JPH03119883A - Image signal processing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing device that transmits, records and reproduces digital image signals, and is particularly suitable for a signal processing device that performs compression/expansion processing on image signals. The present invention relates to a signal processing device.

[Prior Art] Traditionally, image information has been converted into a digital signal, such as in a still image videophone, and then transmitted through a normal telephone line, or it has been transmitted to a large-capacity storage device such as an optical disk, as in an electronic filing device. There are image processing devices that record digital image information. Image information processed by such devices includes current NTSC color signals, high-definition image signals compatible with computer images, and high-definition signals that are expected to become mainstream in various fields in the future. However, if these high-definition image signals were simply converted into digital signals, the amount of information would be extremely large, resulting in problems such as requiring a long transmission time and reducing the number of images that can be stored in a storage device. Therefore, as described in Japanese Patent Publication No. 62-61988, information compression processing is applied to the digital signal to reduce the amount of data, thereby shortening the transmission time and increasing the number of recorded images.

[Problems to be Solved by the Invention] However, when compressing and decompressing image information, data is thinned out or encoded as part of the compression process, so image quality deterioration caused by this is unavoidable. In images obtained through this process, for example, image blurring occurs due to a decrease in resolution. Also, in the electronic filing device mentioned above, editing work for one image is required.

In other words, since the compositing between images and the compression/expansion processing associated with recording and playback are repeated, this image blur becomes noticeable, resulting in a visually very unsightly and strange-looking screen. Ta. however,
Conventionally, such problems have not been considered at all.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image signal processing device that can solve the above problems and display images with little deterioration in image quality.

[Means for Solving the Problems] The above object is to provide means for performing one contour correction after the decompression device of an image signal processing device for obtaining original image data from compressed image information, and to provide a means for performing one contour correction to a display device. This is achieved by using an image that has been subjected to contour correction for output signals and re-recording.

Additionally, a means is provided to additionally record the history of the number of compression/expansion processes when sending to a transmission system or recording to an external storage device, and to determine the degree of contour correction by referring to this number of times of compression during playback and expansion. This is achieved by

[Operation] During image reproduction, the contour of an image signal having image blur due to compression/expansion processing is corrected by the contour correction circuit. Therefore, it is possible to output and display an image whose contours have been corrected and which are less visually unnatural. In addition, when retransmitting or rerecording, compression processing is performed on the image that has undergone one contour correction, so it is possible to transmit and record images with less deterioration in image quality, making it possible to edit and record images with electronic filing devices. The degree of resolution deterioration due to repeated recording and reproduction can be reduced.

Furthermore, when sending to a transmission system or recording to an external storage device,
By adding a history of the number of times of compression/expansion as additional information and referring to this number of times of compression/expansion during playback, contour correction is performed to a degree commensurate with the number of times of compression/expansion. This allows images to be constantly reproduced with optimal contour correction.

[Example] Hereinafter, an example of the present invention will be described using FIGS. 1 to 4.

These are examples in which the present invention is applied to an electronic filing device.

First, the system will be explained with reference to FIG.

Fig. 2 is a system configuration diagram of the electronic filing device, where 1 is an input terminal for inputting an analog image signal, and 2 is an input terminal for converting the analog image signal into a digital image signal (hereinafter simply referred to as a digital signal or data signal). A/
A D conversion device, 3 is an optical disk device for recording digital signals, 4 is a memory used by the MPU (main processing unit) 6 during calculations, 5 is an input device for giving commands to the MPU 6 from outside the system, 6 is a MPU that controls the entire system
(main processing unit), 7 is a signal processing unit that compresses and expands digital signals, here ΔYUV (delta YUV)
It is called. Performs compression/expansion processing of image signals used in CD-4 (Compact Disc Interactive) and the like. Further, 8 is a display device equipped with a frame memory that stores digital signals on multiple sides and a D/A converter that converts the digital signals stored in the frame memory into analog image signals, and 9 displays image signals. CR,T
It is a display. These devices are connected by a signal line called a system bus 10, as shown in Figure 1.
Image data and control signals generated by the MPU 6 are transmitted between each device. In this embodiment, a dedicated display bus 11. is also provided between the signal processing device 7 and the display device 8. , which speeds up data transfer.

First, recording of an image is performed as follows.

When an image recording command is input through the input device 5, the MP
U6 receives this command through system bus 10,
The A/D converter 2 is commanded to input an image. According to this command, the analog image signal input from input terminal 1 is
The signal is converted into a digital signal by the /D converter 2 and becomes a digital signal. The digital signal is sent to the display device 8 through the system bus 10, stored in the frame memory and displayed on the display 9. The MPU 6 sends an image signal compression processing command to the signal processing circuit 7.

Here, a signal processing device 7 as an embodiment of the present invention will be explained using FIG.

