|Publication number||USRE42962 E1|
|Application number||US 09/522,786|
|Publication date||Nov 22, 2011|
|Filing date||Mar 7, 2000|
|Priority date||Mar 19, 1994|
|Also published as||CN1102791C, CN1115464A, CN1218301C, CN1284148C, CN1294567C, CN1313588A, CN1514434A, CN1516129A, DE69535009D1, DE69535009T2, EP0674316A2, EP0674316A3, EP0674316B1, EP1139338A2, EP1139338A3, US5617384, US5715355, US5793779, USRE38502, USRE38638|
|Publication number||09522786, 522786, US RE42962 E1, US RE42962E1, US-E1-RE42962, USRE42962 E1, USRE42962E1|
|Inventors||Jun Yonemitsu, Ryuichi Iwamura, Shunji Yoshimura, Makoto Kawamura|
|Original Assignee||Sony Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (41), Non-Patent Citations (9), Referenced by (4), Classifications (93)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a division of application Ser. No. 08/405,852, filed Mar. 13, 1995 Mar. 17, 1995 now U.S. Pat. No. 5,715,355.
The invention relates to a novel optical disk and, more particularly, to that disk, to a method of recording and reading information on the disk and to apparatus for carrying out that method.
Optical disks have been used as mass storage devices for computer applications, and such optical disks are known as CD-ROMs. The disk which is used as the CD-ROM is modeled after the standard compact disk (CD) that has been developed for audio applications and is basically an audio CD with various improvements and refinements particularly adapted for computer applications. Using such a CD as a standard. the CD-ROM has a data storage capacity of about 600 Mbytes. By using audio CD technology as its basis, the, CD-ROM and its disk drive have become relatively inexpensive and are quite popular.
However, since conventional audio CDs with their inherent format and storage capacity have been adapted for CD-ROMS, it has heretofore been difficult to improve the data storage capacity. In typical computer applications, a capacity of 600 Mbytes has been found to be insufficient.
Also, the data transfer rate that can be obtained from audio CDs generally is less than 1.4 Mbits/sec (Mbps). However, computer applications generally require a transfer rate far in excess of 1.4 Mbps; but it is difficult to attain a faster transfer rate with conventional CD-ROMS.
Yet another disadvantage associated with conventional CD-ROMs, and which is due to the fact that the audio CD format has been adapted for computer applications, is the relatively long access time associated with accessing a particular location on the disk. Typically, relatively long strings of data are read from audio CDs, whereas computer applications often require accessing an arbitrary location to read a relatively small amount of data therefrom. For example, accessing a particular sector may take too much time for the CD controller to identify which sector is being read by the optical pick-up.
A still further difficulty associated with CD-ROMs, and which also is attributed to the fact that such CD-ROMs are based upon audio CD technology, is the error correcting ability thereof. When audio data is reproduced from an audio CD, errors that cannot be corrected nevertheless can be concealed by using interpolation based upon the high correlation of the audio information that is played back. However, in computer applications, interpolation often cannot be used to conceal errors because of the low correlation of such data. Hence, the data that is recorded on a CD-ROM must be encoded and modulated in a form exhibiting high error correcting ability. Heretofore, data has been recorded on a CD-ROM in a conventional cross interleave Reed-Solomon code (CIRC) plus a so-called block completion error correction code. However, the block completion code generally takes a relatively long amount of time to decode the data, and more importantly, its error correction ability is believed to be insufficient in the event that multiple errors are present in a block. Since two error correction code (ECC) techniques are used for a CD-ROM, whereas only one ECC technique is used for an audio CD (namely, the CIRC technique), a greater amount of non-data information must be recorded on the CD-ROM to effect such error correction, and this non-data information is referred to as “redundant” data. In an attempt to improve the error correction ability of a CD-ROM, the amount of redundancy that must be recorded is substantially increased.
Therefor, it is an object of the present invention to provide an improved optical disk having particular use as a CD-ROM which overcomes the aforenoted difficulties and disadvantages associated with CD-ROMs which have been used heretofore.
Another object of this invention is to provide an optical disk which exhibits a higher access speed, thereby permitting quick access of arbitrary locations, such as sectors, to be accessed quickly.
A further object of this invention is to provide an improved optical disk having a higher transfer rate than the transfer rate associated with CD-ROMs heretofore used.
A further object of this invention is to improve the storage capacity of an optical disk, thereby making it more advantageous for use as a CD-ROM.
An additional object is to provide an improved optical disk which stores data with reduced redundancy.
Still another object of this invention is to provide an improved recording format for an optical disk which enhances the error correcting ability thereof.
Another object of this invention is to provide an optical disk having a substantially improved recording density, thereby facilitating use of the disk as a CD-ROM.
A further object of this invention is to provide an improved optical disk having data recorded in sectors, with each sector having a sector header that is easily and rapidly read, particularly because the sector header is not encoded in a form which requires a substantially long amount of time before it is successfully decoded and recognized.
Various other objects, advantageous and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.
In accordance with this invention, an optical disk, a method and apparatus for recording that disk and a method and apparatus for reading data from that disk are provided. The disk has a diameter of less than 140 mm, a thickness of 1.2 mm±0.1 mm, and a plurality of record tracks exhibiting a track pitch in the range between 0.646 μm and 1.05 μm with data recorded in those tracks as embossed pits. The tracks are divided into a lead-in area, a program area and a lead-out are, with table of content (TOC) information being recorded in at least one TOC track in the lead-in area and user information recorded in a plurality of user tracks in the program area. Each track is divided into sectors and the TOC information includes addresses of the start sectors of each user track. The data (both TOC and user information) is encoded in a long distance error correction code having at least eight parity symbols, the encoded data being modulated and recorded on the disk. Preferably, the data is modulated as run length limited (RLL) data.
In the preferred embodiment, the data is recorded with a linear density in the range between 0.237 μm per bit and 0.378 μm per bit. Also, the program area is disposed in a portion of the disk having a radius from 20 mm to 65 mm.
The format of the data advantageously permits rapid access to a desired sector. Reduced redundancy in the recorded data and a higher storage capacity are attained. Advantageously, the optical disk may record data having particular computer application, referred to computer data or video and audio data, the latter being compressed by the so-called MPEG (Moving Picture Image Coding Experts Group) technique. Audio data which also may be recorded preferably is compressed and then multiplexed with the MPEG-compressed video data.
