 5 Frame/Field Coding (hereinafter referred to as MBAFF). In this method, frame coding and field coding can be switched per a pair of two macroblocks placed above and below, as shown in Fig. 40. In a case of frame coding, both macroblocks are coded as a frame structure, while In a case of field coding, a macroblock consisting of
10 odd-numbered lines and a macroblock consisting of even-numbered lines are coded separately.
In MBAFF, as shown in Figs. 41A and 41B, reference pictures are used for reference by switching them between a frame structure and a field structure depending on the coding methods of
15 the macroblock pairs. When a current macroblock pair is coded as a frame structure as shown in Fig. 41A, Pictures PI'^ P3 are referred to as frames. When a current macroblock pair is coded as a field structure as shown in Fig. 41B, the pictures are separated into top fields and bottom fields, Pictures PIT'^PSB, and referred to
20 as respective fields. At this time, the number of reference pictures, which is the number of top and bottom fields. Is twice the number of frames.
However, the maximum number of reference indices (See max_idxl and max_idx2 in Fig. 39) and the command sequences
25 (See idx_cmdl and idx_cmd2 in Fig. 39) for updating the assignment, which are used for assigning reference indices to respective pictures, cannot be applied to both frames and fields at the same time. Therefore, there is a problem that the maximum number of reference indices and the assignment commands cannot
30 be appropriately determined in a case of MBAFF.
Disclosure of Invention
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Against this backdrop, the present invention aims at
providing a picture coding method and a picture decoding method
for applying reference indices appropriately to either frame coding
or field coding in a case of MBAFF.
5 In order to achieve this object, the coding method according
to the present invention is a moving picture coding method for coding a picture with switching between frame coding and field coding adapt)vely on a block-by-block basis, comprising an assignment step of assigning field reference indices to fields using
10 frame reference indices, the field reference indices specifying fields which are referred to at the time of field coding, and the frame reference indices specifying frames which are referred to at the time of frame coding.
According to this structure, frame reference indices can be
15 used for assigning field reference indices. In other words, frame reference indices can be applied appropriately not only to frame coding but also to field coding.
Here, the above-mentioned moving picture coding method may further comprise a specification step of specifying two fields
20 that make up each of the frames specified by each of the frame reference indices, and in the assignment step, a first value may be assigned to one field having a parity same as a parity of a field including a current block to be coded, out of the specified two fields, as each of the field reference indices, the first value being obtained
25 by doubling a value of said each of the frame reference indices, and a second value may be assigned to another field having a parity different from a parity of the field including the current block as said each of the field reference indices, the second value being obtained by adding one to said first value.
30 According to this structure, the value obtained by doubling
the value of the frame reference index and the value obtained by adding one to the doubled value are assigned to the field reference
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indices depending on the field parity. Therefore, the field reference indices can be assigned extremely easily using the frame reference indices.
Here, the above-mentioned moving picture coding method 5 may further comprise a determination step of determining a maximum number of the field reference indices to be a value obtained by doubling a maximum number of the frame reference indices, and in the assignment step, the field reference indices may be assigned within a range of the determined maximum number.
10 According to this structure, the number obtained by
doubling the maximum number of frame reference indices can be assigned as the field reference indices, and thus the effective use of the frame reference indices can be maximized.
Here, the above-mentioned moving picture coding method
15 may further comprise a specification step of specifying two fields that make up each of the frames specified by each of the frame reference Indices, the two fields being a top field and a bottom field, and in the assignment step, a first value may be assigned to the top field, out of the specified two fields, as each of the field reference
20 indices, the first value being obtained by doubling a value of said each of the frame reference indices, and a second value may be assigned to the bottom field as said each of the field reference indices, the second value being obtained by adding one to said first value.
25 The above-mentioned moving picture coding method may
further comprise a specification step of specifying two fields that make up each of the frames specified by each of the frame reference indices, and In the assignment step, a value same as a value of said each of the frame reference indices may be assigned
30 only to one field having a parity same as a parity of a field including a current block to be coded, out of the specified two fields, as each of the field reference indices.
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Here, the above-mentioned moving picture coding method may further comprise an addition step of generating a command sequence indicating how to assign the frame reference indices and a command sequence indicating how to assign the field reference 5 indices independently, coding said two command sequences, and adding said coded command sequences to a coded signal.
The above-mentioned moving picture coding method, wherein the field reference indices consist of top field reference indices and bottom field reference indices, may further comprise 10 an addition step of generating a command sequence indicating how to assign the frame reference indices, a command sequence indicating how to assign the top field reference indices and a command sequence indicating how to assign the bottom field reference indices independently, coding said three command 15 sequences, and adding said coded command sequences to a coded signal.
The above-mentioned moving picture coding method may further comprise a determination step of determining a maximum number of the field reference indices, and in the assignment step, 20 the field reference indices may be assigned to fields within a range of the determined maximum number using the frame reference indices.
Here, in the determination step, the maximum number of the field reference indices may be determined to be a value 25 obtained by doubling a maximum number of the frame reference indices.
