JP4125739B2 - Image encoding method, image decoding method and apparatus - Google Patents

Description

  The present invention relates to an image encoding method and an image decoding method, and more particularly to an encoding technique, a decoding technique, and their apparatuses related to data compression for efficiently recording and transmitting an image signal.

  In recent years, the multimedia era of voice, image, and other contents has been integrated, and conventional information media, that is, means for transmitting information such as newspapers, magazines, televisions, radios, telephones, etc. to people are targeted for multimedia. It has come to be taken up as. In general, multimedia refers to not only characters but also figures, sounds, especially images, etc. that are associated with each other at the same time. To make the above-mentioned conventional information media a multimedia target, the information is converted into a digital format. It is an essential condition.

  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 ( In addition, for a moving image, an information amount of 100 Mbits per second (current television reception quality) or more is required for a moving image, and it is not realistic to handle the enormous amount of information in the digital format as it is with the information media. 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 Kbps to 1.5 Mbps. Not practical.

  Therefore, what is required is information compression technology. For example, in the case of a videophone, H.264 recommended by ITU-T (International Telecommunication Union Telecommunication Standardization Sector). 261 and H.264. H.263 standard video compression technology is used. In addition, 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 digital compression of moving picture signals, and MPEG-1 is so that moving picture signals can be transmitted at a rate of 1.5 Mbps, that is, information on television signals. Is a standard that compresses up to about 1/100. In addition, since the transmission speed for the MPEG-1 standard is mainly limited to about 1.5 Mbps, MPEG-2 standardized to meet the demand for higher image quality requires 2 video signals. Enables TV broadcast quality data transmission at a rate of ~ 15 Mbps.

  Furthermore, MPEG-4 with a higher compression rate has been standardized by a working group (ISO / IEC JTC1 / SC29 / WG11) that has been standardizing with MPEG-1 and MPEG-2. MPEG-4 initially introduced not only high-efficiency coding at a low bit rate, but also a powerful error resilience technology that can reduce subjective image quality degradation even if a transmission path error occurs. .

  H. In conventional image coding such as H.263 and MPEG-4, various signal conversion / compression processes are performed on the image signal to convert the image signal into various types of numerical values, which are appropriately selected according to the meaning of each converted numerical value. The fixed length coding or variable length coding based on the code table is performed. In general, in coding, a compression rate is improved by assigning a codeword having a short code length to a code having a high occurrence frequency and assigning a codeword having a long code length to a code having a low occurrence frequency. The numerical values converted by the signal conversion / compression process differ in the frequency of occurrence depending on the meanings represented by the numerical values. Therefore, by appropriately selecting a code table in which codewords corresponding to those numerical values are described. Thus, the compression rate of image encoding is improved. In conventional image decoding corresponding to conventional image encoding, the same code table as that used in image encoding is used to perform correct decoding.

FIG. 17 is a functional block diagram of a portion related to an encoding function in a conventional image encoding apparatus 500. As illustrated in FIG. 17, the image coding apparatus 500 includes a header / frame coding unit 501, a syntax analysis unit 502, a fixed length / variable length coding unit 503, and a code table selection unit 504.
The header / frame encoding unit 501 receives the moving image signal Vin, and generates information on the header and information on each frame, which is information common to the entire image, from the moving image signal Vin.

  Specifically, the header / frame encoding unit 501 includes, as header part information, a header parameter (Inf_H, not shown) that is common information, a header code value (InfVal_H) obtained by converting the header parameter (InfVal_H), and Generates a header syntax structure signal (Stx_H) indicating the meaning of the numerical value of the header code value, outputs this header syntax structure signal (Stx_H) to the syntax analysis unit 502, and sets the header code value (InfVal_H) to a fixed length The data is output to the variable length coding unit 503. Further, the header / frame encoding unit 501 uses the frame code value (InfVal_F), which is a numerical value obtained as a result of encoding the image signal of each frame, as the image signal information for each frame, and the meaning of the numerical value of the frame code value. The frame syntax structure signal (Stx_F) is generated, the frame syntax structure signal (Stx_F) is output to the syntax analysis unit 502, and the frame code value (InfVal_F) is output to the fixed length / variable length encoding unit 503. To do. In FIG. 17, the header code value (InfVal_H) and the frame code value (InfVal_F) are collectively described as “InfVal_X”, and the header syntax structure signal (Stx_H) and the frame syntax structure signal (Stx_F) are collectively illustrated. It is described as “Stx_X”.

  The syntax analysis unit 502 generates a code table selection signal (Sel_H or Sel_F) based on the header syntax structure signal (Stx_H) or the frame syntax structure signal (Stx_F), and outputs it to the code table selection unit 504. That is, the syntax analysis unit 502 selects a code table selection signal (for example, Sel_H1 to Sel_H1 to Sel_H1) for selecting an appropriate code table from a plurality of code tables based on a value indicated by the header syntax structure signal or the frame syntax structure signal. Sel_H3 or Sel_F1 to Sel_F3) is generated. In FIG. 17, the code table selection signals (Sel_H and Sel_F) are collectively described as “Sel_X”.

  The fixed-length / variable-length encoding unit 503 forms an image encoded signal (Str) based on the header code value (InfVal_H) and the frame code value (InfVal_F). Specifically, the header code value (InfVal_H) is decomposed into unit header code values (Val_H: for example, Val_H1 to Val_H3) that are basic units of encoding, and the code table selection unit 504 is based on these unit header code values. The code table is selected to obtain the header codeword (Code_H), and the header code value (InfVal_H) and the header codeword (Code_H) are combined to form the header stream (Str_H). Further, the fixed-length / variable-length encoding unit 503 decomposes the frame code value (InfVal_F) into unit frame code values (Val_F: for example, Val_F1 to Val_F3) that are basic units of encoding, and outputs these unit frame codes. The code table selection unit 504 selects a code table based on the word to obtain a frame code word (Code_F), and combines the frame code value (InfVal_F) and the frame code word (Code_F) to form a frame stream (Str_F) To do. Furthermore, the fixed length / variable length encoding unit 503 multiplexes the header stream (Str_H) and the frame stream (Str_F) to form an image encoded signal (Str). In FIG. 17, the unit header code value (Val_H) and the unit frame code value (Val_F) are collectively described as “Val_X”, and the header codeword (Code_H) and the frame codeword (Code_F) are collectively referred to as “Code_X”. "

  As described above, the code table selection unit 504 selects a code table based on the code table selection signal Sel_X and the unit header code value or the unit frame code value, and the header code word or the frame code word according to the selected code table. Is generated and output to the fixed length / variable length encoding unit 503.

