WO2008132649A1

WO2008132649A1 - Increased number of direct overwrites when recording on optical discs

Info

Publication number: WO2008132649A1
Application number: PCT/IB2008/051519
Authority: WO
Inventors: Srinivas R Kudavelly; Robert A. Brondijk
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-04-26
Filing date: 2008-04-21
Publication date: 2008-11-06
Also published as: TW200849229A

Abstract

The invention relates to improving the number of Direct Overwrites when user information is recorded onto an optical disc of the rewritable, wherein the user information organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded. When recording onto optical discs, the information is divided into data frames, a data frame comprising identification data and reserved data preceding the information to be recorded and/or error correction data succeeding the information to be recorded; the data frames are transformed into recording frames and the recording frames modulated into a sequence of channel bits to be recorded onto the disc. The gist of the invention is to modify at least a data frame comprising reserved management information such that at least a byte of reserved management information is replaced by freely chosen information. Preferably, the at least one modified byte is the first byte of Main Data in the Data Frame, and preferably the freely chose information is randomly chosen.

Description

Increased number of direct overwrites when recording on optical discs

FIELD OF THE INVENTION

The present invention relates to a method of recording user information onto an optical disc of the rewritable type, the user information organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded. This invention also relates to a recording apparatus enabled to record user information onto an optical disc according of the rewritable type.

BACKGROUND OF THE INVENTION

Rewritable optical discs can be overwritten many times. The reversible recording process is based on the use of an information layer comprising a phase change material that is reversibly changeable between the amorphous and crystalline phase.

Amorphous marks are recorded within the crystalline matrix of the information layer, by irradiating the information layer with sequences of short radiation pulses, for example sequences of laser pulses. The radiation pulses melt the phase change material. If the subsequent cooling after turning off the radiation beam is rapid, the amorphous phase is frozen. If the subsequent cooling after turning off the radiation beam is slow, it allows re- crystallization and induces a crystalline phase. Consequently such a phase change layer allows information to be recorded and erased by modulating the power of the radiation beam between a write power level and an erase level. The readout is performed by detecting differences in optical properties between the amorphous and crystalline phases of the phase change layer thereby reproducing the recording signals.

It is desirable that the number of times the media can be directly overwritten (DOW) before media degradation takes place is as high as possible. For example, in the DVD+RW physical format standard, relevant parts thereof publicly available as ECMA-337 or ECMA-274, it is mandated that the jitter shall stay below 10% for any number of direct overwrites (500). A number of 1000 direct overwrites (DOW), while all parameters stay within their range, is recommended.

DOW (Disc Over Write) means directly overwriting data without erasing it first. A DOW problem occurs if the rewritable material is overwritten several times with the exact same channel code pattern. The problem relates to the viscosity of the melted parts decreasing and a flow of the information layer taking place preferentially in one direction, such that the thickness of said information layer becomes variable. Such effect is amplified when the same channel code pattern is recorded repeatedly in the same position. As a consequence the number of DOWs (Disc Over Write) is heavily reduced when recording the same channel code pattern repeatedly.

US patent application No 2002/0,027,859 describes a method of improving the number of DOW (DiscOver Write) by means of replacing the reserved information in the data frames by random data. It is known that information is recorded onto optical disc in data blocks of 2064 bytes, known as data frames, wherein the first 12 bytes consist of: 4 byte of Identification Data (ID), 2 bytes of ID Error Detection Code (IED), and 6 bytes of reserved information RSV. With respect to the reserved information, it is known that the first byte can be set by the application and it indicated the type of copying allowed. If not specified by the application, it is reserved and set to (00). The remaining 5 bytes are reserved and set to (00). It is known that the DVD formats require that under no circumstance may other data received from the host be recorded in this field. Recorders and recording drives are considered as circumvention devices when these are produced to record, or can easily be modified to record, in any manner, a user-defined number in this field. The reason for this restriction is that, in case of DVD-ROM discs, these bytes are used for recording the CSS keys used for encryption. Therefore, an apparatus as described in US patent application No 2002/0,027,859 US suffers from the disadvantage that it circumvents robustness rules for rewritable media so that it may be used for copying encrypted content.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method of recoding user information onto an optical disc of the rewritable type, the user information organized according to a recording format, the method allowing for improving the number of DOW (Disc Over Write), the method not requiring that the recording apparatus is enabled to modify the reserved information in the data frames. The object of the invention is reached by a method of recording as recited in claim 1. The method comprises dividing the information to be recorded into data frames, transforming data frames into recording frames by means of scrambling one or more data frames and/or applying error correction algorithms and modulating the recording frames to obtain a sequence of channel bits to be recorded onto the optical disc as a sequence of optically detectable marks and modifying at least a data frame comprising reserved management information such that at least a byte of reserved management information is replaced by freely chosen information.