According to this structure, the frame reference indices can be used effectively at the maximum for the field reference indices within the number obtained by doubling the maximum number of 30 frame reference indices.
Here, in the determination step, the maximum number of the field reference indices may be determined to be a value same

as a maximum number of the frame reference indices.
According to this structure, the frame reference indices can be used effectively at the maximum for the field reference indices within the number same as the maximum number of frame
5 reference indices.
Here, the above-mentioned moving picture coding method may further comprise an addition step of determining a maximum number of the frame reference indices independently of the maximum number of the field reference indices, coding said two
10 maximum numbers, and adding said coded maximum numbers to a coded signal.
According to this structure, the maximum number of the field reference indices can be determined independently of the maximum number of the frame reference indices, and the decoding
15 apparatus can notify the determined maximum number via a coded signal.
Here, the above-mentioned moving picture coding method, wherein the field reference indices consist of top field reference indices and bottom field reference indices, may further comprise
20 an addition step of determining a maximum number of the frame reference indices, a maximum number of the top field reference indices and a maximum number of the bottom field reference indices independently, coding said three maximum numbers, and adding said coded maximum numbers to a coded signal.
25 As described above, according to the coding method of the
present invention, the reference indices, the maximum number of the reference indices and the commands that are originally intended for frame coding can also be utilized appropriately in field coding, in a case of MBAFF.
30 Also, the moving picture decoding method, the moving
picture coding apparatus, the moving picture decoding apparatus and the program of the present invention have the same structures,
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functions and effects as mentioned above.
Brief Description of Drawings
Fig. 1 is a block diagram showing a structure of a coding 5 apparatus in a first embodiment of the present invention.
Fig. 2 is an illustration showing an example of
correspondences between picture numbers and first and second
reference indices in a case of frame coding of macroblocks (MB).
Fig. 3 is an illustration showing an example of
10 correspondences between the first and second reference indices,
commands and picture numbers.
Fig. 4 is an illustration showing an example of assigning the
first and second reference indices to the picture numbers of fields
in a case of field coding of macroblocks.
15 Fig. 5 is a flowchart showing the processing of assigning
reference indices and commands executed by a reference index/picture number conversion unit in the coding apparatus.
Fig. 6 is a flowchart showing the processing of assigning
reference indices for field coding to fields.
20 Fig. 7 is a block diagram showing a structure of a decoding
apparatus in the first embodiment of the present invention.
Fig. 8 is a block diagram showing a structure of a coding apparatus in a second embodiment of the present invention.
Fig. 9 is an illustration showing an example of assigning the 25 first and second reference indices to picture numbers of fields in a case of field coding of a macroblock.
Fig. 10 is a flowchart showing the processing of assigning
reference indices executed by a reference index/picture number
conversion unit in the coding apparatus.
30 Fig. 11 is a block diagram showing a structure of a decoding
apparatus in the second embodiment of the present invention.
Fig. 12 is a block diagram showing a structure of a coding
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apparatus in a tfiird embodiment of the present Invention.
Fig. 13 is an illustration showing an example of assigning the
first and second reference indices to picture numbers of fields in a
case of field coding of a macroblock.
5 Fig. 14 is a block diagram showing a structure of a decoding
apparatus in the third embodiment of the present invention.
Fig. 15 is a block diagram showing a structure of a coding apparatus in a fourth embodiment of the present invention.
Fig. 16 is an illustration showing an example of assigning the 10 first and second reference indices to picture numbers of fields in a case of field coding of a macroblock.
Fig. 17 is a block diagram showing a structure of a coding apparatus in a fifth embodiment of the present invention.
Fig. 18 is an illustration showing an example of assigning the 15 first and second reference indices to picture numbers of fields in a case of field coding of a macroblock.
Fig. 19 is a flowchart showing the processing of assigning
reference indices executed by a reference index/picture number
conversion unit in the coding apparatus.
20 Fig. 20 is a block diagram showing a structure of a decoding
apparatus in the fifth embodiment of the present invention.
Fig. 21 is a diagram showing a data structure of a bit stream in a sixth embodiment of the present invention.
Fig. 22 is an illustration showing an example of assigning the 25 first and second reference indices to picture numbers of fields in a case of field coding of a macroblock.
Fig. 23 is a block diagram showing a structure of a coding apparatus in a seventh embodiment of the present invention.
Fig. 24 is a diagram showing an example of a data structure 30 of a bit stream.
Fig. 25 is an illustration showing an example of assigning the first and second indices to picture numbers of fields in a case of
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^ field coding of a macroblock.
Fig. 26 is a diagram showing an example of correspondences between reference indices, commands and picture numbers of fields specifically applied to top fields and bottom fields 5 respectively in a case of field coding.
Fig. 27 is a flowchart showing the processing of assigning reference indices and commands in a case of a mixture of frame coding and field coding.
Fig. 28 is a block diagram showing a structure of a decoding 10 apparatus in the seventh embodiment of the present invention.
Fig. 29 is a diagram showing another example of a data structure of a bit stream.
Figs. BOA, B and C are illustrations of a recording medium for storing a program for realizing the moving picture coding method 15 and moving picture decoding method in each of the embodiments by a computer system.