FIG. 1 is a configuration diagram of a signal processing circuit explaining the first embodiment of the present invention, in which 71 and 76 are data selectors that select input and output of data signals, and 72 is a ΔYUV compression circuit that performs ΔYUV compression processing. , 73 is Δ for performing ΔYUV expansion processing.
A YUV decompression circuit, 75 is a contour correction circuit that performs contour correction of the image signal, and 74 is a signal that controls the above-mentioned circuit by a control signal given from the MPU 6 or the display device 8 through the system bus 10 and the display system dedicated bus 11. This is a companding control signal generation circuit that generates. The signal processing circuit 7 that has received the data compression processing command sends a control signal to the display device 8 through the 1-display system dedicated bus 11, and takes in the digitized image signal in the frame memory through the display system dedicated bus 11 as well. In the signal processing circuit, the data taken in by the data selector 76 is transferred to the ΔYUV compression circuit 7.
2, and is controlled by the companding control signal generation circuit 74 to perform ΔYUV compression processing. Although this ΔYUV compression processing will not be described in detail here, it is a method currently used as an image compression processing means for CD=r. That is, Y, U, which indicates the brightness and color difference from each R, G, and B image signal.
Generate V signal and U.

■The signal is thinned out in the horizontal direction to reduce the amount of information to 1/2, and the difference between the U, V signal and Y signal (luminance signal) obtained through this processing is taken from the previous value, and the difference is coded. This is an information compression method that reduces the amount of data to 1/2 by performing a conversion process, and ultimately compresses the amount of information to 1/3. The compressed data thus obtained is output to the system bus 10 through the data selector 71, and is sequentially recorded on the optical disk device 3 shown in FIG. Needless to say, an index signal (or directory signal) indicating the contents and attributes of the image information to be recorded at this time is also recorded by the MPU 6 at the same time. By doing so, it becomes possible to record three times as many image signals as usual on the optical disc. Needless to say, the command section for performing these series of operations is stored in advance in the memory 4 so that it can be automatically executed in response to commands input from the input device 5. There is nothing different about it.

Next, when reproducing an image, a reproduction command is inputted from the input bag W5 in the same way as during recording when reproducing a zero image. In response to this command, the MPU 6 gives the optical disc device 3 the address on the optical disc of the data to be read and a read command. The optical disk device 3 reads compressed data and index signals recorded on the optical disk based on these instructions and sends them to the system bus. The read compressed data is input to the signal processing device 7. Here, the explanation will be given again using FIG. 1. The input compressed data is input to the ΔYUV decompression circuit 73 by a data selector 71 controlled by a companding control signal generation circuit 74 in the opposite manner to that during recording. Thereafter, under the control of the companding control signal generation circuit 74, a process completely opposite to the compression process is performed to restore the original digital image signal. Thereafter, the contour of this digital image signal is corrected by the contour correction circuit 75 and sent to the display device 8 through the data selector 76.

As a result of the above operations, the frame memory in the display device 8 has the following information:
Image blur caused by compression/expansion processing will be corrected and written, so an image with less discomfort will be displayed on the CRT display 9.Furthermore, when performing editing such as compositing images in this state, gives a data read command to the optical disk device 3 again, writes the image data obtained by decompression processing in the same manner into the same frame memory in the display device 8, and displays them in an overlapping manner. When the image edited in this way is recorded on the optical disk device 8 again, the same processing as described above is performed when recording the image. In other words, since the image that has been subjected to the -degree contour correction process is compressed and recorded, it is possible to obtain a reproduced image with little deterioration in image quality even when the image is reproduced and expanded again. In this way, since contour correction is performed each time compression/expansion processing is performed, an image with less deterioration in image quality can be displayed.

3 and 4 are explanatory diagrams of the contour correction circuit 75 in FIG. 1.

FIG. 3 is a block diagram of the contour correction circuit in FIG. 1, and FIG. 4 is an operation waveform diagram of each part in FIG. FIG. 3 shows a circuit configuration diagram for performing the well-known horizontal contour correction of an image. In FIG. Figure (a
)) is input to the delay circuit 32 and given a certain amount of time delay t as shown in FIG. 4(b). At the same time -(1
/2) is also input to the arithmetic circuit 34 which multiplies it by 2). The output signal of the delay circuit 32 is sent to a delay circuit 33 and adder circuits 36 and 37. The delay circuit 33 further delays the signal by a time t, and its output signal is input to the -(1/2) multiplication circuit 35. The adder circuit 36 adds the output signals of the multiplier circuits 34 and 35 and the delay circuit 32, and outputs a differential signal (d) of the signals. The degree of contour correction is determined by the amplitude of this differential signal (d).6 The addition circuit 37 adds this differential signal (d) and the output signal (b) of the delay circuit 32 to obtain the fourth
As shown in Figure (e), a signal whose contour has been corrected can be obtained.

Next, a second embodiment of the present invention will be described using FIGS. 5 and 6.

Similar to FIG. 1, FIG. 5 shows the signal processing device R7 in FIG.
1, in which the same functions as those in FIG. 1 are designated by the same reference numerals.

FIG. 6 is a block diagram of the contour correction circuit 77 in FIG. 5, and the same parts as in FIG. 3 are designated by the same reference numerals.