The above method is based on the following insights: in order for rapid media degradation to take place, it is necessary that the same channel bit sequence is recorded repeatedly in the same disc area, therefore that the same data frame needs to be recorded repeatedly at the same physical address. When user information is recorded onto an optical disc, this is organized according to a recording format, and management information as mandated by the recording format is also recorded onto the optical disc. For example, such management information may correspond to the table of content or the disc information area of a DVD-RW or DVD+RW optical disc, or to file system information, or to management data, such as the Video Title Set Information when recording video information. Moreover, firstly, such management information is usually made "future proof by introducing reserved management information to be used in future version of such format, the reserved management information being usually set to zero. Secondly, such management information, including the reserved management information is usually recorded at predetermined addresses on the optical disc, e.g. in the lead-in area or starting with a fixed sector in the recordable area. Consequently, recording such reserved management information usually requires rewriting the same bit pattern in the same disc area. In contrast, the probability that the same data frame comprising user information is recorded repeatedly at the same physical address is negligible. Consequently, the main cause for the degradation effect due to repeatedly overwriting the same sequence of bits is the recording of reserved management information. Such effect is alleviated if at least a data frame comprising reserved management information is modified such that at least a byte of reserved management information is replaced by freely chosen information. It is noted that throughout this application freely chosen information indicates information that may be chosen at random, or information that is chosen by the application, the only requirement being that the information is not chosen on purpose chosen to be the same every time such reserved management information is recorded onto the disc.

It is rioted that in the scrambling process the main data from a data goes through a pscudo random generator (feed back register), that runs sequentially through the data. Hence if the first byte of the data frame is different, so are all of the corresponding channel bits that arc recorded onto the disc. If the first N bytes arc the same, after every recording action, so are the first N bytes in the channel bit sequence. So the DOW is improved even if only one byte of the reserved management information is replaced by freely chosen information. Consequently, it is advantageous to choose that the byte which is replaced by freely chosen information is the first byte of reserved management information. In an alternative embodiment, in the modification step, the reserved management information is replaced with freely chosen information.

In an advantageous embodiment, the freely chosen information is randomly chosen. The advantage of writing a "random' sequence above that of a fixed sequence, is that the application needs no knowledge of the data previously recorded on the disc. If a sequence according to well-defined rules is chosen, then the recording apparatus would first have to read and then record a different sequence.

In an embodiment of the method, data frames corresponding to reserved management information that exceeds a predetermined size are modified. As indicated above, if the N^th byte of the data frame is different, so will be the channel bits corresponding to this byte and following byte in the data sector.

The above describe methods are particularly suitable when recording DVD disc, in particular when recording video information onto DVD+RW discs. This application also relates to a recording apparatus for recording user information onto an optical disc of the rewritable type wherein the user information is organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded. The invention also relates to a computer software product which when executed would enable a recording apparatus to record user information according to method of recording as recited in claim 1.