Fig. 31 is a block diagram showing an overall configuration of a content supply system.
Fig. 32 is an external view of a mobile phone.
20 Fig. 33 is a block diagram showing a structure of the mobile
phone.
Fig. 34 is a diagram showing an example of a digital broadcasting system.
Fig. 35 is a schematic diagram for explaining reference 25 relations between pictures in a background art.
Figs. 36A and B are schematic diagrams for explaining reordering of pictures in the background art.
Fig. 37 is a schematic diagram for explaining how to assign
picture numbers to reference indices in the background art.
30 Fig. 38 is a schematic diagram showing assignment of
reference indices updated from the assignment as shown in Fig. 37 using commands in the background art.
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Fig. 39 is a schematic diagram for explaining a structure of a bit stream in the background art.
Fig. 40 is an illustration of macroblock pairs in cases of
frame coding and field coding.
5 Figs. 41A and B are illustrations showing reference frames in
frame coding and reference fields in field coding.
Best Mode for Carrying Out the Invention
10 (First Embodiment)
(Overview of Coding Apparatus and Decoding Apparatus)
First, an overview of a coding apparatus and a decoding apparatus in the present embodiment will be given.
When performing macroblock adaptive frame/field coding
15 (MBAFF), the coding apparatus and the decoding apparatus in the present embodiment handle the maximum number of reference indices and a command sequence in the following manners (1.1) and (1.2), respectively. Here, the reference indices and the commands are same as those as shown in Fig. 38, and the
20 maximum number of the reference indices are same as those as shown in Fig. 39.
(1.1) As for the maximum number of the reference indices, the coding apparatus describes the maximum number of reference indices for frame coding (frame reference indices) in a bit stream
25 to be transmitted when field coding and frame coding are mixed. The coding apparatus handles the maximum number of reference indices as the number of available reference indices in frame coding, while, in field coding, it considers the value obtained by doubling the maximum number for frame coding as the number of
30 reference indices for field coding (field reference indices). For example, when the reference indices for frame coding 0'^2 are assigned, the maximum number of reference indices is "3". In a
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case of frame coding, this number indicates the actual maximum number itself. In a case of field coding, the number "6" obtained by doubling the maximum number of reference indices for frame coding "3" is considered as the maximum number of reference 5 indices for field coding. The same applies to the decoding apparatus.
(1.2) As for the command sequence, the coding apparatus describes commands for frame coding in a bit stream to be transmitted. The coding apparatus assigns the reference indices
10 for frame coding in a case of frame coding, as explained using Fig. 38. Note that if the command sequence is not coded, correspondences between picture numbers and reference indices are established in the manner of default assignment as shown in Fig. 37.
15 In a case of field coding, the assignment of reference indices
is updated for field coding based on the reference indices for frame coding which are already assigned.
To be more specific, the value obtained by doubling the value of the reference index for frame coding is assigned to a field of the
20 same parity as a field including a current macroblock to be coded, among two fields that make up one frame, while the value obtained by doubling the value of the reference index for frame coding and adding 1 (x2+l) is assigned to another field of the opposite parity, as a reference index for field coding, respectively (See Fig. 4).
25 Here, "parity" means an odd or even quality of a field (distinction between a top field consisting of odd-numbered lines and a bottom field consisting of even-numbered lines).
In other words, when a current macroblock to be coded belongs to a top field, the value obtained by doubling a value of a
30 reference index for frame coding is assigned to a top field among two fields, while the value obtained by adding 1 to the doubled value (x2+l) is assigned to a bottom field among the two fields.
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When a current macroblock belongs to a bottom field, the value obtained by doubling the value of the reference index for frame coding is assigned to a bottom field among two fields, while the value obtained by adding 1 to the doubled value (x2+l) is assigned 5 to a top field among the two fields.
On the other hand, the decoding apparatus decodes the maximum number of reference indices for frame coding and the assignment commands included in the transmitted bit stream, and assigns the reference indices to the reference pictures, using the
10 maximum number and the commands, in exactly the same manner as the coding apparatus. ^ cod.. —;;-;;: t transmitted. The coding
bottom field coding m a b,t ^''^^'^' ^^^^^ ,„ding for the
ZZ:l^^^ thiVefe^ence indices fo. hottom field cod.g
for the purpose of field codmg. ._,HPC; the
10
on the other hand, the decoding apparatus decodes the maximum number of reference indices and the assignment commands for frame coding, top field coding and bottom field coding, included in the transmitted bit stream, and using them, it assigns the reference pictures and the reference indices in exactly 15 the same manner as the coding apparatus. (Structure of Coding Apparatus)
Fig. 23 is a block diagram showing the structure of the coding apparatus in the seventh embodiment of the present invention. The coding apparatus in this figure is different from 20 that in Fig. 1 in that the former includes a reference index/picture number conversion unit 109e, instead of the reference index/picture number conversion unit 109.
