KR100229793B1 - Improved image coding system having functions for adaptively determining image coding mode - Google Patents

Abstract

The present invention detects whether a corresponding frame to be encoded is a scene change part, and when the detected image is a scene change part image, removes high frequency components of the input image through filtering, and removes high frequency components regardless of the frame string. The present invention relates to an improved image encoding system having an adaptive encoding mode determination function capable of forcibly performing intra mode encoding on a frame. To this end, the present invention relates to a pixel value average and a standard deviation of a corresponding frame to be encoded. Based on the statistical characteristics and short-term statistics of a plurality of frames for a predetermined time period based on the average and standard deviation of each frame, the scene change of the input image is detected, and if it is determined that the current input image is the scene change part, the frame You can use filtering techniques on that frame Removed using a high-frequency component insensitive to the human visual characteristics, and then performs a forced intra-mode encoding.

Description

Improved Image Coding System with Adaptive Code and Mode Decision

1 is a block diagram of an improved image encoding system having an adaptive encoding mode determination function according to a preferred embodiment of the present invention.

2 is a detailed block diagram of the preprocessing block of FIG.

3 is a view showing a determination region for limiting high frequency components determined as one fixed level for an 8 × 8 pixel block as an example when an input image is a scene change portion according to the present invention;

4 is a view showing a decision region for limiting high frequency components that is adaptively determined based on the complexity of an 8 × 8 pixel block as an example when an input image is a scene change portion according to the present invention;

5 is an exemplary diagram for an 8x8 pixel block as an example in accordance with the present invention;

6 is an exemplary diagram showing a one-dimensional low pass filter coefficient of order 7 as an example according to the present invention;

7 is an exemplary view illustrating a horizontal filtering process at (0,4) and a vertical filtering process at (3,0) as an example according to another exemplary embodiment of the present invention.

8 is an exemplary diagram illustrating a 2D lowpass filter coefficient of 3x3 order as an example according to another embodiment of the present invention.

9 is an exemplary diagram illustrating a two-dimensional filtering process at position (3,3) as an example according to another embodiment of the present invention;

10 is a detailed block diagram of a frame prediction block shown in FIG. 2 according to another embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

100,180: frame memory 110: preprocessing block

115: switching block 120: subtractor

130: image coding block 140: entropy coding block

150: transmission buffer 160: video decoding block

170: adder 190: current frame prediction block

1110: statistical characteristic calculation block 1120: control block

1130: memory block 1140: frame output block

1141: DCT block 1143: quantization block

1145: frequency selector 147: inverse quantization block

1149: IDCT block

The present invention relates to a video encoding system for compressing and encoding a video signal. More particularly, the present invention relates to a video encoding system that detects scene transition of an input video by using average and standard deviation of a plurality of frame signals during a predetermined time input for compression encoding. The present invention relates to an improved video encoding system having an adaptive encoding mode determination function suitable for forcibly controlling an encoding mode based on the detection result and adaptively adjusting an amount of bits generated after encoding accordingly.

As is well known in the art, the transmission of discrete video signals can maintain better image quality than analog signals. When a video signal consisting of a series of image "frames" is represented in digital form, a significant amount of data must be transmitted, especially for high-quality television (aka HDTV). However, since the usable frequency range of the conventional transmission channel is limited, in order to transmit a large amount of digital data, it is necessary to reduce the amount by compressing the transmitted data. Among the various compression methods for compressing data, hybrid coding which combines probabilistic coding with temporal and spatial compression is known to be the most efficient, and these techniques have been proposed by the World Standards Organization for example. It is widely disclosed in recommendations such as MPEG-1 and MPEG-2.

Most hybrid coding techniques use motion compensated DCPM (Differential Pulse Code Modulation), two-dimensional Discrete Cosine Transform (DCT), quantization of DCT coefficients, VLC (variable length coding), and the like. The motion compensation DPCM determines a motion of an object between a current frame and a previous frame, and predicts a current frame according to the motion of the object to generate a difference signal representing a difference between the current frame and a predicted value. This method is described, for example, in Staffan Ericsson's "Fixed and Adaptive Predictors for Hybrid Predictive / Transform Coding", IEEE Transactions on Communication, COM-33, NO.12 (1985, December), or "A motion" by Ninomiy and Phtsuka. Compensated Interframe Cding Scheme for Television Pictures ", IEEE Transactions on Communication, COM-30, NO.1 (January, 1982).