The error correction code used with the present invention preferably is a long distance code having at least eight parity symbols. ECC techniques which have been used heretofore have relied upon so-called short distance codes in which a block of data is divided into two sub-blocks, each sub-block being associated with a number of parity symbols, such as 4 parity symbols. It is known, however, that 4 parity symbols may be used to correct 4 data symbols, and if 4 data symbols in each sub-block are erroneous, the total number of 8 erroneous data symbols can be corrected. But, if one sub-block contains 5 erroneous data symbols, whereas the other sub-block contains 3 erroneous data symbols, use of the short distance code may be effective to correct only 4 data symbols in the one sub-block, thus permitting a total error correction of 7 data symbols. But, in the long distance code, the block of data is not sub-divided; and as a result, all 8 erroneous data symbols, if present in the long distance coded data, can be corrected.
As another feature of this invention, the RLL code that is used preferably converts 8 bits of input data into 16 bits of data for recording (referred to as 16 channel bits) with no margin bits provided between successive 16-bit symbols. In RLL codes used heretofore, 8 data bits are converted into 14 channel bits and three margin bits are inserted between successive 14-bit symbols. Thus, the present invention achieves a reduction in redundancy.
The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will best understood in conjunction with the accompanying drawings in which:
The present invention records different types of data on an optical disk, preferably for use as a CD-ROM but also adapted for use as a digital video disk (DVD). Such data may be file data or application data to be used by a computer, or it may comprise video data which sometimes is referred to herein as motion picture data which includes image information and audio information and which preferably is compressed in accordance with the various conventional video data compression standards, such as those known MPEG-1, MPEG-2, or when still video pictures are recorded, JPEG. It will be appreciated, therefore, that the information on the disk admits of “multimedia” applications.
Before describing the technique used to record data on the optical disk, a brief description is provided of the disk itself. The physical parameters of the optical disk used with the present invention are quite similar to the conventional audio CD; and for this reason, a drawing figure of the disk is not provided. Nevertheless, it will be appreciated that the diameter of the disk is 140 mm or less, preferably 120 mm or 135 mm. Data is recorded in tracks, and will be described in greater detail, having a track pitch in the range between 0.646 μm and 1.05 μm, and preferably in the range of 0.7 to 0.9 μm. Like audio CD data, the data recorded on the optical disk is in the form of embossed pits having a linear density in the range between 0.237 μm per bit and 0.387 μm per bit, although this range could be in the range of 0.3 μm to 0.4 μm per bit. Data is recorded in that portion of the disk having a radius from 20 mm to 65 mm. The disk, whose thickness is 1.2 mm±0.1 mm, is intended to be driven for a playback operation such that its linear velocity is in the range of 3.3 m to 5.3 m per second.
As a result of the linear density and track pitch of the disk, information is optically read from the disk by a pick-up head which projects a light beam of wavelength λ through a lens having a numerical aperture NA such that the projected beam exhibits a spatial frequency l, where l=λ/(2NA). The light source for the optical pick-up preferably is a laser beam whose wave length is λ=635 nm, this laser beam being projected through a lens whose numerical aperture is NA=0.52, resulting in the spatial frequency l=611 nm.
Typical examples of the physical parameters associated with the optical disk are as following:
One proposed structure for recording data on the optical disk is known as the EFM Plus frame (EFM refers to eight-to-fourteen modulation). An EFM Plus frame is formed of 85 data symbols (each symbols is a 16-bit representation of an 8-bit byte) plus two synchronizing symbols thus consisting of 87 16-bit symbols. One sector is comprised of 14×2 EFM plus frames. But, the amount of user information that is present in a sector, that is, the amount of information which contains useful data and thus excludes sector header information, error detection code (EPC) information, et cetera, is 2048 symbols. Accordingly, the efficiency of the EFM Plus format may be calculated as:
That is, the efficiency of the EFM Pius format is approximately 84%, which means that 84% of all of the data that is recorded in a sector is useful data. Therefore, if the storage capacity of the optical disk is 4.4 Gbytes, as mentioned above, the amount of user data that can be stored on the disk is 84%×4.4 Gbytes=3.7 Gbytes.
Of course, if the track pitch is varied and/or if the linear density of the embossed pits is varied, the storage capacity of the disk likewise is varied. For example, if the track pitch is on the order of about 0.646 μm, the storage capacity of the disk may be on the order of about 6.8 Gbytes, whereas if the track pitch is on the order of about 1.05 μm, the storage capacity is on the order of about 4.2 Gbytes. As a practical matter, however, the spatial frequency of the pick-up beam determines the minimum track pitch and minimum linear density because it is desirable that the track pitch be no less than the spatial frequency of the pick-up beam and the linear density be no less than one-half the spatial frequency of the pick-up beam.
When compared to the audio CD, the linear density of the recorded data of the optical disk used in the present invention is approximately 1.7 times the linear density of the audio CD and the recording capacity of the optical disk used with the present invention is approximately 5.5 times the recording capacity of the audio CD. The optical disk of the present invention is driven to exhibit a linear velocity of approximately four times the linear velocity of the audio CD and the data transfer rate of the optical disk of the present invention is approximately 9 Mbps, which is about six times the data transfer rate of the audio CD.
With the foregoing in mind, reference is made to
The user data is coupled to a change-over switch 124 which also is adapted to receive table of content (TOC) information supplied to the switch from an input terminal 122 via a TOC encoder 125. The TOC information identifies various parameters of the disk which are used for accurate reproduction of the user information recorded thereon; and the TOC information also includes data related to the user information per se, such as information that is helpful in rapidly accessing the user information recorded in particular tracks. The structure of the TOC information is described below.