F(g. 24 \s a diagram showing an example of a data structure of a bit stream in the present embodiment. In this figure, 25 idx_cmdl is a set of commands for the first reference picture refl, and includes idx_cmd_frm, idx_cmd_top and idx_cmd_btm. idx_cmd_frm \s a command sequence for reference indices for frame coding. idx_cmd_top is a command sequence for reference indices for top field coding. idx_cmd_btm is a command sequence 20 for reference indices for bottom field coding.
Fig. 25 is an illustration showing an example of assigning the first and second indices to picture numbers of fields in a case of
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reference indices and commands executed by the reference index/picture number conversion unit 109e. As shown in this
10 figure, the reference index/picture number conversion unit 109e assigns reference indices and commands for frame coding (Sll), and when frame coding and field coding are mixed (S12), it assigns reference indices and commands for top field coding (S93) and further assigns reference indices and commands for bottom field
15 coding (S94).
Note that in Fig. 27, no command is assigned in Sll, S93 and S94 when default reference indices are used. (Structure of Decoding Apparatus)
Fig. 28 is a block diagram showing the structure of the
20 decoding apparatus in the seventh embodiment of the present invention. Fig. 28 includes a reference index/picture number conversion unit 206e instead of the reference index/picture number conversion unit 206 In Fig. 7. The reference index/picture number conversion unit 206e establishes correspondences
25 between picture numbers and reference indices for frame coding, top field coding and bottom field coding, respectively, using index assignment commands for them inputted from the bit stream analysis unit 201.
In the present embodiment, command sequences for top
30 field coding and bottom field coding are described separately in a bit stream, but they may be one common command sequence. Fig. 29 is a diagram showing the data structure of the bit stream in that
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case. In this figure, idx_fld is a command sequence common to top field coding and bottom field coding.
Note that the maximum number of reference indices for field coding as described in (7.1) do not have to be specific to top field 5 coding or bottom field coding, but may be common to top field coding and bottom field coding.
Also, the reference indices and commands for field coding as described in (7.2) do not have to be specific to top field coding or bottom field coding, and may be common to top field coding and 10 bottom field coding.
Also, the decoding apparatus in each of the above
embodiments may create a reference table between reference
indices for field coding and picture numbers of fields before
starting decoding of a slice, and refer to the table when decoding a
15 field-coded macroblock.
(Eighth Embodiment)
If a program for realizing the structures of the picture coding method or the picture decoding method as shown in each of the
20 above embodiments is recorded on a memory medium such as a flexible disk, it becomes possible to perform the processing as shown in each of the embodiments easily in an independent computer system.
Figs. 30A, BOB and 30C are illustrations showing the case
25 where the present invention is implemented in a computer system using a flexible disk which stores the picture coding method or the picture decoding method of the above first to seventh embodiments.
Fig. 30B shows a front view and a cross-sectional view of an
30 appearance of a flexible disk, and the flexible disk itself, and Fig. 30A shows an example of a physical format of a flexible disk as a recording medium body. The flexible disk FD is contained in a
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case F, and a plurality of tracks Tr are formed concentrically on the surface of the disk in the radius direction from the periphery and each track is divided Into 16 sectors Se in the angular direction. Therefore, as for the flexible disk storing the above-mentioned 5 program, the picture coding method as the program is recorded in an area allocated for it on the flexible disk FD.
Fig. 30C shows the structure for recording and reproducing the program on and from the flexible disk FD. When the program is recorded on the flexible disk FD, the picture coding method or
10 the picture decoding method as a program is written in the flexible disk from the computer system Cs via a flexible disk drive. When the picture coding method is constructed in the computer system by the program on the flexible disk, the program is read out from the flexible disk using the flexible disk drive and transferred to the
15 computer system.
The above explanation is made on the assumption that a recording medium is a flexible disk, but the same processing can also be performed using an optical disk. In addition, the recording medium is not limited to a flexible disk and an optical disk, but any
20 other medium such as an IC card and a ROM cassette capable of recording a program can be used.
(Ninth Embodiment)
Fig. 31 to Fig. 34 are illustrations of devices for performing 25 the coding processing or the decoding processing as described in the above embodiments and a system using them.
Fig. 31 is a block diagram showing the overall configuration
of a content supply system exlOO for realizing content distribution
service. The area for providing communication service is divided
30 into cells of desired size, and base stations exl07 to exllO which
are fixed wireless stations are placed in respective cells.
In this content supply system exlOO, devices such as a
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computer exlll, a PDA (personal digital assistant) exll2, a camera exllB, a mobile phone exll4 and a camera-equipped mobile phone exll5 are connected to the Internet ex 101 via an Internet service provider exl02, a telephone network exl04 and 5 base stations exl07 to exllO.
However, the content supply system exlOO is not limited to the configuration as shown in Fig. 31, and a combination of any of them may be connected. Also, each device may be connected directly to the telephone network exl04, not through the base
10 stations exl07 to exllO.
The camera exll3 is a device such as a digital video camera capable of shooting moving pictures. The mobile phone may be a mobile phone of a PDC (Personal Digital Communications) system, a CDMA (Code Division Multiple Access) system, a W-CDMA
15 (Wideband-Code Division Multiple Access) system or a GSM (Global System for Mobile Communications) system, a PHS (Personal Handyphone system) or the like.
