JPH06268987A - Digital compressed picture transmission and display device - Google Patents

Abstract

PURPOSE:To improve the operational reliability and safety of a digital picture transmission system by counting an interpolation amount at the time of the interpolation processing of picture data, comparing it with the entire amount of pictures and performing error display when the interpolation amount equal to or more than a certain threshold value is generated. CONSTITUTION:Data demodulated in a demodulation circuit 11 are inputted to an error correction circuit 12, the error correction circuit 12 corrects data errors on a transmission line and the output of the error correction circuit 12 is inputted to a digital picture decoder 30. Further, an error display control circuit 31 is connected to the digital picture decoder 30 and the digital picture decoder 30 outputs error information and the value of the interpolation amount to the error display control circuit 31. The error display control circuit 31 sums up the value of an interpolated area inside a frame, compares it with an entire data amount constituting the picture and performs the error display when the summed-up value of the interpolation amount becomes equal to or more than the threshold value. Thus, erroneous information pictures are recognized by a user.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a digital compressed image transmission system in image communication and image broadcasting, and relates to a display device on the receiving side thereof.

[0002]

2. Description of the Related Art In recent years, digital image transmission and digital image broadcasting systems have been developed, in which the conventional analog image transmission is digitally compressed and converted for transmission. The image compression process in recent years is based on the DCT process (Discreat cosin trans
form (discrete cosine transform processing) is the basic method, and the data compression efficiency is a method that can secure a practical compression rate as compared with the conventional method. The DCT process is a method in which an image is divided into blocks and divided into blocks, and the frequency components included in the region are used as data (for example, literature, Nikkei New Media 1991.3.4 Special Edition).

FIG. 4 shows a block diagram of a receiver in a digital image compression transmission system. This block diagram shows basic functions as a receiving device, and in an actual device, key control for operation, display control, power supply circuit and the like are included. Reference numeral 10 is a tuner for selecting the reception frequency of the display device. The output of the tuner 10 is input to the demodulation circuit 11. The demodulation circuit 11 is a circuit that demodulates the received signal into a digital signal. In digital transmission,
AM modulation and FM modulation used in the current analog transmission are not used, and the transmission format is PSK modulation (phase modulation) or QAM.
A modulation method for transmitting digital information such as modulation (quadrature amplitude modulation) is adopted. The data demodulated by the demodulation circuit 11 is input to the error correction circuit 12. Error correction circuit 12
Is a circuit for correcting a data error on a transmission line, and uses a system for correcting an error by adding an error correction code such as a Viterbi code or a Reed-Solomon code to the data to be transmitted. The output of the error correction circuit 12 is input to the digital image decoder 13. The digital image decoder 13 includes a circuit that processes image-compressed data on the transmission side, performs a process of converting the image data into image data, and outputs the image signal as a video signal. Since the data from the transmitting side is transmitted in frame units, the frame memories 14 and 15 temporarily store the image processed by the digital image decoder 13 and convert it into a field unit which is an NTSC signal format for output. Used as a buffer memory for. The reason why there are two systems of frame memories is that while the data of one frame is output, the data to be output next is decoded by the other frame memory. Further, the frame memories 14 and 15 are alternately switched to output data. An algorithm called motion compensation is also used as part of the data compression method. In other words, if the same data as the previous frame also exists in the next frame, only the amount of movement of that data is transmitted as data and the data compression rate of the previous frame stored in the receiving side is used. Has improved. The image compression method using the DCT process described above will be further described.

In this system, the transmission side divides the image data into N × N pixel units and performs DCT processing as shown in a of FIG. 3C, and further, the data is (N × L) × (N × K). )
It is a method in which the compressed digital data is decoded, converted into an image and displayed on the receiving side. In other words, since the image is digitized, compressed and transmitted, it is possible to provide an image that is less affected by noise on the transmission path and reception conditions. However, as the image processing in the reception state that exceeds the error correction function, the block portion in error when decoding the code is interpolated with the previous frame data,
Apparently there is no disturbance in the image. As the interpolation method, there are a fixed value interpolation method and a method of inferring from a peripheral image in which an error has occurred and performing interpolation. FIG. 3B shows a procedure of interpolation processing when the error exceeds the correction capability.

