JPH0230284A - Receiver in picture transmission system - Google Patents

Abstract

PURPOSE:To prevent deterioration in the picture quality of a picture element block by replacing a picture element data of a picture element block whose received reference value is discriminated to be inadequate with an interpolation picture element data obtained through the use of a picture element data with high correlation. CONSTITUTION:A code fed to an input terminal 40 is applied to a synchronizing separator circuit 44, where a synchronizing code is separated and fed to a timing control circuit 46. The timing control circuit 46 controls a switch 42 to apply a maximum value and a minimum value to an S/P converter 48 and the separated code to an S/P converter 50. A discrimination circuit 60 checks whether or not an output of a maximum value latch circuit 52 is larger than an output of a minimum value latch circuit 54, and regards it to be in the presence of a transmission error if smaller and sends a discrimination signal to a scan converter 64. The scan converter 64 converts the discrimination signal into a signal representing the screen position of a picture element data included in a relevant picture element block and replaces the picture element in error with a picture element of the just preceding screen in a frame memory 68.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device in an image transmission system.

[Conventional technology]

A method of compressing the transmission band of an image signal, specifically a television signal, is to divide one image into pixel blocks each consisting of a predetermined number of pixels, and then calculate the range of the maximum and minimum values of the pixel data in the pixel block. There is a known encoding method that divides pixel data into a predetermined number of sections and converts each pixel data into a code (hereinafter referred to as a division value) indicating the section to which it belongs.

In this method, for each pixel block, any two data of its maximum value, minimum value, and difference (dynamic range) thereof, and divided value data for each pixel are transmitted.

FIG. 2 is a schematic block diagram of a conventional image transmission apparatus that normalizes each pixel data using maximum and minimum values and transmits the divided value data.

It is assumed that the image data handled here is quantized with 8 bits per sample. Digital image data is input to the input terminal 10 in the normal order of horizontal scanning lines, and the pixel blocking circuit 12 converts the image of one frame or one field into vertical (vertical direction) m''#I elements and horizontal ( horizontally) divided into pixel blocks each consisting of n pixels, and sequentially outputs constituent pixel data for each pixel block.

The maximum value detector 14 detects the maximum value from m x n pixels in each pixel block, and the minimum value detector 16 detects the minimum value. The timing adjustment circuit 18 includes the maximum value detector 1
The output of the blocking circuit 12 is delayed by a time corresponding to the detection work time of 4 and the minimum value detector 16, and pixel data is output in a predetermined order for each pixel block. The division value conversion circuit 20 converts a division value ( k
bits). For example, k is about 3.

22.24.26 is a parallel to serial converter,
Convert parallel data to serial data. Under the control of the timing control circuit 32, the switch 30 is configured to:b,
Connect C and A contacts in this order.

That is, for each pixel block, the switch 30
The maximum value data, the minimum value data, and the divided value data of each pixel are applied to the FIFO type buffer 34 in this order. A buffer 34 is provided for adjustment with the transmission bit rate. The synchronization addition circuit 36 adds a synchronization code to the beginning of the data string from the buffer 36, and sends it out from the output terminal 38 to a transmission line or recording medium. In addition to the switch 30, the timing control circuit 34 also collectively controls the operation timing of each of the circuits described above.

When m and n are 4 and k is 3, the amount of data for one pixel block is 128 bits (=8 bits x 16), but with this encoding it becomes 64 bits (=8 + 8 + 3 x 1).
6) and can be compressed to 1/2.

[Problem to be solved by the invention]

However, in this encoding method, the pixel data is once normalized using the dynamic range, and then the normalized data is compressed and encoded, so dynamic range information for each pixel block is essential for decoding. . For example, the maximum value and minimum value data is the compressed code of each pixel (
If a transmission error occurs in the maximum value data or minimum value data, image data cannot be restored for that pixel block.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a receiving device that can restore the image of a corresponding pixel block as much as possible even when reference data for decoding is lost in an image transmission system that performs coding in units of pixel blocks. With the goal.

[Means to solve the problem]

A receiving device according to the present invention divides all pixels constituting an image into pixel blocks each consisting of a plurality of pixels, encodes each pixel value in each pixel block based on a predetermined reference value, and codes the reference value and its code. In an image transmission system that transmits encoded pixel data, a receiving device decodes received encoded pixel data according to a received reference value to restore an image, and determines whether the received reference value is appropriate according to a predetermined rule. and an alternative means for substituting a pixel in a pixel block determined to be inappropriate by the determining means with interpolated pixel data obtained using data of a pixel having a high correlation with the pixel. It is characterized by

[Effect]

The determination means allows it to be known whether or not there is an error in the reference value required for decoding. Furthermore, for data of pixels that cannot be restored due to an error in the reference value, sufficiently similar data can be obtained by appropriately selecting pixels with strong correlation. Therefore, by replacing pixels in a pixel block with an error in the reference value with interpolated pixels obtained using pixels with a strong correlation, it is possible to prevent the image quality from significantly deteriorating in the part of the pixel block. .