A streaming server exl03 is connected to the camera exll3 via the base station exl09 and the telephone network exl04,
20 which allows live distribution or the like using the camera exll3 based on the coded data transmitted from a user. Either the camera exll3 or the server for transmitting the data may code the shot data. Also, the moving picture data shot by a camera exll6 may be transmitted to the streaming server exl03 via the
25 computer exlll. The camera exll6 is a device such as a digital camera capable of shooting still and moving pictures. Either the camera exll6 or the computer exlll may code the moving picture data. An LSI exll7 included in the computer exlll or the camera exll6 actually performs coding processing. Software for coding
30 and decoding moving pictures may be integrated into any type of storage medium (such as a CD-ROM, a flexible disk and a hard disk) that is a recording medium which is readable by the computer
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exlll or the like. Furthermore, the camera-equipped mobile
phone exll5 may transmit the moving picture data. This moving
picture data is the data coded by the LSI included in the mobile
phone exll5.
5 The content supply system exlOO codes contents (such as a
live music video) shot by users using the camera exll3, the camera exll6 or the like in the same manner as the above embodiment and transmits them to the streaming server exlOB, while the streaming server exl03 makes stream distribution of the
10 content data to the clients at their request. The clients Include the computer exlll, the PDA exll2, the camera exll3, the mobile phone exll4 and so on capable of decoding the above-mentioned coded data. In the content supply system exlOO, the clients can thus receive and reproduce the coded data, and further the clients
15 can receive, decode and reproduce the data In real time so as to realize personal broadcasting.
When each device in this system performs coding or decoding, the moving picture coding apparatus or the moving picture decoding apparatus, as shown In each of the
20 above-mentioned embodiments, can be used.
A mobile phone will be explained as an example of the device.
Fig. 32 Is a diagram showing the mobile phone exll5 that uses the moving picture coding method and the moving picture
25 decoding method explained in the above embodiments. The mobile phone exll5 has an antenna ex201 for sending and receiving radio waves to and from the base station exllO, a camera unit ex203 such as a CCD camera capable of shooting video and still pictures, a display unit ex202 such as a liquid crystal
30 display for displaying the data obtained by decoding video and the like shot by the camera unit ex203 and received via the antenna ex201, a body unit including a set of operation keys ex204, a voice
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output unit ex208 such as a speaker for outputting voices, a voice input unit 205 such as a microphone for inputting voices, a storage medium ex207 for storing coded or decoded data such as data of moving or still pictures shot by the camera, and text data and data 5 of moving or still pictures of received e-mails, and a slot unit ex206 for attaching the storage medium ex207 to the mobile phone exll5. The storage medium ex207 includes a flash memory element, a kind of EEPROM (Electrically Erasable and Programmable Read Only Memory) that is an electrically erasable and rewritable
10 nonvolatile memory, in a plastic case such as an SD card.
The mobile phone exll5 will be further explained with reference to Fig. 33. In the mobile phone exll5, a main control unit ex311 for overall controlling the display unit ex202 and the body unit including operation keys ex204 is connected to a power
15 supply circuit unit ex310, an operation input control unit ex304, a picture coding unit ex312, a camera interface unit ex303, an LCD (Liquid Crystal Display) control unit ex302, a picture decoding unit ex309, a multiplex/demultiplex unit ex308, a record/reproduce unit ex307, a modem circuit unit ex306 and a voice processing unit
20 ex305, and they are connected to each other via a synchronous bus ex313.
When a call-end key or a power key is turned ON by a user's operation, the power supply circuit unit ex310 supplies respective units with power from a battery pack so as to activate the
25 camera-equipped digital mobile phone exll5 for making it into a ready state.
In the mobile phone exll5, the voice processing unit ex305 converts the voice signals received by the voice input unit ex205 in conversation mode into digital voice data under the control of the
30 main control unit ex311 including a CPU, ROM and RAM, the modem circuit unit ex306 performs spread spectrum processing of the digital voice data, and the send/receive circuit unit ex301 performs
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digital-to-analog conversion and frequency transform of the data, so as to transmit it via the antenna ex201. Also, in the mobile phone exll5, after the data received by the antenna ex201 in conversation mode is amplified and performed of frequency 5 transform and analog-to-digital conversion, the modem circuit unit ex306 performs inverse spread spectrum processing of the data, and the voice processing unit ex305 converts it into analog voice data, so as to output it via the voice output unit 208.
Furthermore, when transmitting e-mail in data
10 communication mode, the text data of the e-mail inputted by operating the operation keys ex204 on the body unit is sent out to the main control unit ex311 via the operation input control unit ex304. In the main control unit ex311, after the modem circuit unit ex306 performs spread spectrum processing of the text data
15 and the send/receive circuit unit ex301 performs digital-to-analog conversion and frequency transform for it, the data is transmitted to the base station exllO via the antenna ex201.
