Patent Application
20070065103
Reference is made to commonly assigned U.S. patent application Ser. No. 11/173,699 filed Jul. 1, 2005, entitled “Recordable DVD Structure” by Joseph J. Wrobel and U.S. patent application Ser. No. ______, entitled “Recordable DVD Structure” by Joseph J. Wrobel, the disclosures of which are incorporated herein by reference.
The present invention relates to optical recording discs and, more particularly, to an improved recordable Digital Versatile Disc (DVD) format disc structure.
Recordable DVD format discs are well known in the art. Physical standards for the DVD-R type recordable DVD format disc are available from the DVD Format/Logo Licensing Corporation. Physical standards for the DVD+R type recordable DVD format disc are available from the Intellectual Property & Standards group of the Philips Corporation.
In addition there are logical standards for the arrangement of data on the discs. The file structure on DVD media is typically compliant with the Universal Data Format (UDF) Specification defined and maintained by the Optical Storage Technology Association (OSTA). The UDF specification is a specific embodiment of the ISO/IEC 13346 standard (and the equivalent publication ECMA-167) entitled “Volume and File Structure of Write-Once and Rewritable Media using Non-Sequential Recording for Information Interchange”. UDF 1.02 requires that all DVD-Video discs shall be mastered to contain all required data as specified by ISO 13346 and UDF.
In practice, most DVD media also incorporate the file structure specified by the International Standards Organization (ISO) 9660 standard (“Information processing—Volume and file structure of CD-ROM for information interchange”). If a disc contains both UDF and ISO 9660 file systems, then it is known as a UDF Bridge disc. According to the UDF version 2.50 document, consumer DVD players shall only support UDF and not ISO 9660. However, the presence of the ISO 9660 file structure on a DVD disc does not degrade its playability in a consumer DVD player.
The UDF standard applies to both forms of DVD media, ROM and recordable. The most recent version supports multisession recording. Multisession recording is important for write-once media such as DVD-R and DVD+R because it allows a user to add additional information to the disc over time. If a new session is written to a disc in accordance with the appropriate specifications, then a multisession capable DVD player will be able to read all of the information recorded to the disc in all of the sessions.
Multisession recording is beneficial because given the substantial capacity of the DVD format, it is often the case that a disc is written well short of its capacity, and a user would benefit by adding more information at a later time. Multisession recording also finds use in applications in which a first session is recorded with generic content, for example software, and a second session is added with user specific data. An example of such a disc would be an imaging application in which the first session contained image display software and the second session contained images belonging to the end user. The recordable DVD disc bearing the first session software could be sold to the public who could then add their images in a second session to be viewed using the software in the first session.
A multisession disc is closed to further append when a new session is written to the disc with the stipulation that it be the last session. This last session could contain new content or it could be a “dummy” session, i.e. session with no new content. In any case, the disc is finalized, i.e. put in a condition that allows no further additional sessions.
Unfortunately, although there are benefits to multisession DVD discs, the majority of the installed base of consumer DVD players are not multisession capable. They are produced to meet version 1.02 of the UDF specification that was issued before the process for multisession recording was defined in that specification. If a multisession disc is placed into a DVD player that is not multisession capable, the DVD player will only allow access to information stored in the first session; any subsequent information added to the disc is unknown to the DVD player and will be inaccessible to the user.
When a disc is mounted in a DVD player, the DVD player first establishes that the disc is recorded in accordance with the UDF specification. It does this by reading a series of sectors from the disc from the region defined by the UDF specification as the volume recognition area. If the disc complies with the UDF specification, the DVD player will find a series of volume structure descriptors in a volume recognition sequence that is unique to a UDF compliant disc.
Once a disc is established as UDF compliant, the DVD player then reads a data sector at one of the anchor points defined in the UDF specification. This sector will contain the Anchor Volume Descriptor Pointer. Within the Anchor Volume Descriptor Pointer, the DVD player will find the extents of the Main and Reserve Volume Descriptor Sequences recorded on the disc. The Volume Descriptor Sequence contains all the information needed for the drive to access information recorded on the disc including file and directory names, locations and sizes.
For a multisession disc, a new Anchor Volume Descriptor Pointer is written at the anchor points within each newly recorded session. The extents stored within the Anchor Volume Descriptor Pointer direct the DVD player to the new Main and Reserve Volume Descriptor Sequences written within each newly recorded session. A DVD player that is multisession compatible will recognize the presence of additional sessions and use the Anchor Volume Descriptor Pointer in the last recorded session to access the most recent Main and Reserve Volume Descriptor Sequences. This enables the drive to access all the information on the disc. A DVD player that is not multisession compatible will not recognize the presence of additional sessions and use the Anchor Volume Descriptor Pointer in the first recorded session to access the original Main and Reserve Volume Descriptor Sequences. This will limit the drive to access only the information in the first session on the disc.