  FIG. 18 is a diagram showing a stream configuration of a conventional image encoded signal. The encoded image signal Str is composed of frame data FrmData in which image signal information of each frame constituting the image is stored and a sequence header SeqHdr that is information common to each frame. The sequence header SeqHdr includes information on a synchronization signal SeqSync for synchronization between transmission and reception, image size Size of each frame, and frame rate FrmRate. On the other hand, the frame data FrmData is composed of macroblock data MB which is data unique to the macroblocks constituting the frame and a frame header FrmHdr which is data common to each macroblock. The frame header FrmHdr includes a synchronization signal FrmSync for synchronizing the frame and a frame number FrmNo indicating the time for displaying the frame. The macroblock data MB is encoded with a coding flag Cod indicating whether or not the macroblock is encoded, a macroblock encoding mode Mode indicating the encoding method of each macroblock, and motion compensation. In the case where it is set, it is composed of motion information MV representing the amount of motion and pixel value data Coef which is encoded data of each pixel.

  FIG. 19 is a functional block diagram of a portion related to a decoding function in the conventional image decoding apparatus 600. In the figure, components having the same functions and signals having the same functions as those in the functional block diagram of the conventional image coding apparatus 500 in FIG. 17 are given the same reference numerals, and the description thereof is omitted.

  The fixed length / variable length decoding unit 601 separates the encoded image signal Str into a header stream (Str_H) and a frame stream (Str_F). Further, the fixed-length / variable-length decoding unit 601 decomposes the header stream (Str_H) into header codewords Code_H (for example, Code_H1 to Code_H3) which are basic decoding units, and the code table selection unit 602 performs header codewords. A unit header code value (Val_H) corresponding to Code_H is obtained and combined to form a header code value (InfVal_H). Furthermore, as with the header stream (Str_H), the fixed length / variable length decoding unit 601 also applies a frame codeword Code_F (for example, a basic unit of decoding) to the frame stream (Str_F). The code table selection unit 602 obtains a unit frame code value Val_F corresponding to the frame code word Code_F, and combines them to form a frame code value (InfVal_F).

  The header / frame decoding unit 603 decodes the header code value (InfVal_H) to restore the information of the header part, and features the header parameter (Inf_H, not shown) which is the common information and the subsequent header code value. A header syntax structure signal (Stx_H) is output. Here, the header syntax structure signal (Stx_H) is information indicating the meaning of the next codeword necessary for decoding the next codeword of the header part. Further, as in the case of the header code value (InfVal_H), the header / frame decoding unit 603 restores the frame code value InfVal_F of each frame, and decodes the frame syntax structure signal Stx_F indicating the meaning of the code value. The moving image signal Vout is output.

  The syntax analysis unit 604 outputs a code table selection signal (Sel_H) for switching the output of the code table selection unit 602 in order to decode the code word next to the header part using the header syntax structure signal (Stx_H). . That is, the syntax analysis unit 604 generates a code table selection signal (Sel_H) for switching an appropriate code table from a plurality of code tables according to a value indicated by the header syntax structure signal (Stx_H). Further, the syntax analysis unit 604 outputs the code table selection signal (Sel_F) by the frame syntax structure signal (Stx_F), as in the case of the header syntax structure signal (Str_H).

  Here, the frame syntax structure signal Stx_F is information indicating the characteristics of the next codeword necessary for decoding the next codeword. The syntax analysis unit 604 outputs a code table selection signal Sel_F for switching the output of the code table selection unit in order to decode the next code word using the frame syntax structure signal Stx_F. That is, the syntax analysis unit 604 generates a code table selection signal Sel_F for switching an appropriate code table from a plurality of code tables based on a value indicated by the frame syntax structure signal Stx_F. In FIG. 19, as in FIG. 17, “InfVal_X”, “Stx_X”, “Sel_X”, “Val_X”, and “Code_X” are common generic names of signals related to header information and image signal information for each frame. Is used.

  The header stream Str_H in FIGS. 17 and 19 corresponds to the sequence header SeqHdr of the stream configuration of the conventional image encoded signal in FIG. 18 or a combination of the sequence header SeqHdr and the frame header FrmHdr. Str_F corresponds to frame data FrmData or macroblock data MB, respectively.

However, such a conventional image encoding device and a conventional image decoding device require a plurality of code tables in order to increase the compression rate,
(1) Processing for switching code tables is complicated.
There is a problem. These problems are not particularly problematic when encoding / decoding is performed on a high-performance, large-capacity computer, but it becomes difficult to realize with a small memory and a low computing capacity of a portable terminal or the like. In particular, in the conventional image encoding device and the conventional image decoding device, the code table is frequently switched by the code table selection units 504 and 602 by the syntax structure signal (Stx_X), so that the code table switching process is complicated. There was a risk of becoming.

  In addition, variable length coding includes two types of coding: Huffman coding that uses a code table that is relatively easy to decode, and arithmetic coding that is complicated in coding and decoding processing but has high compression efficiency. is there. Arithmetic coding is also a kind of variable length coding, and the probability of use in coding / decoding of arithmetic coding corresponds to a code table. However, when both are mixed together in the same stream, the process for switching between the Huffman coding and the arithmetic coding table in the process of encoding and decoding is very complicated. In such a case, there is a problem that it is difficult to realize.

