KR100627494B1 - Moving picture encoder and method for c0ding moving picture using the same - Google Patents

Abstract

The present invention discloses a video encoder and an encoding method using the same to increase coding efficiency by determining whether a coefficient after quantization exists, a VLC scanning direction, a run, a level, and a sine information in a video encoder. Disclosed is a discrete cosine transform (DCT) for discrete cosine transforming an image signal applied from the outside; A process control unit which quantizes the discrete cosine transformed video signal in the DCT and processes them for variable length encoding and reference image reconstruction; An image memory for storing a reference image reconstructed by the process control unit; A motion predictor that compensates by predicting motion based on a reference image stored in the image memory; And a VLC for performing variable length encoding by using a value processed for variable length encoding by the process control unit.

Video, process, VLC, run, level, sine,

Description

Video encoder and encoding method using the same {MOVING PICTURE ENCODER AND METHOD FOR C0DING MOVING PICTURE USING THE SAME}

1 is a diagram showing the structure of a video encoder for encoding a video signal according to the prior art.

2 is a diagram illustrating a structure of a video encoder for encoding a video signal according to the present invention.

3 is a flowchart for explaining a video encoding process according to the present invention;

4 is a flowchart illustrating a process of processing an image coded signal in a process control unit according to the present invention.

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

11: DCT 14: process control

15: motion predictor 16: video memory

20: VLC

The present invention relates to a video encoder and an encoding method using the same. More specifically, a video coded signal, which has undergone DCT and quantization, is preprocessed and stored for reference image reconstruction and VLC, and then selectively VLC, inverse quantization, and inverse DCT. The present invention relates to a video encoder having an increased coding processing efficiency and a coding method using the same.

The current and future communication environments are rapidly changing beyond the distinction between wired and wireless areas and regional 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 various information in real time or comprehensively.

In addition, the development of the personal mobile communication system is not only a voice communication in the cellular phone or PCS, but also to transmit text information as well as to access the Internet wirelessly using a personal mobile communication terminal, or to watch videos on TV It is being developed to transmit the data.

In particular, a digital television system that processes a video into digital data, transmits the data in real time, receives the video, and displays the video, and the video transmitted in real time is becoming an essential element in a personal portable terminal using the IMT2000.

In the related art, the portable terminal transmits and receives only human voice. However, due to the development of multimedia and the development of digital information processing technology, various information such as voice and video can be transmitted.

Above all, this technology has been commercialized. First of all, the analog video signal is subjected to special digital processing such as quantization and variable length encoding, and then included in the digital information and transmitted. The development of video compression technology, which allows abundant information transmission and reception, contributed greatly.

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, if 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), if 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 that applies an optimized motion decision value and an intra mode compression algorithm to a hardware accelerator structure that can enable 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 structure of a video encoder for encoding a video signal according to the prior art.

As shown in FIG. 1, when a video signal photographing a real object is received, a digital conversion is performed, and then an encoding operation is performed to compress the video signal. The digitally converted video signal is subjected to discrete cosine transform in DCT (Discrete Cosine Transform 1), and the image signal converted in frequency form is quantized in quantization unit 3 and then variable in VLC (Variable Length Coding 10). It is transmitted to the outside through the field encoding (entropy) process.

In this case, when the encoded image is an inter mode, a motion vector capable of predicting the previous image is generated from a motion predictor 9. The decoded image frame is reconstructed by the inverse quantization unit 5 and the inverse DCT 7 and stored in the image memory 8. The image stored in the image memory is a reference for predicting motion of an image to be encoded later. Use it as a video.

When the next input image is defined as a P picture as an inter mode, after motion prediction and compensation are performed on a block of each image frame, the macro block of the intra mode converts the current image value to an intra image frame encoding. The encoding is performed in the same manner.

The video bitstream encoded by the encoder is transmitted to the decoder and decoded through the same procedure as that encoded by the encoder.