In general, two-dimensional DCT converts digital image data blocks, for example, 8 × 8 blocks, into DCT conversion coefficients by using or eliminating spatial redundancy between image data. This technique is described in Chen and Pratt's "Scene Adaptive Coder", IEEE Transactions on Communication, COM-32, NO.3, (1984, March). The DCT transform coefficient may be processed through a quantizer, a zigzag scan, a VLC, or the like to effectively reduce (or compress) the amount of data to be transmitted.

More specifically, the motion compensation DPCM predicts the current frame from the previous frame according to the motion of the object estimated between the current frame and the previous frame. The estimated motion may be represented by a two-dimensional motion vector representing the displacement between the previous frame and the current frame.

Typically, there are several approaches to estimating the displacement of an object. These are generally classified into two types, one of which is a block-based motion estimation method using a block matching algorithm and the other is a pixel-by-pixel motion estimation method using a pixel circulation algorithm.

In the motion estimation method for estimating the displacement of an object as described above, the displacement is obtained for all of the pixels using the pixel-based motion estimation method. This method has the advantage that the pixel value can be estimated more accurately and the scale change (e.g., zooming, which is a movement perpendicular to the image plane) can be easily different, while the motion vector is determined for every pixel. Since a large amount of motion vectors occurs, it is impossible to transmit substantially all of the motion vectors to the receiver.

In addition, in block-by-block motion estimation, a block having a predetermined size of the current frame is moved by one pixel in a search range of a previous frame and compared with the corresponding blocks to determine an optimal matching block having a minimum error value. From this, the interframe displacement vector (the degree of block movement between frames) for the entire block is estimated for the current frame to be transmitted. Here, in determining the similarity between two corresponding blocks between the current frame and the previous frame, the average absolute difference, the mean square difference, etc. are mainly used, as is well known in the art.

On the other hand, the image bit stream encoded by the encoding technique as described above, that is, the encoding scheme such as motion compensation DPCM, two-dimensional DCT, DCT coefficient quantization and VLC (or entropy encoding) is transmitted to the output side of the image encoding system. The next transmission point stored in the buffer is sent to the transmitter for transmission to the remote destination. At this time, the transmission time point here is related to the size (ie, capacity) and transmission rate of the transmission buffer, and is controlled so that a malfunction (data overflow or data underflow) does not occur in the transmission buffer.

More specifically, the amount of bits generated for each frame at the time of encoding is changed due to various factors (for example, scene transition of the input image). In view of this, in the video encoding system, the average transmission rate is constant. Perform control of the output transmit buffer so that it can be maintained. That is, the video encoding system checks the bit generation amount up to the frame currently encoded based on the data fullness state information of the output transmission buffer, and adjusts the bit amount to be allocated in the current frame. In other words, in the conventional typical video encoding system, the amount of bits generated in the encoding system is controlled by controlling the quantization step size (QP) substantially based on the data full state information of the output transmission buffer, that is, if the amount of bits generated before has been large, The bit generation amount is controlled by reducing the bit generation amount by adjusting the step size largely, and in the opposite case, by adjusting the quantization step size small to increase the bit generation amount.

However, as described above, the conventional method of adjusting the bit generation amount by adjusting the quantization step size based on the data fullness state information of the output transmission buffer is performed when encoding and transmitting video data corresponding to each frame at the same data rate. In the case where the input image to be encoded is a scene change image, that is, an image having low correlation between frames on the time axis, the efficiency is lowered in the encoding process such as motion compensation, thereby increasing the amount of bits generated, thereby increasing the quantization step size. As a result, there is a problem that serious image quality deterioration is caused in the reproduced video.

In addition, the video encoding system described above encodes the frame itself at regular intervals between a plurality of omni-directional or bi-directional predictive frame sequences obtained through motion estimation and compensation, as recommended in the MPEG-1 and 2 standards. When an infrastructure frame is inserted and transmitted, an infrastructure frame is generated at regular intervals regardless of whether a video frame input for encoding is a scene change part. The input image is encoded while the inter mode encoding or the intra mode encoding is constantly switched under the control of the system controller.

