WO2008032254A1

WO2008032254A1 - A device for and a method of recording information on a write-once medium

Info

Publication number: WO2008032254A1
Application number: PCT/IB2007/053630
Authority: WO
Inventors: Srinivas R. Kudavelly; Robert A. Brondijk
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2006-09-14
Filing date: 2007-09-10
Publication date: 2008-03-20
Also published as: TW200822073A

Abstract

A device for recording information signals on a write-once disc- like recording medium, the information signals representing user data and management information for accessing the user data. The device comprises recording means (22, 27, 28, 29) for recording the information signals on the medium, reading means (21, 22, 25, 30) for reading recorded information signals from the medium and control means (20) for controlling recording and reading the information signals. Further, the device comprises a safe recording unit (32) for allocating a recovery information area in the data area, for generating recovery information in dependence of the recorded parts of the user data and for, at given instances, recording the recovery information in the recovery information area, the recovery information comprising information enabling generating the management information for the recorded parts of the user data. This is done in order to facilitate possibility of recovering the management information in case of any system failure during recording of the user data, without parsing the user data during a recovery process.

Description

A device for and a method of recording information on a write-once medium

FIELD OF THE INVENTION:

The invention relates to a recording device for recording information signals on a write-once disc-like recording medium, the information signals representing user data and management information for accessing the user data, the medium comprising a data area for recording the information signals, the device comprising: recording means for recording the information signals on the medium; reading means for reading recorded information signals from the medium; and control means for controlling recording and reading the information signals and for recording parts of the user data sequentially, the control means comprising a management unit for generating the management information for the user data and for recording the management information.

The invention further relates to a method of recording information signals on a write-once disc- like recording medium, the information signals representing user data and management information for accessing the user data, the medium comprising a data area for recording the information signals.

The invention also relates to a method of recovering management information for accessing user data recorded in a data area on a write-once disc-like recording medium. In addition, the invention relates to a computer program product for use in recording information signals on a write-once disc- like recording medium by a recording device.

BACKGROUND OF THE INVENTION:

When recording data, such as audio/video information, on magnetic tape such as videocassettes, power failure is not a problem, as said information has been recorded correctly and could be played back up to the moment of failure immediately. However, when recording onto optical discs, a complex data management system is generated and recorded on a disc, comprising management information, such as title menus, said management information enabling playback and trick play. During recording, the video information is encoded in a format such as MPEG-2 and stored onto the optical disc according to a predefined recording format. Once the recording is stopped, for example when the user decides to stop recording, then the recording devices generates/updates and records said management information on discs. Consequently a file system is updated and/or created according to a desired format. Without the management information associated to the recorded video information being present on the disc, the video information cannot be accessed and/or played back, even though the video information as such has been recorded onto the optical disc.

Playback is not possible before said management information has been recorded on disc, said management information being usually gathered in a memory and recorded onto the optical disc after the recording is finished. Therefore, in case of an abrupt interruption of the recording process, such as a power failure, the management information will be not available, so that the recorded information cannot be played back anymore.

US patent application 2006/0013085 discloses a method of recording blocks of information onto an optical disc carrier that comprises recovery information being either a recovery header in a private data stream such as a MPEG-2 private stream or a Logical Volume Integrity Descriptor, said recovery information including a recording start address. Therefore, after a power failure has taken place, a suitably adapted recoding device identifies the recording start address and starts reading out and parsing the recorded blocks of information to identify the end of the improperly ended recording. Once such an end is identified, the recording device proceeds to parsing the recorded data for generating and updating the navigation data and the file system in order to include the new recording. The recovery method of US patent application 2006/001308 carries the disadvantage that parsing the recorded blocks of information to identify the end of the improperly ended recording and parsing the recorded data for generating and updating the navigation data and the file system in order to include the new recording is a time consuming process. Consequently, the user experiences the recovery process negatively, as he is unable to use the recording device during the period of recovery.

SUMMARY OF THE INVENTION:

Therefore, it is an object of the present invention to provide a solution to the above problem of time consuming recovery, the solution enabling more efficient recovery process, for example after a power failure.

For this purpose, according to a first aspect of the invention, in the recording device as described in the opening paragraph, the control means comprise a safe recording unit for allocating a recovery information area in the data area, for generating recovery information in dependence of the recorded parts of the user data and for, at given instances, recording the recovery information in the recovery information area, the recovery information comprising information enabling generating the management information for the recorded parts of the user data. For this purpose, according to a second aspect of the invention, the method of recording information signals, as described in the opening paragraph, comprises steps of: allocating a recovery information area in the data area; recording parts of the user data sequentially; generating recovery information in dependence on the recorded parts of the user data, the recovery information comprising information enabling generating the management information for the recorded parts of the user data; at given instances, recording the recovery information in the recovery information area; generating the management information for the user data; and - recording the management information.