In particular, the macro block type information and the like, which are inter mode encoded, are inserted into the macro block header information together with the macro blocks of the encoded video frame and transmitted.

The decoder decodes the macroblock type information included in and inserted into the video bitstream as described above, and performs decoding according to each macrotype information.

Although shown in the figure, 2a and 2b, which are not described, represent adders.

However, if the encoding is performed in the inter mode and the intra mode as described above, the coefficient value may or may not exist or repeatedly repeats VLC, inverse quantization, and inverse DCT for 64 pixels of each block constituting the macroblock. There is a problem in that the encoding efficiency is lowered.

In particular, the repeated amount of computation imposes a large amount of computation on the video codec, which causes the codec to slow down.

According to the present invention, when a video signal is encoded, a quantized video coded signal is processed and stored in advance in a unit of pixels constituting each block by using a series of processing for reference image reconstruction and VLC. It is an object of the present invention to provide a video encoder having an increased processing efficiency and an encoding method using the same.

In order to achieve the above object, the video encoder according to the present invention,

Discrete Cosine Transform (DCT) for performing discrete cosine transform of an image signal applied from the outside;

A process control unit which quantizes the discrete cosine transformed video signal in the DCT and processes them for variable length encoding and reference image reconstruction;

An image memory for storing a reference image reconstructed by the process control unit;

A motion predictor that compensates by predicting motion based on a reference image stored in the image memory; And

And a VLC for performing variable length encoding by using a value processed for variable length encoding in the process control unit.

Here, the process control unit quantizes the image coded signal processed by the DCT for variable length coding, and then obtains the run, level, and sine values of the pixel coefficients of the image blocks according to the scanning direction of the variable length coding. In the VLC, only the pixel coefficient corresponding to a level value is variably encoded.

The process controller performs quantization according to the input order after DCT for reconstructing the reference image, inverse quantization and inverse DCT, and the process controller inverses only pixel coefficients having level values among the processed pixel coefficient values. It is characterized by DCT.

In addition, the video encoding method according to another embodiment of the present invention,

Performing discrete cosine transform on the video signal input to the video encoder;

Processing and storing the pixels constituting the block in a scanning order for the variable cosine transformed image coded signal, and processing and storing the pixels constituting the block for reconstructing a reference image;

 Pre-storing a run, level, and sine value with respect to a value in which the pixels are processed and stored; And

 Whether the variable length encoding or the reference image reconstruction is performed using the stored run, level, and sine values, and when variable length encoding is performed, a variable value corresponding to the level value is stored among the stored run, level, and sine values. Performing VLC on the pixel coefficients; Characterized in that it comprises a.

Here, when restoring a reference image using the stored run, level, and sine values, inverse quantization and inverse DCT are performed on only pixel coefficients corresponding to level values among the stored run, level, and sine values. It is done.

According to the present invention, when the image signal is encoded, the quantized image coded signal is processed and stored in advance for 8x8 block units for the reference image reconstruction and the VLC, thereby storing the codec of the entire codec.

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

2 is a diagram illustrating the structure of a video encoder for encoding a video signal according to the present invention.

As shown in FIG. 2, the video encoder performs encoding by performing a discrete cosine transform and quantization on a video signal applied from the outside, and reconstructs the quantized video coded signal to reencode the video signal previously applied. In the case of the same signal, encoded data of the transmitted video signal is reduced by using the encoded video.

The video coder quantizes a discrete cosine transform (DCT) 11 for performing discrete cosine transform on the video signal transmitted from the outside, and quantizes the discrete cosine transformed video signal in the DCT in frequency form, and converts the converted video coded signal. The process control unit 14 performs a batch processing for the reference image reproduction and VLC (Variable Length Coding) 20, and the coded signals processed in the scan direction, run, level, and sine form by the process control unit 14 are processed. VLC 20 for variable length encoding, an image memory 16 for storing an image processed by the process control unit for image restoration, and an image block in which motion occurs when an image signal applied from the outside is an inter mode It consists of a motion predictor 15 for motion prediction and compensation.

