MXPA00006062A - File systems supporting data sharing - Google Patents

Abstract

A storage file system is provided for multimedia data, particularly for optical disc storage means. Each successive or alternate file (40, 46) of multimedia data included in the storage means is represented by a respective allocation extent list (42, 48) with each allocation extent (48.1) identifying storage means (44) location (2.1) for the files component fragments. Data may be shared by two or more files (40, 46) with each file having a respective allocation extent list entry referencing that segment and each such allocation extent maintaining byte-accurate pointers to the start and end of the relevant data within the segment. An allocation space table (Figure 4) containing respective entries for each reference to a whole or partial segment, and optionally also a free-space table (Figure 5) identifying those whole or partial fragments available for rewriting, may be provided to allow for rapid reclamation of free space within the storage medium.

Description

The present invention relates to methods and apparatus for data storage and retrieval, and to storage devices for such data - particularly, but not essentially, optical disk storage devices. In recent years there has been a great expansion in the complexity of electronic equipment for the consumer with several different patented and technical standards governing interconnectivity and data storage. In relation to the last feature, the home user in the past has used different mechanical and functional configurations of storage devices, such as a VHS cassette to record video, a compact audio cassette to record audio from Hi-Fi equipment, hard drives and flexible to store data on personal computers. With the advent of recordable optical discs conforming to unified standards such as data distribution, bit rates, etc., are worrisome, such disks can (if configured to the particular registration system) replace many of the triggered options, and consequently, the possibility of a single unified standard can be contemplated, both in terms of the physical configuration and the handling or administration of data for all types of home audio / video / data processing systems. In conjunction with this general increase in the field of storage media, there is an increasing degree of requirement to share data in the expected and actual functionalities of the devices themselves. Of particular relevance to the present invention is the digital recording of audio and / or video (AV) material, with a user waiting for the same type of facilities to arrange and edit stored data that they experience, for example, a personal computer. In terms of available devices, optical media was not particularly suitable for video storage applications due to its limited storage capacity, although this is becoming a minor concern: for example, a disc according to DVD standards -ROM can store in the region of eight hours of compressed video following the MPEG2 protocols. Additional developments are providing optical devices with a capacity of tens of gigabytes per storage device (disk) and real-time video recording applications based on such storage devices are contemplated. Although many efficient schemes for recording and storing program data have been proposed, it will be understood, however, that there are restrictions that have to be observed in the storage of AV material, which differ from those applied in the generation of efficient file structures. and the management of files in a purely data-oriented environment. Of particular relevance is the desire imposed on the system that sections of video data (which can be interspersed with data from an accompanying sound track) can be stored contiguously, so as to allow the encoded video data to be read. sufficiently fast to avoid presenting discontinuities visible to the observer - for example to satisfy the applicable separation restrictions where the video data is encoded by the MPEG. Inefficient storage archive structures can lead to problems in those areas and a number of strategies have been proposed to improve the efficiency of storage and retrieval of multiple media data, particularly for magnetic disk storage, as described in " Multimedia file systems survey: approaches for continuous media disk scheduling "by Ralf Steinmetz, Computer Communications Vol. 18, No. 3, March 1995, p. 133-144. According to Steinmetz, it is possible to share data between files, a particular example of which would be the different versions of a stored file (for example a censored version for children and an uncut version for adults of a movie) on a single disc with the simple reuse of sections with data bits wherever appropriate to avoid the need to store the entire length but only slightly different versions of a file. Currently, however, while the idea of data reuse has been a concern, it has been based on media where data is subdivided into convenient, uniform segments (for example, sectors on a recordable disk) with the ability to share sections of data. files being only supported at the segment level. The results of this have been that any edited editions of a file are forced to include complete segments when only a small part of them has been desired, or the size of the segment has to be too small to allow flexibility in the operations of editing, which wastes disk space and creates an unacceptably high processing load. Therefore, an object of the present invention is to provide storage means (and support means for their implementation) with an internal data structure that supports multiple editions through the reuse of complete record segments or segments. partial A further object is to provide storage means such that they use characteristics of the internal data structure for the efficient recovery of the storage area containing redundant data in complete or partial fragments. According to the present invention there is provided a storage device comprising a first area subdivided into segments for the registration of sequential data, portions of which when read in a predetermined sequence, comprise a data file, the device comprises, in addition , a second area containing a list of allocation points, each of which identifies the start and end of a contiguous part of the first area, and an indicator file containing a list of indicators of the respective entries in the list of allocation points; characterized in that the device contains the least two files defined in respective indicator files and at least one part of a segment is common to the two files, with each file having a respective allocation point for that segment and each allocation point indicating the points start and end within the segment for that part of the segment used in the respective files. By providing the respective allocation points for each data use of a segment, a simplification in the handling of multiple files comprising shared data results. Furthermore, having each allocation point specifying not only the particular segments but also the