WO2009071420A1 - Procédé et dispositif de codage et de décodage - Google Patents

Procédé et dispositif de codage et de décodage Download PDF

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Publication number
WO2009071420A1
WO2009071420A1 PCT/EP2008/065219 EP2008065219W WO2009071420A1 WO 2009071420 A1 WO2009071420 A1 WO 2009071420A1 EP 2008065219 W EP2008065219 W EP 2008065219W WO 2009071420 A1 WO2009071420 A1 WO 2009071420A1
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WO
WIPO (PCT)
Prior art keywords
codes
assignment
record
characters
association
Prior art date
Application number
PCT/EP2008/065219
Other languages
German (de)
English (en)
Inventor
Reinhard Meschenmoser
Dirk Luedtke
Original Assignee
Robert Bosch Gmbh
Denso Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh, Denso Corporation filed Critical Robert Bosch Gmbh
Publication of WO2009071420A1 publication Critical patent/WO2009071420A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/3084—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction using adaptive string matching, e.g. the Lempel-Ziv method
    • H03M7/3088—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction using adaptive string matching, e.g. the Lempel-Ziv method employing the use of a dictionary, e.g. LZ78
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/40—Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

Definitions

  • the present invention relates to a method and apparatus for encoding and decoding a multi-character data set and to a corresponding program and memory device.
  • the coding of data sets is used in almost all areas of information technology, in particular for the compression of data sets and the reduction of their volumes. For example, a record is subdivided into subsets whose statistical distribution is determined. Based on the statistical distribution or frequency of occurrence of each subset in the data set, a unique association between subsets and codes is determined. Methods for determining the assignment are known, for example, as Shannon-Fano coding or as Huffman coding. With these methods, compression or reduction of the data volume is achieved by frequently associating subsets of short codes and rarely occurring subsets with longer codes (see, for example, http://www.inf.fh-flensburg.de/eng/archives/). code / huffman / huffman. htm)
  • An object of the present invention is to further improve the coding, so that, for example, an even higher compression is possible.
  • the present invention is based on the idea that an association between Untermeng - 1 s of a data set and codes to Verwer sw to which an allocation of individual characters and codes from a first set of codes and an assignment of character sequences or subsets of the data set from each multiple characters and codes from a second set of codes.
  • This is advantageous, for example, in the case of a data record in which, on the one hand, a few or a few character strings of a plurality of characters occur very frequently and, on the other hand, many character strings occur very rarely.
  • An example is a record as commonly provided to a navigation device on a CD-ROM, a DVD, HD-DVD, a Blue-Ray disk, a flash memory, or other storage medium.
  • a data set also includes names of streets, squares and local authorities (L selected, municipalities, etc.). In these names, components such as “street”, “allee”, “platz”, “nieder”, “ober”, “neu” are particularly common. Such frequently occurring strings are each assigned a code from the second set of codes.
  • the association comprises an allocation of strings of a plurality of characters and codes from a first set of codes and an assignment of words and codes from a second set of codes, wherein each word comprises at least one of a plurality of characters or one or more character strings.
  • a word is understood to mean, in particular, a word from a spoken language or from a programming language.
  • words in a record become words separated by spaces, separators or reserved characters or strings.
  • the beginning and end of a word are each identified by a reserved character or a reserved string.
  • the present invention is further based on the idea of selecting an assignment of subsets and codes independently of a specific data record and of storing or transmitting the coded data record without the assignment or without information characterizing the assignment. This can save memory space.
  • a record is called, as it is provided to a navigation device. It is desirable to be able to map on a storage medium as much information as possible, in particular as detailed as possible map information from the largest possible geographical area. Abandoning the storage of the association along with the record on the storage medium brings the desired gain in usable storage capacity. For these datasets, a frequent update is desirable to reflect current changes, such as new buildings or construction sites. The statistical distribution of names and parts of names changes only minimally.
  • FIG. 1 shows a schematic representation of an assignment of potential subsets of a data set and code
  • FIG. 2 shows a schematic representation of a data record and a coded data record
  • FIG. 3 is a schematic representation of a navigation device
  • FIG. 4 is a schematic flow diagram of a method for encoding and decoding.
