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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a recording and reproducing apparatus,
and more particularly to an apparatus of the kind which records and
reproduces a variety of data by the use of a recording medium having a
large capacity such as a magneto-optical disk.
2. Description of the Prior Art
Conventionally, hard disk units are known which can write data on a large
capacity disk unit for information storage.
This unit is generally used as data storage for a computer. The information
is recorded in a concentric or spiral track formed on the disk and the
disk is rotated at a predetermined rotational speed.
FIG. 1 is a block diagram schematically showing a prior art recording and
reproducing apparatus. Writing data in and reproducing the same data from
a hard disk unit 1 is effected by a CPU 3 through a data bus 2. The disk
arranged in the hard disk unit is rotated at a constant rotational speed
irrespective of (not synchronized with) the transmission rate of data
inputted on the disk. Instead, the rotational speed is timed by the CPU 3
for recording data on the disk. The data processed by the hard disk unit
may thus be non-sequential data.
Data communication between the hard disk unit 1 and the CPU 3 is effected
via a RAM 4 which serves as a buffer memory. It is further possible to
communicate the data between the RAM 4 and the hard disk unit 1 at a high
speed by the use of a DMA controller, without interruption by the CPU 3,
wherein data is processed non-sequentially.
Data representing a still image or the like can be processed as a one frame
portion of intermittent data by using a frame memory for the RAM 4.
FIG. 2 is a block diagram showing a construction of a circuit for
processing such burst data. Disk controller 5 is arranged between the CPU
3 and the disk unit 1. A required portion of burst data stored in RAM 4 is
recorded in the disk unit 1 through the disk controller 5 under the
control of the CPU 3. This construction is used, for example, in an
electronic mail system.
The "new media era" provides us with a variety of information in many kinds
of media, that is, multi-media information. Such information includes
non-sequential or intermittent data which does not have any correlation
with adjacent data, such as computer data; data which has a correlation
with adjacent data, but is as a whole non-sequential, such as data
representing a still image; data which has a correlation with adjacent
data and is sequential, such as digital audio data; and so on. These data
have different characteristics from each other.
It would be useful to be able to write all the types of data information on
a disk and provide users with the disk. The magneto-optical disk is a
rewritable large capacity storage medium and can store multi-media
information. The magneto-optical disk is different from a hard disk unit
which records and reproduces data under strictly controlled conditions
because it produces errors at a higher ratio than the hard disk unit. Thus
the data stored in the magneto-optical disk is provided with redundant
bits for error correction codes and other functions for detecting and
correcting errors.
However, while the error correction is effective with respect to random
errors, it is not so effective with respect to burst errors. It may be
better to treat data including errors as defective rather than correcting
the errors where computer data is concerned. On the other hand, it is
sufficient to correct errors in data forms like PCM audio data to such a
degree that the errors cannot be audible. Errors in such data which cannot
be corrected can be interpolated by the use of adjacent data having a
correlation with erroneous data so that the errors will not be
conspicuous.
Even so, if data is recorded in the same order as the original data and a
burst error occurs in a portion of that data, then that data portion can
no longer be interpolated.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is the object of the present invention to provide an
apparatus which appropriately records data having different
characteristics.
According to an aspect of the present invention, there is provided an
apparatus for recording input data on a recording medium, comprising:
a memory for storing input data to be recorded in predetermined quantity
units;
a first address control means for determining an address of said memory;
a second address control means for determining an address of said memory;
and
an encoding means for adding at least an error correcting code to each
predetermined quantity unit of input data, and
wherein when the input data has no correlation with adjacent input data,
the input data is sequentially written in said memory by said first
address control means, read out therefrom, encoded by said encoding means,
and recorded on the recording medium without changing the order of the
input data, and when the input data has a correlation with adjacent input
data, the input data is written in said memory by said second address
control means, read out therefrom, scrambled, and then the scrambled data
is encoded by said encoding means and recorded on the recording medium.
According to another aspect of the present invention, there is provided an
apparatus for reproducing data from a recording medium, the data being of
the type in which when the data has no correlation with adjacent data, it
is encoded and recorded in the inputted order thereof on the recording
medium while when the data has a correlation with adjacent data, it is
scrambled, encoded and recorded on the recording medium, said apparatus
comprising:
a memory for storing reproduced data in predetermined quantity units;
a first address control means for determining an address of said memory;
a second address control means for determining an address of said memory;
and
a decoding means for correcting possible errors in the data for each
predetermined quantity unit, wherein when the data has no correlation with
adjacent data, the reproduced data is sequentially written in said memory
at its corresponding address by said first address control means, read out
therefrom, and outputted without changing the order of the reproduced
data, and when the data has a correlation with adjacent data, the
reproduced data is written in said memory by said second address control
means, read out therefrom, descrambled, and outputted.