start and end points within those segments, the restriction of shared data that have to be specified as a complete segment is removed, allowing greater flexibility in the possibilities for edit the stored data. The second area (which may be in the form of a plurality of discrete areas distributed among the segments of the first area) may further comprise an allocation space table containing one entry for each allocation point, the table provides a record of all simple or multiple uses of the segments of the first area. With this table, the entries for which they are created and / or updated with the allocation points, it is not necessary for a device to seek to delete or overwrite segments or partial segments to explore all the allocation points to identify redundant segments, particularly where the Space table is properly arranged to provide a map of the current use of the first area. In this regard, the second area may also contain a free space table, the content of which is derived from the contents of the allocation space table and identifies all segments or parts of segments available for writing. Although the generation and maintenance of the free space table requires extra processing capacity in a host system, it provides remarkable benefits in applications where large volumes are to be stored in various edited forms and recovery of free space is a must. Each of the allocation points can appropriately identify a starting point in terms of a number of bytes or other data subdivisions (eg, MPEG2 data packets) to be ignored at the beginning of a segment, and / or a point final in terms of a number of bytes (or packets) to be ignored at the end of a segment. By specifying start and end points as distances of an end and segment start also specified, backwards compatibility with older systems is possible, which only specify a segment level while retaining or maintaining compliance with the protocols of coding based on blocks or packages such as MPEG. Although the storage medium can be a magnetic disk, in a preferred embodiment the storage device is an optical disk and the data written in segments of the first area comprise digitized audio and / or video material with the indicator files comprising lists of respective reproduction for all or selected parts of the material. This allows, for example, to keep different versions of an AV presentation (such as different editions of a movie) on a single disc - perhaps coupled with the support of the system for the restriction of the parents on the reproduction of some versions without requiring that Each version is stored separately as a distinct and separate entity. Note that the references here to storage in and storage "over" a device or storage medium are used interchangeably, without any being intended to refer to a specific form or configuration of the storage device, unless it is established explicitly. As a disk (optical or magnetic) all the segments of the first area can be of a common size, and each of the first and second areas can comprise tracks or contiguous groupings of a plurality of tracks, respectively. Note, however, that the division into the first and second areas is only necessary from a logical point of view, and the two areas can appear consecutively or adjacent to the chosen storage medium or can still be interleaved if the handling of such an arrangement it is within the capabilities of the reading / writing device. Also, the respective indicator files for multiple files on a disk can be grouped together in a table of files or they can be distributed through the disk. Also, according to the present invention, there is provided a method for formatting the memory space in a storage device or means, a data processing device that operates to manipulate data in a first area of a storage medium or a device. with a format according to such method, and such a processing apparatus operates, furthermore, to implement the method for formatting, all as described in the appended claims to which readers' attention is now directed and the description of the which is incorporated here as a reference. The preferred embodiments will now be described by way of example only, and with reference to the accompanying drawings in which: Figure 1 is a schematic block diagram of a data processing apparatus which can be configured to effect the process of formatting of the present invention; Figure 2 represents the relationship between a data file in the form of a reproducible object specified at the database level for data fragments stored in a sequential recording medium; Figure 3 is similar to Figure 2 and shows a pair of reproducible objects that share common data in respective fragments; Figure 4 represents a table of allocated space for a pair of reproducible objects similar to those of Figure 3; and Figure 5 represents a table of free space derived from the table of allocated space and of Figure 4. Starting with Figure 1, it shows the basic components of a data processing apparatus, such as the one that can be used. to format and store data on the optical disk 10. The apparatus consists of a central processor (CPU) 12 coupled with random access memory (RAM) 14 and read only (ROM) 16 via a collective address driver and data 18. An external interface (EXT I / F) 20 represents the connection of the device with external data sources. As will be recognized, the configuration of this interface will depend on the type of external data source and the total function of the data processing apparatus: for example, where the apparatus is a home video / audio recorder, the interface will provide the means of connection and reception for the source of video / audio signals to be recorded (for example from a satellite receiver), where the apparatus is a personal computer, it can comprise a link to remote data sources by means of, for example, an interface of Internet. Also coupled with the CPU 12, the memories 14, 16, and the interface 20 via the selective conductor 18, are one or more user input means (UIP) 22 and a display 24; for a PC-based apparatus, those devices may comprise, respectively, a keyboard and a monitor, while for a home recording apparatus they may comprise user control buttons and a visual display device of L.E.D. on the front panel of the device. A further component is an interface or interconnection with a storage medium, in this example, an optical disk recording / reproducing unit (DISC R / W) 26 that provides physical means for receiving and reading from / writing to optical disk 10 and an internal set of operation protocols for reading / writing from / to a disk with a format according to a predetermined standard. As will be well understood, the management or administration protocol of the unit 26 can be effected by an internal slave processor with associated memory (not shown) under the control of the CPU 12, or those functions can be handled directly by the CPU 12. with reference to protocol commands maintained at the level of the loading operation in ROM 16 or periodically recharged to RAM 14.