However, as mentioned above, the image frame in the scene change portion has a low correlation between frames on the time axis, and thus, a frame having low correlation between frames has a low efficiency in encoding processing such as motion compensation. There is. Therefore, the intra-mode encoding may be more effective than the inter-mode encoding in the frame of the scene change portion having low correlation between frames, and human time is considered in consideration of quantization accompanied with deterioration of image quality in the playback image of the receiver. If intra coding is performed by removing a portion of a high frequency component that is relatively insensitive to characteristics, more efficient and efficient coding will be possible.

Accordingly, the present invention is to solve the above-mentioned problems of the prior art, the short-time statistics of a plurality of frames for a predetermined time based on the mean and standard deviation of the pixel value of the corresponding frame to be encoded and the mean and standard deviation of each frame Has an adaptive encoding mode determination function capable of detecting a scene change of an input image based on the detection, and forcibly performing intra mode encoding on the input frame irrespective of the frame sequence when the input image is the image of the scene change portion. An improved image coding system is provided.

Another object of the present invention is to detect the scene transition of the input image based on the mean and standard deviation of the pixel value of the corresponding frame to be encoded and the short time statistics of a plurality of frames for a predetermined time based on the mean and standard deviation of each frame. When the input image is the image of the scene change part, the filtering result removes the high frequency component of the input image, and it is adaptive to perform the forced intra mode encoding on the input frame from which the high frequency component has been removed. An improved image encoding system having an encoding mode determination function is provided.

According to an aspect of the present invention, there is provided an intra encoding mode for performing discrete cosine transform, quantization, and entropy encoding on a current frame itself, and a prediction frame obtained through motion estimation and compensation of the current frame. An image encoding system comprising an encoding unit having an inter encoding mode for performing discrete cosine transform, quantization, and entropy encoding on a differential signal between the signals. A statistical characteristic calculation block for extracting a mean MIp and a standard deviation ACT of the pixels representing? A memory block for sequentially storing an average Mp and a standard deviation ACT for each of the extracted frames for a predetermined time period; Computing the predetermined average by calculating the total average (MMIp, MACT) and the total standard deviation (SMIp, SACT) for each of the average (MIp) and the standard deviation (ACT) for each of the plurality of frames corresponding to the stored predetermined time Calculating short-time statistics for a time, wherein the current inputted for the encoding is based on a comparison result between the statistical characteristics of the current input frame present later in time than the frames used for calculating the short-time statistics and the calculated short-time statistics A control block for generating a control signal for determining an encoding mode of the input frame; And an adaptive encoding path for adaptively performing the intra mode encoding and the inter mode encoding and a forced intra encoding path only for the intra mode encoding, wherein the short-time statistics provided from the control block and statistical characteristics of the current input frame. And a switching means for providing the current input frame to the encoding means through the forced intra encoding path in response to a switching control signal generated based on a comparison result between the two. Provide a system.

According to another aspect of the present invention, there is provided an intra encoding mode for performing discrete cosine transform, quantization, and entropy encoding on an input current frame itself, and a prediction frame obtained through the current frame, motion estimation, and compensation. An image encoding system comprising an encoding unit having an inter encoding mode for performing discrete cosine transform, quantization, and entropy encoding on a differential signal between the signals. A statistical characteristic calculation block for extracting a mean MIp and a standard deviation ACT of the pixels representing? A memory block for sequentially storing an average Mp and a standard deviation ACT for each of the extracted frames for a predetermined time period; Computing the predetermined average by calculating the total average (MMIp, MACT) and the total standard deviation (SMIp, SACT) for each of the average (MIp) and the standard deviation (ACT) for each of the plurality of frames corresponding to the stored predetermined time Calculating short-time statistics for a time period, and inputting the data for the protection based on a comparison result between the statistical characteristics of a current input frame existing later in time than the frames used for calculating the short-time statistics and the calculated short-time statistics. A control block generating a filtering control signal of a current input frame; Band limiting means for generating a frame from which a high frequency component is removed by filtering the current input frame and restricting a pass band based on a filter coefficient determined according to the generated filtering control signal; And an adaptive encoding path for adaptively performing the intra mode encoding and the inter mode encoding and a forced intra encoding path only for the intra mode encoding, wherein the short-time statistics provided from the control block and statistical characteristics of the current input frame. And a switching means for providing the coding means with a frame signal from which the high frequency component is removed through the forced intra coding path in response to a switching control signal generated based on a fertilizer result. An improved image encoding system is provided.