The inability for a large portion of the installed base of DVD players to recognize and correctly access all the information on a multisession DVD disc limits the utility of applications that rely on multisession recording.
It is therefore an object of the present invention to provide a structure of a recordable DVD disc that permits a second session to be recorded and accessed by DVD video players that do not recognize multisession media.
It is a further object of the present invention to provide a recordable DVD disc structure that is particularly beneficial for applications in which the first session is generic for many users and the second session is customized to an individual user.
These objects are achieved by a recordable DVD disc, comprising:
a) a recorded first session; and
b) a Root directory in the first session having a VIDEO_TS directory File Identifier Descriptor containing an Information Control Block with an Extent Location having a value that refers to an extent outside the first session.
The UDF specification for multisession recordable DVD discs defines a structure that limits access of a DVD player that is not multisession capable to the first session on the disc. The present invention provides a structure that enables a DVD player that is not multisession capable to access DVD video information recorded in the second session of a two session recordable DVD disc.
A recordable DVD disc 8 holds data in a physical area called a session. Each session includes three zones: a lead-in zone, a data zone and a lead-out zone. The disc 8 with a single recorded session is represented graphically in
A recordable DVD disc 8 with a first recorded session and a second recorded session is represented graphically in
The information as to whether a recorded DVD disc is single session or multisession is stored outside the data zones of the disc 8 as is well-known in the disc making art. If a DVD player is multisession capable, it must read the session information before it begins to read the user data from the disc 8. The session information includes the location and length of each session on the disc 8. The DVD player needs this session information because as each new session is recorded, the structure that contains the current file and directory information is updated and recorded anew in the new session. The structure that contains file and directory information for the current content of the disc 8 is stored in the last recorded session. Once the number and location of the last session is known, the DVD player accesses that session and begins to read information from the user data area of the session. If a DVD player is not multisession capable, then it accesses the first session regardless of the number of sessions recorded on the disc.
A series of procedures is presented in UDF 1.02 for how to read a UDF disc. If a DVD player follows this series, then it must execute a sequence of operations which are summarized in TABLE 1. This sequence of operations occours after the DVD player has recognized that a new DVD disc 8 has been mounted, has completed the necessary electro-mechanical operations to provide focus and tracking, and has accessed a session on the DVD disc 8.
The first operation of the sequence is to determine if the disc 8 is recorded in accordance with the UDF specification. This operation is represented in
The second operation has the purpose of locating the Main Volume Descriptor Sequence. The value of the extent of the Main Volume Descriptor Sequence is found within the Anchor Volume Descriptor Pointer. According to the UDF specification, the Anchor Volume Descriptor Pointer shall be recorded in at least two of the following three locations on the media:
The third operation has the purpose of locating the File Set Descriptor. Referring to
The fourth operation has the purpose of locating the Root directory File Entry. The DVD player retrieves the Root directory File Entry location from the File Set Directory. The logical sector number at which the Root directory File Entry is located is equal to the sum of the logical sector number of the Partition Starting Location and the Root directory File Entry location.
The fifth operation has the purpose of locating the Root directory. The DVD player retrieves the Root directory location from the Root directory File Entry. The logical sector number at which the Root directory is located is equal to the sum of the logical sector number of the Partition Starting Location and the Root directory location.
The sixth operation has the purpose of locating the VIDEO_TS directory File Entry. The DVD player retrieves the VIDEO_TS directory File Entry location from the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory. The logical sector number at which the VIDEO_TS directory File Entry is located is equal to the sum of the logical sector number of the Partition Starting Location and the VIDEO_TS directory File Entry location.
The seventh operation has the purpose of locating the VIDEO_TS directory. The DVD player retrieves the VIDEO_TS directory location from the VIDEO_TS directory File Entry. The logical sector number at which the VIDEO_TS directory is located is equal to the sum of the logical sector number of the Partition Starting Location and the VIDEO_TS directory location.
The eighth operation has the purpose of locating the VIDEO_TS.IFO File Entry. The DVD player retrieves the VIDEO_TS.IFO File Entry location from the Information Control Block in the VIDEO_TS.IFO File Identifier Descriptor located in the VIDEO_TS directory. The logical sector number at which the VIDEO_TS.IFO File Entry is located is equal to the sum of the logical sector number of the Partition Starting Location and the VIDEO_TS.IFO File Entry location.
The ninth operation has the purpose of locating the VIDEO_TS.IFO file. The DVD player retrieves the VIDEO_TS.IFO file location from the VIDEO_TS.IFO File Entry. The logical sector number at which the VIDEO_TS.IFO file is located is equal to the sum of the logical sector number of the Partition Starting Location and the VIDEO_TS.IFO file location.