For this purpose, according to a third aspect of the invention, the method of recovering management information for accessing user data, as described in the opening paragraph, comprises steps of: verifying presence of the management information in the data area; - locating a recovery information area in the data area; locating recovery information recorded in the recovery information area according to the method as described in relation to the second aspect of the invention; reading the recovery information from the recovery information area; generating recovered management information based on the recovery information; recording the recovered management information on the medium. For this purpose, according to a fourth aspect of the invention, the computer program product for use in recording information signals, as described in the opening paragraph, comprises program code means for causing a processor of the recording device, to perform the steps of the method as described in relation to the second or the third aspect of the invention, when the computer program is run on the processor.

The measures according to the invention have the effect that when the recovery information, that is recorded on the medium, comprises information enabling generating said management information - parsing the recorded information, for example an audio/video stream, for the purpose of recovery is not necessary anymore.

It is noted that, in the measures according to the invention, the possibility to perform a recovery is tied to the medium on which the information has been recorded and not to the non- volatile memory of the recording device. When the recovery information is tied to the non- volatile memory of the recording device, the recovery process needs to be initiated before the medium is ejected; otherwise the recorded information is effectively lost. When the recovery information is present on the medium, the recovery process can be initiated at any moment, also in another recording device. In an embodiment of the device, the safe recording unit is adapted to determine the instances in dependence on completion of recording of each data file out of data files, for the user data organized in the data files. This enables recovery of all but the last file before failure, during recording of multiple user data files.

In another embodiment of the device, the user data being streaming data, such as real-time video data, the safe recording unit is adapted to determine the instances in dependence on completion of recording of a predefined amount of the user data. This allows for fine-tuning of the accuracy of the recovery information and consequently the accuracy of the recovery process.

In a further embodiment of the device, the user data being streaming data, such as real-time video data, the safe recording unit is adapted to determine the instances in dependence on a predefined time period. This provides another way of fine-tuning the accuracy of the recovery process. In this case, the amount of (possibly) lost data corresponds to at most the duration of the time period, independent on a rate of data transfer; for example to 5 seconds of video material independent on a recording mode. Advantageously, for the streaming data being recorded as a sequence of addressable units, such as cells in the video data, the safe recording unit is adapted to generate the recovery information further comprising information with respect to the recorded addressable units, said information comprising at least unit start address information. The cell address information provides important information for generating the management information, that, if not available as recovery information, can only be obtained by reading and parsing the complete recorded streaming information.

Preferably, the safe recording unit is adapted to generate the recovery information, which enables generating the management information corresponding to a Video Title Set Information (VTSI) as disclosed in WO 01/01415. Such format of the management information enables playback compatibility on standalone DVD players.

In an embodiment of the device, the control unit is adapted to record the user data adjacent to the recovery information area. This makes it possible to decrease seeking time for retrieving the recovery information during recovery of the management information.

In another embodiment of the device, the safe recording unit is adapted to allocate a dedicated recovery information area for each subsequent recording of the user data. This allows for identification of the appropriate recovery information area corresponding to the failed recording of the user data, for the purpose of finding the relevant recovery information.

In a further embodiment of the device, the safe recording unit is adapted to allocate one recovery information area common for subsequent recordings of the user area. This allows for reserving the recovery information area upfront, independent on a number of subsequent recordings. Advantageously, the control unit further comprises a recovery unit for verifying presence of the management information in the data area, for locating a recovery information area in the data area, for locating recovery information recorded in the recovery information area, for reading the recovery information from the recovery information area, for generating recovered management information based on the recovery information and for recording the recovered management information on the medium. This facilities recovery of the management information by the same device that has recorded the recovery information.

Further preferred embodiments of the device and the methods according to the invention are given in the appended claims, disclosure of which is incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS:

These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which: Figure Ia shows an example of a disc-shaped write-once record carrier,

Figure Ib shows a cross-section taken of the record carrier,

Figure 2 shows an example of a recording device, in accordance with the invention, Figure 3 shows schematically an example of an arrangement of data on a disc- like recording medium suitable for recording video information,

Figure 4 shows schematically an example of a structure of a DVD-Video Zone on a disc-like recording medium of the rewritable type, Figure 5 shows schematically an example of a structure of a data area on a write-once disc- like recording medium after two recordings of video information,

Figure 6 shows a flow diagram of an example of a method of recording information signals on a write-once disc- like recording medium, in accordance with the invention, Figure 7 shows an example of allocating the recovery information area, in accordance with the invention,

Figure 8 shows another example of allocating the recovery information area, in accordance with the invention,

Figure 9 shows a flow diagram of an example of a method of recovering management information for accessing user data, in accordance with the invention. Corresponding elements in different Figures have identical reference numerals/symbo Is .

DETAILED DESCRIPTION OF EMBODIMENTS: Figure Ia shows a disc-shaped write-once record carrier 11 having a track 9 and a central hole 10. The track 9 is arranged in accordance with a spiral pattern of turns constituting substantially parallel tracks on an information layer. The record carrier, hereinafter also called the recording medium, may be optically readable, called an optical disc. Recorded information is represented on the information layer by optically detectable marks recorded along the track. The marks are constituted by variations of a physical parameter and thereby have different optical properties than their surroundings, e.g. variations in reflection. The information layer, or at least a part of it, is of a recordable type, on which marks can be recorded. Examples of a recordable disc are the CD-R, and writable versions of DVD, such as DVD+R, and the high-density writable optical disc called Blu-ray Disc, BD-R. The track 9 on the recordable type of record carrier is indicated by a pre- embossed track structure provided during manufacture of the blank record carrier, for example a pregroove.