First, when recording a signal, the signal is compressed in exactly the same manner as in the first embodiment, and then sent to the optical disk device 3. However, at this time, the index signal indicating the content and attributes of the information should also include the number of companding processes, although no specific example will be given.
This can be easily realized by simply adding a few bits to the index signal using software.

The number of companding processes is incremented each time a companding process is performed.

Next, the time of reproduction will be explained.

During playback, compressed data is read out from the optical disk device 3 together with the index signal, similarly to the first embodiment. The compressed data is input to the signal processing circuit 7 shown in FIG.
3.

Thereafter, the contour is corrected in the contour correction circuit 77. In this embodiment, the data signal indicating the number of companding processes included in the index signal is transmitted to the companding control signal generating circuit 77.
The output signal is input to the decoder 78 through the input signal, and the result is supplied to the contour correction circuit 77 as a coefficient value control signal. The contour correction circuit 77 controls the degree of contour correction based on this control signal, and performs contour correction in accordance with the degree of image quality deterioration caused by multiple compression/expansion operations. A configuration diagram of the contour correction circuit 77 for this purpose is shown in FIG. Input signal (a
) is the same as the first embodiment until the differential signal (d) is obtained. Thereafter, the differential signal (d) is supplied to the coefficient circuit 39. - A coefficient value control signal is supplied to the force coefficient circuit 39 from the decoder 78 in FIG. 5 through an input terminal 40, and the amplitude of the differential signal (d) is determined by this control signal. therefore.

The adding circuit 37 in the latter stage adds a differential signal (f) with an amplitude corresponding to the number of companding processes, and the adding circuit 37 in the latter stage adds an amplitude corresponding to the number of companding processes, for example, the greater the number of times, the larger the differential signal (f). , it is possible to output an image signal with optimal contour correction. Thereafter, the output data signal is sent to the display device 8 through the display system dedicated bus -1 and outputted by the display 9 in the same manner as in the first embodiment. As described above, an image that has undergone optimal contour correction can be displayed.

By the way, when the image obtained in this way is combined with another image, the number of times of companding processing written in the index signals of both images may be different. In this case, the number of times of processing is determined, for example, by comparing the two numbers of times and selecting the larger one, or by finding the average of both.

Although the above has described contour correction in the horizontal direction, it goes without saying that the present invention is also effective in performing contour correction in the vertical direction by giving a line-by-line delay to the signal.

Contour correction can also be performed by calculations performed by an arithmetic processing device; for example, a method called discrete cosine transform (hereinafter referred to as DCT) is known as another compression method. Although this method provides a higher compression ratio than ΔYUV, it requires somewhat more complex calculations, so it is necessary to use a digital signal processor (DSP), a processing device (IC) dedicated to signal calculations, for boat fishing. . In this case, all signal companding processing is performed by software (arithmetic processing within the DSP), so it is advantageous to perform contour correction by software because the circuit size can be reduced. In this case, for example, as shown in Fig. 7, if the contour correction is done only in the horizontal direction, it will be 3x1, and if it is corrected in both the horizontal and vertical directions, it will be 3x1.
The calculation may be performed using a ×3 Laplacian filter. Furthermore, when changing the degree of contour correction, various coefficients may be prepared and selected depending on the number of times of companding.

[Effects of the Invention] As described above, according to the present invention, contour correction processing is performed for image blur caused by compression/expansion of an image signal, so that it is possible to display an image with less blur and no discomfort.

Further, the degree of contour correction is changed according to the number of times of compression/expansion processing, and optimal contour correction is constantly performed, so that image quality deterioration can be reduced even if compression/expansion processing is performed a plurality of times.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a signal processing circuit showing a first embodiment of the present invention, FIG. 2 is a system configuration diagram when the present invention is applied to an electronic filing device, and FIG. 5 is a diagram of a second embodiment of the present invention. FIG. 6 is a configuration diagram of a signal processing circuit showing an embodiment of the present invention, FIG. 6 is a configuration diagram of a contour correction circuit showing a second embodiment of the present invention, and FIG. FIG. 3 is an explanatory diagram of an example of coefficients for filter calculation. 7... Signal processing circuit, 32.33... Delay circuit, 34.35... Multiplication circuit, 36, 37
... Addition circuit, 39 ... Coefficient circuit, 7
5.77...Contour correction circuit, 78...Decoder. Fig. 2: Kuni 30 1, Fig. 3, Fig. 4, Fig. 6, Fig. 17

Claims (1)

[Claims] 1. Compression processing means for performing information compression processing on a digital image signal to obtain compressed data; compressed data sending means for sending the compressed data to a transmission system or a package system such as a storage device; In an image signal processing device, the image signal processing device includes an expansion processing means for performing information expansion processing on the compressed data obtained from the transmission system or the package system to obtain the original digital image signal, and an image signal processing device is provided at a stage subsequent to the expansion processing means. An image signal processing device comprising contour correction means. 2. In claim 1, processing history adding/sending means for adding and sending a compression/expansion processing history when the compressed data is sent to the transmission system or the package system; An image signal processing apparatus comprising: a determining means for determining the degree of contour correction by the contour correction means by referring to the compression/expansion processing history.