  Therefore, the present invention has been made in view of the above problems, and an image encoding method and an image that enable data compression equivalent to the conventional one even with a small memory and a low computing capacity such as a portable terminal. An object is to provide a decryption method.

  In order to achieve the above object, an image encoding method according to the present invention is an image encoding method for encoding information including an image signal in frame units, and the information to be encoded includes , Information on the characteristics of the entire image signal and information on the image signal in frame units are included, and the information on the characteristics of the entire image signal is encoded using a plurality of encoding methods. A plurality of encoding steps, and information related to the image signal in units of frames are encoded using a common encoding method for each frame, and the entire encoded image signal is encoded. And a multiplex encoding step of performing encoding by multiplexing information relating to the feature and information relating to the encoded image signal in frame units.

  Further, in order to achieve the above object, an image decoding method according to the present invention is an image decoding method for decoding information including an image signal of a predetermined unit, the information to be decoded. Includes information common to the entire image signal and information related to the image signal of the predetermined unit, and the information common to the entire image signal is decoded using a plurality of decoding methods. A plurality of decoding steps to be performed and information related to the image signal of the predetermined unit are decoded using a single variable length decoding method or arithmetic decoding method common to each predetermined unit. And a common decoding step.

  As described above, according to the image encoding method and the image decoding method according to the present invention, when encoding information related to the entire image, a plurality of code tables are used as in the past, but for individual image information Uses a single encoding method / decoding method (code table), so that encoding or decoding of individual image information can be realized succinctly with almost no reduction in compression rate, thereby reducing costs, etc. Since it can be planned, its practical value is high.

Embodiments according to the present invention will be described below with reference to FIGS.
(Embodiment 1)
FIG. 1 is a functional block diagram of a portion related to an encoding function in the image encoding device 10 of the present embodiment. In FIG. 1, signals related to the same operations as the signals in the conventional image coding apparatus 500 shown in FIG. 17 are given the same symbols, and descriptions thereof are omitted.

  In the image encoding device 10 according to the present embodiment, a plurality of encoding schemes are applied to the header portion, which is information common to the entire image signal, and a single encoding is applied to the information related to the image signal in frame units. It is characterized in that the method is applied.

  Here, in this specification, the frame is described, but in the case of an interlaced image signal, a field may be used instead of the frame.

  The configuration and operation for creating and encoding the header information, which is information common to the entire image signal, and the operation thereof are exactly the same as those of the conventional image encoding device 500 of FIG.

  As shown in FIG. 1, the image encoding device 10 newly includes a frame encoding unit 13 and a variable length encoding unit 16 as compared with the conventional image encoding device 500. Note that the multiplexing unit 17 extracts a part of the functions in the fixed length / variable length coding unit 503 of the conventional image coding apparatus 500 described above.

  The frame encoding unit 13 is a part that creates individual image signal information from the moving image signal Vin, and a frame code value that is a numerical value obtained as a result of encoding the image signal information of each frame with reference to the header parameter Inf_H. InfVal_F is output to the variable length coding unit 16.

  The variable length encoding unit 16 decomposes the frame code value InfVal_F into a unit frame code value Val_F which is a basic unit of encoding, and converts the unit frame code value Val_F into a frame codeword Code_F using only the code table 16a. The frame stream Str_F is configured by combining the converted frame codewords. As a result, the information related to the image signal in units of frames does not switch the encoding method according to the syntax as in the conventional case, and a common single encoding method is applied to all frames.

  The multiplexing unit 17 multiplexes the header stream Str_H and the frame stream Str_F to configure an image encoded signal Str.

  FIG. 2 is a stream configuration diagram of the image encoded signal Str encoded by the functional block diagram in the image encoding device 10 shown in FIG. As shown in FIG. 2, this stream is composed of a sequence header SeqHdr and a plurality of frame data FrmData. In this case, the sequence header SeqHdr is information common to the entire image signal, and the frame data FrmData is data encoded using only the code table 16a.

  Note that the sequence header SeqHdr and the frame data FrmData do not necessarily have to be transmitted continuously in the same stream, and if the decoding device side controls the sequence header SeqHdr first, the sequence header SeqHdr and the frame data FrmData are transmitted in different streams. May be.

FIG. 3 is a data configuration diagram of the frame data in FIG.
FIG. 3A is a data configuration diagram of general frame data FrmData. In this case, the frame header FrmHdr of the frame data FrmData is encoded by a plurality of encoding methods (code tables) as information common to the entire image signal, and the macroblock data MB is encoded by a single encoding method (for example, the code table). 16a only) is an example of encoding. In this case, since the macroblock data MB that occupies most of the stream in encoding / decoding is encoded by a single encoding method (only the code table 16a), the encoding method (code Therefore, it is possible to simplify and realize an image encoding device having a function equivalent to that of the prior art.

  The frame header FrmHdr and the macroblock data MB need not be transmitted continuously in the same stream. If control is performed so that the decoding apparatus can recognize the frame header FrmHdr first, it may be transmitted in a discontinuous state within the same stream, or may be transmitted in different streams.

  In the stream configuration shown in FIG. 3A, the frame header FrmHdr of the frame data FrmData is information common to the entire image signal. However, the MPEG-1 and MPEG-2 slice structure and the MPEG-4 video packet structure are used. When a plurality of macroblocks are collected to form one frame and common information (header) such as a synchronization signal is further arranged at the head of the macroblock aggregate, the macroblock The header of the aggregate may be information common to the entire image signal, and image data other than the header may be encoded with a single code table 16a. A frame composed of the aggregate of macroblocks is called a slice.

