JP2732940B2 - Image compression / decompression device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image compression / decompression device, and in particular, compresses an image signal and records the data on an image signal recording medium such as a memory card, and expands and reproduces the image signal read from the recording medium. The present invention relates to an image compression / decompression device used for a device that is also used for recording and reproduction.

2. Description of the Related Art As is well known, an electronic still camera records an image signal captured by a solid-state imaging device on a recording medium such as a memory card. In such a case, since the image signal has a large data amount, a taken image signal is, for example, orthogonally transformed, quantized, encoded, and then recorded on a recording medium.

In the case of an electronic still camera that also has a playback function, an image signal recorded on a recording medium is read and decompressed and decoded,
Playback is performed by the display device.

Such an electronic still camera for recording and reproduction requires a compression encoding circuit to compress and encode a photographed image signal and record it on a recording medium, and controls the compression encoding circuit accordingly. Requires a compression controller. Further, in order to decompress and decode an image signal read from a recording medium during reproduction, a decompression decoding circuit and a decompression controller for controlling the same are required.

These compression encoding circuit, compression controller, decompression decoding circuit, and decompression controller usually each have one
Since these circuits are configured by IC circuits of a chip, there is a problem in that these circuits are each configured by a separate circuit, thereby increasing the circuit scale and increasing the size of the device.

Objective The present invention solves the drawbacks of the prior art and reduces the circuit size by using the compression and decompression circuits together, simplifies the communication protocol between these circuits, and reduces the communication between these circuits. It is an object of the present invention to provide an image compression / decompression device with a reduced number of communication lines.

DISCLOSURE OF THE INVENTION According to the present invention, an image compression / expansion device that performs compression encoding and expansion / decompression of an image signal includes compression / expansion means for compressing / encoding the image signal during compression / recording and expanding / decoding the image signal during expansion / reproduction. A compression / expansion control means for controlling compression / expansion / decompression by the compression / expansion means; and a communication line for performing bidirectional communication with the compression / expansion means and the control means. The transmission and reception of image signals are controlled by the same control signal via a line.

DESCRIPTION OF THE EMBODIMENTS Next, an embodiment of an image compression / decompression device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a digital electronic still camera for both recording and reproduction.

This device compresses a video signal obtained by capturing an image of a subject incident from the optical lens
This is a device for recording on a video monitor 32 and reproducing it on a video monitor 32 as a visible image. Further, the apparatus reads out an image signal recorded on the memory card 24, decompresses and decodes the image signal, and reproduces the image signal on the video monitor 32.

The memory card 24 is a semiconductor storage device that stores image signals in a state where the image signals can be stored and held. However, the present invention is not limited to this, and can be effectively applied to other file storage devices such as a magnetic disk and an optical disk instead of the memory card 24.

The imaging element 12 captures an image of a subject incident from the optical lens 10 and outputs a video signal. The image pickup device 12 is, for example, a single-chip solid-state image pickup device having an RGB segment array color filter. The output of the image sensor 12 is connected to the preprocessing circuit 14. The preprocessing circuit 14 performs preprocessing such as white balance adjustment and gradation correction on the video signal input from the image sensor 12. The output of the preprocessing circuit 14 is connected to the AD conversion circuit 16. The AD conversion circuit 16 converts the input analog video signal into a corresponding digital signal.

The output of the AD conversion circuit 16 is connected to the controller 18. The controller 18 controls data exchange with the DCT compression / decompression circuit 20. When recording, the controller 18
DCT compression / expansion circuit for block synchronization signal BSYNC and data
20 and receives a block synchronization signal BSYNC and data output from the DCT compression / decompression circuit 20 during reproduction.
The controller 18 is formed of a one-chip IC circuit, which also serves as a compression controller and a decompression controller, corresponding to the fact that the DCT compression / decompression circuit 20 also serves as a compression encoding circuit and a decompression decoding circuit. The controller 18 also controls writing to and reading from the frame memory 28, and further controls output of data to the reproduction circuit 26.

The controller 18 and the DCT compression / expansion circuit 20 are connected by a STOP (interrupt) signal line, a BSYNC (block synchronization) signal line, and eight data lines. A STOP signal is sent from the controller 18 or the DCT compression / expansion circuit 20 to the STOP signal line. When the STOP signal is sent, the controller 18 or the DCT compression / expansion circuit 20 receiving the STOP signal stops sending the BSYNC signal and data. A BSYNC (block synchronization) signal is sent from the controller 18 or the DCT compression / expansion circuit 20 to the BSYNC signal line. The BSYNC (block synchronization) signal is a synchronization signal for transmitting data divided and transmitted for each block as shown in FIG. The eight data lines are connected to the controller 18 or the DCT compression / expansion circuit 20.
Sends 8-bit data.