In Figure 1, the optical disk 10 is shown with a nominal division in a first area 28 containing a sequence of complete data segments, freely or partially written, and a second area 30 containing a number of control structures (tables of file, allocation point lists, free space structures, etc.) the function of which will be described in detail later. As stated above, the division into first and second discrete areas is necessary only from a logical point of view to distinguish between the structures that only contain data and functional on the disk. In practical terms, although different entities can be registered on areas of a disk's stopped tracks (for example), for an operational modality as savings can be obtained in terms of reduced search delay (and consequently reduced access times) through of the distribution of the second area between the first, for example with file tables and allocation point that describe the use of the complete or partial disk segment that is placed on the disk adjacent to those segments to which reference is made. Figure 2 illustrates the relationship between a data file entry (also known as a reproducible object) specified at the database level and those individual pieces of data stored in various places on the disk that are to be reproduced in the sequence correct to recreate the data file. Each file on the disk is represented by an entry (FE.l) 40 in a table of files written in the second area. The database level, this file entry contains data about the file as a whole (its name, creation date, etc.) or where the file is in multiple sequential parts, the entry will identify only the part and its place in the sequence. At the system level, this entry 40 refers to a list 42 that contains one or more assignment points AX 42.1, 42.2 ... 42. n each of which identifies the start and end of a respective contiguous section (1.1, 1.2, ... ln) of linear storage, as represented by the sequence of storage areas 44 in the lower part of the Figure. In a known manner, for easy access, the linear storage 44 can be divided into a sequence of sectors or logical segments of common size or commonly specified, the size of which can be fixed in a fixed number of bytes (such as 2048) or another determined grouping of data such as modified MPEG blocks. Note that the physical ordering of the segments used does not need to be reflected in the physical order in which the data they contain are going to be reproduced. However, the proximity of successive portions of a file is preferred, since it minimizes delays due to search times and reduces the likelihood of problems with separation restrictions by critical time data such as MPEG audio / video. Each of the allocation points AX 42.1, 42.2 ... 2. n specifies the respective data portion 1.1, 1.2, ... ln both in terms of the start and end points of the segment or segments that contain them, for allow backward compatibility with systems that only specify the granularity of an entire segment, and in terms of the number of bytes (or other arbitrary block divisions) that have to be ignored at the beginning and / or end of each segment. In Figure 3, a second file entry (FE.2) 46 is shown, file entry which has an active list of 48 AX assignment points 48.1, 48.2 each of which identifies the respective portions 2.1, 2.2 of the linear sequence of segments 44. This second file sequence may comprise an entity other than the first 40 or may be a sequential but sequential part of a larger file specified by sequential entries in the file table. In each case, the point to note is the reuse of a part of the data stored in those segments where portions 1.2 and 2.1 overlap. Figure 4 represents a further structure, allocation space table 50, stored in a second area. An additional allocation point AX 48.3, physically and temporally contiguous to its predecessor 48.2 of the second file entry (FE.2) 46 was also added. In general, each allocation point will have a respective entry in the allocation space table 50 (42.1 = ASE1 = 50.1; 42.2 -ASE2 = 50.2; 42. n = ASEn = 50. n; 48.1 = ASEn + 1 = 50. n + l). The exception to this is where pairs of non-overlapping, contiguous portions exist, as specified by allocation points 48.2 and 