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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a storage management system for a memory
card, wherein data such as image data are stored in a memory card in the
form of a file, for example.
2. Description of the Prior Art
In the field of electronic still cameras, for example, a system for storing
in a memory card data representative of an image captured together with
management data representative of the order of storage and indication of
an occupied storage area is proposed by a co-pending Japanese patent
laid-open publication, No. 286077/1988, filed in the name of the same
applicant as of the present application. The image data recording system
thus proposed is capable of optionally erasing individual picture images
and also capable of exchanging or rearranging the sequence of the picture
images. In this system, however, the storage capacity of each storage area
for image data is fixed. Consequently, it has been a defect of this system
that the management of storage areas in terms of efficiently storing a
plurality of picture images of different size is complicated.
Also, in a co-pending Japanese patent laid-open publication, No.
193236/1990, filed in the name of the same applicant as of the present
application, there is proposed a memory management system capable of
efficiently storing data of variable size. According to the prior art, in
the memory management system, for a memory card having a storage area
divided into a plurality of clusters, for managing the storage of
information on each cluster, the relationship of ones of a plurality of
clusters in an image field of information is stored is indicated on a
memory allocation table (MAT) a cluster in which the beginning portion of
the image field of information is stored is indicated on a directory.
In the prior art, the storage areas of the memory card are managed in two
different kinds of storage management areas. Consequently, when such
unusual operation as unloading of a memory card from a camera during
recording operation is carried out, for example, logical inconsistency may
occur in the management information between the two kinds of management
areas. This logical inconsistency may, when subsequently using the card,
cause clusters to be permanently unusable for writing data in and reading
data out of those clusters. In other words, when chained information
between a MAT and a directory is broken for some reasons, clusters
included in the chained information will not be usable thereafter. The
similar situation will occur in a case where the logical inconsistency or
errors are included in the data itself on the management areas.
Further, writing of the data into the memory card is sequentially
performed. Consequently, in such a situation that one block information
such as an image field of information must be stored on a distribution
basis in a plurality of clusters which are scattered on the storage areas
of the memory card, a time required for the storage would be increased. In
addition, in a case where a random access scheme is employed, the control
would be complicated and thus the system would be subjected to a large
load.
The term "memory card" used in this specification means not only a storage
medium which has a semiconductor storage device supported by a card type
of base material and is detachably connected to other equipment but also a
storage medium which is detachably connected to other equipment, such as a
memory cartridge and the like having a semiconductor storage device sealed
in a mold package and detachably connected to other equipment.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a storage
management system for a memory card capable of efficiently coping with
logical inconsistency which would occur on data between storage management
areas, so as to store the information in a short period of time.
In accordance with the present invention, in a storage management system
for a memory card, having a storage area divided into a plurality of
storage units that have a predetermined storage capacity, of managing
storage of information in the plurality of storage units, a MAT indicates
a relationship of ones of the plurality of storage units in which a group
of mutually associated information is to be stored in the form of a
packet, and a directory indicates one of the plurality of storage units in
which a beginning portion of said packet is to be stored. Stored in one of
the plurality of storage units is, as a header, management data
representative of at least either one of the number of occupied ones of
the plurality of storage units and the number of idle ones thereof, the
header including an error check code for use in detecting an error of the
management data.
More specifically, according to the present invention, there is provided a
storage management system for a memory card, wherein the group of mutually
associated information is subjected to a coded compression processing, the
one of the plurality of storage units in which a beginning portion of said
packet is to be stored includes information associated with a scheme of
the coded compression, and logical matching between the information
associated with a scheme of the coded compression and the management data
is checked.
Further, in accordance with the present invention, in a storage management
system for a memory card, having a storage area divided into a plurality
of storage units that have a predetermined storage capacity, of managing
storage of information in each of the plurality of storage units, a MAT
indicates a relationship of ones of the plurality of storage units in
which a group of mutually associated information is to be stored in the
form of a packet, and a directory indicates one of the plurality of
storage units in which a beginning portion of said packet is to be stored.
In such a storage management system, at least one of the plurality of
storage units is provided with a first storage area which stores packet
attribute data including indication as to whether said packet is empty or
occupied, and retrieval of the packet is performed referring to the first
storage area.
