KR0169657B1 - Device for encoding moving picture signals - Google Patents

Abstract

The present invention is a video encoder configured by adding an error detection and compensation unit to an existing video encoder, and detects an error generated during encoding from a phase-inverted image before 1 frame and a motion compensation image before 1 frame, and compensates for the detected error. Motion estimation and compensation are performed on the reconstructed image before 1 frame generated by adding the error compensation image and the interframe difference image reconstructed by the inverse discrete cosine transform unit and the motion compensation image before 1 frame output by the motion compensator. Perform the process. Therefore, there is an advantage that not only can the encoding efficiency be improved at the time of encoding but also the image quality of the reconstructed image can be improved.

Description

Video encoder

1 is a block diagram showing the configuration of a general video encoder.

2 is a block diagram showing the configuration of a video encoder according to the present invention.

* Explanation of symbols for main parts of the drawings

30: subtractor 32: discrete cosine conversion unit

34 quantizer 36 variable length encoder

38: inverse quantizer 40: inverse discrete ring conversion unit

42: buffer 44: phase shifter

46, 52: adder 48: error detector

50: error compensator 54: frame memory

56: motion estimation unit 58: motion compensation unit

60: error detection and compensation unit

The present invention relates to a video encoder, and more particularly, to a video encoder for compensating for motion after detecting and compensating for image data errors generated during an encoding process.

Information is one of the most important resources and is called the information society in modern times. As the amount of information to be accepted and processed is increasing day by day, data compression is indispensable to effectively use the existing transmission band. In particular, since a digital video signal requires a lot of memory to represent information, video information compression has an effect of more efficiently storing, retrieving, and transmitting information.

For this reason, many compression methods for image data have been developed, and these image data compression methods can be divided into lossless coding techniques of lossy coding according to whether information is lost, and spatial redundancy existing in still images is intraframe. It can be divided into interframe encoding using temporal redundancy present in encoding and video.

In addition, it is divided into the first generation coding method which has little information loss and the international standard is completed, and the second generation coding method which uses the characteristics of human visual structure and image. The first generation coding techniques include spatial coding such as Pulse Code Modulation (PCM), Differential PCM (Delta PCM), Delta Modulation (Delta Modulation), and conversion coding such as Karhunen-Loeve, Fourier, Cosine, Harr, Hadamard, and Sine, Hybrid coding combining the above two, and Motion Compensated Coding used for video. Second-generation coding techniques include pyramid coding, anisotropic nonnormal prediction coding, contour-texture-based techniques, and encoding techniques based on directional decomposition.

Since the transmission of video has more considerations than the still image and the compression effect is more prominent, the development of a technique to obtain a high compression ratio is of great interest. In the HDTV broadcasting system or MPEG currently under development, the motion compensation coding uses the pixel circulation algorithm and the block matching algorithm, and the block matching algorithm is less accurate than the pixel circulation algorithm, but the real-time processing and the hardware implementation are simple. It is widely used in video systems in that respect. Here, the block matching algorithm divides an image into blocks of a predetermined size, obtains a motion vector for each block, and performs a discrete cosine transform on the prediction error between the image obtained by the motion vector and the original image, and then the discrete cosine transform coefficient. It is a technique of transmitting together.

In general, video encoders which are widely used have the effect of data compression by removing temporal redundancy through motion processing and spatial redundancy through discrete cosine transform.

FIG. 1 is a block diagram showing the structure of a general video encoder, and is used in many standardized encoders such as H.261, MPEG-1, and MPEG-2.

Referring to FIG. 1, the subtractor 10 generates a difference image between frames by subtracting a motion compensation image of an original image of a current frame and a reconstructed image of a previous frame, which are input in units of frames.

The discrete cosine transforming unit (DCT) 12 outputs a discrete cosine transform coefficient by performing discrete cosine transforming of the inter-frame difference image into, for example, a block of 8x8 pixels in order to remove the correlation between pixels.

The magnetizer Q: 14 quantizes the discrete cosine transform coefficients of the interframe difference image output from the discrete cosine transforming unit 12 at a predetermined quantization interval and outputs the quantized intervals.

The variable length encoder (VLC) 16 variably encodes the inter-frame difference image quantized by the quantizer 14 and transmits the variable length coder to a decoder (not shown) through a buffer (not shown).

That is, among the signals represented by 8 bits, for example, data with high frequency is represented by fewer bits, and data with less frequency is represented by many bits, thereby reducing the total number of bits representing the difference image.

An inverse quantizer (IQ) 18 is connected to the output terminal of the quantizer 14 and restores the quantized interframe difference image to a state before being input to the quantizer 14.

The inverse discrete cosine transform unit (IDCT) 20 is connected to the output terminal of the inverse quantizer 18 and before the inverse quantized inter-frame difference image is inputted to the discrete quantizer 18 by the inverse quantizer 18. Restore to state

The adder 22 adds the inter-frame difference image and the motion compensation image reconstructed by the inverse discrete cosine transform unit 20 and stores the reconstructed image of the previous frame in the frame memory 24.