  FIG. 3B is a data configuration diagram of the frame data having the above slice structure. The slice header SliceHdr is information common to the entire image signal, encoding is performed using a plurality of code tables, and the macro block data MB of each slice Slice is encoded using a single code table 16a. Note that the slice header SliceHdr and the macroblock data MB are not necessarily transmitted continuously in the same stream. If control is performed so that the decoding header can recognize the slice header SliceHdr first, it may be transmitted in a discontinuous state within the same stream, or may be transmitted in different streams.

  FIG. 4 is an example of a code table used in the present embodiment. FIG. 4A is an example of a code table used when variable length coding is performed in the image coding apparatus 10. As shown in FIG. 4A, for data “0” to “2” with high occurrence frequency, the code length of the corresponding code word is short and “3” to “6” with low occurrence frequency are The code length of the corresponding code word is long.

  FIG. 4B is an example of a code table used when fixed-length encoding is performed in the image encoding device 10. As shown in FIG. 4B, the word length of the code word corresponding to each data is constant, but the code length of the code word becomes longer as the maximum number of frame memories in the image encoding device 10 increases. It has become.

  FIG. 5 is a functional block diagram of a portion related to a decoding function in the image decoding apparatus 20 according to the present embodiment. The image decoding device 20 decodes the image encoded signal Str encoded by the image encoding device 10 and outputs a decoded moving image signal Vout. In FIG. 5, signals related to the same operations as the signals in the conventional image decoding apparatus 600 of FIG. 19 are given the same symbols, and the description thereof is omitted.

  The configuration for decoding the header information, which is information common to the entire image signal, and the operation thereof are the same as those of the conventional image decoding apparatus 600 of FIG.

  The separator 21 receives the encoded image signal Str and separates it into a header stream Str_H and a frame stream StrF. The variable length decoding unit 23 converts the frame codeword Code_F constituting the frame stream Str_F into a frame code value Val_F using only the code table 16a, and is a numerical value of a signal encoded from the unit frame code value Val_F. Constructs a frame code value InfVal_F. The frame decoding unit 27 refers to the header parameter Inf_H, which is information common to the entire image signal, decodes the frame code value InfVal_F, and outputs the decoded moving image signal Vout.

  As described above, since the information other than the header information, which is information common to the entire image signal, can be decoded only by the single code table 16a, the decoding method that has been necessary in the past is used. A process of frequently switching (code table) is not required, and an image decoding apparatus having an equivalent function can be simplified and realized.

  The header information, which is information common to the entire image signal, is the sequence header SeqHdr in the stream configuration of the image encoded signal in FIG. 2 and the frame header FrmHdr of the frame data FrmData in FIG. Similarly to the case of the image encoding device 10 described above, the macroblock data MB may be decoded by the single code table 23a. Further, as in the case of the image encoding device 10 described above, when the stream configuration of the image encoded signal has a slice structure, the slice header SliceHdr is information common to the entire image signal, and information other than the slice header is simply set. You may decode with the one code table 23a.

Next, the operation of the image coding apparatus 10 configured as described above will be described.
FIG. 6 is a flowchart showing the flow of the encoding process of the image encoding device 10.

  First, when the moving image signal Vin is input to the header information creation unit 11 (S61), a code table for encoding the header code value InfoVal_H is selected based on the header syntax structure signal Stx_H (S63). The header information creating unit 11 and the fixed length / variable length coding unit 15 create header information based on the moving image signal Vin in the same manner as in the past, and according to the decomposed unit header code value (Val_H). A code table is selected and encoded (S64 to S66), and a header stream is constructed (S67).

  On the other hand, when the frame encoding unit 13 acquires the moving image signal Vin (S61), it encodes information other than the information in the header portion using only the code table 16a (S68) to form a frame stream. (S69).

  The multiplexing unit 17 multiplexes the header stream and the frame stream to form an image encoded signal (S70).

  As described above, according to the image encoding device and the image decoding device in the present embodiment, the macroblock data that occupies most of the encoding process and the decoding process are encoded and encoded using a single code table. Since decoding is performed, it is not necessary to frequently switch a code table that has been necessary in the past, and it is possible to simplify and realize an image coding apparatus having a function equivalent to that in the past.

(Embodiment 2)
FIG. 7 is a functional block diagram relating to the encoding function in the image encoding device 30 of the present embodiment. In FIG. 7, the signals having the same function configuration and the same operation as those in the functional block diagram of the image encoding device 10 in FIG.

  Differences between the image encoding device 30 in FIG. 7 and the image encoding device 10 in FIG. 1 will be described. The part in which the image encoding device 10 creates information of the header part, which is information common to the entire image signal, performs encoding by selecting an appropriate code table from among a plurality of code tables, The image signal information was encoded using one code table. On the other hand, the present image encoding device 30 encodes information in the header portion, which is information common to the entire image signal, by a fixed length encoding method or a normal variable length encoding (Huffman encoding) method using a code table. Encoding is performed, and other individual image signal information is encoded only by arithmetic encoding.

In arithmetic coding, encoding / decoding processing is slightly more complicated than normal variable length coding using a code table such as Huffman coding, but it is known that the compression rate is improved. Therefore, it is possible to quickly determine what kind of decoding the frame data should be performed by performing normal variable-length coding on a variety of header information that is particularly important in the decoding process. Since arithmetic coding is vulnerable to transmission errors and the like, encoding header information, which is important data, with normal variable-length coding has a great effect on improving error tolerance.
Also, when switching between arithmetic coding and normal variable length coding, the processing is particularly complicated, and a redundant number of bits is required to switch from arithmetic coding to normal variable length coding. Therefore, it is not a good idea to frequently switch between arithmetic coding and normal variable length coding.

  The syntax analysis unit 12 outputs an encoding selection signal SelEnc for switching the output of the encoding selection unit 31 to the encoding selection unit 31 according to the header syntax structure signal Stx_H.