48.3 when, for reasons of both saving and data efficiency, a single allocation space entry is written ( ASEn + 2) in table 50. The allocation space table 50 provides, in one place, an indication of the use (complete, partial or empty) of each segment (and consequently each byte) of the first area, table which is updated every time a new time data is created, or a new edition of the existing data, in the storage medium. For ease of creation, as shown the entries to the table can be written in order in the file - that is, the use of each allocation point of the first file is listed before the use of each allocation point in the second file and so on To facilitate the use, for example in systems that look for segments or parts of free segments for the intercalation of auxiliary data that accompanies a stored video sequence, the allocation space table can be arranged in sequential order of the starting points. specified, regardless of which file of the particular portion is used, so that scanning to find localized free space does not require verifying each entry in list 50. Although this will require some additional processing when multiple editions of a stored data block are created over many segments, handling list 50 as a stack (and downloading to read / write in the RAM of the device for updating) is not problematic. In addition, the benefits when looking to recover redundant storage area, perhaps for the use of auxiliary data or for additional AV data when the disk / storage device is full, are remarkable. An extension to the facilitation described above for free space recovery is shown in Figure 5 where, in addition to, (or instead of) the allocation space data table, a free space table 52 is provided in the second area. Instead of perfectly detailing the use of the segment file and segment parts, the free space table is derived from the data and allocation space lists, suitably as start and end points and in sequential physical order, those portions FSE 52.1 - 52.4 of the first area that are not used or, through a subsequent edition of the stored material, those portions that contain data not referred by any assignment point, data which are therefore (notationally) free to overwrite without being subject to any restrictions on the preservation of available data for the creation of additional files. With an allocation space table and a free space table stored, the allocation space table can be written sequentially on the fly, as in Figure 4, while creating respective allocation points, with the update of the space list free disk / storage medium 52 (which can be a longer process) being reserved for a domestic procedure to handle the "idle" moments of the writing system processor and / or at the end of the creation of the edition. In terms of the industrial application of the above storage mechanism, a particular application is in disc-based video recorders where the amount of video material to be stored is relatively large: even the compressed video material takes up a lot of storage space (of the order of 4Mb for 3 seconds of video) and the capacity on disk-based storage media - particularly optical discs - is limited. Such disc-based video recorders preferably support some level of editing ability operated by the user, where the application of the supported edition uses portions of already registered video material. By sharing data between two registers, a saving in disk capacity is achieved and, in circumstances such as multiple editions of a movie being provided on a single disc, the total usage may be little more than that of a single edition of the movie. If the records are, or consist of, data files, then sharing parts of a file in the underlying file system provides an efficient solution for sharing data between records. From reading the present disclosure, other variations will be apparent to those skilled in the art. Such variations may involve other features, which are already known in the methods and apparatuses for handling or administration and storage and the component parts thereof and which may be used in place of or in addition to the features described herein, and the scope of the present invention is determined by the claims appended hereto.

