JPH01144873A - Image error correcting method - Google Patents

Abstract

PURPOSE:To decrease deterioration in the quality of picture by replacing an image based on the moving information of an image signal at a time when an error occurs in an image signal on a transmission line. CONSTITUTION:In an error detection circuit 102, a transmission error on a transmission line is detected by an error detecting check bit, and a detection result is supplied to a switch 109. In a moving information separating circuit 103, moving information multiplexed on the transmission side is separated, and supplied to switches 108, 112. By an inverse quantization circuit 104, an adder 105, a prefix prediction circuit 106, an inter-frame prediction 102, and by a switch 108, a predicted decoding is executed adaptively based on the moving information. And, thus decoded image signal is supplied to the switch 109, a one-line delay circuit 110, and a one-frame delay circuit 111. In the event of an error, a one-frame-preceding image signal is selected for a still image by the switch 109 based on the moving information but a one-line-preceding image signal for a moving image, and the selected signal is outputted to an output terminal 113. As a result, an excellent correction can be ful-filled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to image error correction that corrects, by replacement, image errors that occur in decoded images due to code errors that occur on a transmission path when an image signal is predictively coded and transmitted. It is about the method.

2. Description of the Related Art In recent years, when transmitting image signals, high-efficiency encoding devices (hereinafter referred to as encoders) have been developed, which eliminate redundancy contained in image signals and transmit them more efficiently by performing band compression such as predictive encoding. The development and practical application of a chemical conversion device) is progressing. One of the problems with this encoding device is code error processing in the transmission path. If a code error occurs in the transmission path (when an error correction code is used, an error that exceeds the correction ability occurs), when a predictively encoded image signal is decoded, an erroneous code point will appear in the decoded image. Starting from this point, a trailing image error occurs, resulting in an extremely unsightly image. In conventional encoding devices,
This problem has been dealt with by replacing the erroneous image portion with, for example, an image from one frame before. (For example, JP-A-62-6
1485 Publication) The above-mentioned conventional image error correction method will be described below with reference to the drawings.

FIG. 4 is a block diagram of an interframe predictive decoding device using a conventional image error correction method. In Figure 4, 40
1 is an input terminal for an image signal subjected to interframe predictive coding;
402 is a switch, 403 is an adder, 404 and 405 are frame memories, 406 is a switch, 407 is an error detection unit, and 408 is a display device.

The operation of the interframe predictive decoding device configured as described above will be described below.

On the transmitting side, the difference data of the interframe encoded image signal is inputted to the switch 402 from the input terminal 401. If there is no error in the transmitted data, switch 40
In the adder 403, the difference data inputted to 2 is added to the decoded image signal of the previous frame which has been delayed by one frame in the frame memory 404, thereby being decoded into the original image signal and displayed on the display device 408. When the error detector 407 detects an error based on this decoded image, the delayed error-free decoded image signal of two frames before is added to the adder 403 via the switch 406 in the frame memory 405. It will be done. At this time, the switch 402 is turned off, and the adder 403 outputs the image signal of two frames before as it is and supplies it to the display device 408. Therefore, an error-free image will be displayed on the display bag W408.

Problems to be Solved by the Invention However, in the above configuration, for example, FIG.
When a moving image as shown in a) is transmitted, replacement is performed at the location where the transmission error occurs as shown in the figure). In other words, for still images, correct error correction is performed by replacing frames, but for moving images, the problem is that the correction is incorrect.

In view of the above-mentioned problems, the present invention provides an image error correction method that performs good error correction for both still images and moving images.

Means for Solving the Problems In order to solve the above-mentioned problems, the image error correction method of the present invention, when an image signal is decoded, when a transmission path error occurs, based on the motion information of the image signal, a video error correction method is provided. This method is based on a method in which images are replaced within a field for a still part, and images are replaced between frames for a still part.

The present invention uses the above-described method to replace errors in the still image portion with an image from one frame before, and replace errors in the moving image portion with samples without errors above, below, or before and after within the field. It is possible to obtain a good corrected image even in the moving image part.

Embodiment Hereinafter, an image error correction method according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block configuration diagram showing the configuration of a predictive decoding device using an image error correction method in a first embodiment of the present invention. In FIG. 1, 101 is an input terminal for a predictively encoded image signal, 102 is an error detection circuit, 103 is a motion information separation circuit, 104 is an inverse quantization circuit, 105 is an adder, 106 is a previous value prediction circuit, 107 is an inter-frame prediction circuit, 108 and 109 are switches, 110 is a 1-line delay circuit, 111 is a 1-frame delay circuit, 112 is a switch, 113 is an output terminal for the decoded video signal, 114
is an image error correction unit.