More specifically, according to the present invention, there is provided a
storage management system for a memory card, wherein the group of mutually
associated information provides a first packet including image data
representative of a frame of image, at least one of audio data and digital
data associated with the image data provides a second packet as another
group of mutually associated information, and one of the plurality of
storage units is provided with a second storage area which stores
identification information specifying the second packet corresponding to
the first packet, and the first and second packets are read out in
association with each other referring to the second storage area.
Further more, in accordance with the present invention, in a storage
management system for a memory card, having a storage area divided into a
plurality of storage units that have a predetermined storage capacity, of
managing storage of information in each of the plurality of storage units,
a MAT indicates a relationship of ones of the plurality of storage units
in which a group of mutually associated information is to be stored in the
form of a packet, and a directory indicates one of the plurality of
storage units in which a beginning portion of said packet is to be stored.
In such a storage management system, stored in one of the plurality of
storage units is, as a header, management data representative of at least
either one of a packet number given by the largest number of one of the
packets stored in the plurality of storage units and a packet number given
by the smallest number of one of the empty packets, and a storage unit
number given by the largest number of the plurality of storage units and a
storage unit number given by the smallest number of one of the empty
storage units.
Still further more, in accordance with the present invention, a storing
apparatus for storing information in a memory card having a storage area
divided into a plurality of storage units that have a predetermined
storage capacity comprises card connector means for connecting said memory
card to said apparatus, management data forming means for forming
management data including a MAT indicating a relationship of ones of the
plurality of storage units in which a group of mutually associated
information is stored in the form of a packet, directory indicating ones
of the plurality of storage units in which a beginning portion of the
packet, and either one of the number of ones of the plurality of storage
units which are occupied and the number of ones of the plurality of
storage units which are empty, and control means for controlling the
management data forming means to store the group of mutually associated
information. In such an apparatus, the control means controls the
management data forming means, after completion of storage of information
into the memory card, so as to first form the MAT and the directory, and
then the management data to store those in one of the plurality of storage
units.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the present invention will become more apparent
from the consideration of the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a conceptual view visualizing a concept of a storage management
system for a memory card according to the present invention;
FIG. 2 is a view showing an example of a map of storage areas of the memory
card in an illustrative embodiment of the present invention;
FIGS. 3 and 4 are diagrams for explanation which exemplarily show formats
of a packet attribute in the example of construction of the storage areas
shown in FIG. 2;
FIGS. 5A and 5B are, when combined as shown in FIG. 5, schematic block
diagrams exemplarily showing an application of the present invention to a
digital electronic still camera;
FIG. 6 is a flow chart exemplarily showing a checking operation of
management data in the digital electronic still camera shown in FIGS. 5A
and 5B;
FIG. 7 is a flow chart exemplarily showing a check routine of the number of
clusters in the flow shown in FIGS. 5A and 5B;
FIG. 8 is, similar to FIG. 2, a view showing an example of construction of
storage areas of the memory card in another illustrative embodiment of the
present invention;
FIG. 9 is a view showing an example of an area layout of a header area in
the construction of storage areas shown in FIG. 8;
FIG. 10 is a view showing an example of construction of a packet attribute
area in the storage area layout shown in FIG. 9;
FIG. 11 is a view showing an example of construction of a packet
association information area in the storage area layout shown in FIG. 9;
FIG. 12 is a view showing an example of construction of a start cluster
area in the storage area layout shown in FIG. 9;
FIG. 13 is a view showing an example of construction of a MAT area in the
storage area layout shown in FIG. 9; and
FIGS. 14A and 14B are, when combined as shown in FIG. 14, schematic block
diagrams exemplarily showing another application of the present invention
to a digital electronic still camera.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the accompanying drawings, further details of the embodiments
of a storage management system for a memory card will be given herein
after.
FIG. 1 conceptionally shows an illustrative embodiment of a storage
management system. As shown in the figure, a memory card 10, FIG. 5B, has
a storage area 12 splitted into clusters 14 having a predetermined storage
capacity and is provided with management data areas 16, FIG. 5B, for
storing management data. The remainder of the storage area 12 according to
the illustrative embodiment is used as image data areas 20 in which image
data are stored. The storage capacity of the cluster 14 may be optionally
determined. For example, the capacity may be of a size enough to store a
fraction of a positive integer for image data, which is necessary to
represent a picture image in the form of a standard video signal format,
and called "a packet". The packet may be interpretered to be a data unit
including an audio data related to the image data. In the management data
area 16, as shown in FIG. 2, there are stored a header 16a, a packet
attribute 16c, directory (DIR) 16d and a memory allocation table (MAT)
16e.