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration block diagram of an embodiment of the present invention,
Functionally, it is a receiving device corresponding to the transmitting device shown in FIG. Note that it is assumed here that the maximum value data is always inputted before the minimum value data.

In FIG. 1, the input terminal 40 has the output terminal 3 in FIG.
The code string output from 8 is input via the transmission path. The code string at the input terminal 40 is applied to a switch 42 and a synchronous separation circuit 44 , and the synchronous separation circuit 44 separates the synchronous code and applies it to a timing control circuit 46 . The timing control circuit 46 controls the switch 4 based on the synchronization code.
2 to control the operating timing of each illustrated circuit.

By switching the switch 42, the maximum value MAX and the minimum value M
IN is applied to the serial/parallel (S/P) converter 48 from the a contact, and the division value code is applied to the S/P converter 50 from the b contact. Among the outputs of the S/P converter 48, the first code (if there is no error, the maximum value MAX) is latched by the maximum value latch circuit 52, and the next code (if there is no error, the minimum value old N) is latched by the minimum value latch circuit 54. The latch circuits 52 and 54 hold the maximum and minimum values, respectively, until the maximum and minimum values of the next pixel block are input.

The divided value inverse conversion circuit 56 refers to the maximum value and minimum value latched in the latch circuits 52 and 54, and converts the S/P converter 5.
The output of 0 (divided value data) is converted into a representative value of each divided area and output. The scan converter 58 converts the output of the divided value inverse conversion circuit 56 in units of pixel blocks into a raster format.
Convert to scan.

The determination circuit 60 checks whether the output of the maximum value latch circuit 52 is greater than the output of the minimum value latch circuit. That is,
If the output of the maximum value latch circuit 52 is smaller than the output of the minimum value launch circuit, it can be assumed that there was a transmission error in the maximum value or the minimum value. After the determination signal from the determination circuit 56 is time-adjusted by the timing adjustment circuit 62,
applied to scan converter 64; The scan converter 64 converts the determination signal into a signal indicating the screen position in raster scan of the pixel data included in the corresponding pixel block. Then, the scan converter 64 connects the switch 66 to the a contact point for pixels in the pixel block without an error, and connects the switch 66 to the b contact point for pixels in the pixel block in which an error has occurred.

Immediately, the switch 66 switches the pixel of the pixel block in which the error occurred to the previous screen of the frame memory (or
Furthermore, the previous image signal is used instead.

Therefore, from the output terminal 70, if there is no error,
A restored image signal is obtained from the received data, and if there is an error, an image signal corrected and supplemented with the image from one frame before is obtained. The output of switch 66 is input to frame memory 68, thereby updating the image stored in frame memory.

In this embodiment, the case where maximum value and minimum value data are transmitted as dynamic range information is taken as an example, but the present invention is not limited to this. In addition, even in the case of a transmission method in which vector quantization is performed after division value conversion, or in the case of other transmission methods, transmission errors can be confirmed under some kind of regularity. By checking the consistency, the presence or absence of an error can be uniformly determined, and the previous screen can be used as an alternative according to the result of this determination. In addition, in the above embodiment, pixels with strong correlation are
Although a pixel on the previous screen is selected and the data of this pixel is directly used as interpolation data, interpolated pixel data may be obtained using pixels on a subsequent screen or pixels in an adjacent pixel block.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, if an error occurs in the reference value for decoding, it can be detected without adding redundant data such as an error correction code, and the error can be detected without adding redundant data such as an error correction code. Since the pixels in the pixel block of the error part are replaced with interpolated pixel data obtained from pixels with high correlation, the system becomes more resistant to transmission errors, and image quality deterioration due to transmission errors can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the configuration of an embodiment of the present invention, and FIG. 2 is a block diagram of the configuration of an image transmitting apparatus. 40--Input terminal 44-Synchronization separation circuit 46--
Timing control circuit 52-Maximum value latch circuit 54.
-0. Minimum value latch circuit 56~・Divided value inverse conversion circuit 5
8.64-・- Scan converter 6〇- Judgment circuit 6L- Frame memory 70-・- Output terminal

Claims (1)

[Claims] Image transmission in which all pixels constituting an image are divided into pixel blocks each consisting of a plurality of pixels, each pixel value is encoded based on a predetermined reference value for each pixel block, and the reference value and its encoded pixel data are transmitted. In the system, a receiving device decodes received encoded pixel data according to a received reference value to restore an image, the determining means determining whether the received reference value is appropriate according to a predetermined rule, and the determining means 1. A receiving device comprising an alternative means for substituting a pixel in a pixel block determined to be inappropriate by interpolated pixel data obtained using data of a pixel having a high correlation with the pixel.