Patent Application
20090304366
The present invention relates to a method of recording video information onto an optical disc of the rewritable type. The present invention also relates to a method of formatting said optical disc and a method of playback of video information from said optical disc. This invention also relates to a device for recording or for playback of video information onto/from an optical disc of the rewritable type implementing such recording, formatting and playback methods. The invention is particularly relevant for optical disc recording devices.
Use of different type of optical disc belonging to the DVD (Digital versatile disc) family for recording and storage of both data and audio-video content is becoming widespread. Several types of rewritable media, including DVD-RAM, DVD-RW and DVD+RW are available for such purposes. A known issue is that in time the recording quality degrades, for example due to scratches, fingerprint or damage to media in the re-writing process.
One known solution for alleviating such problem is to make use of the defect management, wherein predefined spare areas of the medium are reserved for defect replacement. Defect management consists of physical addresses of defective physical sectors being maintained in a defect table, and the corresponding logical addresses of said defective physical sectors being mapped to usable physical sectors. However, when defect management is used, the data transfer rate may become slower, as reading information from replacement sectors involves movement of the optical head and seek operations.
Consequently, the optional defect management is not used in the case of recording video content, as a minimum data transfer rate need to be guaranteed in order to avoid image freezing during playback. In general, when recording real time video content, it is left to the application to handle this warning/error codes generated during recording and take corrective actions such as continue recording (ignore the error, which will result in audio-video hiccups during playback) or retry to write the content on the sector generating the warning/error code or retry to write the content on subsequent sectors by skipping said sectors.
US patent application No. 2004/0208097 describe a method of implementing defect management wherein when errors are detected when reproducing non video data, a linear replacing algorithm is applied; while when reproducing video data, the physical identification of error sectors is maintained on a separate list in the defect management area and such sectors are not replaced. It is noted that defect management is always available on DVD-RAM discs and it is optional on DVD-RW and DVD+RW discs. Problems with the above described method are that it is specific to DVD-RAM and it requires that defect management is used.
It is an object of the invention to provide a solution to the above problem of handling defects when recording video information obviated at least one of the above mentioned problems. The object of the invention is reached by a method of recording video information onto an optical disc of the rewritable type according to claim 1. Accordingly, error sector information comprising a list of logical sectors corresponding to the physical sectors wherein errors were encountered during recording is generated and said information recorded onto the optical disc. Consequently, information with respect to the physical sectors wherein errors were encountered during recording is made available to the application at logical level without the need to use defect management. Moreover, said method can be implemented independent of the type of optical disc.
The logical recording space of the optical disc usually comprises a video zone for recording said video information and for recording corresponding management information, the information in the video zone being arranged according to a video recording format. In an advantageous embodiment of the invention, the error sector information is recorded into a predetermined area reserved for recording temporary information or for recording optional information for improving functionality, such as the Video Recorder Manager User Data. When recording an optical disc, a known problem when recording any information not directly mandated by a recording format is that the resulting optical disc may become unsuitable for playback and/or recording for other devices that do not recognize such additional information. Recoding the recovery information within a specified disc area for recording temporary information or for recording optional information for improving functionality, such as the Video Recorder Manager User Data has the advantage that other recording devices expect that said recovery information may be present and the recovery information may not be accessible to them. Therefore legacy devices, that is devices not enabled to perform recovery of video information according to the invention, would be able to use the disc by ignoring the recovery information, so that the recorded optical disc remains compatible with the used recording format.
Usually the video information is recorded as video objects comprising a sequence of contiguously recorded cells. In an advantageous embodiment of the invention, an additional cell comprising the video information recorded in the physical sectors wherein errors were encountered during recording is generated. Cells are the smallest units that can be referenced independently in a playlist. Consequently this provides the advantage that an updated playlist can be generated wherein the parts comprising the defects are skipped from playback, therefore improving robustness. In an embodiment the additional cell is a buffer cell not referenced by any playback sequences comprised in the management information. Hence such cell is not playback and updating playlist is not necessary anymore.
In an embodiment of the invention the error sector information further comprises statistical information with respect to logical sectors corresponding to physical sectors wherein errors were encountered during recording, such as the percentage of said sectors from the total number of sectors on disc. This provides the advantage that the percentage number of error sectors on the disc can be computed and the user informed about the disc status. Furthermore, the user may be queried whether he/she wishes to continue recording and take user consent before recording.
This application also relates to a method of playback of video information, the method comprising determining that a logical sector or a group of logical sectors wherein errors referred to in errors sector information is in playback proximity to a logical sector wherein information recorded therein is being presently played back and deciding to jump the playback to information recorded to a sector succeeding the sector or a group of sectors wherein errors were encountered during recording. When the apparatus is aware that at close proximity erroneous sectors are present, then it can initiate a skip to ensure enhanced playability.