These and other aspects of the invention are apparent from and will be explained with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will be further explained upon reference to the following drawings, in which:

Fig. 1 illustrates schematically an optical disc of the rewritable type; Fig. 2 shows schematically an optical drive wherein the invention is practiced;

Fig. 3 illustrates schematically the data information structure on an optical disc of the rewritable type suitable for recording video information;

Fig. 4 illustrates by means of a flow diagram a method of a method of recording user information onto an optical disc of the rewritable type

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 illustrates schematically an optical disc 11 having a track 12 and a central hole 10. The track 12, being the position of the series of (to be) recorded marks representing information, is arranged in accordance with a single spiral pattern constituting substantially parallel tracks on an information layer. The optical disc may comprise one or more information layers of a recordable type. Known examples of rewritable optical discs are CD-RW, or DVD+/-RW, DVD-RAM or BD-RE. For example, further details about the physical structure and addressing information for DVD+RW or DVD-RW optical discs can be found in references ECMA-337 and ECMA-338, respectively. The information is represented on the information layer by recording optically detectable marks along the track, for instance crystalline or amorphous marks in phase change material. The track 12 on the optical disc is indicated by a pre-embossed track structure provided during manufacture of the blank optical disc. The track structure is constituted, for example, by a pregroove, which enables a read/write head to follow the track during scanning. The track structure of recordable disc comprises variation of a physical parameter, known in the art as a wobble, usually in the form of periodical radial displacements of the groove from an average centerline. The periodic wobble is further modulated so that further information is stored, such as physical addresses indicating the location of units of information. Said information may further include specific synchronizing marks for locating the start of such information blocks. The position information is encoded in groups comprising a predetermined number of modulated wobbles.

Fig. 2 illustrates schematically a recording apparatus for writing information on the optical disc 11 as illustrated with reference to Fig. 1. The recording apparatus is provided with recording means for scanning the track on the optical disc, the recording means comprising a drive unit 16 for rotating the optical disc 11, a head 18, a positioning unit 21 for coarsely positioning the head 18 in the radial direction on the track, and a control unit 17. The head 18 comprises an optical system of a known type for generating a radiation beam 20 guided through optical elements for focusing said radiation beam 20 to a radiation spot 19 on the track 12 of the optical disc 11. The radiation beam 20 is generated by a radiation source, e.g. a laser diode. The head further comprises (not shown) a focusing actuator for moving the focus of the radiation beam 20 along the optical axis of said beam and a tracking actuator for fine positioning of the radiation spot 19 in a radial direction on the center of the track. 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.

For reading information, the radiation reflected by the information layer is detected by a detector of a usual type, e.g. a four-quadrant diode, in the head 18 for generating a read signal and further detector signals, such as a tracking error and a focusing error signal for controlling said tracking and focusing actuators.

For recording information the radiation beam 20 is controlled to create optically detectable marks in the recording layer. For this purpose, the recording apparatus comprises write processing means for processing input information to generate a write signal to drive the head 18, which write processing means comprise an input unit 23; and data processing means comprising a formatter 24 and a modulator 25. The control unit 17 controls the recording and retrieving of information onto and from the optical disc 11 , and may be arranged for receiving commands from a user or from a host computer. To this end, the control unit 17 may comprise control circuitry, for example a microprocessor, a program memory and control gates, for performing the procedures described hereinafter with reference to Fig. 3. The control unit 17 may also be implemented as a state machine in logic circuits. The control unit 17 is connected via control lines 22, e.g. a system bus, to said input unit 23, formatter 24 and modulator 25, to the drive unit 16, and to the positioning unit 21. The input unit 23 receives and pre-processes the user information. For example, when processing audio-video information, the input unit 23, may comprise compression means for compressing input signals such as analog audio and/or video, or digital uncompressed audio/video. Suitable compression means are described for audio in WO 98/16014-A1 (PHN 16452), and for video in the MPEG2 standard (ISO-IEC 13818). The input signal may alternatively be already encoded. The recording format in which this the user information is to be recorded prescribes that management information for managing the recorded user information is also recorded onto the optical disc. Hence the input unit 23, under the control of the control unit 17 is enabled to generate the management information and to format the information to be recorded at application level. The output of the input unit 23 is passed to the formatter 24, the formatter 24 enabled to format the received data into data block to be recorded into physical sectors. This corresponds to dividing the information to be recorded over data frames, a data frame comprising identification data and reserved data preceding the information to be recorded and/or error correction data succeeding the information to be recorded, to transforming data frames into recording frames by means of scrambling one or more data frames and/or applying error correction algorithms. For computer applications units of information may be interfaced to the formatter 24 directly. The formatted data from the output of the formatter 24 is passed to the modulation unit 25, which comprises for example a channel coder, for generating a modulated signal, which drives the head 22. Further the modulation unit 25 comprises synchronizing means for including synchronizing patterns in the modulated signal. The formatted units presented to the input of the modulation unit 25 comprise address information and are written to corresponding addressable locations on the optical disc under the control of control unit 17. The control unit 17 is arranged for recording and retrieving position data indicative of the position of the recorded information volumes.