  • the assignment 40 comprises an assignment 41 of individual characters 11 to a respective code 31 from a first set of Codes 21.
  • the map 40 further comprises an assignment 42 of character strings 12 and codes 32 from a second set 22 of codes and an assignment of words or names 13 and codes 33 from a third set 23 of codes.
  • the different numbers of the boxes reflect again that the individual subsets 11, 12, 13 are assigned codes 31, 32, 33 with different lengths.
  • the strings 12 particularly often include components of names and the words 13 particularly frequent names, as for example in a digital map of a predetermined geographic area occur.
  • the name element "street” as the presumably most frequent part of a name in at least one map of a German-speaking area is assigned a relatively short code 32. Also the sign "e" and the names appearing in most larger communities in the German-speaking area
  • codes 31 are generally assigned to all letters of an alphabet. Further, the lengths of the codes 31, 32, 33 shown in FIG. 1 are fictitious and are not based on an analysis of the statistical distribution of the appearance of the character 11, the name constituents 12, and the names 13.
  • FIG. 2 is a schematic representation of a data record 10 and a coded data record 30, which results from the data record 10 by coding 93.
  • decoding 96 of the encoded data set 30 one again obtains the data record 10.
  • the data record 10 comprises a plurality of words or names 13, each of a plurality of characters 11.
  • character strings 12, which are components of the names 13, can belong to those character strings as above 1, because of their frequent occurrence, own codes 32 are assigned. In this example, these are the strings "yard” and "square".
  • a name associated with its own code due to its frequent occurrence (“station place” in this example) is converted into the corresponding code 33 during encoding 93
  • Name 13 which is not assigned its own code due to its rare occurrence (in this example: "Nölkehof"), is converted into several codes 31, 32, to which individual letters 11 or name components 12 are assigned.
  • FIG. 3 is a schematic illustration of a device 50 by which a data set 10 may be encoded or decoded as described hereinabove or an encoded data set 30 may be decoded.
  • the coding and decoding can be a main purpose or the actual destination of the device. Alternatively, encoding or decoding is a means of accomplishing other tasks.
  • the device is shown here as navigation device, as it can be used for example in motor vehicles for navigation.
  • the device 50 for this purpose comprises a reading device 51 for reading a coded data record stored on a first memory device 53 (for example a CD-ROM, flash memory medium).
  • the device 50 comprises a receiving device 52 for receiving a coded data record from a data source, for example via an air interface.
  • the coded data record read by the reading device 51 from the first memory device 53 or received by the receiving device 52 comprises, in the case of the navigation device 50, digital map information which is a basis of the navigation.
  • the navigation device 50 further comprises a second memory means 54 for storing an association between subsets of a data set and code.
  • the second storage device 54 is, for example, a ROM, an EPROM, an EEPROM, a flash memory, etc.
  • a device 55 for decoding is coupled to the reading device 51 and / or the receiving device 52 and to the second memory device 54.
  • the device 55 is recommended From the reading device 51 or from the receiving device 52, a coded data record begins and from the second memory device 54 an associated association between codes and subsets of the decoded data record. By means of the association stored in and received from the second storage device 54, the device 55 decodes the coded data record.
  • the navigation device 50 comprises a GPS receiver 56 or other means for determining the position, a display 57, a route calculation unit 58 and an input device 59.
  • the display 57 and the input device 59 together form an example of a user interface which may also be different.
  • the arrangement of the reading device 51, the second memory device 54, the device 55 for decoding, the display 57, the route calculation unit 58 and the input device 59 within as well as the receiving device 52 and the GPS receiver 56 outside the navigation device 50 is not mandatory. Rather, the components shown can also be arranged differently.
  • the navigation device 50 has a second memory device 54 for storing an association between subsets of a data set and code. This assignment therefore no longer has to be read together with a coded data record by the reading device 52 from a first memory device 53 or received by the receiving device 52. Furthermore, it is advantageous for the device 55 to be designed to decode an encoded data record read by the reading device 51 or received via the receiving device 52 using an association which comprises an assignment of individual characters and codes from a first set of codes and a Assignment of strings of several characters and codes from a second set of codes.
  • FIG. 4 is a schematic flow diagram of a method of encoding a data set and decoding a coded data set.
  • reference numerals from FIGS. 1 to 3 are used for better understanding.