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

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

As described above, in the hybrid coding system employing coding techniques such as motion compensation DPCM, two-dimensional DCT, DCT coefficient thickening, and VLC (or entropy coding) for efficient encoding of video signals, When encoding into a frame sequence (a frame sequence in which an intra frame is inserted between a plurality of forward or bidirectional predictive frames at regular intervals), encoding is performed in inter mode even though the input image is a scene change part. In view of the above, the present invention adopts a technical means to always apply intra mode encoding to a frame regardless of a frame sequence defined when the image input for encoding is a scene change part.

In addition, when the input image is a scene change image having a low correlation on the time axis between adjacent frames, the quantization step size may be excessively large due to a large amount of bits, which may cause deterioration in image quality (deterioration in image quality due to quantization error). In the present invention, in consideration of this point, when it is determined that the input image is the scene change part, the band of the input image is adaptively limited for a predetermined time (that is, during the scene change), that is, the input image is filtered. By applying a technique to remove high-frequency components that are relatively insensitive to human visual characteristics, it employs a technical means of suppressing an increase in the amount of bits generated after encoding. By minimizing, more natural playback images can be obtained.

1 shows a block diagram of an improved video encoding system having an adaptive encoding mode determination function according to a preferred embodiment of the present invention. As shown in the figure, the video encoding system of the present invention includes a first frame memory 100, a preprocessing block 110, a first switching block 114, a second switching block 116, a subtractor 120, The image encoding block 130, the entropy encoding block 140, the transmission buffer 150, the image decoding block 160, the adder 170, the second frame memory 180, and the current frame prediction block 190 are included. .

Referring to FIG. 1, an input current frame signal is stored in the memory 100 of the first MFP on the input side, and the current frame signal stored in the first frame memory 100 is first switched through a line L11. Connected to one side input b of block 114, it is also provided via line L12 to preprocessing block 110, described in detail later with reference to FIG. Here, the other input c of the first switching block 114 is connected to one output (frame signal output) of the preprocessing block 110 through the line L14, and the switching operation of the first switching block 114 is line L13. Is performed by the control signal CS1 based on the statistical characteristic calculation of the input frame signal provided from the preprocessing block 110 through. The specific switching operation of the first switching block 114 will be described later in detail.

Meanwhile, the preprocessing block 110 constitutes the most characteristic constituent member in the present invention. The statistical characteristics, through the analysis and investigation of the frame signal provided from the first frame memory 100 through the line L12 according to the present invention, That is, a plurality of frames (e.g., an average value and standard deviation of each input frame signal are calculated, and an average Mp (average of pixel values) and a standard deviation ACT (rate of change of pixel values) are calculated for each frame. , Based on the short time statistics calculated based on the statistical characteristic information for a predetermined time (for example, 1 second) for a predetermined time (for example, 30 frames). If the input image is a scene change part, it restricts the passband of each input frame signal, that is, adaptively filters each frame, thereby adaptively applying high frequency components insensitive to human visual characteristics. Through to remove the next line L15 is provided to the input c of the first switching block 114. In this case, the frame signal output from the preprocessing block 110 is not necessarily removed through the filtering and is provided to the input c of the first switching block 114 through the line L15 without removing the high frequency component as necessary. In this case, hardware will be simplified compared to the case of performing filtering. Detailed operation of the preprocessing block 110 will be described later in detail with reference to the accompanying drawings.

On the other hand, the first switching block 114 connects the input frame signal connected to the input b to the output e or to the input c based on the switching control signal CS1 on the line L13 provided from the preprocessing block 110 described above. The filtered frame signal (or unfiltered frame signal) to output d. In this case, the line b-a-e of the first switching block 114 is a line for the adaptive intra or inter coding mode, and the line c-a-d is a line only for the intra coding mode according to the present invention, that is, the input line. This is a forced intra coding mode line applied when a video is a scene change part. That is, the first switching block 114 switches the connection of the lines b-a-e or the lines c-a-d based on the control signal CS1 on the line L13.