The data received in step S21 is decoded into a digital image. Using the decoded result, it is determined in step S22 whether the data has an error. If there is no error, writing to the frame memory is performed in step S24. If there is an error,
In step S23, the data in the same area as the area (or block) in which the error has occurred is read from the previous frame, and is written in the frame memory in step S24.

FIG. 3C, b, c, and d show display examples of decoded images. Image b in the figure is an example of an image of a frame before an error occurs, and image b in the figure
Is an image example when the next frame is normally received without any error. The image d in the figure is an example of an image in which an error has occurred in the shaded area and the replacement processing is performed with the data of the previous frame. If there is no error, the image with the number "56" should be displayed, but an error has occurred and the number "56" is no longer visible as a result of interpolation by the previous image.

[0007]

In analog transmission, the transmission line noise, the reception state, and the like appear on the image as noise and synchronization disturbance, so that the user can easily recognize the state of the image. However, in digital transmission, noise such as analog and synchronization disturbance do not appear on the image, and if an error occurs due to noise or the reception state, the area is interpolated with the data of the previous frame, so at this time the movement If the image is an early image or an image that is not related to the previous frame, erroneous information will be provided depending on the part where the error occurred. For example, if the replaced image as in the previous example is the number "56", which is a significant value, it will give a false recognition.

Therefore, according to the present invention, when compressed image data is decoded and an area in which an error occurs is interpolated by an image of a previous frame, the values of the interpolated area within one frame are cumulatively processed, Compared with the total amount of data that make up the image, if the cumulative value of the interpolation amount exceeds a certain threshold,
By displaying an error, the user can recognize that it is an incorrect information image, and thereby recognize the reception state, thereby improving the operational reliability and safety of the digital transmission system. The purpose is to provide.

[0009]

According to the present invention, in an image decoding display device which is a receiving device of a digital image transmission system, an image interpolation process which is an operation at the time of a data error which occurs when decoding compressed image data. In addition to the above, a means for accumulating the interpolation amount and a means for comparing the accumulated value with the entire image amount and displaying an error when the interpolation amount exceeds a certain threshold value are provided.

[0010]

By the above means, the image data is interpolated due to the noise on the transmission line and the error exceeding the error correction capability of the receiving device caused by the receiving condition. In comparison with the amount, an error can be displayed when an interpolation amount equal to or larger than a certain threshold value occurs. This allows the user to recognize that a part of the image currently displayed includes incorrect image information and that the reception state is not good. Therefore, the operational reliability and safety of the digital image transmission system are improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The figure is
The block diagram of the receiving device in the digital image compression transmission system is shown. This block diagram shows the basic functions of the receiving device. In the actual device, key control for operation, display control, power supply circuit, etc. Is included. Reference numeral 10 is a tuner for selecting the reception frequency of the display device. The output of the tuner 10 is input to the demodulation circuit 11. Demodulation circuit 1
Reference numeral 1 is a circuit for demodulating the received signal into a digital signal. In digital transmission, A like current analog transmission
A modulation method for transmitting digital information such as PSK modulation (phase modulation) or QAM modulation (quadrature amplitude modulation) is used as the transmission format without using M modulation or FM modulation. The data demodulated by the demodulation circuit 11 is input to the error correction circuit 12. The error correction circuit 12 is a circuit that corrects a data error on the transmission path, and uses a method of correcting an error by adding an error correction code such as a Viterbi code or a Reed-Solomon code to the data to be transmitted. The output of the error correction circuit 12 is input to the digital image decoder 30.