  • the method is also applicable to other than the above with reference to FIG. 1 exemplified assignment, for other than the above with reference to FIG. 2 exemplified data set and other than the above with reference to FIG. 3 exemplified devices shown.
  • a first step 91 the statistical distribution of individual characters 11 and of predetermined character strings 12, 13 is analyzed.
  • the analysis in this case refers either to a predetermined data record or to a data record of a specific type.
  • An example of a data record of a specific type is a digital map of a predetermined geographic area, for example Germany. This digital map can be revised or recreated over and over again, including, for example, new roads, streets and squares, longer term construction sites or renaming of local authorities. Digital maps of the same area created over a longer period of time may differ in details important for navigation in the area, but the statistical distribution of individual characters 11 and strings 12, 13 changes only slightly.
  • the statistical distribution is analyzed for all or several data records of the predetermined type or for a representative data record.
  • a second step 92 on the basis of the statistical distribution analyzed in the first step 91, an assignment of subsets of the data set or of the data records is made and codes set. This determination is made, for example, by means of one of the already mentioned methods according to Shannon-Fano or Huffman. If the association includes both an assignment 41 of individual characters 11 and codes 31 from a first group 21 of codes as well as an assignment 42, 43 of
  • the assignment may take place separately for each set 21, 22, 23 of codes.
  • the Huffman method is applied separately to individual characters 11, common word or name components 12, and frequent words or names 13, respectively.
  • the codes thus determined are then preceded, for example, by different prefix bits, for example "1" for codes 33, which are assigned to whole words or names, "Ol" for codes 32, which are assigned to word or name components, and "00" for codes 31 associated with individual characters 11.
  • the assignment is determined in a single step, for example by simultaneously using a modified Shannon-Fano method or a modified Huffman method, all occurring characters 11 and the most frequent word or name components and the most frequent words or names 13 codes 31, 32, 33 are assigned.
  • the assignment defined in the second step 92 can be used for the coding of all data records of this type.
  • the assignment defined in the second step 92 can be stored separately from a data set coded using the assignment as described below.
  • the association may be stored in a memory device 54 of a navigation device 50.
  • the navigation device with the in their Memory device 54 stored and operated over many years with repeatedly updated records as long as they were coded with the stored in the memory device 54 assignment.
  • a data record 10 is encoded using the assignment defined in the second step 92.
  • individual characters 11 are converted by codes 31 and, if the assignment 40 defined in the second step 92 also includes an assignment of character strings 12, 13 and codes 32, 33, character strings 12, 13 into assigned codes 32, 33.
  • a word or a name can, if it is assigned to a code 33, represented by this and otherwise partially or completely o by completely occurring in it strings 12 associated codes 32 and partially or completely by occurring in it individual characters 11 codes 31 become.
  • separation bits may be used. These separation bits respectively separate pure sequences of codes 31 from the first set 21, pure sequences of codes 32 from the second set 22, and pure sequences of codes 33 from the third set 23 of each other.
  • the third step 93 may be performed immediately after the second step 92 or at any later time.
  • the encoded data record 30 generated in the third step 93 is stored, for example on a CD-ROM, a flash memory medium or any other removable medium.
  • a fifth step 95 the encoded data record 30 is read or received.
  • encoded record 30 contains digital map information, it is read by a navigation device 50 from a CD-ROM, for example.
  • a sixth step 96 the encoded data record 30 read or received in the fifth step 95 is decoded using the association established in the second step 92.
  • codes 31, 32, 33 are converted into characters 11 and, if appropriate, into strings 12, 13. If the assignment is not received with the encoded data record 30 or is read by a storage device, it is read by a separate storage device 54.
  • the association 40 may include an association 42 of strings 12 of a plurality of characters 11 and codes 32 of a first set 22 of codes and an assignment 43 of words 13 and codes 33 of a second set 23 of codes.
  • the words 13 are preferably words from a spoken language or from a programming language. It is advantageous to assign codes 33 from the second set 23 to a predetermined number of the most common words 13 in the respective language.
  • the assignment 40 can also be fixed independently of the data record.
  • codes (32, 33) can be formed from the various sets (22, 23) of codes by prefixing prefix bits.
  • a group of codes 32 from the first set 22 is separated from a set of codes 33 from the second set 23 by separating bits.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Navigation (AREA)

