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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording apparatus and a playback
apparatus of image signals, and in particular, to a compression recording
apparatus in which obtained image signals are compressed so as to record
the compressed data on a recording medium, an expansion playback apparatus
in which the compressed data is read from the recording medium so as to be
expanded for a playback operation, and a recoding apparatus in which the
data of image signals is recorded together with data of voice or audio
signals on a recording medium.
2. Description of the Prior Art
In a case where image signals produced by a solid-state imaging apparatus
such as a charge-coupled device, CCD are stored in a storage for example,
a memory card or a magnetic disk, data of the image signals are required
to be compressed, by taking the capacity of the storage into
consideration, to a small capacity. As a method of compressing image data,
there has been known, for example, a orthogonal transform coding, which
will be described below.
First, an image represented by the image signals is subdivided into a
predetermined number of blocks so as to conduct a orthogonal transform on
data of pixels for each subdivided block.
In the image signals, a low-frequency component thereof occupies a large
portion with respect to power, whereas a high-frequency component,
although not occupying a great power portion, is considerably significant
in a sense of information. In addition, visual characteristics vary
between these components. In this situation, the image signals are
converted into such low- and high-frequency components so as to
respectively undergo suitable quantization, thereby storing coded signals
in a storage such as a memory card. On the playback side, the coded
signals read from the storage are reversely transformed to attain the
original signals.
Incidentally, when considering the storage of image signals on a memory
card, it is desirable to use greater compression ratio of the image data.
However, a reproducibility of an image or a picture quality is naturally
influenced by the image data compression ratio. In consequence, since a
high reproducibility is required depending on a purpose of the user, there
may appear a disadvantage if the image data compression ratio is increased
regardless of various cases. On the other hand, it is economically
disadvantageous to prepare a plurality of apparatuses associated with
different compression ratios; in consequence, there is desired an
apparatus capable of changing the image data compression ratio depending
on the requirement, which further leads to a need for a playback apparatus
capable of reproducing an image according to the change in the compression
ratio in the recording operation.
For the requirement above, there has been proposed an apparatus, for
example, in the Japanese Patent Laid-Open No. 61-135286. In this
apparatus, after data of pixels undergo a orthogonal transform, a
coefficient omission threshold value is set such that a subtraction of
this threshold value is conducted on the image data, thereby effecting the
compression of the data. Namely, in the subtraction of the threshold value
from the image data, the threshold value is varied so as to select a
picture quality of the reproduced image. In the case of this apparatus,
after the subtraction of the threshold value is effected on the image
data, a bit allocation to record data in an external memory such as a
memory cartridge, namely, an coding operation is achieved depending on
uniform data. In consequence, in a playback apparatus, after data read
from the external memory is decoded, it is necessary to add thereto the
threshold value employed in the compression of the data; in consequence,
data of the threshold value is required to be supplied to the playback
apparatus for each playback operation.
On the other hand, it has been known to store still image signals together
with audio signals on a storage such as a memory card or a magnetic disk.
In a recording operation on such a storage, for example, it is desirable
that voices attained from an object at the respective image shooting
operations and data of voices, for example, of an explanation of an
obtained image are recorded together with the image data. In such a case,
audio data is recorded on a recording medium together with the image data.
Incidentally, since the amount of image data does not vary between
respective still images, namely, a fixed amount of image data is produced
for each sheet of still picture, a fixed amount of recording area is used
in the storage when a picture is recorded. Consequently, the operator need
only count the number of stored still pictures, in a case where the
storage capacity of the recording medium is known, to obtain the number of
pictures to be further stored therein, namely, the remaining storage area
of the recording medium.
In contrast thereto, for the audio data, the length of the voices
associated with a picture is variable, and hence the amount of the audio
data changes between pictures. Consequently, when the audio data are
stored in a recording medium together with the image or picture data, the
amount of the picture and voice data to be further recorded in the
recording medium, namely, the remaining available storage capacity of the
recording medium cannot be attained only by counting the number of the
pictures already recorded therein. In this situation, it is desired to
display the number of pictures as well as the period of voice available
for the recording operation, namely, the remaining storage capacity for
the pictures as well as for the voice.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a compression
recording apparatus in which when image data is to be subjected to a
compression encoding so as to be stored in a storage, the operator can
select a compression ratio of the image data and selection data of the
compression ratio is stored in the storage together with the image data
and to provide an expansion playback apparatus for reproducing image from
the image data thus stored.