Figure Ib is a cross-section taken along the line b-b of the record carrier 11 of the recordable, write-once, type, in which a transparent substrate 15 is provided with a recording layer 16 and a protective layer 17. The track structure is constituted, for example, by a pregroove 14, which enables a read/write head to follow the track 9 during scanning. The pregroove 14 may be implemented as an indentation or an elevation, or may consist of a material having a different optical property than the material surrounding it. A track structure may also be formed by regularly spread sub-tracks, which periodically cause servo signals to occur. The record carrier may be intended to carry real-time information, for example video or audio information, or other information, such as computer data.

The track structure comprises a periodic variation of the transversal position of the track of the disc, also called wobble. The variations cause an additional signal to arise in auxiliary detectors, for example in a push-pull channel generated by sub detectors or partial detectors in the central spot in a head of a scanning device. The wobble is, for example, frequency modulated and position information is encoded in the modulation. A comprehensive description of the prior art wobble in a writable CD system comprising disc control information encoded in such a manner can be found in US 4,901,300 and US 5,187,699. It is noted that other transversal variations are known which are intended to be detected by variations of reflected radiation by (sub) detectors in a scanning head, such as variations in the width of the track, prepits adjacent to the track, and other.

Figure 2 shows an example of a recording device for recording information on a recording medium 11 such as CD-R, DVD+R, DVD-R or BD-R, in accordance with the invention. The device is provided with scanning means for scanning the track of the record carrier 11, which means include a rotation unit 21 for rotating the record carrier 11, a reading head 22 for scanning the track by a radiation beam 24 and a reading head control unit 25 for controlling generation and positioning of the radiation beam. The head 22 comprises an optical system of a known type for generating the radiation beam 24 guided through optical elements to generate the radiation spot 23 on a track of the information layer of the record carrier. The radiation beam 24 is generated by a radiation source, e.g. a laser diode. The head further comprises (not shown) a focusing actuator for focusing the beam to the radiation spot 23 on the track by moving the focus of the radiation beam 24 along the optical axis of said beam, and a sledge and a tracking actuator for positioning the radiation spot 23 in a direction transverse to the scanning direction of the track on the center of the track. For a disc shaped medium the transverse direction is called radial direction and the tracking actuator is called radial actuator. The tracking actuator may comprise coils for radially moving an optical element or may alternatively be arranged for changing the angle of a reflecting element. Analogously, the focusing actuator may comprise coils for moving the focus of the radiation beam 24. It should be noted that the focusing and radial actuators may be constructed in the form of one actuator for positioning an optical element such as a lens and performing functions of said actuators.

For reading, the radiation reflected by the information layer is detected by a detector of a usual type, e.g. a four-quadrant diode, in the reading head 22 for generating a read signal and further detector signals, including a tracking error and a focusing error signal for controlling said tracking and focusing actuators. The read signal is processed by a read processing unit 30 of a usual type including a decoding unit and an error correction unit and output unit to retrieve the information. The read processing unit may comprise a memory buffer for transitionally storing the main data. Alternatively, the memory buffer can be a separate unit. Hence reading means for reading information include the rotation unit 21, the reading head 22, the reading head control unit 25 and the read processing unit 30.

The device is provided with recording means for recording information on a record carrier of a writable type, for example CD-R, DVD+R, DVD-R or BD-R. The reading head 22 is adapted for recording marks on a record carrier. The recording means cooperate with the head 22 for generating a write beam of radiation, and comprise write processing means for processing the input information to generate a write signal to drive the head 22, which write processing means comprise (optional) an input unit 27, a formatter 28 and a modulator 29. For writing information the power of the beam of radiation is controlled by the modulator 29 to create optically detectable marks in the recording layer. The marks may be in any optically readable form, e.g. in the form of areas with a reflection coefficient different from their surroundings, obtained when recording in materials such as dye, alloy or phase change material, or in the form of areas with a direction of polarization different from their surroundings, obtained when recording in magneto-optical material. Writing and reading of information on/from optical discs and formatting, error correcting and channel coding rules are well-known in the art, for example from the CD and DVD systems.

The input unit 27 processes input user data to units of information, which are passed to the formatter 28 for adding control data and formatting the data, for example by adding error correction codes (ECC) and/or interleaving. For computer applications units of information may be interfaced to the formatter 28 directly - in such case, as an option, the input unit 27 does not have to be present in the apparatus. The formatted data from the output of the formatter 28 is passed to the modulation unit 29, which comprises for example a channel coder, for generating a modulated signal, which drives the head 22. Further the modulation unit 29 comprises synchronizing means for including synchronizing patterns in the modulated signal. The formatted units presented to the input of the modulation unit 29 comprise address information and are written to corresponding addressable locations on the recording medium under the control of a control unit 20. The control unit 20, which controls the recording and retrieving of information, may be arranged for receiving commands from a user or from a host computer. The control unit 20 is connected via control lines 26, for example a system bus, to said input unit 27, formatter 28 and modulator 29, to the read processing unit 30, to the drive unit 21, and to the positioning unit 25. The control unit 20 comprises control circuitry, for example a microprocessor, a program memory and control gates, for performing the procedures and functions according to the invention as described below. The control unit 20 may also be implemented as a state machine in logic circuits.