In the following the functioning of the data processing means will be described in the specific case of DVD systems. The received information arranged according to a recording format, usually called in the art Main Data, is formatted in a number of steps before being recorded on physical sector on the disc by transforming said user information successively into a Data Frame, a Scrambled Frame, an ECC Block,

16 Recording Frames, - 16 Physical Sectors, a Recording Unit.

A Data Frame consists of 2064 bytes arranged in an array of 12 rows each containing 172 bytes. The first row starts with three fields, called Identification Data (ID), ID Error Detection Code (IED), and RSV bytes, followed by 160 Main Data bytes. The next 10 rows shall each contain 172 Main Data bytes, and the last row contains 168 Main Data bytes followed by four bytes for recording an Error Detection Code (EDC). The 2048 Main Data bytes are identified as DO to D2047. The Identification Data (ID) consists of four bytes comprising Sector information and the physical sector number in binary notation wherein the data frame is to be recorded. The ID Error Detection Code (IED) comprises information allowing the detection of errors in the Identification Data. The reserved RSV field consists of 6 bytes. The first byte can be set by the application. If not specified by the application, it is reserved and it is set to (00). The remaining 5 bytes are reserved and always set to (00). It is noted that under no circumstance may other data be recorded in this field. Recorders and recording drives are considered as circumvention devices when these are produced to record, or can easily be modified to record, in any manner, a user-defined number in this field. The Error Detection Code (EDC) is a 4-byte field containing the parities of an Error Detection Code computed over the preceding 2060 bytes of the Data Frame.

The 2048 Main Data bytes are scrambled by means of a scrambling circuit, consisting of a feedback bit shift register in which bits r7 (msb) to r0 (lsb) represent a scrambling byte at each 8-bit shift. At the beginning of the scrambling procedure of a Data Frame, positions rl4 to r0 are preset to the specified value(s). The same pre-set value is used for 16 consecutive Data Frames. After 16 groups of 16 Data Frames, the sequence is repeated. The initial pre-set number is equal to the value represented by bits b7 (msb) to b4 (lsb) of the ID field of the Data Frame. The part of the initial value of r7 to r0 is taken out as scrambling byte SO. After that, an 8-bit shift is repeated 2047 times and the following 2 047 bytes shall be taken from r7 to r0 as scrambling bytes Sl to S2 047. The Main Data bytes Dk of the Data Frame become scrambled bytes D'k where D'k = Dk Θ Sk for k = 0 to 2047 and Θ stands for Exclusive OR. An ECC Block is formed by arranging 16 consecutive Scrambled Frames in an array of 192 rows of 172 bytes each. To each of the 172 columns 16 bytes of Parity of Outer Code are added, then, to each of the resulting 208 rows, 10 bytes of Parity of Inner Code are added. Thus a complete ECC Block comprises 208 rows of 182 bytes each. The bytes of this array are identified as Bi,j as follows, where i is the row number and j is the column number. BiJ for i = 0 to 191 and j = 0 to 171 are bytes from the Scrambled Frames BiJ for i = 192 to 207 and j = 0 to 171 are bytes of the Parity of Outer Code BiJ for i = 0 to 207 and j = 172 to 181 are bytes of the Parity of Inner Code The PO bytes correspond to Reed-Solomon error correction code RS (208,192,17). In each of rows i = 0 to 207, while the PI bytes correspond to Reed-Solomon error correction code RS 182,172,11).