In addition, another object of the present invention is to provide an image
signal recording apparatus in which image data and audio data are recorded
on a recording medium such that the remaining amount of the recording
medium available for the image data and the audio data is displayed.
According to the present invention, the compression recording apparatus for
receiving image signals so as to effect a compression coding on image data
thereof to record the resultant signals on a recording medium includes
blocking means for dividing the image data into blocks, orthogonal
transform means for achieving a orthogonal transform on the image data
blocked by the blocking means, coding means for compressing and for coding
the image data undergone the orthogonal transform by the orthogonal
transform means, selecting means for selecting compression ratio data to
be used for a compression coding effected by the coding means on the image
data undergone the orthogonal transform, and data write means for writing
in a recording medium the image data undergone the compression coding
according to the compression ratio data selected by the selecting means
and the compression ratio data. The data write means writes the image data
undergone the compression coding and the compression ratio data in
respective different areas of the recording medium.
In addition, according to the present invention, the image signal expansion
playback apparatus includes data read means for respectively reading the
image data undergone the compression coding and the compression ratio data
from the recording medium recorded by the image signal compression
recording apparatus and expansion decoding means for achieving an
expansion decoding on the image data undergone the compression coding by
use of the compression ratio data read from the recording medium by the
data read means, thereby conducting an expansion playback of the image
data compressed, coded, and recorded on the recording medium.
In addition, according to the present invention, there is provided an image
signal recording apparatus for recording in a recording medium image data
of image signals produced from imaging means together with audio data of
audio signals collected by voice collecting means including recording code
generating means for generating recording codes depending on amounts of
the image data and the audio data to be recorded in the recording medium,
data input/output control means for writing the image data and the audio
data in the recording medium and for controlling read and write operations
of the recording codes produced by the recording code generating means
with respect to the recording medium, and recording medium remainder
display means for displaying a remaining amount of the recording medium
available for the recording operation wherein the data input/output
control means reads a recording code recorded in the recording medium so
as to cause the recording medium remainder display means to display the
remaining amount of the recording medium available for the recording
operation.
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 schematic block diagram showing an embodiment in which an image
signal compression recording apparatus according to the present invention
is applied to a digital electronic still camera;
FIG. 2 is a block diagram showing an embodiment of an image signal
expansion playback apparatus according to the present invention;
FIG. 3A is a diagram showing an example of an image prior to a blocking
operation effected thereon;
FIG. 3B is a diagram showing an example of an image in which a blocking
operation is effected on the image of FIG. 3A;
FIG. 4A is a diagram showing an example of pixel data;
FIG. 4B is a diagram showing an example of data attained through a
orthogonal transform conducted on the pixel data of FIG. 4A;
FIGS. 4C-4D are diagrams showing examples in which the number of bits is
assigned in an coding of data of FIG. 4B;
FIG. 5 is a schematic diagram showing an example of storage contents in a
recording medium in which image signals are recorded by the apparatus of
FIG. 1;
FIG. 6 is a diagram showing another example of the number of bits assigned
in the coding of data of FIG. 4B;
FIG. 7 is a schematic block diagram showing an alternative embodiment in
which an image signal compression recording apparatus according to the
present invention is applied to a digital electronic still camera;
FIG. 8 is a schematic block diagram showing an embodiment in which an image
signal recording apparatus according to the present invention is applied
to a digital electronic still camera;
FIG. 9 is a schematic block diagram showing an alternative embodiment in
which an image signal recording apparatus according to the present
invention is applied to a digital electronic still camera;
FIG. 10 is a block diagram showing an example of storage contents of a
memory in which data is stored by the apparatus of FIG. 8; and
FIG. 11 is a block diagram showing another example of storage contents of a
memory in which data is stored by the apparatus of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the accompanying drawings, description will be given of an
image signal compression recording apparatus and an image signal expansion
playback apparatus according to the present invention.