Switch 124 selectively couples user data supplied at input terminal 121 and encoded TOC data supplied at input terminal 122 to an or detection code (EDC) adder 127. As will be described, TOC information is recorded on one portion of the disk and user data is recorded on another portion; and switch 124 selects either the TOC information or the user data at the appropriate times. As will be described below in conjunction with, for example,
A sector header adder 128 is adapted to add a sector header to each sector of user information supplied thereto by way of EDC adder 127. As will be described below in conjunction with
User data, including the sector header added thereto by reason of sector header adder 128, is subjected to error correction encoding carried out by an ECC circuit 132 in combination with a memory 131 and a memory control section 133, the latter being controlled by system controller 110. An example of ECC encoding that may be used with the present invention, subject to modification so as to be applicable to the data recorded on the optical data is described in U.S. Pat. No. Re. 31,666. In one embodiment of the present invention, the ECC encoding produced by circuit 132 is convolution coding and is described in greater detail below in conjunction with
The sequential order of the data bytes in the C1 code words stored in memory 131 is rearranged by, for example, delaying the odd bytes so as to form an odd group of data bytes and an even group of data bytes. Since each group consists of only one-half of the data bytes included in the C1 code word, an odd group of data bytes of one C1 code word is combined with an even group of data bytes of the next-following C1 code word, thus forming a disarranged order of bytes. This disarranged order improves the burst error immunity of the ECC encoded data. The disarranged order of the ECC-encoded bytes is supplied from memory 131 to a modulator 140 which, preferably, carries out 8-to-16 modulation, although 8-to-14 (EFM) modulation could be used, if desired.
Memory controller 133 supplies to memory 131 the necessary read and write addresses to enable the generation of the C2 parity bytes in cross-interleaved form and also to rearrange the sequential order of the data bytes into the aforementioned disarranged order.
In the preferred embodiment of the ECC encoding technique, a long distance code, also known as the L format, is use. The L format results in C1 code words that are arranged as shown in
Modulator 140 serves to converts 8-bit bytes supplied thereto from memory 131 into 16-bit symbols. Each symbol is run length limited (RLL), as will be described. It will be appreciated that, by generating 16-bit symbols, the accumulated digital sum value (DSV), which is a function of the run length of the digital signal, that is, the number of consecutive 0s or the number of consecutive 1s, is limited to permit the DC component which is produced as a function of such consecutive 0s or 1s, to remain at or close to 0. By suppressing the DC, or lower frequency component of the digital signal that is recorded, errors that otherwise would be present when that digital signal is reproduced are minimized.
Modulator 140 thus produces a recording signal which is coupled to cutting apparatus 150. This apparatus is used to make an original disk from which one or more mother disks may be produced and from which copies may be stamped for distribution to end users. That is, such stamped disks constitute the CD ROMs.
In one embodiment, the cutting apparatus includes an electro-optical modulator 151 which relies upon the so-called Pockels effect to modulate a light beam that is used to “cut” an original disk. This original disk is used by a mastering apparatus 160 to produce a master of the original disk. The mastering apparatus relies upon conventional techniques, such as development and vacuum deposition, to produce a plurality of mother disks. Such mother disks are used in stompers which ejection mold copies that subsequently are packaged and distributed. Blocks 171 and 172 in
The technique used to reproduce the information recorded on optical disk 100 now will be described in conjunction with the block diagram shown in
The demodulated data reproduced from disk 100 is supplied to a ring buffer 217. The dock signal extracted by phase locked loop clock reproducing circuit 214 also is supplied to the ring buffer to permit the “clocking in” of the demodulated to data. The demodulated data also is supplied from demodulator 215 to a sector header detector 221 which functions to detect and separate the sector header from the demodulated data.
Ring buffer 217 is coupled to an error correcting circuit 216 which functions to correct errors that may be present in the data stored in the ring buffer. For example, when data is recorded in the long distance code formed of, for example, C1 code words, each comprised of 136 symbols including 116 symbols representing data (i.e. C2 data), 12 symbols representing C2 parity and 8 symbols representing C1 parity, error correcting circuit 216 first uses the C1 parity symbols to correct errors that may be present in the C1 word. A corrected C1 word is rewritten into ring buffer 217; and then the error correcting circuit uses the C2 parity symbols for further error correction. Those data symbols which are subjected to further error correction are rewritten into the ring buffer as corrected data. Reference is made to aforementioned U.S. Pat. No. RE 31,666 for an example of error correction.
In the event that an error in the sector header is sensed, error correcting circuit 216 uses the C1 parity symbols to correct the sector header, and the corrected sector header is rewritten into a sector header detector 221. Advantageously, the C2 parity symbols need not be used for sector header error correction.
As mentioned above, the input data symbols supplied four error correction encoding exhibit a given sequence, but the error correction encoded symbols are rearranged in a different sequence for recording. In one arrangement, the odd and even symbols are separated and the odd symbols of a C1 code word are recorded in an odd group while the even symbols of that C1 code word are recorded in an even group. Alternatively, odd and even symbols of different C1 code words may be grouped together for recording. Still further, other sequential arrangements may be used to record the data. During playback, error correcting circuit 216 and ring buffer 217 cooperate to return the recovered data symbols to their original, given sequence. That is, the data symbols may be thought of as being recorded in a disarranged order and the combination of the error correcting circuit and ring buffer operate to rearrange the order of the symbols in a C1 code word to its properly arranged sequence.
Error corrected data stored in ring buffer 217 is coupled to error detecting circuit 222 which uses the EDC bits added to the recorded data by EDC adder 127 (
In addition, TOC information that is recovered from disk 100, after being error corrected by error correcting circuit 216 and error detected by EDC detector 222, is coupled to a TOC memory 223 for use in controlling a data playback operation and for permitting rapid access to user data. The TOC information stored in memory 223, as well as sector information separated from the reproduced data by sector header detector 221 are coupled to a system controller 230. The system controller responds to user-generated instructions supplied thereto by a user interface 231 to control disk drive 225 so as to access desired tracks and desired sectors in those tracks, thereby reproducing user data requested by the user. For example, the TOC information stored in TOC memory 223 may include data representing the location of the beginning of each track; and system controller 230 responds to a user-generated request to access a particular track to control disk drive 225 such that the requested track is located and accessed. Particular identifying information representing the data in the accessed track may be recovered and supplied to system controller 230 by sector header detector 221 so that rapid access to such data may be achieved. A further description of the TOC information and sector information useful for controlling the disk drive in the manner broadly mentioned above is discussed in greater detail below.
It will be appreciated from the ensuing discussion of
One embodiment of the disk configuration shown broadly in
In one embodiment, the data recorded on a given disk may admit of different applications. However, it is preferred that all of the data recorded in a respective track admit of the same application.