Sixteen Recording Frames are obtained by interleaving one of the 16 PO rows at a time after every 12 rows of an ECC Block. Thus the 37 856 bytes of an ECC Block are re-arranged into 16 Recording Frames of 2 366 bytes. Each Recording Frame consists of an array of 13 rows of 182 bytes.

The 8-bit bytes of each Recording Frame are transformed into 16-bit Code Words with the run length limitation that between 2 ONEs there shall be at least 2 ZEROs and at most 10 ZEROs (RLL(2, 10)). The 16-bit Code Words are NRZI-converted into

Channel bits before recording on the disc. The Channel clock period is the time between 2 consecutive Channel bits.

Returning to the functioning of the recording apparatus, during the recording operation, marks representing the information are formed on the optical disc. 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 magnetization different from their surroundings, obtained when recording in magneto-optical material. A detailed description of the functioning of the write processing means according to the invention will be described later with reference to fig 4.

For reading, the read signal is processed by a read processing unit comprising a demodulator 26, a de-formatter 27 and output unit 28 for outputting the information. The functioning of the demodulator 26, the de-formatter 27 and the output unit 28 are controlled by the controller 17. Hence, retrieving means for reading information include the drive unit 16, the head 18, the positioning unit 21 and the read processing unit.

The optical disc 11 is intended for carrying user information according to a standardized format, to be playable on standardized playback 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 will be described, by way of example, with reference to Fig 3. The recordable space is usually subdivided into a lead-in area (LI) 31, a data zone (DZ) for recording the information and a lead-out area (LO) 32. The lead-in area (LI) 31 usually comprises basic disc management information and information how to physically access the data zone (DZ). 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 zone (DZ) is further arranged according to an application format, for example comprising a predefined structure of files and directories. Further, at logical level, the user information in the data zone 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.

Usually, in case video information is recorded onto the optical disc, this is usually recorded in a separate volume from other data. For example, Fig. 3 further illustrates such an arrangement as used in the case of recording video information and user information onto a DVD+RW disc. The data zone (DZ) is organized as single volume space and may be further divided into a video section and data section. The Video section comprises a video file system 33, a Video Recorder Manager (VRM) scratch area 34, a Video Recorder Manager Information (VRMI) 35 a Video Recorder Manager User Data (VRM UD) 36, a DVD Video Zone (DVD-VZ) 37 and a backup copy of the Video Recorder Manager Information (VRMI-BK) 38. The optional data section succeeds the video section and it comprises a File system area 39 and the data files 40. The hashed areas in Fig. 3 indicate that the previously described elements of the data zone (DZ) need not be recorded contiguously. The VRM scratch area 34 is an area used by recorders to temporally store data. The Video Recorder Manager Information (VRMI) 35 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) 35 further comprises information whether a data section is present on the disc. The Video Recorder Manager User Data (VRM UD) 36 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 33 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.DAT (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: IDEO 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)

Fig. 4 illustrates by means of a flow diagram a method of recording user information onto an optical disc of the rewritable type.

In step 41 the user information to be recorded, such a video stream or computer data, is received by the recording apparatus. The recording format in which this the user information is to be recorded prescribes that management information for managing the recorded user information is also recorded onto the optical disc. Such management information has been described previously with reference to Fig. 3 and may correspond, by the way of example, to UDF file management data, or to video management data such as Video Recorder Manager Information (VRMI) or Video Title Set Information.

In step 42 the required management information to be recorded in addition to the user information is generated. In step 43 it is determined whether said management information further comprises reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded.

At the application level, there are many degrees of freedom. All DVD applications are file based, and all files formats, even the file system itself, make use of "reserved" fields. These reserved fields are fields usually carry information that is not used for any purpose. While such information could in principle have any value is usually set by the application format to zero. A few examples of such reserved management information are given herein, where the DVD+RW system are taken as an example:

The basic disc management information corresponds to the formatting disc control blocks (FDCB), examples thereof being available in ECMA-338. The physical information table comprises 2kByte of data, wherein the first 256 bytes describe basic disc parameters such as disc size, structure, data zone allocation , basic write strategy parameters, while bytes 256 to 2047 are reserved and all set to zero according to the DVD+RW format. These bytes which are all set to zero and do not carry any information to be used by the recording apparatus are an example of reserved management information.