The DCT compression / expansion circuit 20 is a compression / expansion circuit that performs compression encoding and decompression decoding, and is formed by a one-chip IC circuit. At the time of compression encoding, the luminance signal Y and the color difference signal R transmitted from the controller 18 for each block are provided.
-Y and BY are each compression-encoded. The compression encoding is performed, for example, by subjecting an image signal of each block to two-dimensional orthogonal transformation, normalization, and Huffman encoding. The image signal compressed and encoded by the compression / expansion circuit 20 is stored in the memory card 2 for each of the luminance signal Y and the color difference signals RY and BY.
Recorded in 2. At the time of decompression decoding, the compressed luminance signal Y and color difference signals RY and BY sent from the memory card 22 for each block are decompressed and decoded and output to the controller 18.

A memory card 24 is connected to the DCT compression / expansion circuit 20 via an interface 22. Interface 22 is DCT
An interface circuit 22 for recording data compressed and encoded by the compression / expansion circuit 20 on the memory card 24 and sending the data recorded on the memory card 24 to the DCT compression / expansion circuit 20.

The frame memory 28 is a memory for temporarily storing the video signal sent from the AD conversion circuit 16 or the DCT compression / expansion circuit 20. The video signal written to the frame memory 28 as a field signal from the AD conversion circuit 16 is read out as a frame signal, subjected to YC processing in a YC processing circuit (not shown), and output as a luminance signal Y and color difference signals RY and BY. Is generated, divided into data for each block, sent to the DCT compression / decompression circuit 20, and compression-encoded.

The compression / expansion circuit 20 read from the memory card 22
The video signal decompressed and decoded is once written in the frame memory 28, read out, sent to the reproduction circuit 26, and reproduced on the video monitor 32 as a visible image.

The reproduction circuit 26 includes a luminance signal Y and color difference signals RY and BY.
Is a circuit for synchronizing the data into, for example, an RGB signal.
The video signal converted by the reproduction circuit 26 is output to a video monitor 32
And the visible image is reproduced on the video monitor 32. The reproduction circuit 26 may output a video signal in the form of a luminance and color difference signal in the NTSC format. In any case, the circuit 26 is configured to output the video to the video monitor 32 in the form of a soft copy.

The control unit 30 is a control unit that controls each functional unit of the present apparatus. In particular, a CMEX (compression, compression,
expansion) signal. The compression or expansion operation by the DCT compression / expansion circuit 20 is selected by the CMEX signal from the control unit 30, and either the compression or expansion operation is performed in the DCT compression / expansion circuit 20.

The controller 18 and the DCT compression / expansion circuit 20 are connected to the STOP (interrupt) signal line and the BSYNC (block synchronization) as described above.
They are connected to each other by a signal line and eight data lines, and are further connected to the control unit 30 by a CMEX signal line. Therefore, it is connected by a total of 11 communication lines,
Selection of compression or decompression operation by these communication lines,
Control of data transmission is performed.

According to the present apparatus, at the time of shooting and recording, an image of a subject enters from the optical lens 10 and is imaged by the image sensor 12. The video signal output from the image sensor 12 is subjected to pre-processing such as white balance adjustment and gradation correction in a pre-processing circuit,
The digital signal is converted by the conversion circuit 16 and
Sent to 18. The image data of the field signal based on the image array of the image sensor sent to the controller 18 is stored in the frame memory 28. The image data stored in the frame memory 28 is read out as a frame signal under the control of the controller 18 and sent to a YC processing circuit 24 (not shown).
From the image data by the pixel array of the image sensor, the luminance signal Y,
Image data of the color difference signals RY and BY is created and stored in the frame memory 28 again.

This image data divides the data of one screen into a plurality of blocks of 8 × 8 pixels under the control of the controller 18, and the image data of the luminance signal Y and the color difference signals RY and BY is read for each block, It is sent to the DCT compression / decompression circuit 20.
In transmitting image data from the controller 18 to the DCT compression / expansion circuit 20, a BSYNC signal as shown in FIG.
The image data is sent from the controller 18 to the DCT compression / expansion circuit 20 via the BSYNC signal line, thereby controlling the transmission of image data for each block. That is, the BSYNC signal is sent first, and then the image data for each block is sent through eight data lines (8-bit bus).