Still another embodiment of the data configuration recorded on the optical disk is illustrated in
In the embodiments of
As mentioned above, in the preferred embodiment TOC information is recorded in 32 sectors. Preferably, although not necessarily, each sector is comprised of 2048 bytes and an example of the TOC information recorded in a TOC region is set out in the following Table 1.
Table of Contents Information
Track information (1-st Track)
Track Information (2-nd Track)
Track Information (3-rd Track)
Track Information (N-th Track)
From the foregoing table, it is appreciated that the TOC information includes one sector dedicated to disk information, described more particularly with respect to Table 2, and up to 31 sectors in which track information (see Table 3) is recorded. The TOC region also includes a reserved area for the recording of information that may be useful in the future. In a practical adaptation of the optical disk of the present invention, user information may be recorded in N tracks where, for example, N=256. The track information which is recorded in the TOC region relates to the data that is recorded only in a corresponding track, as will be described in conjunction with Table 3.
The data which constitutes the disk information recorded in the TOC region is shown in the following Table 2:
TABLE 2 Disk Information Field Name Byte(s) HD-CD ID 8 Disk Type 1 Reserved for Disk Size 1 Lead Out Sector Address 3 Reserved for Multi Session Parameters 20 Reserved for Writable Parameters 20 Volume Number 1 Total Volume Number 1 Catalog Number 16 Reserved for Application ID Strings 8 Disk Title in English/ISO646 16 Local Language Country Code 3 Length of Disk Title in Local Lan. (=N) 1 Disk Title in Local Lang. N First Track Number 1 No. of Track Entry 1 Reserved 1947-N TOTAL 2048
The fields which identify the disk information are described more particularly as follows:
This field, comprised of 8 bytes, contains a character string that identifies the data structure recorded on the disk, including the data structure which is used to represent TOC information, the data structure used to represent track information and the data structure of a sector. For example, if the character string is “HD-CD001”, the data structure recorded on the disk is of the type illustrated in
This 1-byte data identifies the type of disk as, for example, a read only disk, a write once read many (WORM) disk or an erasable disk (such as the writable optical disk known as the “Mini” disc).
Reserved For Disk Size
This 1-byte field is used to identify the size of the optical disk. For example, a disk diameter of 120 millimeters may be identified by a byte whose value is “1”, a disk whose diameter is 80 millimeters may be identified by a byte whose value is “2”, and so on. In addition or, alternatively, this field may be used to identify the storage capacity of the disk.
Lead Out Sector Address
This 3-byte field identifies the address of the first sector in the lead-out area
Reserved For Multisession and Writable Parameters
These two-fields, each formed of 20 bytes, store information which is particularly useful for erasable disks or for WORM disks and is not further described herein.
This 1-byte data field is used when several disks constitute a collection of data for a particular application. For example, if the collection includes 2, 3, 4, etc. disks, this field identifies which one of those disks is the present disk.
Total Volume Number
This 1-byte field identifies the total number of disks which constitute the collection in which the present disk is included.
This 16-byte field is used to identify the type of information or program that is recorded on the disk. Such identification constitutes the “catalog number” and is represented as UPC/EAN/JAN code presently used to identify various goods.
Reserved For Application ID Strings
This 8-byte field is intended to identify the particular user application for this disk medium. At present, this field is not used.
Disk Title In English/ISO646
This 16-byte field stores the title of the disk in the English language, as represented by the ISO646 standard. Although the actual title of the disk may be in another language, its English translation or a corresponding English identification of that title is recorded in this field. In other embodiments, the field may contain a lesser or greater number of bytes so as to accommodate English titles of lesser or greater length.
Local Language Country Code
This 3-byte field is intended to identify the actual language of the title of the disk. For example, if the actual title of the disk is in Japanese, this field records the “local language country” as Japan. If the title is in French, this field records the “local language country” as France. The code recorded in this field may exhibit a numerical value corresponding to a particular country or, alternatively, the field may be as prescribed by the ISO3166 standard. If it is desired not to utilize this field, the character string recorded therein may be 0xFFFFFF.
Length of Disk Title in Local Language
This 1-byte field identifies the number of bytes that are used in the “Disk Title In Local Language” field (to be described) to represent the title of the disk in the local language. If the actual disk title is not recorded in a language other than English, the “Disk Title In Local Language” field is left blank and the numerical value of this “Length Of Disk Title In Local Language” field is 0.
Disk Title In Local Language
This N-byte field represents the actual title of the disk in the local language. It is expected that different languages will adopt different standards to represent disk titles, and such local language standards are expected to be used as the data recorded in this field. It is appreciated that the number of bytes which constitute this field is variable.
First Track Number
This 1-byte field identifies the number of the track which constitutes the first track that contains user information. For example, if the TOC information is recorded in a single track, and if this single track is identified as track 0 in the program area, then the number of the track which constitutes the “First Track Number” is 1.
Number of Track Entries
This 1-byte field identifies the total number of user tracks that are recorded. It is appreciated that if this field contains a single byte, a maximum of 256 user data tracks, that is, tracks which contain user information, may be recorded.
The data recorded in the track information fields of the TOC data shown in Table 1 now will be described in conjunction with the following Table 3:
Time Code at Start Point
Mastering Date & Time
Reserved for Application ID Strings
The information recorded in each of the fields which constitute the track information of Table 3 now will be described in greater detail.
This 1-byte field identifies the number of the track represented by this track information. Since one byte is used to identify the track number, it is appreciated that a maximum of 256 user data tracks may be recorded. Of course, a single track number is used to identify a respective track, and no two tracks on this disk are identified by the same track number. Although it is preferred that the successive tracks are numbered sequentially, it also is appreciated that, if desired, each track may be assigned a random number and this random number is identified by the “Track Number” field.
This 1-byte data identifies the error correction code which is used to encode the user data recorded in this track. For example, the ECC type may be either long distance error correction code, known as the L format, or short distance error correction code, known as the S format. The difference between the L format and the S format is described below.
This 1-byte data identifies the data transfer rate by which data is recovered from this track. For example, if a reference data transfer rate is 1.4 Mbps, the “Speed Setting” field may exhibit a value representing 1× this reference rate or 2× the reference rate or 4× the reference rate or 6× the reference rate.