The tenth operation has the purpose of playing the content on the disc. Once the VIDEO_TS.IFO file is located, the other files required by a DVD video player to present the DVD video information on the disc may be accessed as needed.
If a DVD player is not multisession compatible and is dealing with a single session disc, then the process described above is carried out in the first (and only) session, and all the structure needed to access the user data and directories on the disc will be correctly read. If a DVD player is not multisession compatible and is dealing with a multisession disc, then the process described above is still carried out in the first session, and the structure found will only permit access to the user data and directories in the first session. The DVD video content in subsequent sessions is inaccessible.
In order to permit all the data on a multisession disc to be available to a DVD player that is not compatible with a multisession disc, the present invention enables the DVD player to access the last structure recorded on the disc. By altering the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session such that it refers to an extent outside the first session, a DVD player that is not compatible with a multisession disc will be led to access DVD video information stored outside the first session.
In order for the access of the DVD video information in the second session to be successful, the altered value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session must direct the DVD player to the VIDEO_TS directory File Entry in the second session. Since, in general, the first session of the disc will be written without foreknowledge of the detailed contents of the second session, the problem must be addressed in reverse. That is, the VIDEO_TS directory File Entry in the second session must be recorded at the logical sector number to which the DVD player will be directed by the altered value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session.
This may be accomplished by reading the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session prior to writing the second session and modifying the UDF structure creation software so the VIDEO_TS directory File Entry is appropriately positioned, but this is a rather complicated task. A simpler approach would be to run the UDF structure creation software unaltered when creating the second session, then to copy the VIDEO_TS directory File Entry to the logical sector number to which the DVD player will be directed by the altered value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session. This latter approach requires that the logical sector number chosen for the copy of the VIDEO_TS directory File Entry is unused by any other file or structure and is accessible within the second session. Fortunately, there are a number of locations that meet these requirements. For example, in the first 256 logical sectors of the second session, less than half are allocated to UDF Descriptors. The remaining sessions are unallocated and not reserved. In particular, logical sector numbers 80 through 255 inclusive are not generally allocated to UDF descriptors, making this region a prime candidate for the location of a copy of the VIDEO_TS directory File Entry.
In addition to the VIDEO_TS directory File Entry, one may choose to place copies of other structures in this region as well. For example, one could place a copy of the VIDEO_TS directory immediately after the VIDEO_TS directory File Entry. This would permit the DVD player to rapidly access the directory. It would also provide compatibility with DVD players that expect the VIDEO_TS directory to follow immediately after the VIDEO_TS directory File Entry. If it were desired for the copy of the VIDEO_TS directory FILE Entry to direct the DVD player to a copy of the VIDEO_TS directory, then the location of the VIDEO_TS directory within the VIDEO_TS directory FILE Entry would need to be appropriately modified.
A general method for creating a two session recordable DVD video disc that is compatible with DVD video players that do not recognize multisession DVD media is outlined below:
1) Prepare a binary image of a first session for recording on a recordable DVD disc including both binary data and a file system compatible with the Universal Disk Format Specification. (A binary image contains the actual data that should exist on the DVD disc.) Alternatively the first session can be recorded in standard fashion and subsequently the binary image generated by reading the first session from the disc as a binary image.
2) Based on the size of the binary image of the first session, compute what the starting sector of the second session would be if the first session were recorded in a mode compatible with multisession recording. Alternatively, a second session can be recorded after the first session, and the starting sector of the second session read from the disc using appropriate software tools.
3) Modify the binary image of the first session by changing the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session. The value of the Extent Location must refer to an extent outside the first session. If the location that the VIDEO_TS directory File Entry will occupy in the second session is known, then the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session is set to this location. If the location that the VIDEO_TS directory File Entry will occupy in the second session is not known, then the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session is set to a location in the second session that is unallocated and can be used by the second session authoring software to locate a copy of the VIDEO_TS directory File Entry. In the latter case, a preferred location would be within the first 256 logical sectors of the second session and preferably within logical sector numbers 80 and 255 inclusive.
4) Record the modified binary image of the first session in a mode compatible with multisession recording.
5) Use authoring software for creating the second session that reads the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session and creates a copy of the VIDEO_TS directory File Entry at that location in the binary image of the second session.
6) Record the second session.
When a disc created as outlined above is played by a DVD player that does not recognize multisession DVD media, the DVD player will attempt to locate the VIDEO_TS directory File Entry by reading the value of the Extent Location within the Information Control Block in the VIDEO_TS directory File Identifier Descriptor located in the Root directory of the first session. This value will lead the DVD player to the location of the copy of the second session VIDEO_TS directory File Entry, and then on to the DVD video information stored within the second session.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
