WO2009071420A1

WO2009071420A1 - Method and device for coding and decoding

Info

Publication number: WO2009071420A1
Application number: PCT/EP2008/065219
Authority: WO
Inventors: Reinhard Meschenmoser; Dirk Luedtke
Original assignee: Robert Bosch Gmbh; Denso Corporation
Priority date: 2007-12-07
Filing date: 2008-11-10
Publication date: 2009-06-11
Also published as: DE102007059122A1

Abstract

An allocation (40) of subsets (11, 12, 13) of the data set (10), which comprise in each case one or more characters (11) and codes (31, 32, 33), is used in a method for coding and decoding a dataset (10) having characters (11). The allocation (40) comprises an allocation (41) of individual characters (11) and codes (31) from a first quantity (21) of codes and an allocation (42, 43) of character sequences (12, 13) in each case from several characters and codes (32, 33) from a second quantity (22, 23) of codes.

Description

Method and device for coding and decoding

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.

State of the art

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.

This object is solved by the subject matters of the independent claims. Preferred developments are defined in the dependent claims. Disclosure of the invention

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. In addition to the location and arrangement of roads, paths and squares, such a data set also includes names of streets, squares and local authorities (Länder, 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.

Alternatively, 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.

In the present case, a word is understood to mean, in particular, a word from a spoken language or from a programming language. For example, words in a record become words separated by spaces, separators or reserved characters or strings. Alternatively, in a record, for example, 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.

Again, as an example, 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.

Brief description of the drawings

Preferred developments of the present invention will be explained in more detail with reference to the accompanying figures. Show it:

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; and

4 is a schematic flow diagram of a method for encoding and decoding.

Embodiments of the invention

1 shows a schematic representation of an assignment 40 between potential subsets 11, 12, 13 of a data set and codes 31, 32, 33. 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.

As examples of individual characters, the letters A, B, C, D, E, Y are called. Concrete codes are not shown in Fig. 1, these can be determined for example by the Shannon-Fano method or the Huffman method. The

Representation of the codes 31 from the first set 21 as well as the described codes 32, 33 from the second and third sets 22, 23, however, comprises in each case a plurality of boxes which, for example, each represent 1 bit. The different numbers of the boxes reflect again that the individual subsets 11, 12, 13 are assigned codes 31, 32, 33 with different lengths.

In the example shown in FIG. 1, 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

"Bahnhofsplatz" and "Bahnhofsstraße" are assigned relatively short codes 31 and 33, respectively. Less common letter 11 (in our fictitious example: A, B, C, D), less common name parts 12 (in our fictitious example: "yard", "way", "place", "avenue", "upper") and less common names (in our example: "Schillerstrasse") are assigned longer codes 31, 32, 33. Very rare characters (in our example: Y) are assigned long codes 31. Rarely occurring name components or names are not assigned any codes.

The assignment shown with reference to FIG. 1 can have a significantly greater extent. For example, 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. By 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. Several 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.

As an example, 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). Alternatively or additionally, 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.

Furthermore, 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.

It is advantageous that 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.

4 is a schematic flow diagram of a method of encoding a data set and decoding a coded data set. In the description of the method, reference numerals from FIGS. 1 to 3 are used for better understanding. However, 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.

In 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.

In the first step 91, the statistical distribution is analyzed for all or several data records of the predetermined type or for a representative data record.

In 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

For example, to combine strings 12, 13 and codes 32, 33 from one or more further sets 22, 23 of codes, the assignment may take place separately for each set 21, 22, 23 of codes. In this case, for example, 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.

Alternatively, 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.

If, in the first step 91, the statistical distribution is analyzed for a plurality of data records of a specific type or for a representative data record of the specific type, the assignment defined in the second step 92 can be used for the coding of all data records of this type.

Especially in this case, but not only in this case, the assignment defined in the second step 92 can be stored separately from a data set coded using the assignment as described below. For example, the association may be stored in a memory device 54 of a navigation device 50. For the reasons described above, 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.

In a third step 93, a data record 10 is encoded using the assignment defined in the second step 92. In this case, 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.

If, as described above for the second step 92, the assignment is determined separately for each set 21, 22, 23 of codes, instead of the use of prefix bits described therein in the encoded data set 30, 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.

In a fourth step 94, 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. Alternatively, the co- transmitted data record 30, for example, via an air interface parts.

In a fifth step 95, the encoded data record 30 is read or received. When encoded record 30 contains digital map information, it is read by a navigation device 50 from a CD-ROM, for example.

In 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. In this case, in the direction opposite to the direction in the third step 93, 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 embodiments illustrated above with reference to the figures can be varied in several ways. For example, 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.

Also for this variant, most of the optional modifications described above are possible. For example, in the case of an encoding method, the assignment 40 can also be fixed independently of the data record. Further, codes (32, 33) can be formed from the various sets (22, 23) of codes by prefixing prefix bits. Alternatively, in the encoded data set 30, 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.

Claims

claims

Method for coding or decoding a data record (10) having a plurality of characters (11) by means of an assignment order (40) of subsets (11, 12, 13) of the data record (10), each having one or more characters (11) and codes (31, 32, 33), the association (40) comprising an assignment (41) of individual characters (11) and codes (31) from a first set (21) of codes and an assignment (42, 43) of strings (12, 13) each of a plurality of characters and codes (32, 33) from a second set (22, 23) of codes.

2. The method of claim 1, wherein

the record comprises words (13) from a language spoken in a predetermined geographic area,

the assignment (40) comprises an assignment (42) of syllables (12) each of a plurality of characters (11) that are components of the words (13) and codes (32) of the second set of code (22).