Claims (14)

CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, the content is claimed in the following CLAIMS:

1. A storage device, comprising a first area subdivided into segments for the registration of sequential data, portions of which when read in a predetermined sequence, comprise a data file, the device comprises, in addition, a second area that contains a list of allocation points, each of which defines the start and end of a contiguous part of the file area, and a file of indicators that contains a list of indicators of the respective entries in the list of points of assignment; characterized in that the device contains at least two files defined in the respective indicator files and at least a part of a segment is common to the two files, with each file having a respective allocation point for that segment and each allocation point indicating the start and end points within the segment for that part of the segment used in the respective files.

2. The storage device according to claim 1, characterized in that the second area further comprises a table of allocation space containing an entry for each allocation point, the table provides a record of all or of a single or multiple uses of the segments of the first area. The storage device according to claim 2, characterized in that the second area also contains a free space table, the content of which is derived from the contents of the allocation space table and identifies all the segments or Parts of segments available for writing. The storage device according to any of claims 1 to 3, characterized in that each allocation point identifies a starting point in terms of a number of bytes to be ignored from the beginning of a segment. The storage device according to any of claims 1 to 4, characterized in that each allocation point identifies an end point in terms of a number of bytes to be ignored at the end of a segment. The storage device according to any of claims 1 to 5, characterized in that the storage device is an optical disk and the data written to segments of the first area comprises digitized audio and / or video material with the files of indicators comprising respective playlists for all or selected parts of the material. 7. A method for formatting a memory space in a storage medium, for the subsequent access of a data reading apparatus, comprising the steps of: distributing a first area of the memory space in a plurality of segments for the record of sequential data, portions of which when read in sequence comprise a data file; generating and writing to a second area of the memory space a list of allocation points, each of which identifies the start and end of an adjacent part of the first area; generate and write to the second area of the memory space a file of indicators as a list of indicators of the respective entries in the list of allocation points; characterized in that the storage medium contains at least two files with at least a part of a segment being common to the two files, where a file of respective indicators is generated and written by each file and a respective allocation point is generated for each use of a segment, those allocation points include an indication of the physical assignments of the start and end points within the segment for that part of the segment used in the respective files. 8. The method of compliance with the claim 7, characterized in that it also comprises the step of generating and writing to the second data area an allocation table, the table contains a record of a single or multiple uses of all the segments of the first area. 9. The method of compliance with the claim 8, characterized in that it also comprises the step of generating and writing in the second area a free space table, the content of which is derived from the allocation space table and identifies all the segments or parts of segments available for the writing. 10. A data processing apparatus operable to manipulate data in the first storage media area with a format given by the method according to claim 7, the apparatus is characterized in that it comprises a data processor coupled with read / write means of storage media configured to receive and access the storage medium, and an input to receive data identifying those segments or parts of segments comprising a file, the processor is arranged to generate and store an indicator file together with a list of allocation points for the segment data, those allocation points include an indication of the physical location of the start and end points within each segment used in a file of the segment data for that file. The apparatus according to claim 10, characterized in that it further operates to implement the method for formatting according to claim 7, wherein the processor is configured to partition the memory space of a storage device received in the first and second areas and to distribute, in addition, the first area in the plurality of segments. 12. The apparatus according to claim 10 or 11, characterized in that the processor is further configured to periodically update, or to generate and update periodically, an allocation space table in the second area, which table contains an entry for each allocation point and provides a record of the use of only one or multiple files of all segments of the first area. The apparatus according to claim 12, characterized in that the processor is further configured to periodically update, or to periodically generate and update, a free space table in the second area, the content of such a table is derived by the processor from the contents of the allocation table and provides a record for those segments or parts of segments of the first area available for writing. The apparatus according to any of claims 10 to 13, characterized in that the storage means is a writable optical disk and the read / write means are configured accordingly, the data written to the segments in the first area of the they comprise digitized audio and / or video material with the indicator file being read as respective playlists for all or selected parts of the material.