The operation of the predictive decoding device configured as described above will be described below.

In the encoding device on the transmitting side, the previous value prediction and the inter-frame prediction are adaptively switched according to the motion information of the image signal, and the difference data of the encoded image signal and the motion information are combined with an error detection check. A signal containing bits is generated and input to the input terminal 101 of the decoding device via a transmission path. In the error detection circuit 102, a transmission error in the transmission line is detected by the error detection check bit, and the detection result is supplied to the switch 109. The motion information separation circuit 103 separates the motion information multiplexed on the transmitting side and supplies it to the switches 108 and 112. Inverse quantization circuit 104. Adder 105° Previous value prediction circuit 106. In interframe prediction 107 and switch 108, predictive decoding is adaptively performed based on the motion information, and the decoded image signal is transferred to switch 109.1 line delay circuit 11.
It is supplied to the 0 and 1 frame delay circuit 111. If there is an error, the switch 109 selects the image signal of the previous frame in the case of a still image, or selects the image signal of the previous frame in the case of a moving image, based on the motion information, and outputs it to the output terminal 113. Output from

As described above, according to the present invention, when an error occurs in a line in a moving image as shown in the example of FIG. Since the correction is performed by replacing the line, better correction is possible than when correction is performed only using the image before the frame.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of the error correction section for explaining the error correction method in the second embodiment of the present invention. FIG. 3 shows a modification of the configuration of the image error correction unit 114 in FIG.
is a motion information input terminal, 304 and 305 are switches, 3
06 is a one-line delay circuit, 307 is a one-frame delay circuit, and 308 is an output terminal for an image signal subjected to image error correction.

The operation of the image error correction section configured as above will be explained. Unlike the example in FIG. 1, in this embodiment, the one line delay circuit 306 and the one frame delay circuit
By taking the input No. 7 from the error correction output, replacement can be performed in accordance with the motion even when an error spans multiple frames or multiple lines.

Although this embodiment has been described in a manner in which motion correction is not performed on the signal before the frame, frame replacement is possible by adding and transmitting motion vector information and motion information based on it on the sending side. It is possible to perform more appropriate correction by increasing the amount of correction.

In addition, in this embodiment, image replacement within a field has been explained using line replacement as an example, but this can also be done by line interpolation using multiple lines. This can also be done by replacement or interpolation.

Further, in this embodiment, predictive coding was used as the coding method, but this is not limited to simple A/D conversion digital coding (PCM) or other high-efficiency coding (for example, orthogonal transform coding). , subsampling encoding)
But it is possible.

Furthermore, although this embodiment has been described as a method for correcting errors in a transmission path, it is also applicable to recording/reproducing systems such as magnetic recording/reproducing.

Effects of the Invention As described above, the present invention performs image replacement based on motion information of the image signal when an error occurs in the transmission path of the image signal, so that image correction for the moving image can be performed satisfactorily. Image quality deterioration can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a predictive decoding device using the image error correction method according to the first embodiment of the present invention, and FIG. 2 is an explanatory diagram of an example of an image error corrected image according to the first embodiment of the present invention. Third
The figure is a block diagram of an image error correction unit using the image error correction method in the second embodiment of the present invention, FIG. 4 is a block diagram of a predictive decoding device using the conventional image error correction method, and FIG. t
ag, (bl is an explanatory diagram of an example of a conventional image error correction image. 102...Error detection circuit, 103...
・Motion information separation circuit, 104...Inverse quantization circuit, 105...Adder, 106...Previous value prediction circuit, 107...Interframe prediction circuit, 1
08,109...Switch, 110...
・1 line delay circuit, 111...1 frame delay circuit, 112...switch, 114...
...Image error correction unit, 304, 305...Old...Switch, 306...L line delay circuit, 307...
...1 frame delay circuit, 403... Adder, 404... Frame memory, 405...
...Frame memory, 406...Switch, 4
07...Error detection unit, 408...Display device. Name of agent: Patent attorney Toshio Nakao
= Figure 2 Figure 3

Claims (1)

[Claims] When decoding an encoded image signal, when a transmission path error occurs, image replacement or interpolation within the field is performed for the moving image portion, and image replacement within the field is performed for the still image portion, based on the motion information of the image signal. is an image error correction method characterized by performing image replacement or interpolation between frames.