FIG. 1 shows an embodiment in which an image signal recording apparatus
according to the present invention is applied to a digital electronic
still camera. Incidentally, other components of the camera not directly
related to the explanation of the present invention, for example,
mechanisms for a shutter, an iris, and a film are omitted.
The apparatus of FIG. 1 includes a master lens 12 followed by an imaging or
image pickup device 14 for converting an optimal image of an object
focused by the master lens 12, the imaging device 14 being provided with a
color filter 16 on a surface thereof. The imaging device 14 is operative
in response to a synchronization or sync signal supplied from a sync
signal generate circuit 34 through a signal line 120 so as to convert the
optical image of an object. The image signal produced from the imaging
device 14 is sent via a signal line 102 to an analog-to-digital (AD)
converter circuit 18, which converts the image signal sent from the
imaging device 14 into a digital signal. Incidentally, between the imaging
device 14 and the AD converter 18, although not shown, there may be
disposed means for the gamma correction and the white balance processing.
The color image signal converted by the AD converter circuit 18 into the
digital signal is fed via a signal line 104 to a block generator or
blocking circuit 22.
The blocking circuit 22 achieves a block generation on the image signal
including pixels of red, R; green, G; and blue, B components supplied from
the AD converter 18 so as to produce a predetermined number of blocks
therefrom. The blocking operation is effected, for example, such that an
image of FIG. 3A is subdivided into a plurality of areas or blocks 62, 62,
62, . . . as shown in FIG. 3B. Although the block 62 of FIG. 3B is
favorably constituted with, for example, 16.times.16=256 pixels, the
number of pixels constituting the block need only be selected to be
identical to the number of pixels included in an image signal. According
to this embodiment, for simplification of the explanation, the block
includes 4.times.4=16 pixels.
The image signal blocked in the blocking circuit 22 is supplied via a
signal line 108 to a orthogonal transform circuit 24, which effects a
orthogonal transform for each block of the image signal thus blocked. The
blocked image signal includes, for example, values of respective pixel
levels prior to the orthogonal transform as shown in FIG. 4A. In this
example of FIG. 4A, the pixel at the upper-left corner has a level of 120
in the digital data, the pixel on the right thereof has a level of 127,
and the third pixel possesses a level of 108; furthermore, the pixel at
the left end of the second row has a level of 107 and the pixel on the
right thereof is of a level of 120.
Conducting an orthogonal transform on the data, there is provided, for
example, data shown in FIG. 4B. As to the orthogonal transform, the
Hadamard transform, the cosine transform, and the Fourier transform have
been known, for example. In the data having undergone the orthogonal
transformation as shown in FIG. 4B, the abscissa and ordinate axis
directions are associated with the frequency components respectively along
the horizontal and vertical directions of the screen. In addition, in the
data arrangement, data of the lower-frequency components and data of the
higher-frequency components are respectively located in the upper-left and
lower-right positions, namely, the change ratio between the adjacent
pixels increases in this direction. In a general image, as already
described, the low-frequency component occupies a larger portion with
respect to power and the high-frequency component appears only in a
smaller portion. As a consequence, in the data undergone the orthogonal
transform as shown in FIG. 4B, the greater value appears in the upper-left
position and the value decreased as the location moves to the right and
downward.
The signal on which the orthogonal transform is effected by use of the
orthogonal transform circuit 24 is delivered via a signal line 110 to an
encoder 26.
The encoder 26 encodes image data inputted thereto depending on data for
the encoding sent from a lookup table 38 via a signal line 138.
The encoding is effected, in a case where the input image data is, for
example, data of an array as shown in FIG. 4B, such that a predetermine
number of bits are allocated to each data item. That is, depending on an
image pattern of each subdivided block, data associated with the encoding
is supplied from the lookup table 38 to the encoder 26 so as to effect the
encoding operation according to the image pattern of each block, namely, a
larger number of bits are allocated to an image pattern associated with
the greater variation in the block and a smaller number of bits are
allocated to an image pattern for which the smaller change occurs in the
block.