Meanwhile, the frame signal on the line L16 (the input frame signal itself or the filtered frame signal) is directly provided to the image coding block 130 via the output g of the second switching block 116 and the line L17 in the intra mode encoding. Or provided to the subtractor 120 and the current frame prediction block 190 in inter mode encoding. Here, the second switching block 160 switches the contact points according to control from a system controller, for example, a microprocessor, not shown. In the intra mode encoding, the input f on the line L16 is connected to the line through the output g. The input f on line L16 is connected to the input of subtractor 120 through its other output in inter mode encoding. Therefore, in the image encoding block 130 described later, the current frame signal itself (input frame signal filtered through the preprocessing block 110 or the input frame signal) on the line L17 by using a technique such as DCT or quantization during intra mode encoding. In the inter-mode encoding, the error signal on the line L18 (difference value between the current frame signal on the line L16 and the predicted frame signal on the line L21) may be encoded using a technique such as DCT or quantization. In other words, in the intra mode encoding, the input frame signal itself is encoded (DCT, quantization, entropy encoding, etc.) without using motion estimation and compensation techniques. Since the encoding here is substantially the same as that of the inter mode encoding. In the following description, it is assumed that inter-mode encoding is used as an example for the purpose of better understanding and convenience of explanation.

First, motion compensated prediction for a moving object provided from the current frame prediction block 190 described later through line L21 from the current frame signal provided through line L16 and second switching block 116 in subtractor 120. Subtracted current frame signal, and the resultant data, i.e., an error signal representing the difference pixel value, is obtained by using discrete cosine transform (DCT) and one of the quantization methods well known in the art. By encoding a series of quantized DCT transform coefficients. At this time, the quantization of the error signal in the image encoding block 130 is based on the step size based on the quantization parameter QP determined according to the data fullness state information provided from the output transmission buffer 150 described later through the line L23. Is adjusted.

Also, in the image encoding block 130, when the input image is the scene change portion, the filtered input frame signal (or the input) on the line L17 provided through c-a-d of the first switching block 116 according to the present invention. The frame signal itself is subjected to coding such as DCT and quantization, that is, forced intra mode coding, considering only correlation on the spatial axis without using motion estimation and compensation techniques.

Next, the quantized DCT transform coefficients on line L19 are sent to entropy coding block 140 and image decoding block 160, respectively. Here, the quantized DCT transform coefficients provided to the entropy coding block 140 are encoded by, for example, a variable length coding scheme, and provided to the transmission buffer 150 at the output side. It is delivered to the transmitter not shown for transmission.

On the other hand, the quantized DCT transform coefficients on the line L19 provided from the image coding block 130 to the image decoding block 160 are converted into a reconstructed frame signal through inverse quantization and inverse discrete cosine transform, and then the next adder ( 170, the adder 170 adds the reconstructed frame signal from the image decoding block 160 and the predicted current frame signal provided from the current frame prediction block 190 to be described later through the line L21. The previous frame signal is generated, and the reconstructed previous frame signal is stored in the second frame memory 180. Therefore, the immediately previous frame signal for every frame encoded through this path is continuously updated, and the reconstructed previous frame signal thus updated is sent to the current frame prediction block 190 described below for motion estimation and compensation. Is provided.

On the other hand, in the current frame prediction block 190, the previous frame reconstructed using a block matching algorithm based on the current frame signal on the line L16 and the reconstructed previous frame signal on the line L20 provided from the second frame memory 180 described above. Line L21 predicts the current frame in a predetermined block (e.g., 16x16 or 8x8 DCT block) in a preset search range (e.g., 32x32 or 16x16 search range) of the frame. The predicted current frame signal is generated and provided to the subtractor 120 and the adder 170, respectively.

The current frame prediction block 190 also generates a set of motion vectors for the selected block (16 × 16 or 8 × 8 blocks) on line L22 and provides it to the entropy coding block 140 described above. The sets of motion vectors detected here are the most predicted in the block of the current frame (16x16 or 8x8 block) and the preset search area (e.g., 32x32 or 16x16 search range) in the previous frame. It is the displacement between similar candidate blocks. Accordingly, in the entropy coding block 140 described above, the quantized DCT transform coefficients on the line L19 together with the sets of the motion vectors on the line L22 generate an encoded bit stream by, for example, a variable length coding technique. .