If there is no room for storing data in the built-in buffer in the DCT compression / expansion circuit 20,
The STOP signal (low level) shown in FIG. 2 is sent to the controller 18 through the STOP signal line, whereby the B signal from the controller 18 to the DCT compression / expansion circuit 20 is transmitted as shown in FIG.
The transmission of the SYNC signal and the image data is stopped. When the DCT compression / expansion circuit 20 is ready to store data again, the STOP signal is released (changed to high level) and the BS
The YNC signal and the image data are sent to DCT compression / expansion circuit 20.

In the DCT compression / decompression circuit 20, orthogonal transform, normalization, and Huffman coding are performed. Therefore, since the variable length coding is performed by the Huffman coding, the data rate output to the interface 22 is not constant. For this reason, when the code amount per block increases or when the writing speed of the memory card 24 is low, the output to the interface 22 is delayed.
0 cannot receive new data. Therefore, even in such a case, the STOP
A signal is output.

The image data sent to the DCT compression / expansion circuit 20 in this manner is compression-encoded as described above, and
Is recorded on the memory card 24 via the.

On the other hand, at the time of reading / reproducing, the image data recorded on the memory card 22 is read and sent to the DCT compression / decompression circuit 20 for decompression and decoding. The decompressed image data for each block is sent to the controller 18. In this case, the BSYNC signal and image data shown in FIG. 2 are sent from the DCT compression / expansion circuit 20 to the controller 18. Frame memory 28
Cannot receive data when the DRAM is refreshing, or when switching the ROW address in DRAM page mode or static column mode.
A STOP signal is output from 18 to the DCT compression / expansion circuit 20. STO
When the P signal is output, the transmission of the BSYNC signal and the image data is stopped.

The image data sent to the controller 18 is stored in the frame memory 28, the blocks are combined and read out, and sent to the reproduction circuit 26. In the reproduction circuit 26, for example, RG
It is converted to a B signal and sent to the video monitor 32, where a visible image is reproduced.

According to the present apparatus, as described above, the compression encoding circuit and the decompression decoding circuit are shared by a one-chip circuit, and the controller for controlling these circuits is also a one-chip circuit for compression encoding and decompression decoding. It is also used by Therefore, the circuit scale can be reduced and the device can be downsized.

Further, as described above, the image data exchange between the controller 18 and the DCT compression / expansion circuit 20 at the time of compression recording and decompression decoding is performed in block units, so that address data can be reduced, and the BSYNC signal line and the STOP This is performed by a total of eleven signal lines, that is, a signal line, a CMEX signal line, and eight data lines. Therefore, the number of communication lines required for data transfer and control can be reduced. In addition, variable-length encoded data can be recorded and reproduced using a memory card that can perform recording or readout timing management even when discontinuous.

Effects According to the present invention, the compression / expansion means performs both compression encoding and decompression decoding of an image signal, and the compression / expansion control means controls both operations of the compression / expansion means. Therefore,
The circuit scale can be reduced, and the device can be downsized.
Further, since the compression / decompression means and the compression / decompression control means transmit and receive data using the same control signal, the number of communication lines for transmitting data and control signals can be reduced, and the communication protocol can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a digital electronic still camera for both recording and playback. FIG. 2 is an example of signals transmitted and received between the controller and the DCT compression / expansion circuit in FIG. FIG. Explanation of Signs of Main Parts 18 Controller 20 DCT Compression / Expansion Circuit 22 Interface 24 Memory Card 26 Reproduction Circuit 28 Memory

Claims (4)

(57) [Claims] An image compression / expansion apparatus for compressing / encoding and decompressing an image signal, the apparatus comprising: a compression / expansion means for compressing / encoding an image signal at the time of compression / recording; A compression / expansion control means for controlling the compression encoding and decompression decoding by the compression / expansion means; and a bidirectional communication line for connecting the compression / expansion means and the control means for controlling data transfer of image signal data. An image compression / expansion apparatus, wherein the compression / expansion means and the control means control transmission / reception of image signals by the same control signal via the communication line. 2. The image compression apparatus according to claim 1, wherein said compression / expansion means and said compression / expansion control means mutually output data stop signals, thereby interrupting data input. Stretching device. 3. The apparatus according to claim 1, wherein said compression / expansion means and said compression / expansion control means mutually output a data stop signal, thereby interrupting data input, and mutually synchronizing data blocks. An image compression / decompression device for outputting a signal and outputting data in synchronization with the synchronization signal. 4. The apparatus according to claim 1, wherein the apparatus records an image signal captured on a recording medium and reads and reproduces the image signal recorded on the recording medium. The image signal used in the camera is sent from the compression / expansion control means to the compression / expansion means, and the image signal read from the recording medium is sent from the compression / expansion means to the compression / expansion control means. An image compression / decompression device characterized by the above-mentioned.