In an embodiment the device is a storage system only, for example an optical disc drive for use in a computer. The control unit 20 is arranged to communicate with a processing unit in the host computer via a standardized interface (not shown). Digital data is interfaced to the formatter unit 28 and from the read processing unit 30 directly. In this case, the interface acts as an input unit and an output unit; as an option, the input unit 27 does not have to be present in the device.

In an embodiment the device is arranged as a stand alone unit, for example a video playback/recording device for consumer use. The control unit 20, or an additional host control unit included in the device, is arranged to be controlled directly by the user. The device includes application data processing, for example audio and/or video processing circuits. The user information presented to the input unit 27 may comprise analog audio and/or video, or digital uncompressed audio/video signals; in this case the input unit 27 may comprise compression means for these signals. The read processing unit 30 may comprise suitable audio and/or video decompression units.

In an embodiment of the device, the control unit 20 is arranged for controlling the recording by locating each block at a physical address in the track. Physical addresses are translated into logical addresses and vice versa. The logical addresses constitute a contiguous data storage space to be used for storing sequences of information blocks, such as files under control of a file management system, for example UDF. Such file system has its own file system data, which include information about all kind of structures relating to user data stored on a recording medium. In particular, file system data may include volume structures representing the structures of logical and/or physical volumes, file entries representing the structures of files containing the user data, directory entries describing grouping of files, and a space bitmap representing allocated or unallocated space for storing data on a record carrier. It should be pointed out that file entries may also contain references to other file entries. Information blocks can be grouped into larger units. For example, in the DVD system, 16 information blocks each of 2 Kbytes of data are grouped into so-called ECC blocks of 32 Kbytes, for the purpose of error correction.

The recording medium 11 is intended for carrying user information according to a standardized format, to be readable on standardized read devices. The recording format includes the way information is recorded, encoded and logically mapped onto the recording space provided by the track 12 and it is described, by way of example, with reference to Figure 3. The recordable space is usually subdivided into a lead-in area (LI) 41, a data area (DA) for recording the information and a lead-out area (LO) 42. The lead-in area (LI) 41 usually comprises basic disc management information and information how to physically access the data area (DA). For example, said basic disc management information corresponds to the table of contents in CD systems or the formatting disc control blocks (FDCB) in DVD systems.

The user information recorded in the data area (DA) is further arranged according to an application format, for example comprising a predefined structure of files and directories. Further, at logical level, the user data in the data area is arranged according to a file system comprising file management information, such as ISO 9660 used in CD systems, available as ECMA- 119, or UDF used in DVD systems, available as ECMA- 167.

When video information is recorded onto the optical disc, it is usually recorded in a separate volume from other user data, such as computer data. Figure 3 illustrates such an arrangement as used in the case of recording video information and other user data onto a DVD+RW disc. The data area (DA) is organized as single volume space and may be further divided into a video section for recording video information and a data section for recording other user data. The video section comprises a video file system 43, a Video Recorder Manager (VRM) scratch area 44, a Video Recorder Manager Information (VRMI) 45 a Video Recorder Manager User Data (VRM UD) 46, a DVD Video Zone (DVD-VZ) 47 and a backup copy of the Video Recorder Manager Information (VRMI-BK) 48. The optional data section succeeds the video section and it comprises a file system area 49 and the data files 50. The hashed areas in Figure 3 indicate that the previously described elements of the data area (DA) need not be recorded contiguously. The VRM scratch area 44 is an area used by recorders to temporally store data. The Video Recorder Manager Information (VRMI) 45 comprises information with respect for identifying the type of recorder that has generated the DVD-Video menus on the disc. The Video Recorder Manager Information (VRMI) 45 further comprises information whether a data section is present on the disc. The Video Recorder Manager User Data (VRM UD) 46 are optional data structures that may be stored in one or more files, which may be recorded to add functionality and to improve performance on some recorders.

The video file system 43 comprises a video volume usually comprising at least a VIDEO RM directory and a VIDEO TS directory in the root directory. The VIDEO RM directory usually comprises the following files:

- VIDEO RM. D AT (comprising the VRM scratch information), - VIDEO RM.IFO (comprising VRMI information), and

- VIDEO RM. BUP (comprising VRMI backup information).