  The encoding selection unit 31 selects either the fixed length encoding method or the variable length encoding method by the encoding selection signal SelEnc, and the fixed length encoding unit 32 or the variable length encoding unit 33 according to the selected encoding method. Is encoded to form a header stream Str_H, which is output to the multiplexing unit 17.

  The arithmetic encoding unit 34 performs arithmetic encoding on the frame code value InfVal_F with reference to the header parameter Inf_H, configures an arithmetically encoded frame stream Str_F, and outputs the frame stream Str_F to the multiplexing unit 17.

  The multiplexing unit 17 multiplexes the header stream Str_H and the frame stream Str_F to configure an image encoded signal Str.

  As described above, the image encoding device 30 according to the present embodiment performs encoding such that the encoding method is switched according to the syntax for the information of the header part, which is information common to the entire image signal, By encoding only individual image signal information by arithmetic encoding, an image encoding apparatus that can simplify the switching process of the encoding method without degrading the encoding efficiency can be realized.

  FIG. 8 is a functional block diagram relating to the decoding function in the image decoding device 40 of the present embodiment. In FIG. 8, signals related to the same functional configuration and the same operation as those in the functional block diagram of the image decoding device 20 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Differences between the image decoding device 40 of FIG. 8 and the image decoding device 20 of the first embodiment will be described. When decoding the header information, which is information common to the entire image signal, the image decoding apparatus 20 selects an appropriate code table from a plurality of code tables and performs decoding. On the other hand, the other individual image signal information is decoded by using one code table, whereas the present image decoding apparatus 40 decodes information of the header portion which is information common to the entire image signal. In this case, decoding is performed as an inverse process of fixed-length decoding or normal variable length coding (Huffman coding) using a code table, and other individual image signal information is decoded only by arithmetic coding. Note that the image decoding device 40 in FIG. 8 is a device that decodes the image encoded signal Str encoded by the image encoding device 30 in FIG.

  The syntax analysis unit 26 outputs a decoding selection signal SelDec that switches the output of the decoding selection unit 41 according to the header syntax structure signal Stx_H. The decoding selection unit 41 selects one of the fixed length decoding method and the variable length decoding method by the decoding selection signal SelDec, and the fixed length decoding unit 42 or the variable length decoding unit 43 according to the selected decoding method. The header code value InfVal_H decoded in step S3 is output to the header information decoding unit 25.

  The arithmetic decoding unit 44 performs arithmetic decoding on the frame stream Str_F with reference to the header parameter Inf_H, and configures an arithmetically decoded frame code value InfVal_F. The frame decoding unit 27 decodes the frame code value InfVal_F with reference to the header parameter Inf_H, which is information common to the entire image signal, and outputs a decoded moving image signal Vout.

  As described above, the information of the header part, which is information common to the entire image signal, is encoded efficiently with switching according to the syntax, and the individual image signal information is encoded only by arithmetic coding. It is possible to realize an image decoding device that simplifies the switching process without degrading the encoding efficiency.

  In addition to the image encoding devices 10 and 30 and the image decoding devices 20 and 40, the header information and the individual image signal information are separated, and each information is encoded and decoded by a plurality of code tables. It can also be realized by using.

  FIG. 9 is a functional block diagram of a portion related to the encoding function of the image encoding device 50 that separates the header portion information and the individual image signal information and encodes each piece of information as described above.

  FIG. 10 is a functional block diagram of a portion related to the decoding function of the image decoding device 60 corresponding to the image encoding device 50 of FIG.

  FIG. 11 shows a table summarizing the encoding method or the decoding method in the first embodiment and the second embodiment. As shown in FIG. 11A, for example, as in method 1, information of the header part (“header information” in the figure) and image signal information relating to the image signal for each frame (“frame information” in the figure) In the case of encoding, a conventional encoding scheme using a code table (hereinafter referred to as “code table encoding”) and an arithmetic encoding scheme (hereinafter referred to as “arithmetic encoding”) are used. Conceivable. Further, each of the header information and the frame information may be subjected to arithmetic coding (method 2) or code table coding (method 3).

  Furthermore, as shown in FIG. 11B, when code table coding is used for both header information and frame information, “single” code table is used, and “multiple” code table is used. A method is conceivable. Specifically, a code table using a single (method 3-1) or a plurality of code tables (method 3-3) may be applied to both header information and frame information. Further, a plurality of code tables for header information, a single code table for frame information (method 3-2), or a single code table for header information, and a plurality of code tables for frame information (method 3- The code table of 4) may be applied.

  Needless to say, even in the scheme 1, a single code table or a plurality of code tables can be applied to the header information. Here, since a plurality of code tables are uniquely determined by the header part, which is information common to the entire image signal, and information related to the image signal in frame units, the number of code tables applied in advance. Thus, the code table switching can be minimized.

  The encoding method or decoding method according to the first and second embodiments includes a plurality of encoding / decoding methods (code tables) for information related to the entire image, as in the related art. The individual information related to the signal is characterized by using a common encoding / decoding method. In general, in the information relating to the entire image, the frequency of occurrence of the codeword of each code constituting the information is greatly different. Therefore, unless a plurality of encoding / decoding methods are prepared, the compression rate is greatly reduced. On the other hand, since the frequency of codewords does not change as much as the information related to the entire image for individual information, the compression rate does not decrease so much even if a common encoding / decoding method is used. In addition, since most of the processing time for encoding / decoding is necessary for processing of individual information rather than information related to the entire image, encoding / decoding of individual information is preferably performed by a single encoding method. If it can be realized easily, there is a great advantage in realizing the apparatus. In particular, fixed-length coding and variable-length coding are easier to detect synchronization signals for synchronization, and fixed-length coding and variable that multiple coding methods are suitable from the viewpoint of high compression. Compare the advantage of switching between multiple coding methods, including switching of long coding, with the advantage of a single coding method in which encoding and decoding can be easily realized with a single coding method. It seems to be effective in fields of use where there are significant advantages.

