KR20040031868A - Method for coding moving picture - Google Patents

Abstract

PURPOSE: A method for encoding motion pictures is provided to reduce an amount of encoding calculation with reducing the size of a memory necessary for encoding by storing only coefficient values of macro blocks for intra coding. CONSTITUTION: If video signals are applied to an encoder, the video signals are transformed through DCT(Discrete Cosine Transform) and quantized to be encoded by macro blocks(S501). Among the encoded video signals, only vertical and horizontal DC and AC coefficients of first ends of the macro block to be directly used for intra prediction are stored(S502). Intra mode prediction is progressed by using the DC and AC coefficients(S503). In video frames applied thereafter, only intra macro blocks are selectively encoded(S504).

Description

Video coding method {METHOD FOR CODING MOVING PICTURE}

The present invention relates to a video encoding method, and more particularly, to a video encoding method capable of reducing the amount of calculation while reducing the memory load and volume when intra coding an image signal.

The current and future communication environment is rapidly changing beyond the distinction between wired and wireless areas, and between regions and countries.In particular, future communication environments such as IMT-2000 require users as well as video and audio. The trend is to build an environment that provides a variety of information in real time or comprehensively.

In addition, the development of a personal mobile communication system is not only a voice communication even in a cellular phone or a PCS, but also transmits text information as well as wirelessly accesses the Internet using a personal mobile communication terminal to acquire various information. Reached to the extent possible.

Moreover, the digital television system that processes video in digital data, transmits it in real time, and receives and displays it is one step further in order to maximize the benefits of digital information. A series of studies and their achievements are visible.

In particular, the research on compressing and processing video signals into digital data and real-time transmission of high-speed and high-definition data at higher speeds and richer amounts of information has already been made, and the commercialization is expected to be made at a considerable level. In addition, the transmission and reception of such digital video information is being provided to terrestrial broadcasting systems (sometimes cable broadcasting systems) including satellite broadcasting.

Recently, with the development of digital signal processing technology, methods of compressing and transmitting a large amount of video information through a limited bandwidth transmission channel have been developed. However, when an error occurs on the transmission channel, the quality of the reconstructed image is greatly reduced. Occurs.

At this time, error concealment techniques have been studied to recover near to the original image by supplementing the lost information from the neighboring information that is normally restored without using an error correction code to maximize the limited bandwidth.

In particular, in the case of an MPEG (Moving Picture Experts Group), when an error occurs, all information until the next sync signal is found is lost. In addition, since the motion compensation encoding technique is used, the influence of the damaged portion is continued over the subsequent frames.

The present invention is an IMT-2000 video terminal applying a motion determination value and an intra mode compression algorithm optimized for a hardware accelerator structure capable of enabling fast encoding and quality improvement of video data. Motion decision value of MPEG compression method, which is generally used for wireless image communication, is the most important because it has the largest amount of computation and directly affects the quality and the amount of bits.

Therefore, many studies on motion judgments have been made continuously, and recently, the motion judgments have the same image quality and bit rate as the full search using the diamond search pattern, and are most commonly used. A three step search method is used.

1 is a diagram illustrating a video encoder system according to the present invention.

As shown in FIG. 1, when an analog video signal photographing a real object is received, a digital conversion is performed, and a coding operation is performed to encode the same. The video signal converted into a digital video signal is subjected to discrete cosine transform in DCT (Discrete Cosine Transform: 1), and the video signal converted into frequency form is quantized in quantization unit 3 and then VLC (Variable Length Coding: 10). ) Is transmitted to the outside through entropy process.

In this case, when the encoded digital image is in the inter mode, a motion vector capable of predicting the previous image is generated from a motion predictor 9. The dequantized image data is inversely quantized by the inverse quantization unit 5 together with an entropy process for transmitting an encoded image to the outside to estimate the motion from the image frames, and then inverse discrete cosine in the inverse DCT 7. The reconstructed image is stored in the image memory 8 by the conversion.

If the video to be encoded is not the first video stored in the video memory 8, encoding is performed for intra prediction.

The intra prediction is to enable decoding at the decoder by referring to macroblocks in an image frame to be encoded.

2 is a diagram for describing an intra mode encoding process according to the prior art.

As shown in FIG. 2, when an image signal is encoded by discrete cosine transform and quantization, it is transmitted to the outside through variable length encoding, but thereafter, an inverse discrete cosine transform and inverse quantization is performed for intra mode prediction of an applied image signal. Save to memory via.

In the intra mode, since the prediction is performed by encoding only macroblocks in a video frame to be encoded, the calculation mode is larger than that of the inter mode, and takes up a lot of memory.

Since intra-mode encoding is performed in units of macroblocks in an image frame, memory corresponding to the entire image frame is allocated, and then predicted using DC and AC values of adjacent macroblocks and macroblocks in the macroblock to be encoded. Proceed.

In this process, the H.263 standard encodes the scans in GOB units one by one. As shown, intra encoding is performed using stored memory coefficient values of adjacent A macroblocks and C macroblocks, which are X macroblocks. .

Subsequently, when encoding the Y macroblock, encoding prediction is performed using coefficient values of the intra-encoded X macroblock and the upper D macroblock.

However, when encoding an image signal as described above, a memory for pixel values of the entire screen is allocated to each of the encoded image frames, and then DC and AC are calculated from coefficients of the upper macro block and the adjacent macro block of the macro block to be currently encoded. The values are compared to determine the prediction direction.

As a result, not only the memory is heavily loaded, but also the amount of computation for encoding loading and storing is increased.

In addition, the volume of the codec is increased due to the increase in the memory size and the amount of computation, which makes it difficult to use in recent miniaturization terminals.