The motion estimation unit (ME) 26 generally uses a block matching algorithm, estimates a similar portion between the input current image and the reconstructed image of the previous frame stored in the frame memory 24, and calculates the result of the position shift. Will output

The motion compensator (MC) 28 outputs the motion compensation image compensated by the motion vector to the subtractor 10 and the adder 22, respectively, by compensating the motion position of the reconstructed image of the previous frame stored in the frame memory 24, respectively. .

In summary, the above-described conventional video encoder generates a difference image by subtracting a motion compensation image that compensates for the movement of the previous frame from the image of the current frame by using the motion vector between the previous frame and the current frame, and encodes the difference image. However, when the specific image data processing, that is, the motion vector generation procedure is complicated, an error occurs in the generated motion vector, or the quality of the reconstructed image is degraded due to excessive quantization error.

Therefore, in order to solve the above-mentioned problems, the present invention detects the presence or absence of an error of a motion compensation image before 1 frame from the motion compensation image before 1 frame and the phase reversed image generated after motion estimation and compensation, The present invention provides a video encoder for motion compensating an error compensated image generated by compensating a motion compensated image of one frame before the frame with respect to the reconstructed image of one frame before the error.

In order to achieve the above object, a video incubator according to the present invention includes: a subtractor for subtracting and generating a motion compensation image for an original image of a current frame and a reconstructed image before one frame;

Discrete cosine transform unit for outputting a discrete cosine transform coefficient by the discrete cosine transform to convert the difference image output from the subtractor from the spatial domain to the frequency domain:

A quantizer for quantizing and outputting the discrete cosine transform coefficients of the difference image output from the discrete cosine transform unit at a predetermined quantization interval:

A variable length encoder for variable length encoding and outputting the quantized difference image by the quantizer;

An inverse quantizer for restoring the difference image quantized by the quantizer to a state before being input to the quantizer;

An inverse discrete cosine converting unit for restoring the inverse quantized difference image by the inverse quantizer to a state before being input to the discrete cosine converting unit:

Error detection and compensation unit for detecting the occurrence of an error for the motion compensation image before the first frame from the image before 1 frame and the motion compensation image before the 1 frame, and generating and outputting the error compensation image according to the detection result ;

An adder for outputting the difference image reconstructed by the inverse discrete cosine transform unit, the motion compensation image before the one frame, and the error compensation image output from the error detection and compensation unit, and outputting the reconstructed image of the previous frame;

A frame memory for storing, in frame units, an original image of one frame before the motion and error outputted from the adder;

A motion estimation unit for estimating a similar portion between the image of the current frame and the reconstructed image of one frame before and stored in the frame memory and outputting a result of the position movement as a motion; And

And a motion compensation image for outputting the motion position of the reconstructed image of the previous frame stored in the frame memory by the motion vector, the motion compensation image for outputting to the subtractor, the adder, the error detector, and the compensator. Characterized in that.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

2 is a block diagram showing the configuration of a video encoder according to the present invention, wherein the video encoder includes the subtractor 30, the discrete cosine transform unit (DCT: 32), and the quantizer (Q: 34) variable length encoder (VLC). : 36), inverse quantizer (IQ: 38), inverse discrete cosine transformer (IDCT: 40), adder 52, frame memory 54, motion estimator (ME: 56), motion compensator (MC: 58) ) And an error detection and compensation unit 60.

In addition, the error detection and compensation unit 60 includes a buffer 42, a phase changer 44, an adder 46, an error detector 48, and an error compensator 50.

Looking at the operation according to the configuration of Figure 2 as follows.

Here, the subtractor 30, the discrete cosine transformer 32, the quantizer 34, the variable length coder 36, the inverse quantizer 38, the inverse discrete cosine transformer 40, the frame memory 54, the motion weight Since the government 56 and the motion compensator 58 are the same as in FIG. 1, the description of the operation will be omitted, and the operation of the adder 52 and the error detection and compensation unit 60 will be mainly described.

In the error detection and compensation unit 60, the buffer 42 is generated as a previous frame by synchronizing the image of the current frame by one frame and synchronized with the motion compensation image of the previous frame. Save video in frame unit. Therefore, the image output from the buffer 42 becomes the image one frame before the current frame.

The phase inverter 44 phase-inverts the image one frame before output from the buffer 42 and outputs the image to the adder 46.

The adder 46 adds an image of one frame before the phase inverted by the phase inverter 44 and a motion compensation image of one frame before that output from the motion compensator 58 to be output to the error detector 48.