  Arithmetic coding is also a type of variable-length coding, and arithmetic coding is high in compression efficiency. However, it is complicated processing especially when switched to fixed-length coding or general variable-length coding (Huffman coding). Therefore, it is preferable to use only arithmetic coding as a single encoding method for individual information, and use information other than arithmetic code for information relating to the entire image.

(Embodiment 3)
A program for realizing the image encoding method or the image decoding method shown in the first embodiment or the second embodiment is recorded on a computer-readable storage medium such as a flexible disk, and the above embodiments are used. It is also possible to implement the processing shown in a computer system such as a personal computer.

  FIG. 12 is an explanatory diagram when the computer system is used by using the flexible disk 1201 storing the image encoding method or the image decoding method described in the first embodiment and the second embodiment.

  FIG. 12A shows an example of a physical format of the flexible disk 1201 as a recording medium. FIG. 12B shows an external view, a cross-sectional structure diagram, and a flexible disk when the flexible disk is viewed from the front. The flexible disk 1201 is built in the case 1202, and the surface of the disk is concentrically formed from the outer periphery. A plurality of tracks are formed toward the periphery, and each track is divided into 16 sectors in the angular direction. Therefore, in the flexible disk 1201 storing the program, a program for realizing the image encoding method or the image decoding method is recorded in an area allocated on the disk.

  FIG. 12C shows a configuration for recording and reproducing the program on the flexible disk 1201. When recording the program on the flexible disk 1201, the computer system 1204 is used to write the program for realizing the image encoding method or the image decoding method via the flexible disk drive 1203. When the image encoding method is constructed in the computer system 1204 by a program in the flexible disk, the program is read from the flexible disk 1201 via the flexible disk drive 1203 and transferred to the computer system.

  In this embodiment, the case where a flexible disk is used as the recording medium has been described. However, the recording medium may be realized using an optical disk. Further, the recording medium is not limited to this, and any other recording medium such as an IC card or a ROM cassette capable of recording a program can be similarly implemented.

(Embodiment 4)
Hereinafter, application examples to the system using the image encoding device and the image decoding device described in the above embodiment will be described.

  FIG. 13 is a block diagram showing the entire content supply system 100 for providing a content distribution service. This content supply system 100 is constituted by, for example, a cellular phone network 104, and a computer 111, a PDA (Personal Digital Assistants) 112, a camera 113, a cellular phone 114, and the like are connected via base stations 107 to 110. . The telephone network 104 is connected to the Internet 101 via the Internet service provider 102.

  The camera 113 is, for example, a digital video camera or the like and can shoot a moving image. The mobile phone 115 is a mobile phone such as PDC (Personal Digital Communications), CDMA (Code Division Multiple Access), W-CDMA (Wideband-Code Division Multiple Access), or GSM (Global System for Mobile Communications). Or, it is a terminal device of PHS (Personal Handyphone System).

  The streaming server 103 is connected to the telephone network 104 via the server connection dedicated network 105 or the Internet 101, and enables live distribution of encoded data of images taken by the camera 113. In this case, the image encoding process may be performed by the camera 113 or the server 113a connected to the camera. Alternatively, image data of an image captured by the camera 116 may be transmitted to the streaming server 103 via the computer 111. Here, the camera 116 is a digital camera, for example, and can capture a still image. In this case, the image data may be encoded by the camera or the computer 111. Further, the above encoding process is executed in the LSI 117 built in the camera 116 or the computer 111. Further, image data taken with a mobile phone 115 with a camera may be transmitted. The image data at this time is data encoded by an LSI built in the mobile phone.

  Note that image encoding / decoding software may be stored in a recording medium (for example, a storage medium such as a CD-ROM, a flexible disk, or a hard disk) that can be read by the computer 111 or the like.

  FIG. 14 is a diagram showing an example of the appearance of the mobile phone 114. As shown in FIG. 14, the mobile phone 114 receives the antenna 201, the camera unit 203 that employs a CCD system capable of shooting a moving image or a still image, the video captured by the camera unit 203, and the antenna 201. A display unit 202 such as a liquid crystal display for displaying video and the like, a main body unit 204 having an operation key group, an audio output unit 208 including a speaker for outputting audio, an audio including a microphone for inputting audio, etc. An input unit 205, a storage medium 207 for storing captured / received moving image and still image data, received mail data, and the like, a slot unit 206 for mounting the storage medium 207, and the like are provided. The storage medium 207 is an SD card, for example, and stores a flash memory 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. is there.

  In the content supply system 100, content (for example, a video of music live) captured by the user with the camera 113, the camera 116, or the like is encoded and transmitted to the streaming server 103 in the same manner as in the above embodiment. On the other hand, the streaming server 103 streams the content data to the requested client. Examples of the client include a computer 111, a PDA 112, a camera 113, a mobile phone 114, and the like that can decode the encoded data.

  With the above configuration, the content supply system 100 can receive and reproduce the encoded data at the client, and further receive, decode, and reproduce the personal broadcast in real time at the client. Make it feasible.