The above and other objects, features, and advantages of the present
invention will become apparent from the following detailed description of
the preferred embodiment taken in conjunction with the accompanying
drawings, throughout which like reference numerals designate like elements
and parts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram schematically showing a prior art data recording
and reproducing system;
FIG. 2 is a block diagram schematically showing another prior art data
recording and reproducing system;
FIG. 3 is a block diagram schematically showing, by way of example, a whole
arrangement of a recording and reproducing apparatus according to the
present invention;
FIGS. 4A and 4B are diagrams showing an example of a sector format of a
magneto-optical disk;
FIG. 5 is a diagram showing a construction of the data portion arranged in
one sector; and
FIG. 6 is a diagram showing a construction of the data portion when data is
scrambled.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of an apparatus for recording and reproducing data according
to the invention will hereinafter be described, wherein a magneto-optical
disk is used as an example of a recording medium.
On a magneto-optical disk 11, as shown in FIG. 4, there are concentric or
spiral tracks 12 formed such that one track is traced for each rotation of
the disk 11. Data is recorded on and reproduced from each track 12. Each
of the tracks 12 on the disk 11 is formed of a plurality of sectors 0, 1,
2, . . . n-1, n equally divided in the direction of its circumference. On
each sector, there is recorded a predetermined amount of data and
redundant bits, such as an error correcting code and an error detecting
code, which are added to the predetermined amount of data.
As shown in FIG. 4A, one track is formed of (n+1) sectors, and in this
example, is determined as 31, that is, one track is formed of 32 sectors.
A format for data recorded in one sector is constructed, for example, as
shown in FIG. 4B. To be specific, one sector is comprised of a header
portion, a data portion, and gap portions GAP which are placed behind each
of the header and data portions.
In the header portion, there is recorded a preamble signal at its head and
following thereto there is twice recorded the grouping of: an address
synchronizing signal ASYNC for synchronizing the address data, an address
signal ADD, comprising track address data TA and sector address data SA,
and an error correcting code ECC for correcting possible errors in the
address signal.
Further, in the data portion, there are recorded a preamble signal at its
head and following thereto, a data synchronizing signal DSYNC and data to
be recorded on the magneto-optical disk with an error correcting code
(ECC) for correcting possible errors in the data.
The unit quantity of data to be recorded in the data portion of each sector
is generally 512 bytes, considering that the disk is used as a storage
medium for a computer. FIG. 5 shows the construction of the data portion
for the above-mentioned case.
Referring to FIG. 5, the data recorded in each sector is 512 bytes, i.e.,
D.sub.0 -D.sub.511. Preceding the 512 bytes of data there are additionally
recorded 12-bytes of supplementary data comprising a track number TrNo, a
sector number SeNo, a user area and data identification information ID.
Then, a 4-byte CRC code for detecting errors is produced and added at the
end of the preceding 524-bytes of data. The 528-bytes of data thus formed
is arranged in a matrix having 24 byte rows and 22 byte columns, as shown
in FIG. 5.
Then, a first error correcting code C.sub.1 having 4 bytes (e.g., (28, 24)
Reed-Solomon code) is added to each row of the 528-bytes of data including
the 4-byte CRC code. In the same manner, a second error correcting code C2
having 4 bytes (e.g., (26, 22) Reed-Solomon code) is added to each column
of the 528-bytes of data.
Referring again to FIG. 5, there is recorded at the head of each row a
synchronizing signal (hereinafter simply called "Re-SYNC") indicative of
the head of each row, by which the data is sequentially recorded and read
along the row direction.
Reference is now made to an example of the invention which records a
variety of information on a disk defined by the above-mentioned sector
format as well as a reproducing apparatus associated therewith.
Referring now to the block diagram of FIG. 3, reference numeral 11
designates a magneto-optical recording disc including, e.g., a
spiral-shaped track on which the above data is recorded. A recording and
reproducing head (not shown) in the apparatus is controlled such that the
head correctly scans the previously formed track.
Reference numeral 31D.sub.1 designates a first digital data input terminal
to which is inputted digital data such as data from a computer, in which
adjacent data have no correlation with each other. Reference numeral
31D.sub.2 designates a second digital data input terminal to which is
inputted time sampled analog data, for example, analog audio data sampled
at various predetermined sampling frequencies with each value being
sampled as one word made of a predetermined number of bits, digital data
at various transmission rates of data, and so on. Such digital data has a
correlation between adjacent data and can be interpolated with the
adjacent data. Reference numeral 31A designates an input terminal to which
are supplied analog signals, e.g., audio signals.