Abstract

Selon un procédé de codage ou de décodage d'un jeu de données (10) présentant un caractère (11), on utilise une association (40) de sous-quantités (11, 12, 13) du jeu de données (10), qui comprennent chacune un ou plusieurs caractères (11), et de codes (31, 32, 33). L'association (40) comprend une association (41) de caractères individuels (11) et de codes (31) issus d'une première quantité (21) de codes, et une association (42, 43) de suites de caractères (12, 13), constituées chacune de plusieurs caractères, et de codes (32, 33) issus d'une deuxième quantité (22, 23) de codes.
PCT/EP2008/065219 2007-12-07 2008-11-10 Procédé et dispositif de codage et de décodage WO2009071420A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007059122.7 2007-12-07
DE200710059122 DE102007059122A1 (de) 2007-12-07 2007-12-07 Verfahren und Vorrichtung zum Codieren und Decodieren

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WO2009071420A1 true WO2009071420A1 (fr) 2009-06-11

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0395906A2 (fr) * 1989-05-03 1990-11-07 Robert Bosch Gmbh Méthode de compression de données de noms de rue

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0395906A2 (fr) * 1989-05-03 1990-11-07 Robert Bosch Gmbh Méthode de compression de données de noms de rue

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
BELL T ET AL: "MODELING FOR TEXT COMPRESSION", ACM COMPUTING SURVEYS, ACM, NEW YORK, NY, US, US, vol. 21, no. 4, 1 December 1989 (1989-12-01), pages 557 - 591, XP000972666, ISSN: 0360-0300 *
COOPER D ET AL: "Text compression using variable- to fixed-length encodings", JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE USA, vol. 33, no. 1, January 1982 (1982-01-01), pages 18 - 31, XP002515613, ISSN: 0002-8231 *
KATZOURAKI M ET AL: "A NATURAL-SUCCESSION BASED TEXT COMPRESSION TECHNIQUE", PROCEEDINGS OF THE MEDITERRANEAN ELECTROTECHNICAL CONFERENCE. (MELECON). ATHENS, MAY 24 - 26, 1983; [PROCEEDINGS OF THE MEDITERRANEAN ELECTROTECHNICAL CONFERENCE. (MELECON)], NEW YORK, IEEE, US, vol. 2, 1 May 1983 (1983-05-01), pages B11.11 - 01/02, XP000744616 *
PIKE J: "TEXT COMPRESSION USING A 4 BIT CODING SCHEME", THE COMPUTER JOURNAL, XX, XX, vol. 24, no. 4, 1 January 1981 (1981-01-01), pages 324 - 330, XP000748322 *
RADHAKRISHNAN T: "Selection of prefix and postfix word fragments for data compression", INFORMATION PROCESSING & MANAGEMENT UK, vol. 14, no. 2, 1978, pages 97 - 106, XP002515612, ISSN: 0306-4573 *
SESSA M I ET AL: "A text compression algorithm", INFORMATION SYSTEMS, PERGAMON PRESS, OXFORD, GB, vol. 15, no. 3, 1 January 1990 (1990-01-01), pages 391, XP024234544, ISSN: 0306-4379, [retrieved on 19900101] *

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