  Further, the cellular phone 114 will be described with reference to FIG. The mobile phone 114 includes a main control unit 311 that comprehensively controls each unit of the display unit 202 and the main unit 204, a power supply circuit unit 310, an operation input control unit 304, an image encoding unit 312, a camera control unit 303, an LCD (Liquid Crystal Display) control unit 302, image decoding unit 309, demultiplexing unit 308, recording / reproducing unit 307, modulation / demodulation circuit unit 306, and audio processing unit 305 are connected to each other via a bus 313. When a call or a power key is turned on by a user operation, the power supply circuit unit 310 is supplied with electric power from the battery pack to start up the camera-equipped mobile phone 114 in an operable state. The mobile phone 114 converts the voice signal collected by the voice input unit 205 in the voice call mode into digital voice data in the voice processing unit 305 based on the control of the main control unit 311 including a CPU, ROM, RAM, and the like. The modulation / demodulation circuit unit 306 performs nest spectrum spreading processing, the transmission / reception circuit unit 301 performs digital / analog conversion processing and frequency conversion processing, and then transmits the result via the antenna 201. In addition, the mobile phone 114 amplifies the signal received by the antenna 201 in the voice call mode, performs frequency conversion processing and analog-digital conversion processing, performs spectrum despreading processing in the modulation / demodulation circuit unit 306, and performs analog despreading processing in the voice processing unit 305. After being converted into an audio signal, it is output via the audio output unit 208. Further, when an e-mail is transmitted in the data communication mode, text data input via the operation input control unit 304 of the main body unit 204 is sent to the main control unit 311. The main control unit 311 performs spread spectrum processing on the text data in the modulation / demodulation circuit unit 306, performs digital analog conversion processing and frequency conversion processing in the transmission / reception circuit unit 301, and then transmits the text data to the base station 110 via the antenna 201.

  When transmitting image data in the data communication mode, the main control unit 311 supplies image data captured by the camera unit 203 to the image encoding unit 312 via the camera control unit 303. When image data is not transmitted, the camera unit 203 can directly display the captured image data on the display unit 202 via the camera control unit 303 and the LCD control unit 302.

  The image encoding unit 312 converts the image data supplied from the camera unit 203 into encoded image data by compressing and encoding the image data using the encoding method described in the above embodiment, and converts the encoded image data into the demultiplexing unit 308. Send it out. At the same time, the mobile phone 114 sends the voice collected by the voice input unit 205 during photographing by the camera unit 203 to the demultiplexing unit 308 as digital voice data via the voice processing unit 305.

  The demultiplexing unit 308 multiplexes the encoded image data supplied from the image encoding unit 312 and the audio data supplied from the audio processing unit 305 by a predetermined method, and modulates / demodulates the resulting multiplexed data. The circuit unit 306 performs spread spectrum processing, the transmission / reception circuit unit 301 performs digital-analog conversion processing and frequency conversion processing, and then transmits the signal via the antenna 201.

  When data of a moving image file linked to a home page or the like is received in the data communication mode, the signal received from the base station 110 via the antenna 201 is subjected to spectrum despreading processing by the modulation / demodulation circuit unit 306, and the resultant multiplexing is obtained. Data is sent to the demultiplexing unit 308.

  In addition, in order to decode the multiplexed data received via the antenna 201, the demultiplexing unit 308 separates the multiplexed data into the encoded image data and audio data, and the bus 313. The encoded image data is supplied to the image decoding unit 309 and the audio data is supplied to the audio processing unit 305.

  Next, the image decoding unit 309 generates reproduced moving image data by decoding the encoded image data with a decoding method corresponding to the encoding method shown in the above embodiment, The image data included in the moving image file linked to the homepage is displayed, for example, by being supplied to the display unit 202 via the LCD control unit 302. At the same time, the audio processing unit 305 converts the audio data into an analog audio signal, and then supplies the analog audio signal to the audio output unit 208. Thus, for example, the audio data included in the moving image file linked to the home page is reproduced. The

  Note that the present invention is not limited to the above system, and recently, digital broadcasting using satellite waves or terrestrial waves has become a hot topic. As shown in FIG. 16, the digital broadcasting system also includes at least the encoding of the above embodiment. Either the method or the decoding method can be incorporated. Specifically, in the broadcasting station 409, a coded bit stream of video information is transmitted to a satellite 410 for communication or broadcasting via radio waves. The satellite 410 that has received the signal receives a radio wave for broadcasting, receives the radio wave with a home antenna 406 having a satellite broadcast receiving facility, and encodes a bit stream with a device such as the television receiver 401 or the set top box 407. Is decoded and reproduced. In addition, the decoding method described in the above embodiment can also be implemented in a playback device 403 that reads and decodes an encoded bitstream recorded on a storage medium 402 that is a recording medium. In this case, the reproduced video signal is displayed on the monitor 404. Further, a configuration in which a decoding device is mounted in a set top box 407 connected to a cable 405 for cable television or an antenna 406 for satellite / terrestrial broadcasting and this is reproduced on the television monitor 408 is also conceivable. At this time, the encoding device may be incorporated in the television instead of the set top box. In addition, a car 412 having an antenna 411 can receive a signal from the satellite 410 or the base station 107 and the like, and a moving image can be reproduced on a display device such as a car navigation 413 that the car 412 has.

  The configuration of the car navigation 413 is, for example, the configuration shown in FIG. 15 except for the camera unit 203 and the camera control unit 303, and the same applies to the computer 111, the television receiver 401, and the like. It is done. In addition to the transmission / reception type terminal including both the encoder / decoder, the terminal such as the mobile phone 114 is implemented in three ways: a transmitting terminal having only an encoder and a receiving terminal having only a decoder. Possible format.

  As described above, by implementing the above encoding method and decoding method, any of the apparatuses and systems described in the above embodiments can be realized.

  INDUSTRIAL APPLICABILITY The present invention can be applied to an image encoding device, an image decoding device, and a method thereof, and even with a small memory and a low computing capacity such as a portable terminal, data compression equivalent to the conventional one can be performed. This is useful for the image encoding apparatus described above.