In the illustrative embodiment, basically, a single packet of image data 22
is stored in an optional cluster 14. Stored in the MAT area 16e are data,
that is, MAT data, indicating the relationship of the clusters 14 which
have stored the single packet of image data. The MAT data, for example, in
conjunction with the cluster 14, in which a part of the single packet of
image data 22 is stored, includes identification information, such as
numerical figures, pointing out another cluster in which stored is another
part of the remainder of the image data 22, which is directly associated
with the former part of the image data 22. When there is no remainder of
the image data 22, the MAT data indicates with a predetermined code "ALL
1" (a binary value), for example, that represents that cluster 14 is the
last one in the packet 22. More in detail, in MAT area 16e, there are
stored the numerical figures of the subsequent cluster 14, using two bytes
on each cluster. According to this embodiment, when the cluster 14
includes no image data, for instance, in an unused state or an erased
state, the value of MAT 16e is given with "ALL 0", and when the MAT 16e is
the end of packet 22, the value of MAT 16e is given with a predetermined
code, such as "ALL 1", that is, hexadecimal "FFFF". Further, in a case
where there is other cluster 14 following the packet 22, the value of MAT
16e is given with a value indicating the numerical figure of such a
subsequent cluster 14.
Stored in the directory area 16d is information indicating a start cluster
and a data assortment. The start cluster information is identification
information, such as a start cluster No., indicating the cluster 14 which
has stored the first portion of the image data on a unit image basis, that
is, on each packet 22. Thus, in which cluster 14 an image field of data
has been is specified. The information indicating a data assortment
indicates an assortment of information stored in the memory card 10, for
example, image data, audio data, character data, program and so on.
In an application of the memory card 10 having the storage capacity of 64M
bits, 1024 pieces of the clusters 14 each having the capacity of 64K bits
can be established. The respective clusters 14 are provided with numbers
#0 to #1023 in the sequence of physical arrangement. Stored in the
clusters #0 and #1 are management data. The management data, in the
illustrative embodiment as shown in FIG. 2, includes header 16a, packet
attribute 16c, directory 16d and MAT 16e that are stored in the respective
sub-areas. Stored in the remaining clusters #1 to #1023 are image data for
example that also include header information particular to individual
images.
A single packet 22 is stored in one or more clusters 14. Consequently, it
can also be said that a packet is a logical area in which stored image
data representative of an image field. Given to the packets 22 are
numerical figures in the practical sequence, for example, in the sequence
of storing image data, etc. When some pocket 22 is erased, the number
given to that packet becomes a space, which will later on be alloted to
new image data to be stored in that packet thereafter. A packet of the
image data 22 is stored in a single cluster 14 or a plurality of clusters
14. In the last cluster 14, there sometimes happens to exist a space area
14a, FIG. 1. The number of packets 22 that can be stored in the memory
card 10 is equal to the number obtained by subtracting 2 from the total
number of the clusters 14 in the memory card 10.
In the directory 16d, the number of the first cluster 14 on each packet 22
is stored. In the illustrative embodiment, as there are 1024 clusters, 10
bits are used for the start cluster numbers and other bits are left
unused. Unused directory is indicated as "ALL 0".
Further, according to the present illustrative embodiment, the management
data area 16 is provided with a packet attribute area 16c. The packet
attribute 16c includes information indicating, on each packet 22, as to
whether it is used or not, and in addition, may include indication
concerning, for example, yes or no of writing over, yes or no of copy and
yes or no of reading out. More in detail, the packet attribute area 16c
may be provided, as shown in FIG. 3, by a bit map scheme in which one bit
per a packet is allocated in an indication, and each of the bits indicates
whether or not the associated packet 22 has been occupied. In the
illustrative embodiment, binary "1" indicates the state of the packet 22
being occupied, while binary "0" indicates the state of the packet 22
being empty. A bit map pointer 17 indicates a specific packet position on
the bit map.