Start and End Sector Addresses (SA)
These 3-byte fields identify the address of the start sector of the track identified in the “Track Number” field and the address of the end sector of that track Since the number of sectors included in a track is variable, the start and end sector addresses of a given track are not fixed. Hence, these fields are useful when carrying out a high speed access operation of a desired track.
Time Code At Start Point
This 4-byte field identifies a time code for the start sector in the track identified by the “Track Number” field. It will be appreciated that if the user information represents video data, such video data may be recorded with conventional time codes and the start sector of the track which contains such video data is recorded in this “Time Code At Start Point” field. If time codes are not recorded with the user information, this field may be left blank or may be provided with no data, such as the character code 0.
This 4-byte data represents the overall playback time for the program information that is recorded in the track identified by the “Track Number” field. For example, if the user information in this track is an audio program, the playing time for this track may be on the order of about 10 minutes. If the user information constitutes compressed video data, the playing time may be 2 or 3 or even up to 15 minutes.
Mastering Date and Time
This 7-byte field identifies the date and time of creation of the master disk from which this optical disk was made.
Reserved For Application ID Strings
This 8-byte field is intended to store information representative of the particular application for which the data record in the track identified by the “Track Number” field is to be used. This differs slightly from the “Application ID” field in Table 2 because the Table 2 field is intended to identify the type of application or use intended for the entire disk, whereas the “Application ID” field of Table 3 simply the identifies the type or use of the data recorded in a particular track on that disk.
Referring now to
It is seen that a sector is comprised of a sector header which contains 24-bytes arranged as shown in
A more detailed explanation of the different fields which constitute the sector shown in
This 4-byte field is formed of a predetermined bit pattern which is readily detected and which is unique and distinctive from the data pattern included in any other field of a sector. The accurate detection of the sync pattern may be confirmed sensing errors which are interpretated from the information reproduced from the sector. If a large number of errors are detected continually, it is safely assumed that the sync pattern has not been accurately sensed. Alternatively, and preferably, the demodulator which is used to convert 16-bit symbols to 8-bit bytes (or, more generally, to convert an m-bit symbol to an n-bit byte) may include suitable conversion tables which are not operable to convert the sync pattern to a byte. The sync pattern is assumed to be present when the demodulator is unable to find an n-bit byte which corresponds to a received m-bit symbol.
Cyclic Redundancy Code (CRC)
This 2-byte field is derived from the subcode data, the cluster position data and the sector address and mode data included in the sector header. Such CRC data is used to correct errors that may be present in these fields.
This 5-byte field is described below.
This 1-byte field identifies the particular order in the cluster in which this sector is located. For example, if the cluster is formed of a 8 sectors, this field identifies the particular sector as the first, second, third, etc. sector in the cluster.
This 3-byte field constitutes the unique address for this sector. Since the address is represented as 3-bytes, a maximum of 64K sectors theoretically may be recorded.
Mode and Sub-Header
These fields are conventionally used in CD-ROMs and the data represented here is the same as that conventionally used in such CD-ROMs.
2,048 bytes of information are recorded in the user data field. For example, computer data compressed video data, audio data and the like may be recorded. If video data is recorded, the MPEG standard may be used to compress that data as described in standard ISO1381-1.
Error Detection Code
This 4-byte data is cyclic code which is added by EDC adder 127 (
A detailed discussion of the sub-code field now is provided in conjunction with
If the value of the address portion is 1, as shown in
This data identifies the number of the track in which the sector containing this sub-code is recorded.
This byte exhibits the structure shown in
This indicates the particular application intended for the user data that is recorded in this sector. Examples of typical applications are shown in
This data indicates whether the user data is ECC encoded in, for example, the L format or the S format, as shown in
If the value of the sub-code address is 2, as represented in
If the value of the address portion is 3, as depicted in
If the value of the address portion is 4, as shown in
The ECC format which preferably is used with the present invention is the L format. A schematic representation of an encoded “data frame” is depicted in
The manner in which the C1 code word structure is generated now will be briefly described, 116 data bytes, or symbols, known as a C2 word, are supplied to, for example, the ECC encoder formed of memory 131 and ECC circuit 132 of
As a preferred aspect of this ECC encoding, the data symbols which are combined occupy successive positions in the respective preliminary C1 words. That is, if the data symbol in the first preliminary C1 word is the nth data symbol, the data symbol in the second preliminary C1 word is the (nth+1)th data symbol, the data symbol in the third preliminary C1 word is the (n+2)th data symbol, and so on.
When 12 C2 parity symbols are generated in the manner just described, those 12 C2 parity symbols are inserted into the C2 hold section of this first preliminary C1 word, thus forming a precursory C1 word. Then, 8 C1 parity symbols are generated by conventional parity symbol generation in response to the data and parity symbols included in this precursory C1 word. The generated C1 parity symbols are inserted into the C1 hold section thus forming the C1 code word.
In the C1 code word shown in
An example of the S format ECC encoding is schematically illustrated in
When compared to the ECC format used in, for example, CD-ROMs of type that have been proposed heretofore, the use of the L format or S format in accordance with the present invention permits a reduction in redundancy from about 25% of prior art CD-ROMs to about 15% in the present invention.
A sector formed of ECC encoded data in the L format or the S format is shown in
As an aspect of this invention, the sequence of the symbols included in a C1 code word as recorded in a track differs from the sequence of the symbols that are supplied for recording. That is, and with reference to
Let it be assumed that data symbols are recorded on the disk in the order Dk and let it be further assumed that each C1 code word is formed of m symbols, with n of those symbols constituting a C2 code word (i.e. 116 data symbols and 12 C2 parity symbols) and m–n of those symbols constituting the C1 parity symbols. The relationship among i, j, k, m and n for recording thus is:
k=m×i+2×j−m, when j<m/2
k=m×i+2×j−(m−1) when j≧m/2
If the data symbols appear on the disk in the recorded sequence D0, D1, D2 . . . such data symbols are grouped into an odd group followed by an even group. For example, and assuming 136 symbols, data symbols D0–D67 constitute an odd group of odd numbered data symbols and data symbols D68–D135 constitute an even group of even data symbols. It will be understood that “odd” and “even” refer to the original sequence in which those data symbols had been presented for recording. In the foregoing equations, i is the sequential order in which the C1 code words are presented for recording, j is the sequential order of the m symbols in each C1 code word presented for recording and k is the order in which the m symbols are recorded on the disk. That is, Dj≠Dk.