The VIDEO RM directory may comprise other VRM user data files. The VIDEO TS directory usually comprises the following files:

- VIDEO TS. IFO (comprising the Video Manager General information (VMGI)),

- VIDEO TS. BUP (comprising a backup of VMGI), and

- a sequence of files for each video title set (VTS), the sequence comprising VTS 01 0.IFO (Video Title Set Information (VTSI) for title #1), VTS OI l. VOB (VTSTT VOBS for VTS #1) and VTS 01 0.BUP (comprising a backup of VTSI for title #1) Figure 4 illustrates schematically a possible structure of a DVD-Video Zone

(DVD-VZ) 47 on an optical disc of the rewritable type. In the order of recording, it usually comprises a Video Manager (VMG), Video Title Set Information (VTSI) for each video title set (VTS), one or several video title sets (VTS) comprising the video information (TITLEl, TITLE2) and backups (VTSI #1_BK, VTSI #2_BK) of the Video Title Set Information (VTSI) for each video title set (VTS). The Video Manager (VMG) comprises Video Manager Information (VMGI), optionally a video object set VMGM VOBS and a backup copy of VMGI (VMGI BK). The Video Title Set Information (VTSI) comprises management information for enabling playback and trick play of the video titles. A suitable example of the structure of the Video Title Set Information (VTSI), corresponding to the DVD+RW Video recording format, has been disclosed in WO 01/01415, to be inserted here by reference. It is noted that in general the Video Objects for all Titles on the disc are put into a single VTS Title Video Object Set (VTSTT VOBS) irrespective of the VTS they belong to. It is further noted that usually video object corresponding to different video coding modes have separate VTSI files associated. VTSI files for all VTSes are put in front of this VTSTT VOBS with increasing VTS number.

In a known real-time recording method, the video information is encoded in a format such as MPEG-2 and stored onto the optical disc as a sequence of cells forming a recording within a video title set (VTS). While recording, information for building the Video Title Set Information (VTSI) and updating other management structures such as VMG are stored, usually in volatile memory of the recorder. Once the recording is stopped, for example due to the user decided to stop the recording, then the stored information in the volatile memory of the recording device is used for generating Video Title Set Information (VTSI) and the other management structures are updated so that the newly recorded video information can be accessed and played back.

For the DVD+RW system, the video file system 43 and other management information for accessing the video information, such as VMG and VTSI files, are recorded in front of the actual video information in the data area on a disc. This is necessary for compatibility with DVD read-only players. Consequently, recording of any video information is started at some distance from the beginning of the data area, leaving a reserved space necessary for recording management information.

In case of a write-once medium, such as DVD+R disc, writing the management information at the required position in the reserved space would block further recording on the same disc in a compatible way. Therefore, for each recording of user video information, corresponding management information is generated and recorded after video information, as schematically illustrated by means of an example in Figure 5, where two recordings, 52 and 55, are indicated. The reserved space 51 is intended for writing the final complete management information for accessing all video information, during so-called closing or finalization of a medium. Management information, recorded after first and second recording of video information, is indicated by reference signs 53 and 56, respectively. Different positioning of management information parts, such as VMG or VTSI, than in Figure 4, should be noted. In addition, so-called reserved space allocation table 54 (57), RSAT, is written after completion of each recording. This table contains information about mapping of locations in the reserved space 51 to locations in area(s) 53 (56), where the management information is recorded. This provides the mechanism for treating the reserved space 51 on a write-once medium as a virtual rewritable area and allows for accessing management information on not finalized medium; reading from locations in the reserved space results in reading from other locations according to the mapping in the reserved space allocation table. In this way, the management information 53 (56) appears as if recorded in the reserved space 51. For the purpose of the teaching of the invention, hereinafter the term management information may also encompass the mapping information.

It should be pointed out that the reserved space allocation table is a special case of a virtual allocation table, VAT, known from the UDF file system and used on sequentially written media like CD-R.

The control unit 20 includes a management unit 31 for generating management information related to user data, which data can be for example video information, and for recording said management information on a medium. Further, in accordance with the invention, the control unit 20 includes a safe recording unit 32 for allocating a recovery information area in the data area, for generating recovery information in dependence of the recorded parts of the user data and for, at given instances, recording the recovery information in the recovery information area, the recovery information comprising information enabling generating the management information for the recorded parts of the user data. Thus, the control unit 20, the management unit 31 and the safe recording unit

32 are capable of performing an example of a method of recording information signals according to the invention, as illustrated in Figure 6 by means of a flow diagram. This method comprises:

- allocating a recovery information area in the data area in a step 100; - recording parts of the user data sequentially in a step 101;

- generating recovery information in dependence on the recorded parts of the user data in a step 102, the recovery information comprising information enabling generating the management information for the recorded parts of the user data;

- at given instances, recording the recovery information in the recovery information area in a step 103;

- generating the management information for the user data in a step 105; and

- recording the management information in a step 106. The steps 105 and 106 are performed after checking that no more user data is to be recorded, in a step 104. Thus, for example in case of video information, assuming that the recording has not been interrupted and a stop recording command is received (for example the user decided to stop the recording), the recording device updates and/or creates the file system as mandated by the corresponding recording format, in the steps 105 and 106, so that the content can be accessed and played back. It is noted that without the file system update, the recording cannot be accessed even though the video information as such is present on the disc. Further embodiments with respect to the details of what the recovery information is, where and when it is recorded on a medium are given below.