According to the present invention, when encoding an image signal, only a coefficient value in a macro block is stored for intra prediction, and then used as information for intra prediction, thereby reducing a memory size and a calculation amount required for the encoding process. The purpose is to provide.

1 illustrates a video encoder system according to the prior art.

2 is a view for explaining an intra mode encoding process according to the prior art.

3 is a diagram for explaining a process of storing coefficients in a macro block for intra coding according to the present invention;

FIG. 4 is a view for explaining how to selectively store coefficients of a macro block among macro blocks in an image frame according to the present invention; FIG.

5 is a flowchart for explaining a video encoding method according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: DCT3: quantization unit

5: inverse quantization unit 7: inverse DCT

8: Image Memory 9: Motion Predictor

10: VLC

In order to achieve the above object, a video encoding method according to the present invention,

Performing discrete cosine transform and quantization of the video signal and encoding the macroblock in macroblock units;

Storing only the vertical and horizontal DC and AC components of the first stage of the blocks in the macroblock for intra mode prediction of the encoded image signal; And

And intra-coding the image signal applied afterwards by using horizontal and vertical DC components and AC components of the stored blocks.

Here, only the vertical, horizontal DC and coefficients of the upper and adjacent ends of the macroblock for intra coding are stored, and after the first image frame of the video signal, only the DC and AC coefficients of the intra-encoded macroblock are selectively stored to be intra It is characterized by the use in the encoding process.

According to the present invention, when intra coding an image signal, only DC and AC coefficients in macroblock units are used for intra prediction, thereby reducing the amount of computation while reducing the memory allocation.

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

3 is a diagram illustrating a process of storing coefficients in a macro block for intra coding according to the present invention.

As shown in FIG. 3, the macro block constituting the image frame includes four 8 * 8 pixel blocks and two color difference blocks. In the present invention, after allocating a memory corresponding to a value of mode pixels in an image frame to be intra-mode encoded, intra prediction is performed from adjacent macroblocks, and DC, AC of macroblocks required for intra-coding prediction is performed. Only the coefficient values are stored in memory, which greatly reduces the memory size.

That is, for intra mode encoding, only the first vertical, horizontal DC and AC coefficient values used for intra prediction are stored among the six pixel blocks in the macro block.

The horizontal coefficient values for the six pixel blocks in one macro block store only 48 pixel coefficient values including DC and AC coefficient values as shown, and the vertical coefficient values similarly include DC and AC coefficient values. Only the 48 pixel count values included are stored.

Therefore, conventionally, memory for all macro blocks in an image frame is allocated for intra mode encoding, and then intra prediction is performed using DC and AC coefficient values in each macro block. However, in the present invention, DC is actually used. In addition, only the AC coefficient values are stored in memory for intra prediction.

Thus, when the memory is allocated during intra coding, in the case of the QCIF video format (1 / 4CIF), the memory of 38016 size is conventionally allocated, but in the present invention, the memory of 1056 size can be allocated, and the size is significantly reduced.

In addition, since only the coefficients stored during intra encoding are loaded and predicted, the incubation time is shortened and the amount of calculation is reduced.

FIG. 4 is a diagram for describing a method of selectively storing coefficients of a macro block among macro blocks in an image frame according to the present invention.

As shown in FIG. 4, when an image frame continues to be input after the first image signal, macro blocks included in the image frame may be intra coded or intra coded.

By selectively selecting only intra-coded macroblocks in the video frame to store coefficient values, the number of memories can also be significantly reduced.

In addition, by using the stored coefficients of the selected macro block to perform intra mode prediction later, the amount of encoding computation can be reduced.

5 is a flowchart for explaining a video encoding method according to the present invention.

As shown in FIG. 5, the encoder performs intra mode encoding and inter mode encoding. An inter mode encoding is an encoding method for reducing an encoding amount by using a previous encoded video signal as it is, and intra mode encoding is an encoding to be referred to. It is a method of predicting the first encoded video signal having no video.

When an image signal is applied to the encoder, discrete cosine transform and quantization are performed. In the case of the first image frame, since there is no image to be referred to by the decoder, encoding is performed to predict from macroblocks in the image frame. )

In the present invention, the memory for the entire image frame is not allocated from the encoded video signal during intra mode encoding, and only the coefficients of DC and AC values of macro blocks directly used during intra prediction are stored (S502).

Intra mode prediction is performed using the coefficient values of the macro block, and in the encoded video signal applied later, only the intra coded macro block is stored, thereby reducing the amount of calculation.

In addition, the intra macroblock is selectively encoded in an image frame that is subsequently applied, thereby reducing the amount of intra-mode encoding. (S504)

As described in detail above, the present invention stores only coefficient values of macroblocks for intra encoding, thereby reducing the amount of encoding computation while reducing the memory size required for encoding.

In addition, only coefficients of an intra-encoded macroblock may be selectively encoded among macroblocks included in an image frame, thereby reducing encoding memory and computation amount in a subsequent encoding process.

The present invention is not limited to the above-described embodiments, and various changes can be made by those skilled in the art without departing from the gist of the present invention as claimed in the following claims.

Claims (3)

Performing discrete cosine transform and quantization of the video signal and encoding the macroblock in macroblock units; Storing only the vertical and horizontal DC and AC components of the first stage of the blocks in the macroblock for intra mode prediction of the encoded image signal; And And intra-encoding an image signal that is subsequently applied by using horizontal and vertical DC components and AC components of the stored blocks. The method of claim 1, And only vertical, horizontal DC, and coefficients of the upper and adjacent ends of the macroblock for intra coding are stored. The method of claim 1, And after the first image frame of the image signal, only DC and AC coefficients of the intra-encoded macroblock are selectively stored and used in the intra encoding process.