When picture data is transmitted in data communication mode, the picture data shot by the camera unit ex203 is supplied to
20 the picture coding unit ex312 via the camera interface unit ex303. When the picture data is not transmitted, it is also possible to display the picture data shot by the camera unit ex203 directly on the display unit 202 via the camera interface unit ex303 and the
LCD control unit ex302.
25 The picture coding unit ex312, which includes the picture
30
coding apparatus as explained In the present invention, compresses and codes the picture data supplied from the camera unit ex203 by the coding method used for the picture coding apparatus as shown in the above embodiments so as to transform it into coded picture data, and sends it out to the multiplex/demultiplex unit ex308. At this time, the mobile phone exll5 sends out the voices received by the voice input unit ex205
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during shooting by the camera unit ex203 to the multiplex/demultiplex unit ex308 as digital voice data via the voice processing unit ex305.
The multiplex/demultiplex unit ex308 multiplexes the coded 5 picture data supplied from the picture coding unit ex312 and the voice data supplied from the voice processing unit ex305 by a predetermined method, the modem circuit unit ex306 performs spread spectrum processing of the multiplexed data obtained as a result of the multiplexing, and the send/receive circuit unit ex301
10 performs digital-to-analog conversion and frequency transform of the data for transmitting via the antenna ex201.
As for receiving data of a moving picture file which is linked to a Web page or the like in data communication mode, the modem circuit unit ex306 performs Inverse spread spectrum processing of
15 the signal received from the base station exllO via the antenna ex201, and sends out the multiplexed data obtained as a result of the processing to the multiplex/demultiplex unit ex308.
In order to decode the multiplexed data received via the antenna ex201, the multiplex/demultiplex unit ex308 separates
20 the multiplexed data into a bit stream of picture data and a bit
stream of voice data, and supplies the coded picture data to the
picture decoding unit ex309 and the voice data to the voice
processing unit ex305 respectively via the synchronous bus ex313.
Next, the picture decoding unit ex309, which Includes the
25 picture decoding apparatus as explained in the present invention, decodes the bit stream of picture data by the decoding method corresponding to the coding method as shown in the above-mentioned embodiments to generate reproduced moving picture data, and supplies this data to the display unit ex202 via
30 the LCD control unit ex302, and thus moving picture data included in a moving picture file linked to a Web page, for instance, is displayed. At the same time, the voice processing unit ex305
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converts the voice data into analog voice data, and supplies this
data to the voice output unit ex208, and thus voice data included in
a moving picture file linked to a Web page, for instance, is
reproduced.
5 The present invention is not limited to the above-mentioned
system, and at least either the picture coding apparatus or the picture decoding apparatus in the above-mentioned embodiments can be incorporated into a system for digital broadcasting as shown in Fig. 34. Such ground-based or satellite digital broadcasting has
10 been in the news lately. More specifically, a coded bit stream of video information is transmitted from a broadcast station ex409 to a communication or broadcast satellite ex410 via radio waves. Upon receipt of it, the broadcast satellite ex410 transmits radio waves for broadcasting, a home-use antenna ex406 with a satellite
15 broadcast reception function receives the radio waves, and a television (receiver) ex401 or a set top box (STB) ex407 decodes the bit stream for reproduction. The picture decoding apparatus as shown in the above-mentioned embodiments can be implemented in the reproduction apparatus ex403 for reading off
20 and decoding the bit stream recorded on a storage medium ex402 that is a recording medium such as a CD and DVD. In this case, the reproduced video signals are displayed on a monitor ex404. It is also conceived to implement the picture decoding apparatus in the set top box ex407 connected to a cable ex405 for a cable
25 television or the antenna ex406 for satellite and/or ground-based broadcasting so as to reproduce them on a monitor ex408 of the television ex401. The picture decoding apparatus may be incorporated into the television, not in the set top box. Or, a car ex412 having an antenna ex411 can receive signals from the
30 satellite ex410, the base station exl07 or the like for reproducing moving pictures on a display device such as a car navigation system ex413 in the car ex412.
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Furthermore, the picture coding apparatus as shown in the above-mentioned embodiments can code picture signals for recording on a recording medium. As a concrete example, there is a recorder ex420 such as a DVD recorder for recording picture 5 signals on a DVD disc ex421 and a disk recorder for recording them on a hard disk. They can be recorded on an SD card ex422. If the recorder ex420 includes the picture decoding apparatus as shown in the above-mentioned embodiments, the picture signals recorded on the DVD disc ex421 or the SD card ex422 can be 10 reproduced for display on the monitor ex408.
As the structure of the car navigation system ex413, the
structure without the camera unit ex203, the camera interface unit
ex303 and the picture coding unit ex312, out of the units shown in
Fig. 33, is conceivable. The same applies to the computer exlll,
15 the television (receiver) ex401 and others.
In addition, three types of implementations can be
conceived for a terminal such as the above-mentioned mobile
phone exll4; a sending/receiving terminal including both an
encoder and a decoder, a sending terminal including an encoder
20 only, and a receiving terminal including a decoder only.
As described above, it is possible to use the moving picture
coding method or the moving picture decoding method in the
above-mentioned embodiments in any of the above-mentioned
apparatuses and systems, and using this method, the effects
25 described in the above embodiments can be obtained.