Next, a frame signal or a high frequency which is the most characteristic part of the present invention and determines whether or not the input image is a scene change part and selectively removes high frequency components of the input image through filtering when the input image is a scene change part. An operation process in the preprocessing preprocessing block 110 that provides the frame signal itself without the component removed as an input frame signal on the line L17 for forced intra mode encoding will be described in detail.

FIG. 2 shows a detailed block diagram of the preprocessing block shown in FIG. As shown in the figure, the preprocessing block 110 of the present invention includes a statistical characteristic calculation block 1110, a control block 1120, a memory block 1130, and a frame output block 1140.

Referring to FIG. 2, the statistical characteristic calculation block 1110 receives an input image on the line L12 and calculates a parameter for determining whether the current image is an image for scene change. The average MIp and the standard deviation ACT of the video signal are used. That is, as an example, when the current input image is Ip, the pixel value of the Ip image at the position of (x, y) is Ip (x, y).

Therefore, the average MIp and standard deviation ACT of each input frame signal are obtained by the following equations, respectively.

[Equation 1]

[Formula 2]

In [Equation 1] and [Equation 2], M and N respectively represent integer and horizontal and vertical magnitudes of the video signal. Then, the parameters thus extracted, that is, the average value MIp and the standard deviation ACT of each frame, are provided to the next control block 1120.

In the present invention, the reason for using the average value MIp and the standard deviation ACT extracted as described above as the statistical characteristic information to be used for determining whether the scene is a transition part is that the input video signal is extracted as described above if it is not a scene transition part. This is because the statistical characteristics (mean and standard deviation) of do not differ significantly from the previous video signal. On the contrary, if the input video signal is a scene change part, the statistical properties of the extracted video signal appear much different from the statistical properties of the previous video signal. Therefore, in the present invention, it is determined whether or not to change the scene for the input image by using the temporal change of the statistical characteristic value, this determination will be performed in the control block 1120 described later.

That is, the control block 1120 determines whether the current input image is a scene change part by using parameters provided from the statistical characteristic calculation block 1110, that is, average (MIp) standard deviation (ACT) values of each frame. This determination signal is provided to the next operation block 1140 via the line L14. That is, in the scene change part of the video signal, there is not much similarity between the previous video and the current video due to the change in time. As a result, the encoding efficiency is low during the processing of the coding system such as motion compensation. By generating a bit of, a large quantization error in the quantization step (which causes a deterioration of image quality due to a blocking phenomenon in the reconstructed reproduced image on the receiver side) is accompanied. Accordingly, the present invention detects the scene change of the input image in order to reduce such a phenomenon occurring during the scene change of the image.

More specifically, in the control block 1120, the statistical characteristics (short-term statistics) for a predetermined time and the parameters (average, standard deviation) of the current frame input from the statistical characteristic calculation block 1110 are used to detect the scene transition of the input image. In order to determine whether the scene transition is compared, the process of obtaining such short-time statistics is as follows.

First, the process of obtaining statistical characteristics for a predetermined time with respect to the input image may have various methods. In the present invention, the parameter average and standard deviation of each frame with respect to the frame for 1 second are used. The control block 1120 inputs MIp and ACT values for each frame provided from the statistical characteristic calculation block 1110 to calculate averages and standard deviations for these values for one second. For this calculation, the control block 1120 stores the MIp and ACT values input every frame in the statistical characteristic calculation block 1110 in the memory block 1130.

That is, the parameters extracted from the currently input image (frame) are called MIp (0), ACT (0), and the parameters extracted from the previous image are MIp (1), ACT (1), MIp (i), If ACT (i) (i is an integer value between 1 and 30), parameters input before 30 frames are MIp (30) and ACT (30), and these values are stored in the memory block 1130. Value. Accordingly, the control block 1120 calculates the average MMIp and the standard deviation SMIp of these values from the 30 values from the average MIp (1) to the MIp (30) of each frame, and similarly, the standard deviation ACT (1) of each frame. By calculating the mean MACT and standard deviation SACT of these values from the 30 values from ACT 30 to), short time statistics (statistical characteristics for one second) are calculated.