The process control unit 14 performs RUN, LEVEL, and SIGN processing in the variable length encoding scan direction for each pixel in block units in order to variably encode the quantized image coded signal. And store and perform run, level, and sine processing according to the order in which the quantized coded signals are input, and then perform inverse quantization and inverse DCT on pixel coefficients having the level value. To reproduce.

Although shown in the figure, 12a and 12b, which are not described, represent adders for summing signals.

The video encoder having the above structure performs discrete cosine transform and quantization when an input video signal is an intra-frame, and then there is no previous reference image for image prediction. Intra mode encoding is performed to predict an image block.

However, when the input video signal is a P picture having motion based on the intra frame-coded video frame, whether to perform intra coding on each block in which motion has occurred or to obtain a motion prediction value is first encoded. The encoding performance is improved by appropriately selecting whether to reproduce an image using blocks in the received image frame.

In particular, in the present invention, coding efficiency is improved by reproducing the reference image after quantization in the intra mode or the inter mode, or by collectively processing a series of processes for performing VLC in the process control unit.

That is, each of the 8 * 8 blocks constituting the macroblock initializes the coefficient values for the pixels, and then processes the pixels according to the scan direction for the pixels of the block for variable length coding on the quantized block coefficient values. , Save.

In addition, in order to reconstruct and store a reference image for motion compensation, the pixel values are processed and stored in the order of being quantized by the quantization unit and input to the process control unit 14.

The VLC 20 determines whether a level LEVEL value exists by using a quantization step in the scan direction according to the 64 pixels constituting the block for variable length encoding, and executes when the level value does not exist. Increase the value and set the count value to "0".

If there is a coefficient value, the absolute value is taken to be the level value. After sine determination, according to the sign, if it is positive, it is "0" if it is positive and "1" if it is negative. Save the run value in advance.

In this way, the VLC 20 processes only pixel coefficients corresponding to the number of levels for the run, level, and sine values stored and processed by the process control unit 14.

As a result, the calculation amount of the variable-length encoding process is reduced, thereby improving coding speed and efficiency.

In addition, the processor control unit 14 processes and stores the level and the sine previously obtained for inverse quantization and inverse DCT to restore the reference image, thereby eliminating the need for an inverse quantization routine.

After that, the block information with coefficients is selectively used in the coding block processing and the VLC. That is, the block without coefficients does not need to perform VLC and inverse DCT, and thus does not need to be called, thereby improving coding efficiency.

Since the position information of the pixel coefficients constituting the block has the inverse DCT within the range by knowing the row and column information of the last position where the coefficients exist during the inverse DCT, the pixel 64 of the bend Because the inverse DCT processing routines for are only needed for the coefficients in the final position, the computation in the inverse DCT routines can be reduced.

Therefore, the processor control unit may reduce the amount of computation by restoring the reference image by performing inverse quantization and inverse DCT on coefficients having a level value among the coefficient values of the pixels constituting the block.

3 is a flowchart for explaining a video encoding process according to the present invention.

As shown in FIG. 3, discrete cosine transform and quantization are performed on the input video signal. In this case, discrete cosine transform is performed regardless of whether the input video signal is inter mode or intra mode (S301).

The video signal inputted to the video encoder is subjected to discrete cosine transform, and applied to the process control unit in order to process the discrete cosine transformed video coded signals in a batch (S302).

The process control unit performs quantization on the discrete cosine transformed image coded signal, and then processes and stores them for VLC and reference image reproduction.

First, the quantized video coded signals are initialized for each of the 64 pixels in block units, and then the quantized pixel coefficients are processed and stored according to the scan direction for the VLC.

In order to reconstruct the reference image, processing is performed for inverse quantization and inverse DCT according to the quantized order (S303).

In this way, the process control unit stores the run, level, and sine values of the pixels in the block unit processed and stored, and the VLC and the pixel coefficients for which the level values exist for the run, level, and sine values of the stored blocks. Inverse quantization and inverse DCT (S304).