The digital image decoder 30 includes a circuit for processing the image-compressed data on the transmission side, converting it into image data, and outputting it as a video signal. Since the data from the transmitting side is transmitted in frame units, the frame memories 14 and 15 temporarily store the image processed by the digital image decoder 13 and convert it into a field unit which is an NTSC signal format for output. Used as a buffer memory for. The reason why there are two systems of frame memories is that while the data of one frame is output, the data to be output next is decoded by the other frame memory. Further, the frame memories 14 and 15 are alternately switched to output data. An algorithm called motion compensation is also used as part of the data compression method.

Further, an error display control circuit 31 is connected to the digital image decoder 30. The digital image decoder 30 outputs error information and the value of the interpolation amount to the error display control circuit 31. The error display control circuit 31 counts the amount of interpolation in decoding to make an error determination.

FIG. 1B shows an error display control circuit 31.
The operation (portion surrounded by a dotted line) is shown in a flowchart. The digital image decoder 30 decodes the data received in step S21 into a digital image. Using the decoded result, it is determined in step S22 whether the data has an error. If there are no errors,
Writing to the frame memory is performed in step S24.
If there is an error, data in the same area as the area (or block) in which the error has occurred is read from the previous frame in step S23, and the operation of the error display control circuit 31 (step S31) is performed. In step S31, the cumulative amount of interpolation is processed. When N × N dots are interpolated using Pe as the cumulative value, the calculation of Pe = Pe + (N × N) is performed. Pe is the total amount of interpolation in units of frames, and although not shown in the operation chart, Pe is reset at the beginning of each frame. Next, in step S32, the data amount of the entire image and the interpolation amount are compared, and it is determined whether the interpolation amount is greater than or less than the threshold value. Letting A be the threshold value, X be the number of dots in the horizontal direction of the image, and Y be the number of dots in the vertical direction.
(X · Y)) is used and is established when the interpolation amount is larger than the threshold value A. The value of A is a value determined by the system and has no particular limiting element. If the interpolation amount exceeds the threshold value, an error is displayed in step S33. As an error display, for example, as shown in FIG. 2 (A), there is an example of displaying "Error" in characters on the screen, but it is not limited to this. Any means that allows the user to recognize the presence of an error can be realized by light, sound, characters, a level meter, or directly by color switching of the error part. Further, as shown in FIG. 2B, a numerical value indicating the degree of error may be set based on the interpolation amount, and the degree and rate of the error may be numerically displayed and displayed as the credibility. The portion replaced by may be designated by a cursor or the like.

In the example of FIG. 2, an oblique line is shown in a portion where an error occurs and the image of the previous frame is replaced. After the error display, writing to the frame memory is performed (step S24).

In some images, the error portion may contain important information. For example, sports (swimming, 100m
The time display in the athletics etc.) or the numerical values such as stock information are important information for the user to make various judgments. In such a case, if an error is displayed, an erroneous determination can be prevented.

[0018]

As described above, according to the present invention,
When interpolating the area in which an error has occurred with the image of the previous frame, the values of the interpolated area within one frame are cumulatively processed and compared with the total amount of data making up the image. When the threshold value is exceeded, an error message is displayed to let the user recognize that the image is incorrect, and the reception status can be recognized accordingly. Operation reliability and safety in the digital transmission system Can be improved.

[Brief description of drawings]

FIG. 1 is a diagram shown for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing an error occurrence and a display example thereof.

FIG. 3 is an explanatory diagram of the configuration and operation of a conventional digital compressed image decoder.

[Explanation of symbols]

10 ... Tuner, 11 ... Demodulation circuit, 12 ... Error correction circuit, 14, 15 ... Frame memory, 30 ... Digital image decoder, 31 ... Error display control circuit.

Claims (1)

[Claims] 1. An image decoding display device which is a receiving device of a digital image transmission system, when a compressed image data is decoded, a data error occurs, and when an image interpolation process is performed, the interpolation amount is accumulated and a cumulative value is obtained. And a means for comparing the accumulated value and the total amount of the image and displaying an error when the interpolation amount reaches a certain threshold value or more. apparatus.