It should be noted that the present invention is not limited to the above embodiments, and many variations or modifications thereof are possible without departing from the scope of the invention.
30
Industrial Applicability
The present invention is suitable for a picture coding
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apparatus for performing coding with switching between frame coding and field coding on a block-by-block basis in a picture and a picture decoding apparatus. More specifically, it is suitable for a Web server for distributing moving pictures, a network terminal for 5 receiving them, a digital camera for recording and replaying moving pictures, a camera-equipped mobile phone, a DVD recorder/player, a PDA, a personal computer and the like.

CLAIMS
1. A moving picture coding method for coding a picture with switching between frame coding and field coding adaptively on a block-by-block basis, comprising an assignment step of assigning field reference Indices to fields using frame reference indices, the field reference indices specifying fields which are referred to at the time of field coding, and the frame reference indices specifying frames which are referred to at the time of frame coding.
2. The moving picture coding method according to Claim 1,
further comprising a specification step of specifying two fields that
make up each of the frames specified by each of the frame
reference indices,
wherein in the assignment step, a first value is assigned to
one: field having a parity same as a parity of a field including a
current block to be coded, out of the specified two fields, as each of
the ; field reference indices, the first value being obtained by
, doubling a value of said each of the frame reference Indices, and a
second value is assigned to another field having a parity different
from a parity of the field including the current block as said each of
the field reference indices, the second value being obtained by
adding one to said first value.
3. The moving picture coding method according to Claim 2, further comprising a determination step of determining a
maximum number of the field reference indices to be a value
obtained by doubling a maximum number of the frame reference
indices,
' wherein in the assignment step, the field reference indices
are assigned within a range of the determined maximum number.
4. The moving picture coding method according to Claim 1,
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further comprising a specification step of specifying two fields that
make up each of the frames specified by each of the frame
reference indices, the two fields being a top field and a bottom
field,
5 wherein in the assignment step, a first value is assigned to
the top field, out of the specified two fields, as each of the field reference indices, the first value being obtained by doubling a value of said each of the frame reference indices, and a second value is assigned to the bottom field as said each of the field 10 reference indices, the second value being obtained by adding one to said first value.
5. The moving picture coding method according to Claim 1,
further comprising a specification step of specifying two fields that
15 make up each of the frames specified by each of the frame
reference indices,
wherein in the assignment step, a value same as a value of
said each of the frame reference indices is assigned only to one
field having a parity same as a parity of a field including a current 20 block to be coded, out of the specified two fields, as each of the
field reference indices.
6. The moving picture coding method according to Claim 1,
further comprising an addition step of generating a command
25 sequence indicating how to assign the frame reference indices and a command sequence indicating how to assign the field reference indices independently, coding said two command sequences, and adding said coded command sequences to a coded signal.
30 7. The moving picture coding method according to Claim 1,
wherein the field reference indices consist of top field reference indices and bottom field reference indices, and
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said moving picture coding method further comprises an addition step of generating a command sequence indicating how to assign the frame reference indices, a command sequence indicating how to assign the top field reference indices and a 5 command sequence indicating how to assign the bottom field reference indices independently, coding said three command sequences, and adding said coded command sequences to a coded signal.
10 8. The moving picture coding method according to Claim 1, further comprising a determination step of determining a maximum number of the field reference indices,
wherein in the assignment step, the field reference indices are assigned to fields within a range of the determined maximum
15 number using the frame reference indices.
9. The moving picture coding method according to Claim 8,
wherein in the determination step, the maximum number of
the field reference indices is determined to be a value obtained by 20 doubling a maximum number of the frame reference indices.
10. The moving picture coding method according to Claim 8,
wherein in the determination step, the maximum number of
the field reference indices is determined to be a value same as a 25 maximum number of the frame reference indices.
11. The moving picture coding method according to Claim 8,
further comprising an addition step of determining a maximum
number of the frame reference indices independently of the
30 maximum number of the field reference indices, coding said two maximum numbers, and adding said coded maximum numbers to a coded signal.
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12. The moving picture coding method according to Claim 8,
wherein the field reference indices consist of top field
■ reference indices and bottom field reference indices, and
5 said moving picture coding method further comprises an
!! addition step of determining a maximum number of the frame
i reference indices, a maximum number of the top field reference
. indices and a maximum number of the bottom field reference
indices independently, coding said three maximum numbers, and
10 ^adding said coded maximum numbers to a coded signal.
13. A moving picture decoding method for decoding a picture
with switching between frame decoding and field decoding
^'adaptively on a block-by-block basis, comprising an assignment 15 step of assigning field reference indices to fields using frame !! reference indices, the field reference indices specifying fields which ii are referred to at the time of field decoding, and the frame ;! reference indices specifying frames which are referred to at the
■ time of frame decoding.