The lead-in Area starts with an Initial zone, comprising the sectors between radii 22mm and 23.4 mm, the Main Data of the Data Frames in this Zone, when recorded, being prescribed to be set all to (00). The Initial Zone is followed by an Inner Disc Test Zone, which comprises 2048 Sectors for drive testing, the Main Data of the Data Frames in this Zone, when recorded, being prescribed to be set all to (00).

When recording video information, the VIDEO TS. IFO file comprises the VMGM_MAT structure, which comprises several reserved field which are prescribed to be set all to (00). Similarly, for VTS 01 0.IFO files comprise the VTSI MAT structure, which comprises several reserved field which are prescribed to be set all to (00).

In step 44, the formatting of information according to the invention takes place. When generating Data Frames wherein the Main Data corresponds to the reserved management information, according to the invention, the Main Data of such Data Frame is modifying such that at least a byte of reserved management information is replaced by freely chosen information. This step according to the invention is based on the insight that the number or Direct Overwrites (DOW) is an issue on rewritable discs that may or may not be addressed by the recording apparatus at a lower level for a particular disc, such that a solution at application level, suitable for all discs and recording apparatuses is desirable. The basic idea is to fill in freely chosen information in at least one byte of reserved management information every time such a reserved management information is to be recorded. The wording freely chosen information indicates information that may be chosen at random, or information that is chosen by the application, the only requirement being that the information is not chosen on purpose chosen to be the same every time such reserved management information is recorded onto the disc. Due to the scrambling, the Main Data from a data goes through a pseudo random generator (feed back register), that runs sequentially through the Main Data. Hence if the first byte of the data frame is different, so are all of the corresponding channel bits that are recorded onto the disc. If the first N bytes are the same, after ever}_' recording action, so are the first N bytes in the channel bit sequence. So the DOW is improved even if only one byte of the reserved management information is replaced by freely chosen information. Consequently, it is advantageous to choose that the byte which is replaced by freely chosen information to be the first byte of reserved management information. In an alternative embodiment, in the modification step, all reserved management information is replaced with freely chosen information. Advantageously, the freely chosen information is randomly chosen. The advantage of writing a "random' sequence above that of a fixed sequence, is that the application needs no knowledge of the data previously recorded on the disc. If a sequence according to well-defined rules is chosen, then the recording apparatus would first have to read and then record a different sequence. In an embodiment of the method, data frames corresponding to reserved management information that exceeds a predetermined size are modified.

In step 45, the Data Frames are transformed into recording frames by known means of scrambling one or more Data Frames and/or applying error correction algorithms, as described hereinbefore with reference to Fig 2. Finally, the recording frames are modulated to obtain a sequence of channel bits that is recorded onto the optical disc as a sequence of optically detectable marks;

In order to implement the invention in a recording apparatus, the apparatus is provided with processing means (29) under the control of the control unit (17), which are enabled to perform steps 43 and 44 of the above method, namely identification that reserved management information is to be included in the Main Data of a Data Frame and modification of the reserved management information according to the invention. For this purpose, in an embodiment the processing means (29) may be separately provided, as standalone hardware unit, between the input unit (23) and the formatter (24). In an alternative embodiment, the processing means may be incorporated into the control unit 17, wherein it can be advantageously implemented by means of suitable firmware.

For recording apparatuses functioning under the control of general purpose computer, such as optical drives in a PC, the processing means (29) may be provided at (software) application level, by means of adapting known software applications at the computer level controlling the functioning of recording apparatus, such as burner software running on a PC, to include the functionality of identifying reserved management information to be recorded on disc and modifying such reserved management information according to the invention.