Data for the allocation of the number of bits is set in response to a
control signal delivered via a signal line 136 to the lookup table 38
according to mode select data sent from an image or picture quality mode
setting unit 88 via a line 242 to a controller 36. Incidentally, according
to this embodiment, the image quality mode setting unit 88 is provided
with two kinds of mode select switches for the standard mode and the high
image quality mode so as to be selected by the operator. For example, in a
case where the standard mode is selected in the image quality mode setting
unit 88, an amount of data containing a total of 32 bits (compression
ratio=1/4) is assigned to a block as shown in FIG. 4C; and in FIG. 4B, the
bit allocation is effected as follows, namely, 8 bits are allocated to
data 200, 4 bits to data 150, 130, and 150, 2 bits to data 100, 90, 70,
and 80, and one bit to data 50, 40, 60, and 20 so as to encode these data
items. To those data items arranged in other manner, the bit allocation is
not achieved. That is, of the data undergone the processing such as the
orthogonal transform, the data items located in the left or right portion
of the predetermined range are ignored and hence are not stored. The
reason why only the low-frequency component is stored and the
high-frequency component is neglected is that the low-frequency component
occupies most of the portion of the general image and hence an image can
be approximately reproduced even when the high-frequency component is
ignored.
In addition, when the high image quality mode is selected in the image mode
setting unit 88, an amount of data containing a total of 64 bits
(compression ratio=1/2) is assigned to a block as shown in FIG. 4D; and in
FIG. 4B, the bit allocation is effected as follows, namely, 8 bits are
allocated to the data 200, 6 bits to the data 150, 130, and 150, 4 bits to
the data 100, 90, 40, 70, and 80, 3 bits to the data 60 and 50, and 2 bits
to the data 50, 10, 5, and 10. By storing also the high-frequency
component in this fashion, it is possible to develope a high
reproducibility in the playback operation.
Data coded by the encoder 26 is supplied via a signal line 112 to a
connector 30 so as to be stored in a memory 32 connected to the connector
30. As the memory 32, a storage such as a memory card in which, for
example, a semiconductor memory is mounted on a substrate in a card-like
shape is advantageously employed so as to store therein an encoded still
picture.
The connector 30 is also supplied from the lookup table 38 via a signal
line 240 with the lookup table data for the coding such as the bit count
allocation data described above and the mode selection data, which are
also stored in the memory 32.
The sync signal generator 34 is operative in response to a control signal
sent from the controller 36 via a signal line 126 so as to generate a sync
signal, which is respectively sent via the signal lines 120 and 122 to the
imaging device 14 and the AD converter 18, respectively.
The controller 36 is a control section to control the components of this
apparatus and sends control signals respectively via the signal line 126
to the sync signal generator 34, via a signal line 128 to the blocking
circuit 22, via a signal line 130 to the orthogonal transform circuit 24,
via a signal line 132 to the encoder 26, and via the signal line 136 to
the lookup table 38, thereby controlling operations of the respective
components. In addition, the controller 36 supplies a control signal for a
write operation via a signal line 244 to the connector 30 so as to record
the data items sent to the connector 30 at the pertinent addresses in the
memory 32.
The operation of this apparatus will next be described.
The optical image of the object focused by the master lens 12 is converted
by the imaging device 14 from an optical image into a video signal, which
is delivered via the signal line 102 to the AD converter 18. The video
signal is then converted into a digital signal in the AD converter 18 so
as to be sent via the signal line 104 to the blocking circuit 22, which
produces therefrom blocked image data to be fed via the signal line 108 to
the orthogonal transform circuit 24 effecting a orthogonal transform for
each block. Data undergone the orthogonal transform is transmitted via the
signal line 110 to the encoder 26, which encodes the data by use of the
lookup table 38 such as a selected compression ratio of the data, thereby
delivering the encoded data via the signal line 112 to the connector 30.
The image data sent from the encoder 26 to the connector 30 is stored at a
predetermine address in the memory 32 in response to a control signal fed
thereto from the controller 36 via the signal line 244 thereto. For
example, as shown in FIG. 5, image data items of each block outputted from
the encoder 26 are stored in the block area of the memory 32.