Next, on the line L14 using the four short-time statistics MMIp, SMIp, MACT, SACT calculated as described above, and the parameters MIp (0) and ACT (0) of one frame input to the current control block 1120. The output signal B to be calculated is calculated by the following equation.

[Equation 3]

In the above formula, && means an AND operation. Therefore, the output signal B calculated as described above and generated on the line L14 is provided to the frame output block 1140. When the output signal B on the line L14 is 0, MIp (the characteristic of the video signal currently input) The value of 0) means that it is not a scene change part because there is not much change compared with the previous short time characteristic. On the other hand, when the output signal B on the line L14 is 1, the characteristic of the currently input video signal is the previous short time. Compared to the characteristic, it means that it is a scene change part because there are many changes. That is, the control block 1120 detects whether or not the average of the pixel value of the current input frame is suddenly changed by using the short time statistics obtained from the frame for the previous predetermined time based on the statistical characteristics of each frame, and based on the detection result. It is determined whether the current input video is a scene change video.

As a result, in the frame output block 1140, based on the output signal B on the line L14, the current frame signal on the line L12 provided from the first frame memory 100 of FIG. A frame signal is generated on the line L15, or a band signal having a predetermined high frequency component is removed by performing an appropriate band limiting process or special filtering. That is, when filtering the input frame signal on the line L12, in the frame output block 1140, as shown in FIG. 3 as an example, all values below Z (1,7) and Z (2,6) are zero. Mapping to (0) value limits the bandwidth and performs filtering.

The output frame signal from which the high frequency component has been removed is then connected to the forced intra coding mode line L17 via the c-a-d path of the first switching block 114 of FIG. Accordingly, in the image encoding block 130 of FIG. 1, the frame signal on the line L17 from which the high frequency component is relatively insensitive to the human visual characteristics is removed, and the encoding is performed in consideration of the correlation on the spatial axis through a technique such as DCT or quantization. will be.

On the other hand, the frame output block 1140 is switched to provide a frame output on the line L15 only when the input image is a scene change part by switching the frame signal on the line L12 without employing a filtering technique for removing high frequency components of the input frame. In the case of the configuration, the amount of generated data may be slightly increased compared with the filtering technique, but another advantage is that hardware implementation is easy. Therefore, it may be selectively (or adaptive) applied according to the application range of the image encoding system to be employed.

On the other hand, in the control block 1120, when the frame output block 1140 described below according to the present invention is configured to filter the input frame signal to generate a frame signal from which high frequency components have been removed, The output signal B may be calculated as shown in the following equation so that the input frame may be filtered adaptively (or selectively) in consideration of the complexity of the input image without filtering the input frame.

[Equation 4]

Therefore, the output signal B calculated as described above and generated on the line L14 is provided to the frame output block 1140. When the output signal B on the line L14 is 1, MIp (the characteristic of the video signal currently input) The value of 0) and ACT (0) is not a changeover part because there is not much change compared with the previous short-time characteristic.In contrast, if the output signal B on the line L14 is 2, 3, 4, the current input This means that the characteristic of the video signal is a changeover part because there is a lot of change compared to the previous short-time characteristic. That is, the control block 1120 detects whether or not the average of the pixel value of the current input frame is suddenly changed by using the short time statistics obtained from the frame for the previous predetermined time based on the statistical characteristics of each frame, and based on the detection result. It is determined whether the current input video is a scene change video.

As a result, in the frame output block 1140, on the basis of such an output signal B on the line L14, a corresponding band limiting process corresponding to the current frame signal on the line L12 provided from the first frame memory 100 of FIG. In other words, adaptive filtering is performed. That is, when filtering the input frame signal on the line L12, the frame output block 1140 corresponds to the output signal B from the control block 1120 based on the complexity of the input image, as shown in FIG. 4 as an example. Values below the output value (that is, values below the dotted line in FIG. 4) are mapped to zero values to limit the bandwidth and perform filtering. In other words, according to the present embodiment, the high frequency component rejection level of the input frame signal is selectively (or adaptively) adjusted according to the complexity of the input frame.