When the C1 code words having data symbols in the sequence D0, D1, . . . D135 are played back from the disk, the data symbols stored in ring buffer 217 of
where i is the sequential order of the C1 code words that are read out of the ring buffer, j is the sequential order of the sequence of the m symbols in each C1 code word that is read out of the ring buffer and k is the disarranged order in which the m symbols are recorded on the disk.
Although the present invention preferably records data in the L format of ECC encoding, the teachings herein may be employed with S format ECC encoding. Discrimination between the L format and S format may be made by sensing the ECC byte in the track information field of the TOC data, such as the ECC byte shown in Table 3, or by sensing the ECC byte included in the subcode field shown in
Yet another technique for discriminating between L format and S format ECC encoding employs the addition of a discrimination bit immediately following the sector sync pattern.
Still another technique for discriminating between the L and S ECC formats is based upon the ability of the ECC correcting circuit 216 of
The ECC encoded data, whether in the L format or the S format, constitute convolution codes. A group of C1 code words may be thought of as a block and such C1 code words may be block coded in the manner shown schematically in
Each block consists of 8 sectors, whereby a block includes more than 16K bytes. Error correction can be carried out on a block-by-block basis.
The modulation technique used to modulate the C1 code words for recording on disc 100 (e.g., the modulation technique used by modulator 140 of
One type of modulation is 8-to-14 modulation (EFM) which is used as the standard in compact discs, and one example of such EFM processing is described in Japanese patent application 6-2655. In conventional EFM, an 8-bit byte is converted into a 14-bit symbol (the bits of the symbols are known as “channel” bits because they are supplied to the recording channel) and successive symbols are separated by margin bits. Heretofore three margin bits were used, and these three bits were selected to assure that the Digital Sum Value (DSV) accumulated from successive symbols is reduced. EFM is a run length limited (RLL) code and, preferably, the shortest run length permitted in EFM consists of two consecutive zeros which are spaced between is, and the longest run length is limited to 10, wherein 10 consecutive zeros may be present between is.
If two margin bits are used rather than 3, the possible combinations of such margin bits are: 00, 01, 10 and 11. In EFM, a margin bit state 11 is prohibited. Hence, only three different combinations of margin bits can be used to link (or separate) successive symbols: 00, 01 and 10. But, depending upon the bit stream of one or the other symbols which are linked by the margin bits, one or more of these possible states may be precluded because, to use the precluded state may result in an undesirable DSV.
A string of data symbols may include parity symbols, and
Let it be assumed that margin bits separate data symbols D1 and D2. Let it be further assumed that the number of consecutive zeros at the leading end of data symbol D2 is represented as A and the number of zeros at the terminating end of data symbol D1 is B. If A+B is equal to or exceeds 8 successive zeros (A+B≧8) then the margin bit combination 00 is inhibited (Minh=00).
If the most significant bit C1 of data symbol D2 is “1” (A=0) or if the next most significant bit C2 is “1” (A=1) or if the least significant bit C14 of data symbol D1 is “1”, the margin bit combination 01 is inhibited (Minh=01).
If the least significant bit C14 of data symbol D1 is “1” (B=0) or if the next least significant bit C13 is “1” (B=1), or if the most significant bit C1 of data symbol D1 is “1”, the margin bit combination 10 is inhibited (Minh=10).
The foregoing 3 conditions are not mutually exclusive; and from
Turning now to
The flow chart then advances to inquiry S2 which determines if the number of inhibited combinations for the margin bit pattern M1 is equal to 2. If so, the flow chart advances to step S3 and only a single margin bit combination can be selected. For example, if the most significant bit of data symbol D2 is “1”, NI1=2 and Minh=01, 10. Step S3 thus permits only margin bit combinations 00 to be selected as the margin bit pattern M1.
However, if inquiry S2 is answered in the negative, then two or three different margin bit combinations can be selected. The flow chart advances to step S4 where the inhibited margin bit combination Minh for the n-th margin bit pattern (n72) is determined. But, if the number of inhibited combinations for the second margin bit pattern is 2, that is, if NI2=2, then the n-th margin bit pattern is construed as the (m+1)th margin bit pattern. That is, if NI2=2, only one margin bit combination can be selected for the remaining margin bit patterns Mn. The flow chart then advances to step S5 wherein data symbol D2 is linked to data symbol D3 which is linked to data symbol D4. . . to data symbol Dn by the respective margin bit combinations which are not inhibited.
Thereafter, in step S6, since the margin bit patterns up to Mn have been selected, and since the data symbols up to Dn are known, the accumulated DSV up to Dn is calculated. The DSV determined for this data symbol simply is added to the DSV which has been accumulated from previous data symbols. Then, in step S7, the margin bit pattern M1 is selected as the particular margin bit combination which minimizes the DSV that is projected to be accumulated up to data symbol Dn.
It will be appreciated that steps S4–S7 rely upon a projected DSV; and although the margin bit pattern under consideration is margin pattern M1, the technique for selecting the appropriate margin bit combination for pattern M1 as based upon look ahead data symbols D2, D3, . . . Dn.
Successive data symbols are coupled to registers 14–17 wherein each data symbol is stored. Thus, register 17 stores data symbol D1, register 16 stores data symbol D2, register 15 stores data symbol D3, register 14 stores data symbol D4 and adder 13 now supplies data symbol D5 to the input of register 14. Data symbols D4 and D5 are coupled to discriminator 30 which examines these data symbols to determine if any of the bit patterns therein correspond to those shown in
The output of register 17 is coupled to a frame sync converter 18 which converts the 14-bit pseudo frame sync signal S1 f to a 24-bit frame sync signal Sf. This 24-bit frame sync signal Sf is coupled to parallel-to-serial register 19. Those data symbols D1, D2, . . . which are supplied successively to frame sync converter 18 are not modified thereby and are supplied as is, that is, in their 14-bit configuration, to the parallel-to-serial register. Register 19 converts those bits which are supplied thereto in parallel to serial output form. In addition, after a 14-bit data symbol is serially read out of the register, a 2-bit margin pattern produced by a margin bit generator 50 is serially read out of the register. Parallel-to-serial register 19 is clocked with a channel bit clock having a frequency of 24.4314 MHz such that the serial bit output rate of register 19 is 24.4314 Mbps. These serial bits are modulated by an NRZI modulator 20 and coupled to an output 21 for recording.