FIG. 4 shows an example of the packet attribute 16c in which a single
packet 22 comprises one byte of which 4 bits are used for indication of
the packet attribute. The first bit b1 of the most significant bit MSB
indicates yes or no of writing over, writing protection being represented
by "1", and allowance of writing over being represented by "0". In this
case, it may be interpreted that the writing over includes erasing. The
second bit b2 indicates empty or occupation of packet 22, "1" representing
occupation, "0" representing empty. The third bit b3 indicates yes or no
of copying of information stored in the memory card, a copy inhibition
being represented by "1", a copy allowance being represented by "0".
Similarly, the forth bit b4 indicates yes or no of reading out of
information stored in the memory card, reading out inhibition being
represented by "1", reading out allowance being represented by "0". For
instance, regarding a packet which became unusable on storage area 20, the
indication "11X1XXXX" is indicated as the packet attribute 16c, where "X"
is a bit representing "don't care".
As explained above, according to the illustrative embodiment, there is
provided such a treatment that the attribute among the management data
related to the packet 22, particularly, one related to the
occupation/empty is independent of the directory 16d. This makes it
possible to retrieve the packet attribute area 16c independently of
directory 16d, and thus, as will be described in detail after, possible to
perform simply and promptly retrieval of the packet 22, in a memory card
10 which employs such a system that address of the storage area and data
are transferred on a serial basis.
Stored in the header 16a are the number of occupied clusters, the number of
remaining clusters, a maximum active packet number, first free packet
number and parity 16b. The number of occupied clusters is data
representative of total numbers of the clusters 14 in which image data are
effectively written on the storage area 20. The number of remaining
clusters is data representative of the number of clusters 14 which are
available for writing of the image data on the storage area 20, that is,
the number of empty clusters 14. There is sometimes a memory card 10 of
which ROM area, not shown, stores data representative of a storage
capacity of the storage area. In case of such a card, the number of
occupied clusters and/or the number of remaining clusters are available
for check, upon comparison of their numbers with the storage capacity, of
retionality thereof.
The maximum active packet number of the header 16a is data representative
of a packet having the largest packet number among the packets 22 stored
in the storage area 20. In this case, while there sometimes happens to
exist erased one among a series of active packets, the largest packet
number becomes the maximum active packet number. When the memory card 10
is mounted on a regenerative apparatus to read out the image data 20 on
the card, the regenerative apparatus loads thereinto, as will be explained
later, the packet attribute 16c and directory 16d. In such a case,
referring to the maximum active packet number makes it possible to grasp
the amount of use of those, and thus possible to restrict the loading
area. The first free packet number indicates youngest number among the
free packets on the storage area 20. The first free packet number can be
written, for example, when the image data are reproduced by the
regenerative apparatus. This makes it possible, when the memory card 10 is
mounted on the electronic still camera to perform an image recording, to
reduce a processing load of the camera.
A header 16a may include a maximum active cluster number and a first free
cluster number in addition to or instead of the maximum active packet
number and the first free packet number. The maximum active cluster number
is data representative of a cluster having the largest cluster number
among the clusters 14 stored in the storage area 20. In this case also,
while there sometimes happens to exist empty one among a series of active
clusters, the largest cluster number becomes the maximum active cluster
number. The first free cluster number indicates youngest number among the
free clusters on the storage area 20. The maximum active cluster number
and the first free cluster number may provide the similar effects as
discussed on the maximum active packet number and the first free packet
number.
The header 16a includes a parity area 16b and be provided with one byte as
a storage area designated with one address. The parity is obtained by
means of calculation of the parity located in an address direction of bits
associated with the respective digits all over the byte of the header 16a,
that is, in a vertical direction, and is stored in a memory location of
the final address of the header data area 16a. This calculation is
realized by means of performing addition on each digit on a binary basis
and deleting carry. Thus, it is possible to check normality of data
contents of the header data area 16a. While the present illustrative
embodiment utilizes the parity check, it is possible to emply a checking
code system capable of correcting errors, for example, CRC code, etc.
Header 16a may include, in addition to the parity area 16b, a user area for
storing user data, for example, a card number, a name and so on, with
which a user can provide the memory card. Further, the header 16a may
include format version data for identification indication which indicates
assortment of the card 10, for example, such that the card is for an
image. The format version data is utilized, in a case where memory cards
other than a predetermined kind of cards 10 are connected to a recording
apparatus and a regenerative apparatus, for example, in such a case that a
memory card for use in data processing is mounted on an electronic still
camera, for protection of those apparatuses and cards.