In addition, the mode select data supplied from the lookup table 38 is also
stored at a predetermined address of the memory 32 according to a control
signal similarly sent from the controller 36 via the signal line 244
thereto, for example, in the header area of the memory 32 as shown in FIG.
5.
The data of the still picture shot by the electronic still camera is stored
together with the mode select data in the memory such as a memory card.
FIG. 2 shows an example of a playback apparatus which reproduces an image
obtained by the electronic still camera of FIG. 1 and then stored in the
memory 32. This playback apparatus includes a connector 40 to be connected
to the memory 32. The connector 40 is linked to a signal line 142. The
image data stored in the memory 32 is read out to the connector 40 from
the memory 32 beginning from an address specified by a control signal sent
thereto from a controller 56 via a signal line 270 so as to be inputted
via the signal line 142 to a decoder 44. In addition, the mode select data
loaded in the header area of the memory 32 is read out to the connector 40
from the memory 32 beginning from an address specified by a control signal
similarly delivered thereto from the controller 56 via the signal line 270
so as to be supplied via a signal line 272 to the decoder 44.
The decoder 44 decodes the data supplied thereto so as to produce data, for
example, as shown in FIG. 4B. The decoded data from the decoder 44 is
inputted via a signal line 144 to a orthogonal inverse transform circuit
46 so as to be subjected to a orthogonal inverse transform therein. The
data of each block undergone the orthogonal inverse transform is delivered
via a signal line 146 to a block combine circuit 48 such that data items
of the blocks are combined so as to produce the original image data. The
data combined by the block combine circuit 48 is transmitted via a signal
line 150 to a digital-to-analog (DA) converter 52 so as to be converted
into an analog signal, which is then fed via a signal line 152 to a CRT
54, thereby reproducing the color image stored in the memory 32 on a
screen of the CRT 54.
The controller 56 is a control section to control the respective components
of the apparatus and outputs control signals respectively via a signal
line 156 to the decoder 44, via a signal line 158 to the orthogonal
inverse transform circuit 46, via a signal line 160 to the block combine
circuit 48, and via a signal line 164 to the DA converter 52, thereby
controlling operations of the respective components. In addition, the
controller 56 sends a control signal for a read operation via the signal
line 270 to the connector 40, so that the image data and the mode select
data respectively stored at predetermined addresses in the memory 32 are
read out therefrom.
Next, the operation of the playback apparatus will be described.
When the memory 32 is mounted on the playback apparatus, image data stored
at a predetermined address in the memory 32 is read out to the connector
40 in response to a control signal from the controller 56 so as to be
supplied via the signal line 142 to the decoder 44. That is, the image
data items of the respective blocks stored in the block areas of FIG. 5
are read out to the connector 40 so as to be inputted to the decoder 44.
In addition, the mode select data stored at the predetermined address of
the memory 32 is also read out to the connector 40 in response to a
control signal from the controller 56 and is then delivered via the signal
line 272 to the decoder 44.
The image data received by the decoder 44 is decoded by use of data for a
decoding operation selected according to the mode select data sent via the
signal line 272 to the decoder 44 such that the decoded data is fed via
the signal line 144 to the orthogonal inverse transform circuit 46, which
in turn conducts a orthogonal inverse transform on the data, thereby
attaining data for each block, for example, as shown in FIG. 4A. The data
in the unit of a block sent via the signal line 146 to the block combine
circuit 48 are combined therein so that the resultant data is sent via the
signal line 150 to the DA converter 52, which conducts a DA conversion on
the data to obtain an analog signal. The analog signal is delivered via
the signal line 152 to the CRT 54, thereby displaying a playback image of
the original still image on the screen of the CRT 54.
As described above, according to the electronic still camera of FIG. 1, the
image data produced by the imaging device 14 is processed so as to
generate data blocks such that the orthogonal transform is carried out for
each data block, which is then encoded so as to be stored in the memory
32. In consequence, since the image data is compressed and is then stored
in the memory 32, a large amount of image data can be stored in the memory
32 having a small capacity. Furthermore, the compression ratio of the
image data can be selected by use of a lookup table, and hence the picture
quality in a playback operation of the compressed image data to be stored
in the memory 32 is selected for the encoding of the image data. The
operator may determine the number of pictures to be stored in the memory
32 by selecting the compression ratio as described above.