The modulated NRZI serial bits also are fed back to a DSV integrator 40 which integrates the DC component of such serial bits. The DSV integrator thus accumulates the DSV of the data symbols and margin bit patterns.
Margin bit generator 50 functions in accordance with the flow chart shown in
The foregoing has described an EFM technique in which a margin bit pattern is inserted between successive 14-bit data symbols. As a result, each 8-bit byte is converted into a 14-bit data symbol plus a 2-bit margin pattern. A preferred embodiment of an 8-to-16 modulator which eliminates the generation of margin bit patterns, which minimizes the accumulated DSV and which is constrained to run length limited (2, 10) code now will be described. Referring to
The tables are categorized as follows: if the last bit of the immediately preceding 16-bit symbol ends as a “1” or if the last two bits of that 16-bit symbol end as “10”, the next 16-bit symbol is selected from table T1a or table T1b, depending upon whether it is desirable that this next selected 16-bit symbol exhibit a positive DSV (thus calling for table T1a) or a negative DSV (thus calling for table T1b).
If the immediately preceding 16-bit symbol ends with two, three or four successive 0s, the next-following 16-bit symbol is selected from either table T2 (that is, from either table T2a or table T2b) or from table T3 (that is, from table T3a or table T3b).
If the immediately preceding 16-bit symbol ends with six, seven or eight successive 0s, the next-following 16-bit symbol is selected from table T4.
The first 16-bit symbol that is generated immediately following a frame sync pattern is selected from table T1.
The 16-bit symbols produced from tables T2 and T3 differ from each other in the following important respects: all 16-bit symbols read from table T2 include a “0” as the first bit and a “0” as the thirteenth bit.
All 16-bit symbols read from table T3 include a “1” as the first or thirteenth bit or a “1” as both the first and thirteenth bit.
In the 8-to-16 conversion scheme used with the present invention, it is possible that the very same 16-bit symbol may be generated in response to two different 8-bit bytes. However, when the 16-bit symbol representative of one of these bytes is produced, the next-following 16-bit symbol is produced from table T2; whereas when the 16-bit symbol representative of the other byte is produced. the next-following 16-bit symbol is produced from table T3. It is appreciated that, by recognizing the table from which the next-following 16-bit symbol is produced, discrimination between the two bytes which, nevertheless, are converted into the same 16-bit symbol may be readily achieved.
For example, let it be assumed that an 8-bit byte having the value 10 and an 8-bit byte having the value 20 both are converted to the same 16-bit symbol 0010000100100100 from table T2. But, when this 16-bit symbol represents the byte having the value 10, the next-following 16-bit symbol is produced from table T2, whereas when the aforenoted 16-bit symbol represents the byte having the value 20, the next-following 16-bit symbol is produced from table T3. When the symbol 0010000100100100 is demodulated, it cannot be determined immediately if this symbol represents the byte having the value 10 or the byte having the value 20. But, when the next-following 16-bit symbol is examined, it is concluded that the preceding symbol 0010000100100100 represents the byte 10 if the next-following symbol is from table T2, and represents the byte having the value 20 if the next-following symbol is from table T3. To determine whether the next-following 16-bit symbol is from table T2 or table T3, the demodulator merely needs to examine the first and thirteenth bits of the next-following symbol, as discussed above.
Table Ta (for example, table T1a) includes 16-bit symbols having a DSV which increases in the positive direction. Conversely, the 16-bit symbols which are stored in table Tb have a DSV which increases in the negative direction. As an example, if the value of an 8-bit byte is less than 64, this byte is converted into a 16-bit symbol having a relatively large DSV. Conversely, if the value of the 8-bit byte is 64 or more, this byte is converted into a 16-bit symbol having a small DSV. Those 16-bit symbols which are stored in table Ta have positive DSV and those 16-bit symbols which are stored in table Tb have negative DSV. Thus, an input byte is converted into a 16-bit symbol having positive or negative DSV, depending upon which table is selected for conversion, and the value of the DSV is large or small,small, depending upon the value of the input byte that is converted.
The tables T1a, T1b, . . . T4a, T4b in
Table selector 76 senses the ending bits of the 16-bit symbol supplied from switch 75 to output terminal 78 to determine whether fundamental table T1, T2, T3 or T4 should be selected, in accordance with the table selecting conditions discussed above. It is appreciated that the table selector thus controls switch 75 to select the 16-bit symbol read from the proper fundamental table. For example, if it is assumed that the 16-bit symbol supplied to output terminal 78 ends with six, seven or eight successive 0s, switch 75 is controlled by the table selector to couple its input x4 to the output terminal such that the next-following 16-bit symbol is read from fundamental table T4. DSV calculator 77 calculates the accumulated DSV, which is updated in response to each 16-bit symbol supplied to output terminal 78. If the DSV increases in the positive direction, DSV calculator 77 controls selector switches 71–74 to couple the outputs from their respective tables Tb. Conversely, if the accumulated DSV is calculated to increase in the negative direction, selector switches 71–74 are controlled by the DSV calculator to couple the outputs from their respectively tables Ta. It is expected, therefore, that if the preceding 16-bit symbol exhibits a larger negative DSV, switches 71–74 are controlled to select the next 16-bit symbol having a positive DSV; and the particular table from which this next 16-bit symbol is read is determined by table selector 76. Thus, the accumulated DSV is seen to approach and oscillate about 0.
An example of a 16-to-8 bit converter, that is, a demodulator compatible with the 8-to-16 bit modulator of
An input terminal 81 is supplied with a 16-bit symbol, and this symbol is stored temporarily in a register 82 and then coupled in common to inverse conversion tables IT1–IT4. In addition, a table selector 83 is coupled to input terminal 81 and to the output of register 82 so that it is supplied concurrently with the presently received 16-bit symbol and the immediately preceding 16-bit symbol. Alternatively, table selector 83 may be thought of as being supplied with the presently received 16-bit symbol (from the output of register 82) and the next-following 16-bit symbol. The table selector is coupled to an output selector switch 88 which couples to output terminal 89 either conversion table IT1 or conversion table IT2 or conversion table IT3 or conversion table IT4.