The error detector 48 detects whether an error occurs in the motion compensation image one frame before from the output of the adder 46. In other words, if the output of the adder 46 is zero, it means that the image of one frame before the phase inverted and the motion compensation image of one frame before generated by the motion vector are the same. This means that no error occurred in the motion compensation image. On the other hand, when the output of the adder 46 is not zero, it means that the image of one frame before and the motion compensation image generated by motion compensation by the motion vector are not the same. However, in this case, the reconstructed image before one frame used as a reference image for generating a motion compensation image before one frame is a quantization process in the quantizer 34 and an inverse quantization process in the inverse quantizer 40 as a previous step. Go through the back. Therefore, the motion compensation image before one frame cannot be the same as the image before one frame due to the quantization error generated therefrom. However, in consideration of the maximum quantization error that can occur during encoding, a threshold value that is an absolute value of the maximum difference value between an image before one frame and a motion compensation image before one frame is experimentally set. That is, the error detector 48 compares the output value of the adder 46 with the set threshold value, and if the output value of the adder 46 is smaller than the threshold value, the error detector 48 determines that no error has occurred in the motion compensation image before one frame. If the output value of the adder 46 is larger than the threshold value, it is determined that an error has occurred in the motion compensation image before one frame.

In the error compensator 48, if an error does not occur according to the error occurrence of the motion compensation image before 1 frame detected by the error detector 46, the error compensator includes an error compensated image having a zero value as a whole. Output to the adder 52.

On the other hand, when an error occurs, the difference image output from the adder 46 is generated as an error compensated image and output to the adder 52.

In the adder 52, the inter-frame difference image reconstructed by the inverse discrete cosine transform unit 40 and the motion compensation image before one frame output from the motion compensator 58 and the error output from the error detection and compensator 60 The compensation image is added and stored in the frame memory 54 as a reconstructed image of one frame before motion and error is compensated.

On the other hand, the motion estimation unit 56 and the motion compensation unit 58 compensates for the motion of one frame before the frame by compensating the motion position of the reconstructed image one frame before, which is stored in the frame memory 54 by the motion vector, as in the prior art. Output the video.

As described above, in the video encoder according to the present invention, an error generated during encoding is detected from a phase-transformed image before 1 frame and a motion compensation image before 1 frame, and an error compensation image and an inverse discrete output generated to compensate for the detected error are included. Coding efficiency is improved by performing motion estimation and compensation process on the reconstructed image before 1 frame generated by adding the inter-frame difference image reconstructed by the cosine transform unit and the motion compensation image before 1 frame output from the motion compensator. Not only can it increase, but there is an advantage of improving the quality of the reconstructed image.

Claims (3)

A subtractor 30 for generating a difference image by subtracting an original image of a current frame and a motion compensation image of one frame before the frame is input: a difference image output from the subtractor 30 from a spatial domain to a frequency domain Discrete cosine transform unit 32 for outputting discrete cosine transform coefficients by the discrete cosine transform to transform: The quantized discrete cosine transform coefficients of the difference image output from the discrete cosine transform unit 32 at a predetermined quantization interval A quantizer 34 for variable length coding to output the quantized difference image quantized by the quantizer 34. A quantizer 34 for inputting the quantized difference image quantized by the quantizer 34 to the quantizer. Inverse quantizer 38 for restoring to a state before the restoration: Restoring the inverse quantized difference image in the inverse quantizer 38 to a state before being input to the discrete cosine transforming unit 32 Inverse discrete cosine transform unit 40: an error detection and compensation unit for detecting an error occurrence of an image before 1 frame and a motion compensation image before 1 frame, and generating and outputting an error compensation image according to a detection result 60; To add the difference image reconstructed by the inverse discrete cosine transform unit 40, the motion compensation image one frame before, and the error compensation image output from the error detection and compensation unit 60, and output the reconstructed image of the previous frame. An adder (52) L a frame memory (54) for storing a reconstructed image of a frame before the frame compensated for the motion and error output from the adder (52); A motion estimation unit (56) for estimating a similar portion between the image of the current frame and the reconstructed image of one frame before and stored in the frame memory (54) and outputting a result of the position movement as a motion vector; And a motion compensator for outputting a motion compensation image of one frame or more, which is compensated by the motion vector, of the reconstructed image of the previous frame, stored in the frame memory, to the subtractor, adder, and error detection and compensation unit. 58). According to claim 1, wherein the error detection and compensation unit 60 includes a buffer for outputting the image of the current frame as one frame before the delay of the image of the current frame by one frame; A phase inverter (44) for phase inverting the image of the previous frame output from the buffer (42); An adder (46) for adding the one-frame previous image phase-inverted by the phase inverter (44) and the motion compensation image of the previous frame output from the motion compensation unit; An error detector 48 for comparing the difference image output from the adder 46 with a predetermined threshold value and detecting the occurrence of an error with respect to the motion compensation image before one frame according to a comparison result; And an error compensator 50 for supplying the difference image output from the adder 46 or the image having zero value to the adder 52 as an error compensation image according to the detection result of the error detector 48. Video encoder, characterized in that consisting of). The video encoder according to claim 2, wherein the threshold value is a value obtained by taking an absolute value with respect to a maximum difference value that may occur between the image before one frame and the motion compensation image before one frame in consideration of a quantization error.