Frequency of updating/recording the recovery information, or in other words the instances at which this happens, can be defined in dependence on particular application and/or structure of user data.

For example, in case of recording of user data organized in a number of data files in one recording operation, the recovery information can be written after completion of recording of each data file. For this purpose, the recovery information may comprise information related to a part of VAT reflecting changes in a file system due to recording of a particular file. In this case, each part of the user data in the step 101 corresponds to one data file.

In case of a continuous flow of data with repeatable structure, also called streaming data, such as real-time video information, the recovery information is written each time a predefined amount of the data is recorded. For example, each time a complete ECC block of data is recorded. Alternatively, the recovery information is written at regular time intervals, or in other words at instances separated by a predefined time period. For example, this time period can correspond to 5 seconds of video information.

In an embodiment of the method of recording information signals according to the invention, a file entitled "VIDEO PS. D AT" (PS standing for Power Safe) is created in the recovery information area. This embodiment is used in the case of the known DVD+RW Video recording format, which is substantially disclosed in WO 01/01415. With respect to the recovery information written in the file "VIDEO_PS.DAT", it comprises information regarding the sequence of cells recorded so far and also the start recording address from where recording has been initiated. With such information available on the optical disc, recovery of the recorded information is possible. Advantageously the recovery information further comprises information enabling generating the management information, for example of the Video Title Set Information (VTSI) structures for the new title that is being recorded. Parsing a recorded stream is a time consuming activity and would be experienced negatively by the end user. Consequently, if the required information is already present with the recovery information, such parsing is not necessary anymore. In an embodiment of the invention, in order to update the file system, the device stores "volume data", that is cell, chapter, virtual chapter information, such as start and/or end addresses, as recovery information. In more details, an example of suitable recovery information has the logical structure of the file VIDEO PS. DAT as shown in Table 1.

Table 1 - logical structure of VIDEO PS. DAT

An example of a logical structure of an array of chapter markers (CHAPMARK_DB[256]) is disclosed in Table 2.

Table 2 - logical structure of CHAPMARK DB

The term VR CHAPTER refers to "virtual chapter" in the context of

DVD+RW Video format standard. Virtual Chapters are similar to Chapter except that virtual chapters do not start on a cell boundary. As a consequence of this, virtual chapters cannot be played on standard DVD players. An example of a logical structure of the array of virtual chapter markers (CHAPMARK_DB[256]) is disclosed in Table 3.

Table 3 - logical structure of VR CHAPMARK DB

An example of a logical structure of an array for storing cell attributes (CELL DB) is disclosed in Table 4.

Table 4 - logical structure of CELL DB

In an embodiment of the method of recording information signals, the

"VIDEO_PS.DAT" may comprise, apart from cell information, start address of the recording, the information regarding recording mode, aspect ratio. Such information also enables playback of the recorded stream.

It is noted that the VIDEO_PS.DAT as illustrated in the embodiment above comprises information with respect to both chapters and virtual chapter, therefore the information stored therein is sufficient for generating and/or updating not only the VTSI information, but also the VRMI information. In an embodiment of the method of recording information signals, preferably the contents of the VIDEO_PS.DAT file is updated at regular intervals, for example every 5 seconds. The updated information is written based on the trigger from the device that video information that has been buffered has been actually written on the optical disc. By this approach when power failure occurs the device only recovers video information that is actually present on the optical disc. This acts as a synchronization mechanism, such that the recovery process does not create management information for a recording that is neither "short" nor "more" than the actual video information present on the optical disc. If the recovery information was being updated periodically, for example every 5 seconds the recording device is able to create valid title for the interrupted recording up to 5 seconds accuracy to the instance power failure occurred. For example, if the recording has been started at 1 :00:00 pm [h:mm:ss] and power failure occurred at 1 :30:00 pm , then a recording device according to the invention can recover the recording till 1 :29:55 pm.

Figure 7 shows an example of allocating the recovery information area. In this example two recordings are shown as in Figure 5. For each recording 52 and 55, a dedicated separate recovery information area 58 and 59 is allocated, respectively. Each allocation is performed before corresponding recording is started. In the case illustrated by Figure 7, the second recording 55 was not completed correctly, for example because of a power failure. In the method of recording information signals, this is a situation when at least the step 106 was not (fully) executed. As a result, the information 56 and 57 is missing or recorded only in part, which renders it unusable. However, a recovery process, as described further in the text, can re-create management information based on the recovery information written in the area 59. In the example of Figure 7 the user data are recorded adjacent to the corresponding recovery information area. In an embodiment of the device, the control unit 20 is adapted to record the user data adjacent to the corresponding recovery information area.

Figure 8 shows another example of allocating the recovery information area. In this example one recovery information area 60 is allocated. This area is common for all recordings. Recovery information for subsequent recordings, for example for the recordings 52 and 55, is written sequentially one after other as indicated by 61 and 62, respectively.