The manner in which table selector 83 operates now will be described. As mentioned above, the first symbol that is produced immediately following the frame sync pattern is read from conversion table T1 in
If, as mentioned above, a 16-bit symbol may represent one or the other of two different 8-bit bytes, table selector 83 senses whether the next-following 16-bit symbol, as supplied thereto from input terminal 81, is from conversion table T2 or conversion table T3. This determination is made by examining the first and thirteenth bits of such next-following 16-bit symbol. If the table selector senses that the next-following 16-bit symbol is from table T2, output switch 88 is suitably controlled to select the inverse conversion table which converts the 16-bit symbol presently provided at the output of register 82 to its proper 8-bit byte. A similar operation is carried out when table selector 83 senses that the next-following 16-bit symbol had been read from conversion table T3 in
The present invention converts an 8-bit byte into a 16-bit symbol, whereas the prior art converts an 8-bit byte into a 14-bit symbol and inserts three margin bits between successive symbols. Consequently, since the present invention uses only 16 bits in its bit stream as compared to the prior art use of 17 bits, the modulation technique of the present invention results in an effective reduction in data of 16/17, or about 6%.
While the present invention is particularly applicable to a CD-ROM on which computer data, video data, a combination of video and audio data or computer files may be recorded, this invention is particularly useful in recording and reproducing digital video discs (DVD) on which video data and its associated audio data are recorded. Such data is compressed in accordance with the MPEG standard; and when compressed video data is recorded on the disc, the subcode information included in each sector header (
If the subcode address value is 4, the subcode field appears as shown in
Audio signals, such as analog left-channel and right-channel signals L and R are digitized by an analog-to-digital converter 104 and compressed in an analog data compression circuit 105. This compression circuit may operate in accordance with the Adaptive Transform Acoustic Coding technique (known as ATRAC) consistent with MPEG-1 audio compression or MPEG-2 audio compression standards. It is appreciated that this ATRAC technique presently is used to compress audio information in recording the medium known as the “Mini Disc” developed by Sony Corporation. The compressed audio data is supplied from compression circuit 105 to an audio buffer memory 106 from which it subsequently is coupled to a multiplexor 107 for multiplexing with the compressed video data. Alternatively, compression circuit 105 can be omitted and the digitized audio data can be supplied directly to a buffer memory 106 as, for example, a 16-bit PCM encoded signal. Selective information stored in the audio buffer memory is coupled to the system controller for use in generating the subcode information that is recorded in the sector header.
Additional information, identified in
Title data is generated by a character generator 111 which, for example, may be of conventional construction. The title data is identified as fill data and key data and is compressed by a compression circuit 112 which encodes the title data in variable run length coding. The compressed title data is coupled multiplexor 107 for subsequent application to the input terminal 121 shown in
Preferably, multiplexor 107 multiplexes the compressed video, audio and title data, together with the sub-information, in accordance with the MPEG-1 or MPEG-2 standard, as may be desired. The output of the multiplexor is coupled to input terminal 121 of
Post processor 256 also is adapted to superimpose graphical title information on the recovered video data, as will be described below, such that the recovered title data may be suitably displayed, as by superposition on a video picture.
The separated audio data is supplied from demultiplexor 248 to an audio buffer memory 252 from which it is expanded in an expansion circuit 253 and reconverted to analog form by digital-to-analog convertor 254. Expansion circuit 253 operates in accordance with the MPEG-1 or MPEG-2 or mini disc standard, as may be desired. If the audio data that is recorded on disc 100 has not been compressed. expansion circuit 253 may be omitted or bypassed.
As depicted in
The separated title data is applied to title buffer memory 233 from demultiplexor 248 from which the title data is decoded by a title decoder 260 that operates in a manner inverse to the operation of compression circuit 112 (
Demultiplexor 248 monitors the remaining capacities of buffer memories 249, 252 and 233 to sense when these memories are relatively empty or filled. The purpose of monitoring the remaining capacities of the buffer memories is to assure that data overflow therein does not occur.
System controller 230 and user interface 231 of
While the present invention has been particularly shown and described with reference to preferred embodiments, it will be readily apparent to those of ordinary skill in the art that various changes and variations may be made without departing from the spirit and scope of the invention. To the extent that such variations and changes have been mentioned herein, the appended claims are to be interpreted as including such variations and changes as well as all equivalents to those features which have been particularly disclosed.
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|U.S. Classification||714/701, 714/769, 369/275.3, 714/755|
|International Classification||G11B7/24, H04N5/926, H04N9/82, H04N5/85, H04N5/16, G11B27/034, H04N5/913, G11B27/10, G11B20/12, H04N9/804, G11B7/004, H04N5/92, G11B27/00, G11B7/007, G11B7/00, G11B27/32, H04N9/806, G11B7/013, G11B20/18, G11B20/14, G11B20/10, G11B7/125, G11B7/0045, G11B27/30|
|Cooperative Classification||G11B2020/1294, G11B2020/1465, G11B27/105, H04N2005/91321, G11B2220/2545, G11B7/013, G11B20/1217, G11B2220/218, H04N5/85, H03M13/2921, H04N9/8042, G11B20/1866, G11B2220/2562, G11B2020/1457, G11B2020/10888, G11B20/18, H03M13/1515, G11B20/1426, G11B27/329, G11B27/034, G11B2020/1267, G11B7/24079, G11B7/24085, G11B2020/1222, G11B20/1833, H04N9/8227, H04N9/8063, G11B2020/1853, H03M13/2924, H04N5/9208, H03M13/09, G11B27/3063, G11B7/00745, G11B2020/1461, H04N9/8244, G11B2020/1238, G11B27/005, G11B2220/213, H04N5/926, H04N9/8205, G11B20/00768, H04N9/8233, H03M13/15, G11B20/12, G11B2220/2529|
|European Classification||G11B20/12D, H04N9/804B, G11B27/00V, H04N5/926, H04N5/92N6D, G11B27/30C2, H04N5/85, G11B27/32D2, G11B20/18E, G11B20/14A2B, G11B7/007S, G11B27/10A1, G11B7/013, G11B27/034, G11B20/18D, H03M13/29B7, G11B20/00P11B1B, H03M13/29B7C, G11B7/24085, G11B7/24079|