In this manner, inverse quantization and inverse DCT are performed on all pixel coefficients constituting the block in order to reconstruct the reference image. As it proceeds, the amount of computation is reduced and the coding efficiency is improved (S305).

In the VLC, variable length coding is performed only on the level value stored in the process control unit, thereby reducing the amount of computation of the VLC.

4 is a flowchart for explaining a process of processing an image coded signal in a process control unit according to the present invention.

As shown in FIG. 4, when the video signal is discrete cosine transformed in the DCT of the video encoder, it is applied to the process control unit (S401).

The image coded signal applied to the process control unit is quantized, and then processes and stores quantization values of 8 * 8 block pixels according to the VLC scanning order for reconstruction of the VLC and the reference image (S402).

The quantized video coded signal is processed and stored according to the order in which the quantized signal is input in units of blocks for inverse quantization and inverse DCT (S402).

Thereafter, the corresponding run, level, and sine values are stored in advance with respect to the quantization values stored for each of the blocks constituting the macro block, with the number of levels exceeding the run, level, and sine values being increased (S403).

The VLC and the reference image reconstruction process are distinguished according to whether the run, level, and sine values are used for variable length encoding or reference image reconstruction for the pixel values constituting the block (S404).

In the case of VLC of the image coded signal processed by the process control unit, only the pixel coefficients corresponding to the number of previously obtained and stored levels are variable-encoded to reduce the calculation amount of the VLC (S405).

In addition, when reproducing a reference image by restoring the image coded signal processed by the process control unit, inverse quantization is performed only on a block having a level value among the stored run, level, and sine values, and reverse DCT is performed. The reference image is restored (S406 and S407).

Therefore, in the present invention, the video coder performs a process of reconstructing the video signal after DCT again and the process of performing the VLC process in advance by the process control unit to reduce the coding calculation amount and improve the coding efficiency.

As described in detail above, the present invention processes and stores pixels constituting a block in advance for VLC, inverse quantization, and inverse DCT after quantizing an image signal, and only for a level coefficient having a double pixel coefficient value. The processing has the effect of improving the coding efficiency.

Accordingly, the computation rate of the inverse quantization and inverse DCT processes for generating and storing the reference image and the VLC computation can be reduced, thereby improving the encoding speed.

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 (7)

Discrete Cosine Transform (DCT) for performing discrete cosine transform of an image signal applied from the outside; A process control unit which quantizes the discrete cosine transformed video signal in the DCT and processes them for variable length encoding and reference image reconstruction; An image memory for storing a reference image reconstructed by the process control unit; A motion predictor that compensates by predicting motion based on a reference image stored in the image memory; And And a VLC for performing variable length encoding by using a value processed for variable length encoding by the process control unit. The method of claim 1, The process control unit quantizes the image coded signal processed by the DCT for variable length encoding, and then calculates the run, level, and sine values of the pixel coefficients of the image blocks according to the scanning direction of the variable length encoding. Video encoder, characterized in that. The method according to claim 1 or 2, And the VLC variably encodes only pixel coefficients corresponding to level values. delete The method according to claim 1 or 4, And the process control unit inverts only pixel coefficients having a level value among the processed pixel coefficient values. Performing discrete cosine transform on the video signal input to the video encoder; Processing and storing the pixels constituting the block in a scanning order for the variable cosine transformed image coded signal, and processing and storing the pixels constituting the block for reconstructing a reference image;  Pre-storing a run, level, and sine value with respect to a value obtained by processing and storing the pixels;  Whether the variable length encoding or the reference image reconstruction is performed using the stored run, level, and sine values, and when variable length encoding is performed, a variable value corresponding to the level value is stored among the stored run, level, and sine values. And performing a VLC on the pixel coefficients. The method of claim 6, When reconstructing a reference image using the stored run, level, and sine values, inverse quantization and inverse DCT are performed on only pixel coefficients corresponding to level values among the stored run, level, and sine values. Video encoding method.

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