Digital data inputted to the terminals 31D.sub.1 and 31D.sub.2 are supplied
to a selector 33 while analog signals inputted to the terminal 31A are
first supplied to an A/D converter 32 to be converted into corresponding
digital signals. The sampling frequency of the A/D converter 32 can be
changed to various values, e.g., 32 kHz, 44.1 kHz, 48 kHz, and so on.
Further, it is possible that the sample can be selected from various
numbers of bits, e.g., 8-bits, 12-bits, 16-bits and so on. In the case of
such digitally converted analog signals, particularly in the case of
digitally converted audio signals, the resulting signal has a correlation
among data words so that an erroneous word can be interpolated by words
located at the vicinity of said erroneous word. This is because the
changes in amplitude of an analog signal are not as likely to be abrupt as
in the case of a digitally generated signal. The digital signal from the
A/D converter 32 is supplied to the selector 33.
The selector 33 selects, by manual operation or a control signal SS
supplied thereto from an external circuit (not shown), one of the signals
from the input terminals 31D.sub.1, 31D.sub.2 or the output of the A/D
convertor 32. The digital signal selected by the selector 33 is stored in
a RAM 34. In this case, the write and read addresses in the RAM 34 can be
changed in accordance with the input data selected by the selector 33.
To be specific, reference numeral 36 designates a sequential address
control means which generates a sequential address for the writing and
reading addresses, and reference numeral 37 designates a scrambled address
control means which generates writing and reading addresses which follow a
predetermined order for the cases where one of the two reading and writing
of addresses is sequential and the other of the two addresses is
scrambled. One of the addresses generated by the address control means 36
and 37 is selected by a selector 35 to be supplied to address terminals of
the RAM 34. The selector 35 is controlled by a selection signal SS in
ganged relation with the selector 33.
When the digital data from the input terminal 31D.sub.1 is to be selected
by the selector 33, the address generated by the sequential address
control means 36 and selected by the selector 35 is supplied to the RAM 34
in which each of the 512-bytes of data is sequentially written at an
address corresponding thereto, i.e., D.sub.0, D.sub.1, D.sub.2, . . . as
shown in FIG. 5.
The RAM 34 generally comprises two chips of RAM devices. Data is written
into a vacant one of them and read out from one into which data has been
fully written. In the read-out procedure, data is sequentially read from
the RAM 34 in the same order as the writing by the sequential address, and
supplied to an ECC encoder 38 wherein the additional information and
redundant data C.sub.1 and C.sub.2 are added thereto as shown in FIG. 5 to
thereby form the data portion for each sector. The data portion thus
formed is supplied to a recording process circuit 39 wherein the header
portion is added thereto, as shown in FIG. 4, adequately modulated, and
recorded on the magneto-optical disk 11 as one sector.
When the data from the A/D converter 32 or the data from the input terminal
31D.sub.2 is to be selected by the selector 33, the selector 35 supplies
the RAM 34 with the address generated by the scrambled address control
means 37. If it is assumed at this time that the audio data concerned is
an 8-bit 2-channel stereo, first samples L.sub.0, R.sub.0 of the left and
right channels are respectively written at the first and second byte
positions D.sub.0, D.sub.1 of the 512-bytes of data shown in FIG. 5, and
the next samples L.sub.1, R.sub.1 respectively written at the 257th and
258th byte positions D.sub.257, D.sub.258, that is, the first and second
byte positions of the latter half of the 512-bytes of data. Then,
following in the same manner, samples of even number channels are written
in the former half of the 512 bytes of data, and samples of odd number
channels in the latter half of the 512-bytes of data, that is, data is
written in a scrambled manner.
The data thus scrambled is sequentially read out along the row direction,
i.e., D.sub.0, D.sub.1, D.sub.2, . . . , following the reading address
signals generated by the control means 37. In other words, data is read
out in a scrambled state and supplied to the ECC encoder 38 wherein the
additional information and redundant data C.sub.1 and C.sub.2 as shown in
FIG. 6 are added thereto. The data portion thus formed is supplied to the
recording process circuit 39 wherein the header portion is added thereto,
as shown in FIG. 4, adequately modulated, and recorded as one sector on
the magneto-optical disk 11.
The selection signal SS is supplied to the ECC encoder 38 causing an
identification signal, which indicates whether the data to be recorded is
scrambled or not, to be recorded in an ID portion of the supplementary
information portion. This identification signal may be recorded in the
header portion. Further, the identification signal may be recorded in a
track directory allocated at the most inner or the most outer track of the
disk 11 in which information relative to data to be recorded on the disk
is recorded.