By the way, as exemplarily shown in cluster #4 in FIG. 2, data 14c
indicating an image quality mode is stored in a first cluster of some
packet 22. The image quality mode 14c indicates a mode of an encoding
compression of image and/or audio data for forming the packet 22. For
example, the image data varies a packet of total data quantity in
accordance with a standard mode, and the encoding compression mode such as
a high density compression mode having a compression ratio, one bit per
pel for example, and thus varies the required number of clusters capable
of storing a packet of compressed image data. According to the present
illustrative embodiment, when the image data 20 is stored in the memory
card 10 in a recording apparatus such as an electronic camera, the image
quality mode 14c is written into a first cluster 14b of the packet. This
makes it possible for a regenerative apparatus, when regenerated, to
identify the number of clusters 14 to be accessed.
FIGS. 5A and 5B show an illustrative embodiment wherein such a storage
management system as mentioned above is applied to a digital electronic
still camera. In the illustrative embodiment, the storage management
system comprises a digital electronic still camera 52 being detachably
connected to a memory cartridge 10 through a connector 50. The camera 52
is a still picture photographing device which photographs a scene by an
image picking-up device 56 through an optical lens system 54 to store the
image data representative of the field in a memory card 10. The picking-up
device 56 produces an output, which is in turn subjected to signal
processing, such as color regulation, in a signal processing circuit 58
and converted into the corresponding digital data through an
analog-to-digital (A/D) converter circuit 60. Those digital data are
processed with color separation and compression encoding in a signal
processing circuit 62 and then transmitted to the connector 50 through a
data selector 64.
The camera 52 has a console and display 66, which receives various manual
instructions such an exposure, data compression mode and write protect
designations, and also indicates the state of the system to the user, such
as alarm indicative of the state in which any idle cluster is not
available to storing a record of image data. Console and display 66
generates data representing the designations fed therein to a system
control 68. The information on the state of the camera 52 is fed to the
console and display 66 from the system control 68.
The system control 68 is a control unit which not only controls the entire
operations of the camera 52 but also writes data in the memory card 10.
Connected to the system control 68 is a compression ratio setting circuit
70 which is a circuit for setting a compression ratio of codes for image
data to a signal processing circuit 62 in accordance with a data
compression mode indicated by the console and display 66 under the control
of the system control 68. As the compression coding method, an orthogonal
transform such as a two-dimensional cosine transform, or the sub-sampling,
and the quantization are advantageously applicable.
The data selector 64 is a selector circuit which sends out image data from
the signal processing circuit 62 and control data involved in the system
control 68 selectively through the connector 50 to the memory card 10.
Connected to the data selector 64 are a management data alteration circuit
72 and a management data read-out circuit 74. The management data
alteration circuit 72 is a circuit which generates data to be written in
the management area 16 of the memory card 10. The management data read-out
circuit 74 reads out management data stored in management data area 16 of
the memory card 10 and then feeds those to the system control 68.
The memory card 10 has an addressing circuit 76 to which an address
specifying a storage location in the memory card 10 is given from the
system control 68 through the connector 50. The memory card 10 has an
address bus 78 and a data bus 80 for storage data areas 16 and 20. The
former is connected to the addressing circuit 76 and the latter to the
connector 50.
In an operational condition, when the memory card 10 is connected through
the connector 50 to the camera 52, the system control 68 causes the
management data read-out circuit 74 to read out the header 16a stored in
management data area 16 of the memory card 10. More in detail, an address
of an area of the header 16a is designated by addressing circuit 76
through address bus 78, so that the header 16a is read out by the
management data read-out circuit 74 through the connector 50 and the data
selector 64.
The system control 68 first checks a format version included in the thus
read out header 16a. According to the present illustrative embodiment, if
such a format version has no indication for image, the console display 66
displays such an indication that the associated memory card is to be
excluded. Further, if it includes a card number of a user, it also be
displayed. Next, as shown in FIG. 6, there is performed a parity check on
the header 16a. A result of the parity check is compared with the parity
16b (step 100). This parity check is, as aforementioned, achieved by means
of performing addition on each digit on a binary basis in an address
direction of bits associated with the respective digits all over the byte
of the header 16a and deleting carry.
If a result of the parity check is preferable, the system control 68
carries out check 101 as to the number of clusters. This check is to
calculate a total number of clusters in the storage area from a card
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