Accordingly, in an embodiment of the method of recording information signals, the step 100 is performed only once. This is done before a first recording of user data on a medium, for example during so-called initialization of the medium.

In embodiments of the device, the safe recording unit 32 is adapted to perform functions/procedures as described above in reference to different embodiments of the method of recording information signals.

Figure 9 illustrates a method of recovering management information for accessing user data recorded in a data area on a write-once medium, in accordance with the invention. This method, hereinafter also called a recovery procedure, comprises: - verifying presence of the management information in the data area in step

200;

- locating a recovery information area in the data area in step 201;

- locating recovery information recorded in the recovery information area according to any embodiment of the method of recording information signals as described above, in step 202;

- reading the recovery information from the recovery information area in step 203;

- generating recovered management information based on the recovery information in step 204; and - recording the recovered management information on the medium in step 205. In an embodiment of the method of recovering management information, the step 200 is a part of a disc-recognition procedure, wherein it is checked whether an optical disc comprising recorded video information or suitable for recording video information has been inserted into the device. The disc-recognition is initiated for following scenarios:

- user opens the tray and closes the tray with or without a disc inside the tray;

- after a system failure occurs, for example a power failure, the system autonomously triggers the disc-recognition.

The step 200 may comprise checking whether a disc has been finalized. If this is the case, no further recording is possible and the recovery procedure is terminated.

Alternatively, this check is performed before start of the recovery procedure - the recovery procedure is applied only to not finalized discs.

Verifying presence of the management information comprises reading data written in last recording operation starting at the last written location 63 as indicated in Figures 7 and 8, and looking for the management information in the read data. In case of systems using VAT or RSAT, it is enough to check for presence of VAT or RSAT (for example as indicated by the reference sign 57 in Figure 6), as such presence implies no need for recovery of the management information. If it is verified that the management information is present, for example by existence of valid VAT or RSAT, the recovery procedure is terminated, otherwise the next step 201 is executed, for example as in case of missing elements 56 and 57 in Figure 7 or Figure 8.

In an embodiment of the method of recovering management information, the step 201 comprises locating the recovery information area by using information contained in so-called Disc Control Blocks, DCB, on the disc. There may be only one recovery information area 60 common for all recordings or, alternatively, each recording may have its own dedicated recovery information area 58 (59), as explained above with reference to Figures 7 and 8. In case of only one recovery information area 60, its location on the disc may be predefined, for example according to a standardized format. This has advantage that location of the recovery information area is known in advance.

Individual recovery information areas 58, 59 may be adjacent to corresponding user data 52, 55 in order to decrease seeking time for retrieving the recovery information and/or in order to satisfy a requirement of sequential writing. In an embodiment of the recovery procedure, the step 202 comprises finding (the most recent version of ) the "VIDEO_PS.DAT" file containing the recovery information.

If no recovery information is located in the step 202, the recovery procedure is terminated. In an embodiment of the recovery process its continuation, after the recovery information is detected in step 202, is made conditional on user confirmation. In an alternative embodiment, the device may be provided with an "Auto recovery" feature. Such device, for example when being re-powered after a power failure, automatically recovers the management information without user confirmation and upon successful recovery the recording device enters Standby Mode.

In an embodiment of the recovery procedure, the file system is re-created / updated in the steps 204 and 205, based on the contents inside the "VIDEO P S. D AT" file.

In an embodiment of the recovery procedure, the recovered management information 64 is recorded right after the last written location 63 as indicated in Figures 7 and 8.

With respect to implementation of previously described recovery methods in the recording device, the control unit 20 further comprises a recovery unit 33 for verifying presence of the management information in the data area, for locating a recovery information area in the data area, for locating recovery information recorded in the recovery information area, for reading the recovery information from the recovery information area, for generating recovered management information based on the recovery information and for recording the recovered management information on the medium.

In embodiments of the device, the recovery unit 33 is adapted to perform functions/procedures as described above in reference to different embodiments of the method of recovering management information.

In an embodiment of the device, the control unit 20 and/or any of the management unit 31, the safe recording unit 32 and the recovery unit 33, are implemented in a software program. The software program running in suitable processor is controlling the execution of the recording process and/or the recovery process. The software program may be an executable file to be entered in the device, for example in the form of an update of the software already present in a program memory, like EPROM flash memory, in the device.

Embodiments of a computer program product for use in recording information signals on a write-once disc-like recording medium by a recording device, according to the invention, comprise program code means for causing a processor of the recording device, to perform functions/procedures as described in reference to embodiments of the device and/or the methods presented above, when the computer program is run on the processor. Whilst the invention has been described with reference to preferred embodiments thereof, it is to be understood that these are not limitative examples. Thus, various modifications may become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims and the embodiments. Further, the invention lies in each and every novel feature or combination of features described above. It is noted, that the invention may be implemented by means of a general purpose processor executing a computer program or by dedicated hardware or by a combination of both, and that in this document the word "comprising" does not exclude the presence of other elements or steps than those listed and the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements, that any reference signs do not limit the scope of the claims, that "means" may be represented by a single item or a plurality and that several "means" may be represented by the same item of hardware.