The RAM 34 is shown as distinguished from a RAM arranged in the encoder 38
for a better understanding of the operation of the apparatus of the
invention, however, in a practical device, these RAMs are replaced by one
RAM system which can serve for the both purposes. To be specific, the
redundant data C.sub.1 and C.sub.2 are produced for the data in the one
RAM by the ECC encoder 38 and written in the RAM, and then the written
data with the redundant data is read out from the RAM and supplied to the
recording process circuit 39.
If the rotational speed of the disk 11 is determined as 1406 1/4 rpm, the
data transmission rate is 3.072 Mbps (1.536 Mbps.times.2). If data, the
sampling frequency of which is 8 kHz and the word length of which is 8
bits, is recorded on the disk it is possible to record 48 channels on a
disk. In the case of an audio signal having a sampling frequency of 32 kHz
and a word length of 8 bits, it is possible to record 12 channels. It is
also possible to record 4 channels of an audio signal having a sampling
frequency of 48 kHz and a word length of 16 bits.
If the rotational speed of the disk is changed, data having a different
transmission rate can be recorded in each sector as a 512-byte data block.
The data recorded as described above is reproduced in the following manner.
The data reproduced from the disk 11 by the head (not shown) is demodulated
by a reproducing process circuit 40, supplied to an ECC decoder 41 wherein
possible errors are corrected, and the 512-byte data portion is stored in
a RAM 42.
In the reproducing system, it is required to switch the address of the RAM
42, corresponding to whether or not the recorded data is scrambled.
Reference numeral 44 designates a sequential address control means
corresponding to the sequential address control means 36 in the recording
system, and reference numeral 45 designates a descrambled address control
means corresponding to the scramble address control means 37 in the
recording system.
One of the output addresses from the address control means 44 and 45 is
selected by a selector 43 according to the recorded data and supplied to
the RAM 42.
The output from the ECC decoder 41 is supplied to an identification signal
decoding circuit 46 wherein it is determined from the identification
signal stored in the ID portion of the supplementary information portion
whether or not the data is scrambled. If the recorded data is not
scrambled, the selector 43 selects the address from the sequential address
control means 44 which is then supplied to the RAM 42, whereby the data is
written in and read out from the RAM 42 in the order of the address. The
read-out data is supplied to a selector 47.
If the recorded data is scrambled, the selector 43 selects the address from
the descrambled address control means 45 which is then supplied to the RAM
42, wherein the scrambled data from the ECC decoder 41 is descrambled so
as to be sequentially stored in the RAM 42 in the original order. Since
the data is rearranged in the original order, the data is sequentially
read from the RAM 42 in accordance with the sequential address. The
read-out data is then supplied to the selector 47.
The selector 47 outputs data, under control of a selection signal generated
from the identification signal decoding circuit 46 and in accordance with
the recorded data, to one of two digital data output terminals 49D.sub.1,
49D.sub.2 or a D/A converter 48 whose output signal is delivered to an
output terminal 49A. The signals output from the terminals 49D.sub.1 and
49D.sub.2 correspond to the type of data input to terminals 31D.sub.1 and
31D.sub.2, respectively.
As described above, when the data is scrambled and then recorded, even if a
burst error occurs during a reproducing procedure and cannot be corrected
by the ECC decoder, assuming that all of the data in the former half of
one sector is erroneous, there are still left the odd-numbered sampled
data so that the even-numbered sampled data therebetween can be easily
interpolated by, e.g., an average value interpolation.
If the identification signal is recorded in the header portion or in the
directory, the reproduction can be made in the same way as described
above.
Further, since the identification signal is recorded in a predetermined
portion separate from the data, the identification signal decoding circuit
46 may be supplied with the signal inputted to the input side of the ECC
decoder 41.
Also in the reproducing system, the RAM 42 and a RAM arranged in the ECC
decoder 41 are generally replaced by one RAM system. To be specific, the
data and redundant data written in the one RAM are first read out to
correct possible errors in the ECC decoder 41, and the corrected data is
written in the RAM. Then, the corrected data written in the RAM is read
out.
Further, the RAM 34 in the recording system and the RAM 42 in the
reproducing system may be commonly used.
Although in the above embodiment the magneto-optical disk is given as an
example, the present invention is not limited thereto.
As described above, according to the present invention, the data is
recorded on the disk in accordance with the characteristics of the data to
be recorded, so that data having a correlation with adjacent data can be
easily interpolated.
Further, for recording data which have no correlation with adjacent data,
it is possible to facilitate the address control in the memory and thereby
simplify the software therefor.
The above description is given on a single preferred embodiment of the
invention but it will be apparent that many modifications and variations
could be effected by one skilled in the art without departing from the
spirit or scope of the novel concepts of the invention so that the scope
of the invention should be determined by the appended claims only.
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