3 is a functional block diagram of a portion related to an encoding function in the image encoding device according to Embodiment 1. FIG. It is a stream block diagram of the image coding signal encoded with the functional block diagram in the image coding apparatus shown in FIG. (A) is a data block diagram of general frame data. FIG. 6B is a data configuration diagram of frame data having the above-described slice structure. (A) is an example of a code table used when variable length coding is performed in the image coding apparatus. (B) is an example of a code table used when fixed-length encoding is performed in the image encoding device. 6 is a functional block diagram of a portion related to a decoding function in the image decoding apparatus according to Embodiment 1. FIG. 6 is a flowchart showing a flow of encoding processing of the image encoding device in the first embodiment. FIG. 10 is a functional block diagram relating to an encoding function in the image encoding device according to the second embodiment. FIG. 12 is a functional block diagram relating to a decoding function in the image decoding apparatus according to the second embodiment. It is a functional block diagram of a portion relating to a coding function of an image coding apparatus that divides information of a header part and individual image signal information and codes each information. FIG. 10 is a functional block diagram of a portion related to a decoding function of an image decoding device corresponding to the image encoding device in FIG. 9. It is the figure which showed the table | surface which put together the encoding method in Embodiment 1 and Embodiment 2. FIG. (A) is a figure which shows the example of the physical format of the flexible disk which is a recording medium in Embodiment 3. FIG. (B) is the external view which looked at the flexible disk from the front, a cross-section figure, and the figure which shows a flexible disk. (C) is a diagram showing an example of a system configuration for recording and reproducing a program on a flexible disk. FIG. 10 is a block diagram showing an entire content supply system for providing a content distribution service in a fourth embodiment. It is an example of the external view of a mobile phone. It is an example of a functional block diagram of a mobile phone. 1 is an example of a system configuration diagram of a digital broadcasting system. It is a functional block diagram of the part which concerns on the encoding function in the conventional image coding apparatus. It is a figure which shows the stream structure of the conventional image coding signal. It is a functional block diagram of the part which concerns on the decoding function in the conventional image decoding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image coding apparatus 11 Header information preparation part 12 Syntax analysis part 13 Frame coding part 15 Fixed length and variable length coding part 16 Variable length coding part 16a Code table 17 Multiplexing part 20 Image decoding apparatus 21 Separation part DESCRIPTION OF SYMBOLS 22 Fixed length / variable length decoding part 23 Variable length decoding part 23a Code table 25 Header information decoding part 26 Syntax analysis part 27 Frame decoding part 30 Image coding apparatus 31 Encoding selection part 32 Fixed length encoding part 33 Variable length coding unit 34 Arithmetic coding unit 40 Image decoding device 41 Decoding selection unit 42 Fixed length decoding unit 43 Variable length decoding unit 44 Arithmetic decoding unit 50 Image coding device 54 Fixed length / variable length coding Unit 60 Image Decoding Device 61 Fixed Length / Variable Length Decoding Unit 100 Content Supply System 101 Internet 102 Internet Over bis provider 103 streaming server 104 telephone network 105 server connection network 107 to 110 base station 111 computer 112 PDA
113 Camera 113a Server 114, 115 Mobile phone 116 Camera 117 LSI
DESCRIPTION OF SYMBOLS 201 Antenna 202 Display part 203 Camera part 204 Main body part 205 Audio | voice input part 206 Slot part 207 Storage media 208 Audio | voice output part 301 Transmission / reception circuit part 302 LCD control part 303 Camera control part 304 Operation input control part 305 Voice processing part 306 Modulation / demodulation circuit part 307 Recording / playback unit 308 Demultiplexing unit 309 Image decoding unit 310 Power supply circuit unit 311 Main control unit 312 Image encoding unit 313 Bus 401 TV receiver 402 Storage media 403 Playback device 404 Monitor 405 Cable 406 Antenna 407 Set top box 408 Television Monitor 409 Broadcasting station 410 Satellite 411 Antenna 412 Car 413 Car navigation 500 Image encoding device 501 Frame encoding unit 502 Syntax analysis unit 503 Fixed length / Variable length coding unit 504 Code table selection unit 600 Image decoding device 601 Fixed length / variable length decoding unit 602 Code table selection unit 603 Frame decoding unit 604 Syntax analysis unit 1201 Flexible disk 1202 Case 1203 Flexible disk drive 1204 Computer system

Claims (5)

An image decoding method for decoding information including an image signal of a predetermined unit, wherein the information to be decoded includes information common to the entire image signal and the image signal of the predetermined unit The information common to the entire image signal is header information, the information related to the image signal in the predetermined unit is slice data, and the slice data can include a plurality of macroblock data. Yes,
For the information common to the entire image signal, a plurality of decoding steps for decoding using a plurality of decoding methods;
Wherein for the information relating to the predetermined unit image signals, the single that are common in each predetermined unit, every macroblock variable length decoding method or an arithmetic decoding method utilizes included in the predetermined unit An image decoding method comprising: a common decoding step for decoding data . The variable length decoding method, decoding method der Ru請 Motomeko 1 picture decoding method according to utilize a plurality of variable length code tables. An image decoding apparatus for decoding information including an image signal of a predetermined unit, wherein the information to be decoded includes information common to the entire image signal and the image signal of the predetermined unit The information common to the entire image signal is header information, the information related to the image signal in the predetermined unit is slice data, and the slice data can include a plurality of macroblock data. Yes,
For information common to the entire image signal, a plurality of decoding means for decoding using a plurality of decoding methods;
Wherein for the information relating to the predetermined unit image signals, the single that are common in each predetermined unit, every macroblock variable length decoding method or an arithmetic decoding method utilizes included in the predetermined unit image decoding apparatus which comprises a common decoding means for decoding the data. A program for executing an image decoding method for decoding information including an image signal of a predetermined unit, the information to be decoded includes information common to the entire image signal and the predetermined Information relating to the unit image signal, information common to the entire image signal is header information, information relating to the image signal of the predetermined unit is slice data, and the slice data includes a plurality of macroblocks. Can contain data,
The program is stored in the computer
For the information common to the entire image signal, a plurality of encoding steps for decoding using a plurality of decoding methods;
For the information relating to the image signal of the predetermined unit, all of the predetermined units include a single variable length decoding method or an arithmetic decoding method that is alternatively selected in common for each predetermined unit. A common encoding step for encoding the macroblock data of
A program that executes A computer-readable recording medium on which the program according to claim 4 is recorded.

Images