Claims

CLAIMS:

1. A recording device for recording information signals on a write-once disc- like recording medium, the information signals representing user data and management information for accessing the user data, the medium comprising a data area for recording the information signals, the device comprising: - recording means (22, 27, 28, 29) for recording the information signals on the medium; reading means (21, 22, 25, 30) for reading recorded information signals from the medium; and control means (20) for controlling recording and reading the information signals and for recording parts of the user data sequentially, the control means comprising:

- a management unit (31) for generating the management information for the user data and for recording the management information; and

- a safe recording unit (32) for allocating a recovery information area in the data area, for generating recovery information in dependence of the recorded parts of the user data and for, at given instances, recording the recovery information in the recovery information area, the recovery information comprising information enabling generating the management information for the recorded parts of the user data.

2. A recording device as claimed in claim 1, the user data organized in data files, wherein the safe recording unit (32) is adapted to determine the instances in dependence on completion of recording of each data file out of the data files.

3. A recording device as claimed in claim 1, the user data being streaming data, such as real-time video data, wherein the safe recording unit (32) is adapted to determine the instances in dependence on completion of recording of a predefined amount of the user data.

4. A recording device as claimed in claim 1, the user data being streaming data, such as real-time video data, wherein the safe recording unit (32) is adapted to determine the instances in dependence on a predefined time period.

5. A recording device as claimed in claim 3 or 4, the streaming data being recorded as a sequence of addressable units, such as cells in the video data, wherein the safe recording unit (32) is adapted to generate the recovery information further comprising information with respect to the recorded addressable units, said information comprising at least unit start address information.

6. A recording device as claimed in claim 3 or 4, wherein the safe recording unit (32) is adapted to generate the recovery information enabling generating the management information comprising Video Title Set Information (VTSI).

7. A recording device as claimed in claim 1, wherein the control unit (20) is adapted to record the user data adjacent to the recovery information area.

8. A recording device as claimed in claim 1, wherein the safe recording unit (32) is adapted to allocate a dedicated recovery information area for each subsequent recording of the user data.

9. A recording device as claimed in claim 1, wherein the safe recording unit (32) is adapted to allocate one recovery information area common for subsequent recordings of the user data.

10. A recording device as claimed in claim 1, wherein the control unit (20) further comprises a recovery unit (33) for verifying presence of the management information in the data area, for locating a recovery information area in the data area, for locating recovery information recorded in the recovery information area, for reading the recovery information from the recovery information area, for generating recovered management information based on the recovery information and for recording the recovered management information on the medium.

11. A method of recording information signals on a write-once disc-like recording medium, the information signals representing user data and management information for accessing the user data, the medium comprising a data area for recording the information signals, the method comprising steps of: allocating a recovery information area in the data area; recording parts of the user data sequentially; generating recovery information in dependence on the recorded parts of the user data, the recovery information comprising information enabling generating the management information for the recorded parts of the user data; at given instances, recording the recovery information in the recovery information area; generating the management information for the user data; and recording the management information.

12. A method as claimed in claim 11, the user data organized in data files, wherein the instances are determined in dependence on completion of recording of each data file out of the data files.

13. A method as claimed in claim 11, the user data being streaming data, such as real-time video data, wherein the instances are determined in dependence on completion of recording of a predefined amount of the user data.

14. A method as claimed in claim 11, the user data being streaming data, such as real-time video data, wherein the instances are determined in dependence on a predefined time period.

15. A method as claimed in claim 13 or 14, the streaming data being recorded as a sequence of addressable units, such as cells in the video data, wherein the recovery information further comprises information with respect to the recorded addressable units, said information comprising at least unit start address information.

16. A method as claimed in claim 13 or 14, wherein the management information comprises Video Title Set Information (VTSI).

17. A method as claimed in claim 11, wherein the user data are recorded adjacent to the recovery information area.

18. A method as claimed in claim 11, wherein for each subsequent recording of the user data a dedicated recovery information area is allocated.

19. A method as claimed in claim 11, wherein one recovery information area is allocated common for subsequent recordings of the user data.

20. A method of recovering management information for accessing user data recorded in a data area on a write-once disc-like recording medium, the method comprising steps of: - verifying presence of the management information in the data area;

- locating a recovery information area in the data area;

- locating recovery information recorded in the recovery information area according to the method as claimed in any of claims 11 - 19;

- reading the recovery information from the recovery information area; - generating recovered management information based on the recovery information; and

- recording the recovered management information on the medium.

21. A method as claimed in claim 20, wherein the recovery information area is adjacent to the user data.

22. A method as claimed in claim 20, wherein the data area comprises one recovery information area common for different recordings of the user data.

23. A method as claimed in claim 20, wherein the recovered management information comprises Video Title Set Information (VTSI).

24. A computer program product for use in recording information signals on a write-once disc-like recording medium by a recording device, the computer program comprising program code means for causing a processor of the recording device, to perform the steps of the method as claimed in any of claims 11 - 23, when the computer program is run on the processor.