In addition, the compression of the image data is achieved when the image
data is encoded, which enables the circuit configuration to be simplified.
According to the apparatus of FIG. 1, since the mode select data is stored
in the memory 32 at an address different from an address where the image
is stored therein, when a playback operation is conducted on the data by
use of the playback apparatus of FIG. 2, it is possible to achieve a
decoding operation according to the mode of encoding operation
accomplished by the apparatus of FIG. 1. Incidentally, in this embodiment,
although the mode select data is stored in the header area of the memory
32, the mode select data may also be stored, for example, so as to be
added to each image data in the memory 32.
According to the present invention, in the apparatus of FIG. 1, although
the picture quality mode setting unit 88 is provided with two kinds of
mode select switches, namely, for the standard mode and the high picture
quality mode, it is also possible to dispose a mode as an alternative
embodiment in which when an object is shot by a digital electronic still
camera, only the contour thereof is reproduced, that is, there may be
arranged a contour extract mode to obtain a playback image of image data
like a line drawing. In this contour extract mode, the playback operation
is carried out such that when image data is encoded in the encoder 26, the
bit count allocation is achieved only for data of the high-frequency
component for which a large difference appears between adjacent pixels in
the data array described above. According to the contour extract mode, for
example, as shown in FIG. 6, a total of 8 bits (compression ratio 1/16)
are allocated to a block, which enables the number of bits to be allocated
to be minimized, as a consequence, the compression ratio of the image data
may be increased and hence it is possible to store a larger amount of
image data in the memory 32. Incidentally, in a case where the encoding is
accomplished in the contour extract mode, it is necessary to set the
decode data such that the decoding can be achieved in this mode also in
the playback apparatus of FIG. 2.
FIG. 7 shows an alternative embodiment in which an image signal compression
recording apparatus according to the present invention is applied to a
digital electronic still camera.
In this embodiment, an AD converter 18 produces an output, which is
supplied via a signal line 104 to a memory 70. The memory 70 is supplied
with a control signal from a memory controller 72 via a signal line 170. A
digital signal sent from the AD converter 18 is temporarily stored in the
memory 70 such that the stored data is fed in a blocked form of image data
to a orthogonal transform circuit 24 in response to a control signal from
the memory controller 72, which is supplied with a control signal from a
controller 36 supervising the overall apparatus via a signal line 174 and
with a sync signal from a sync signal generator 34 via a signal line 172.
The other components of this apparatus are identical to those of the
apparatus of FIG. 1.
In the embodiment of FIG. 7, a signal of an image data read out from the AD
converter 18 is stored in the memory 70 so as to be read therefrom in a
blocked format according to a control signal from the memory controller
72. In consequence, the memory 70 and the memory controller 72 correspond
to the blocking circuit 22 of the apparatus of FIG. 1 and hence generates
image data blocks. Since the other operations are the same as those of the
embodiment of FIG. 1, description thereof will be omitted.
Also in the apparatus of this embodiment, the compression ratio of the
image data can be selected by use of the lookup table 38, and hence it is
possible to select a picture quality in the playback operation of the
compressed data stored in the memory 32 so as to encode the image data. In
addition, since the mode select data for the encoding operation is stored
in the memory 32 at an address different from an address where the image
data is stored therein, in a playback operation of the playback apparatus,
the decoding can be accomplished in association with the encoding mode
adopted in the apparatus of FIG. 7 by reading out the pertinent data.
As a method for setting the compression ratio of the image data, other than
the method in which the compression ratios are specified with a plurality
of predetermined values as shown in the foregoing embodiments such that a
desired compression ratio is to be selected therefrom, it is also possible
that the operator inputs a desired compression ratio from numeric input
means disposed in the picture quality mode setting unit 88, thereby
setting the compression ratio.
FIG. 8 shows an alternative embodiment in which an image signal recording
apparatus according to the present invent | | |