3. The method according to claim 1 or 2, wherein

the association (40) comprises an association (43) of words (13) and codes (33).

4. The method according to any one of the preceding claims, wherein the assignment (40) is predetermined independently of the data set (10).

5. A method for encoding or decoding a character (11) having record (10) by means of an assignment (40) of subsets (11, 12, 13) of the record (10), each comprising one or more characters (11), and Codes (31, 32, 33), the association being independent of the data set.

6. The method according to any one of the preceding claims, wherein

the association (40) comprises an association (43) of words (13) from a predetermined set of words (13) and codes from a third set (23) of codes.

A method according to the preceding claim, wherein the predetermined set of words (13) comprises a predetermined number of most common words (13).

A method according to any one of the preceding claims, wherein codes (31, 32, 33) are distinguished from the different sets (21, 22, 23) by prefixing prefix bits.

9. Method according to one of claims 1 to 8, wherein in the coded data record (30) a group of codes (31) from the first set (21) of a group of codes (32, 33) from the second set (22) is separated by separating bits.

10. The method according to any one of the preceding claims, wherein

the dataset (10) names (13) of streets, squares or in a predetermined geographic area.

11. The method according to the preceding claim, and

the association (40) comprises an assignment (41) of individual characters (11) and codes (31) and an association (42) of name components (12) of the names of the streets, squares or codes (32).

12. A method according to the preceding claim, wherein the predetermined set of name components (12) comprises a predetermined number of name components (12) with the most frequent occurrence in the names (13) of the streets, squares or territorial entities in the predetermined geographic area ,

13. The method according to any one of claims 8 to 10, wherein

the mapping (40) comprises an association (43) of names (13) from a predetermined set of names (13) of streets, squares or territorial entities and codes from a third set (23) of codes.

A method according to the preceding claim, wherein the predetermined set of names (13) comprises a predetermined number of names (13) with the most frequent occurrence in the streets, squares or localities in the predetermined geographical area.

15. A method of coding according to one of the preceding claims, further comprising the following step: Storing (94) the coded data set (30) without the assignment (40) in a memory device (53).

16. A decoding method according to any one of claims 1 to 15, further comprising the step of:

Reading (95) the coded data set (30) and the mapping (40) from two different memory devices (53, 54).

17. Method according to the preceding claim, wherein the coded data record (30) is read by a removable data carrier (53), and the assignment is read by a memory device (54) which is part of a navigation device (50).

18. Method for coding or decoding a data record (10) having a plurality of characters (11) by means of an assignment (40) of subsets (11, 12, 13) of the data record (10), each comprising one or more characters (11), and codes (31, 32, 33),

wherein the assignment (40) comprises an assignment (41, 42) of characters (11) or character sequences (12) of a plurality of characters (11) and codes (31, 32) from a first set (21, 22) of codes and a Comprising assignment (43) of words (13) and codes (33) from a second set (23) of codes,

wherein one word (13) each comprises at least one of a plurality of characters (11) or one or more character strings (12).

19. Method according to claim 18, wherein the words (13) assigned to the codes (33) from the second set (23) of codes are net words, words from a spoken language or from a programming language.

20. The method of claim 18 or 19, wherein the assignment (40) is fixed independently of the record.

21. The method according to any one of claims 18 to 20, wherein a predetermined number of words (13) with the most frequent occurrence of the codes (33) from the second set (23) of codes is assigned.

A method according to any one of claims 18 to 21, wherein codes (31, 32, 33) are distinguished from the different sets (21, 22, 23) of codes by prefixing prefix bits.

23. The method according to any one of claims 18 to 22, wherein in the coded record (30) a group of codes (31, 32) from the first set (21, 22) of a group of codes (33) from the second set ( 23) is separated by separating bits.

A method for compressing or decompressing a data set (10; 30), the method for compressing or decompressing comprising a method according to any one of the preceding claims.

25. A program with instructions for controlling a method according to any one of the preceding claims.

26. Device (50), with:

a reading or receiving device (51, 52) for reading or receiving a coded record (30); storage means (54) for storing a fixed association (40) between subsets (11, 12, 13) of a record (10) and codes (31, 32, 33) independent of a read or encoded coded record (30);

means (55) for decoding the encoded data set (30) using the fixed map (40) read from the memory means.

27. The device (50) according to the preceding claim, wherein the memory means (54) for storing an association

(40) having an association (41) of individual characters (11) and codes (31) from a first set (21) of codes and an assignment (42, 43) of character strings (12, 13) respectively a plurality of characters (11) and codes (32, 33) from a second set (22, 23) of codes.

28. Device (50), with:

a reading or receiving device (51, 52) for reading or receiving a coded record (30);

means (55) for decoding the encoded dataset (30) using an association (40) between subsets (11, 12, 13) of a dataset (10) and codes (31, 32, 33) representing an association ( 41) of individual characters (11) and codes (31) from a first set (21) of codes and an assignment (42, 43) of character strings (12, 13) each comprising a plurality of characters (11) and codes (32, 33) from a second set (22, 23) of codes.

A device (50) according to any one of the preceding apparatus claims, wherein the device (50) is a navigation device.

30. Device (50) according to one of the preceding device claims, wherein the device (50) is designed to carry out a method according to one of the preceding method claims.

31. A memory device (53) having a coded data record (30), wherein the memory device (53) does not include an assignment (40) on which the coding of the coded data record (30) is based.

32. Memory device (53) according to the preceding claim, in which

the coded record (30) is a compressed record,

the coded data record (30) comprises names of streets, squares and local authorities in a predetermined geographic area in coded form.

A memory device (53) as claimed in the preceding claim, wherein the coded record (30) represents a map of the predetermined geographical area in coded form.