This invention can be summarized as follows: the invention related to improving the number of Direct Overwrites when user information is recorded onto an optical disc of the rewritable, wherein the user information organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded. When recording onto optical discs, the information is divided into data frames, a data frame comprising identification data and reserved data preceding the information to be recorded and/or error correction data succeeding the information to be recorded; the data frames are transformed into recording frames and the recording frames modulated into a sequence of channel bits to be recorded onto the disc. The gist of the invention is to modify at least a data frame comprising reserved management information such that at least a byte of reserved management information is replaced by freely chosen information. Preferably, the at least one modified byte is the first byte of Main Data in the Data Frame, and preferably the freely chose information is randomly chosen.

It should be noted that the above-mentioned embodiments are meant to illustrate rather than limit the invention. And that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verbs "comprise" and "include" and their conjugations do not exclude the presence of elements or steps other than those stated in a claim. The article "a" or an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements and by means of a suitable programmed computer. A computer program may be stored/distributed on a suitable medium, such as optical storage or supplied together with hardware parts, but may also be distributed in other forms, such as being distributed via the Internet or wired or wireless telecommunication systems. In a system/device/apparatus claim enumerating several means, several of these means may be embodied by one and the same item of hardware or software. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A method of recording user information onto an optical disc of the rewritable type, the user information organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded, the method comprising: dividing the information to be recorded into data frames, a data frame comprising identification data and reserved data preceding the information to be recorded and/or error correction data succeeding the information to be recorded; transforming data frames into recording frames by means of scrambling one or more data frames and/or applying error correction algorithms; modulating the recording frames to obtain a sequence of channel bits to be recorded onto the optical disc as a sequence of optically detectable marks; the method further comprising: modifying at least a data frame comprising reserved management information such that at least a byte of reserved management information is replaced by freely chosen information.

2. A method according to claim 1, characterized by, the byte is the first byte of reserved management information.

3. A method according to claim 2, characterized by, in the modification step, replacing the reserved management information with freely chosen information.

4. A method according to claims 2 or 3, characterized by the freely chosen information being randomly chosen.

5. A method according to claim 4, characterized by modifying data frames corresponding to reserved management information that exceeds a predetermined size.

6. A method according to claims 2 or 3, characterized by the optical disc being a DVD disc, the reserved management data corresponding to reserved fields of the formatting disc control blocks (FDCB),or wherein the information to be recorded corresponds to video information and the reserved management data corresponding to reserved fields of the information files (*.IFO).

7. A recording apparatus for recording user information onto an optical disc of the rewritable type, the user information organized according to a recording format, the recording format prescribing that management information for managing the recorded user information is also recorded onto the optical disc, the management information further comprising reserved management information, the reserved management information being prescribed by the recording format independent of the user information to be recorded, the apparatus comprising: a formatter (24) enabled to dividing the information to be recorded over data frames, a data frame comprising identification data and reserved data preceding the information to be recorded and/or error correction data succeeding the information to be recorded; the formatter (24) further enabled to transforming data frames into recording frames by means of scrambling one or more data frames and/or applying error correction algorithms; - a modulator (25) modulating the recording frames to obtain a sequence of channel bits to be recorded onto the optical disc as a sequence of optically detectable marks, the apparatus characterized in that it further comprises: a processing means (30) for modifying at least a data frame comprising reserved management information such that at least a byte of reserved management information is replaced by freely chosen information.

8. A recording apparatus according to claim 7, characterized in that, the processing means (30) is enabled to modify the first byte of reserved management information.

9. A recording apparatus according to claim 8, characterized in that, the processing means (30) is enabled to replace the reserved management information with freely chosen information.

10. A recording apparatus according to claims 8 or 9, wherein the freely chosen information being randomly chosen.

11. A recording apparatus according to claim 8, characterized in that, the processing means (30) is enabled to modify data frames corresponding to reserved management information that exceeds a predetermined size.

12. A recording apparatus according to claims 8 or 9, wherein the optical disc is a DVD disc, the reserved management data corresponding to reserved fields of the formatting disc control blocks (FDCB), or wherein the information to be recorded corresponds to video information and the reserved management data corresponding to reserved fields of the information files (*.IFO).

13. A computer software product, which, when loaded and executed into firmware of a recording apparatus or when loaded and executed into a computer controlling the operation of a recording apparatus, it enables the recording apparatus to performing the methods of any of claims 1-6.