20 ^' :■
. 14. The moving picture decoding method according to Claim 13, further comprising a specification step of specifying two fields that make up each of the frames specified by each of the frame reference indices,
25 wherein in the assignment step, a first value is assigned to
one field having a parity same as a parity of a field including a
current block to be decoded, out of the specified two fields, as each
i: of the field reference indices, the first value being obtained by
doubling a value of said each of the frame reference indices, and a
30 :■ second value is assigned to another field having a parity different from a parity of the field including the current block as said each of the field reference indices, the second value being obtained by
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adding one to said first value.
15. The moving picture decoding method according to Claim 14, further comprising a determination step of determining a maximum number of the field reference indices to be a value obtained by doubling a maximum number of the frame reference indices,
wherein in the assignment step, the field reference indices are assigned within a range of the determined maximum number.
10
16. The moving picture decoding method according to Claim 13,
further comprising a specification step of specifying two fields that
make up each of the frames specified by each of the frame
reference indices, the two fields being a top field and a bottom
15 field,
wherein in the assignment step, a first value is assigned to the top field, out of the specified two fields, as each of the field reference indices, the first value being obtained by doubling a value of said each of the frame reference indices, and a second
20 value is assigned to the bottom field as said each of the field reference indices, the second value being obtained by adding one to said first value.
17. The moving picture decoding method according to Claim 13,
25 further comprising a specification step of specifying two fields that
make up each of the frames specified by each of the frame reference indices,
wherein in the assignment step, a value same as a value of
said each of the frame reference indices is assigned only to one
30 field having a parity same as a parity of a field including a current
block to be decoded, out of the specified two fields, as each of the
field reference indices.
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18. The moving picture decoding method according to Claim 13, further comprising a command sequence decoding step of decoding a coded signal including a command sequence indicating how to assign the frame reference indices and a command sequence indicating how to assign the field reference indices,
wherein in the assignment step, the frame reference indices and the field reference indices are assigned according to said two decoded command sequences.
10
19. The moving picture decoding method according to Claim 13,
wherein the field reference indices consist of top field
reference indices and bottom field reference Indices,
said moving picture decoding method further comprises:
15 a command sequence decoding step of decoding a coded
signal including a command sequence indicating how to assign the frame reference indices, a command sequence indicating how to assign the top field reference indices and a command sequence indicating how to assign the bottom field reference indices, and
20 in the assignment step, the frame reference indices, the top
field reference indices and the bottom field reference indices are assigned according to said three decoded command sequences,
20. The moving picture decoding method according to Claim 13,
25 further comprising a determination step of determining a
maximum number of the field reference indices,
wherein In the assignment step, the field reference indices are assigned to fields within a range of the determined maximum number using the frame reference indices.
30
21. The moving picture decoding method according to Claim 20, wherein in the determination step, the maximum number of
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the field reference indices is determined to be a value obtained by doubling a maximum number of the frame reference indices.
22. The moving picture decoding method according to Claim 20,
5 wherein in the determination step, the maximum number of
the field reference indices is determined to be a value same as a maximum number of the frame reference indices.
23. The moving picture decoding method according to Claim 20,
10 wherein in the determination step, a maximum number of
the frame reference indices and the maximum number of the field reference indices are determined by decoding a coded signal including said two maximum numbers.
15 24. The moving picture decoding method according to Claim 20, wherein the field reference indices consist of top field reference indices and bottom field reference indices, and
in the determination step, a maximum number of the frame
reference indices, a maximum number of the top field reference
20 indices and a maximum number of the bottom field reference
indices are determined by decoding a coded signal including said
three maximum numbers.
25. A moving picture coding apparatus for performing coding 25 with switching between frame coding and field coding adaptively on a block-by-block basis in a picture, comprising an assignment unit operable to assign field reference indices to fields using frame reference indices, the field reference indices specifying fields which are referred to at the time of field coding, and the frame reference 30 indices specifying frames which are referred to at the time of frame coding.
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26. A moving picture decoding apparatus for performing
decoding with switching between frame decoding and field
decoding adaptively on a block-by-block basis in a picture,
comprising:
5 an assignment unit operable to assign field reference indices
to fields using frame reference indices, the field reference indices
specifying fields which are referred to at the time of field decoding,
and the frame reference indices specifying frames which are
referred to at the time of frame decoding; and
10 a decoding unit operable to decode the frames specified by
the frame reference indices or the fields specified by the field reference indices.
27. A program for causing a computer to execute a moving
15 picture coding method for performing coding with switching
between frame coding and field coding adaptively on a ibiock-by-block basis in a picture, the program causing the computer to assign field reference indices to fields using frame reference indices, the field reference indices specifying fields which 20 are referred to at the time of field coding, and the frame reference indices specifying frames which are referred to at the time of frame coding.
28. A program for causing a computer to execute a moving
25 picture decoding method for performing decoding with switching
between frame decoding and field decoding adaptively on a block-by-block basis in a picture, the program causing the computer to assign field reference indices to fields using frame reference indices, the field reference indices specifying fields which 30 are referred to at the time of field decoding, and the frame reference indices specifying frames which are referred to at the time of frame decoding.
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29. A moving picture coding method for coding a picture with switching between frame coding and field coding adaptively on a block-by-block basis, substantially as herein described with reference to the accompanying drawings.