This application also relates to a method of formatting, the method comprising reading the error sector information and storing said error sector information in a temporary buffer, formatting the optical disc, recording the error sector information. This ensures that the enhanced playability/recordability of the optical disc are maintained after the formatting operations, as the information with respect to defect sectors is preserved.
The invention also relates to an optical recording apparatus for recording video information onto an optical disc of the rewritable type, enabled to either record and/or playback video information according to a suitable method according to the invention.
The invention also relates to a computer software program that when executed on suitable processor enables an optical recording apparatus to either record and/or playback video information according to a suitable method according to the invention.
These and other aspects of the invention are apparent from and will be explained with reference to the embodiments described hereinafter.
The features and advantages of the invention will be further explained upon reference to the following drawings, in which:
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. The smallest independently addressable unit is known as a physical sector.
The recording device 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 device 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, thereby constituting suitable means for performing the procedures described hereinafter with reference to
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, and for video in the MPEG2 standard (ISO-IEC 13818). The input signal may alternatively be already encoded. The output of the input unit 23 is passed to the formatter 24 for adding control data and formatting the data according to a recording format, e.g. by adding error correction codes (ECC) and/or interleaving. 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.
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. Writing and reading of information for recording on optical disks and usable formatting, error correcting and channel coding rules are well-known in the art, e.g. from the CD system (IEC 908).
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 is 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 recording format, to be playable on standardized playback devices. The recording format includes the way information is recorded, encoded and logically mapped onto the recording area provided by the track 12 and it will be described, by way of example, with reference to
The user information recorded in the data zone (DZ) is further arranged according to a logical format, for example comprising a predefined structure of files and directories. Further, at logical level, the user data 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. Such file management information is mapped on a predefined location on the optical disc 11, usually in or directly after the lead-in area (LI). The user information recorded in the data zone (DZ) may be further arranged according to a recording format, for example comprising a predefined structure of files and directories.
Usually, in case video information is recorded onto the optical disc, this is usually recorded in a separate volume from other data. For example,
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:
The VIDEO_RM directory may comprise other VRM user data files.
The VIDEO_TS directory usually comprises the following files:
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). It is further noted that the single VTS_Title Video Object Set (VTTS_VOBS) may comprises several video objects (VOB#1, VOB#2 . . . VOB#i), each video object comprising a contiguously recorded sequence of cells (cell #1, cell#2 . . . cell#i). The Video Title Set Information (VTSI) further comprises one or more program chains. A program chain is the logical unit to present a part of a Title or Menu. It is composed of the PGC Information (PGCI) on which the order and the essence of the presentation are described and one or more Cells to be presented.
In initialization step 51 (CHK/INIT ES.DAT) a disc is introduced in the recording apparatus. If the disc is a rewritable disc, the apparatus checks whether the disc is new or not and whether error sector information is available on the disc. If the disc is new (not formatted) in the de-icing step during formatting an empty file corresponding to the error sector information is created. Preferably, such file is placed din the VRM User Data Area. In following said filed will be referred as “VIDEO_ES.DAT”. The existence of “VIDEO_ES.DAT” is indication that the disc contains “error sectors”, for example due to improper handling of the discs, scratches, deterioration due to extensive usage. The main content of the error sector information is a list of logical sectors corresponding to the physical sectors wherein errors were encountered during recording. Preferably the VIDEO_ES.DAT is set as a read-only file, so that it is not deleted inadvertently.
It is noted that in an alternative embodiment of the method the “VIDEO_ES.DAT” file contains apart from the list of logical sectors corresponding to the physical sectors wherein errors were encountered during recording, it contains statistical information like total number of error sectors, total sectors available. Consequently, in this embodiment it is possible that the percentage number of error sectors on the disc is computed and the user is queried whether he/she wishes to continue recording. Using the “VIDEO_ES.DAT” information, the recording apparatus can inform the user about the actual “size/storage” capacity of the disc. The recording is initiated after receiving user confirmation to proceed.
In recording step 42 (RECORD), the recording process is started and the video information is recorded onto the optical disc. In step 53 (ERROR?) it is checked whether a “warning/error code” was returned by the recording means during the real time recording. If not, the recording continues. When such “warning/error code” is received, in step 54 (STORE) the error sector inventory information is updated. In an alternative embodiment such information is not directly recorded onto the disc, but it is kept in a memory buffer and only recorded in step 55 (UPDATE ES.DAT) either periodically (for example each 5 seconds) or after the recording has finished.
It is noted that when the method according to the invention is implemented in an optical recording apparatus, the apparatus is a-priori aware of the erroneous sectors by loading the information in the VIDEO_ES.DAT and can skip those sectors during overwriting a previous recording. Hence this enhances the recording reliability of the optical recording apparatus. Consequently this provides the advantage that an updated playlist can be generated wherein the parts comprising the defects are skipped from playback, therefore improving robustness. In a further embodiment, the additional cell is chosen to be a buffer cell. Buffer cells are cells that are not referenced by any program chain comprised in the Video Title Set Information (VTSI). Hence such buffer cell is not playback and updating playlist is not necessary anymore.
In step 71 (FMT/DEL_CMD) a format/delete all command is received. In step 72 (STORE) the error sector information or information allowing recovering the error sector information is stored in a memory. In step 73 (FMT) the format process takes place as described above. In step 74 (RECOV ES.DAT), the error sector information recorded back on the disc is recovered. An optical recording apparatus according to the invention will not delete the error sector information (e.g. the “VIDEO_ES.DAT” file) even if the optical disc is formatted or all the recordings are deleted.
It is noted that during the real-time recording, in case of recording on an unrecorded part of the disc, the optical recording apparatus is not “aware” about the potential “error sectors” on the disc, that is the optical recording apparatus does not known whether a specific area of the disc has manufacturing errors and recording thereon results in errors. Consequently, when optical recording apparatus attempts to record information onto such areas comprising defect, a “warning/error code” will be returned. Known optical recording apparatuses handle such “warning/error code” by taking one of the following actions:
Using the errors sector information as described above it is possible to guarantee the reliability of real-time by means of combining the method of recording video information onto an optical disc as described with reference to
When an optical disc is inserted into an optical recording apparatus, the first step is a disc recognition step. According to the invention, as part of the disc recognition step, the optical recording apparatus checks the disc for the possible recording speeds for the recordable disc (say, 2.4×, 4×, 8×). Also, the optical recording apparatus knows the max recording speed capability of the optical drive.
In the recording step, when user sends a command for a real-time recording, according to the invention the optical recording apparatus performs a “pseudo archiving” sub-step by recording dummy information (for example ECC blocks filled with zero or other freely chosen information) at the maximum possible disc speed (for example 8×). During this sub-step error sector information is gathered (if any needs to be gathered) as described in steps 53 and 54 of the method of recording. Optionally, this “pseudo-archiving” operation may also be used to configure the recording real time AV buffer, for example by introducing buffer cells to skip any erroneous sector. The real time AV buffer content is over-written at 2.4× over the dummy information by changing the drive speed. Hence the “pseudo-archiving” is intermixed with a sub-step of recording the real-time information (e.g. the AV content). A real time recording according to this embodiment of the invention is performed in sequence of two alternating sub-step process, namely pseudo-Archiving at a high recording speed, preferably the maximum allowed recording speed, and real time recording of the information at 2.4× by dynamically changing the drive engine speed.
In a particular embodiment, pseudo-archiving comprises recording dummy data written in steps of groups of ECC block (e.g. 16 zero filled EC C blocks), which is system configurable value based on the available hardware memory.
It is noted that, as part of stop recording command from the user, the error sector information is stored on the VRM user data area on the disc.
In an embodiment of the invention, the user may configure the behaviour of the optical recording apparatus, that is the user may chose between a reliable real time recording mode wherein the two sub-step process (pseudo archiving and real time recording) as described above is invoked, or the regular recording mode, comprising using existing/recorded error sector information on the disc.
Upon receiving user confirmation for the choice of the reliable mode two step process, there are several options available for implementing such reliable recording mode:
Whenever an optical disc is de-iced, or first recording on a empty optical disc is initiated, then the optical recording apparatus create a “VIDEO_ES.DAT” file in the “VRM User Data” area as described hereinabove. During the progress of recording the “VIDEO_ES.DAT” will be updated every 5 seconds with as and when error sectors are encountered [or] when stop recording is invoked by the user, then VIDEO_ES.DAT file is updated at one shot.
With respect to implementation of previously described recording and formatting methods in the optical recording apparatus as described with reference to
With respect to implementation in a playback device of the previously described methods, preferably the control unit 17 is enabled to determining that a logical sector or a group of logical sectors wherein errors referred to in errors sector information is in playback proximity to a logical sector wherein information recorded therein is being presently played back. The apparatus may further comprise means 29 for deciding to jump the playback to information recorded to a sector succeeding the sector or a group of sectors wherein errors were encountered during recording. It is noted that said means 29a may be integrated into the control unit 17, for example by means of suitable programmed firmware.
The disclosure can be summarized as follows: this invention relates generally to a method of recording video information onto an optical disc of the rewritable type. The invention relates to determining in real time whether errors were encountered during recording a physical sector and generating error sector information comprising a list of sectors wherein errors were encountered during recording. The error sector information is recorded on disc, preferably in VRMI user data to playback compatibility with standard players. During playback, error sector are skipped from reading. Advantageously, a buffer cell is created for information recorded in error sectors so that seamless playback is possible. Advantageously, when formatting the disc, the error sector information is not deleted. Advantageously, the error sector information is used to inform the user about the disc quality.
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 measured cannot be used to advantage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06126777.9 | Dec 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2007/055142 | 12/17/2007 | WO | 00 | 6/17/2009 |