Then, the output frame signal from which the high frequency component is adaptively (or selectively) removed as described above is transmitted to the forced intra coding mode line L17 via the c-a-d path of the first switching block 114 of FIG. Connected. Accordingly, in the image encoding block 130 of FIG. 1, the correlation of the spatial signal on the spatial axis through DCT, quantization, or the like is applied to the frame signal on the line L17 in which the high frequency component relatively insensitive to the human visual characteristics is selectively or adaptively removed. You will be encoding.

In addition, the control block 1120 sequentially updates MIp and ACT values for each frame stored in the memory block 1130 according to the sequential input of the current frame, that is, MIp (0) and ACT (0) for one new frame. ), The values of the previously stored MIp (30) and ACT (30) are the values of the MIp (29), ACT (29), the values of the MIp (29), ACT (29) MIp (28), ACT A newly updated short time statistic for one input image by sequentially replacing the value of (28) and finally replacing the values of MIp (1) and ACT (1) with values of MIp (0) and ACT (0). This update process is performed each time a frame is input. As a result, the time for which the parameter for each frame extracted by the general characteristic calculation block 1110 is stored in the memory block 1130 corresponds to 30 frames, and after 30 frames, the parameter is not used to calculate short-time statistics. As such, the memory block 1130 that stores the parameters of each frame for short-term statistical calculation may be simply configured using, for example, a first-in, first-out buffer.

Meanwhile, in the control block 1120, the short-time statistics and the current input for the previous input image for a predetermined time (eg, 1 second) calculated using the MIp and ACT values of 30 frames stored in the memory block 1130. Control signal for switching the contact point in the first switching block 114 of FIG. 1 based on the determination result when determining whether the current input image is a scene change part based on the statistical characteristic parameters MIp and ACT of the image. CS1 (e.g., a logic signal having a high or low level) is generated on line L13.

In other words, in the control block 1120, when it is determined that the current input image is not the scene change part, as a result of comparing the short-time statistics for a predetermined time with respect to the previous image and the statistical characteristics (MIp, ACT) of the current input image, A logic signal of high or low level is generated on the line L13 to control the lines b-a-e of the first switching block 114 shown in FIG. 1 to be connected, whereas the current input image is a scene change part. When it is determined, a logic signal of low or high level is generated on the line L13 to control the line c-a-d of the first switching block 114 shown in FIG. 1 to be connected. As a result, based on the control signal CS1 on the line L13 provided from the control block 1120, when the lines b-a-e of the first switching block 114 are connected, the current input frame signal on the line L11 itself is an adaptive intra. Frame signal or high frequency component on the line L15 provided by the above-described frame output block 1140 when the line c-a-d of the first switching block 114 is connected to the line L16 for inter-mode encoding. This removed frame signal will be connected on the forced intra mode encoding line L17 according to the present invention.

On the other hand, when the frame output block 1140 is configured to generate a frame signal from which high frequency components have been removed through filtering, on the line L15 as an input frame signal, the method for removing the high frequency components is one-dimensional. Low pass filtering, 2D low pass filtering, band limiting using Discrete Fourier Transform (hereinafter abbreviated as DFT) and band limiting using Discrete Cosine Transform (abbreviated as DCT) Techniques;

As described above, when a frame from which a high frequency component relatively insensitive to human visual characteristics is removed is provided as an input frame signal on a forced intra coding mode line L17 according to the present invention, among the techniques for removing the high frequency component One one-dimensional low pass filtering technique is performed by multiplying an input video signal by a low pass filter. That is, when the value of each pixel for an image of one block of N × M (for example, 8 × 8 blocks) is f (x, y), one block is 8 as shown in FIG. 5 as an example. In the case of a block of x8, the position values x and y of the pixels in the horizontal and vertical directions have integer values between 0 and 7, and each value has a level value between 0 and 255. That is, as can be seen from Fig. 5, the position values in the horizontal and vertical directions of each pixel of the 8x8 block have a value of f (0,0) to f (7,7).

On the other hand, as the one-dimensional low pass filter in the present invention, as shown in Fig. 6 as an example, it is assumed that the one-dimensional low pass filter coefficient has a seven orders. The low pass filter is an example of a low pass filter that band-limits the signal to have a frequency bandwidth of fs / 4 since the frequency bandwidth is fs / 2 when the sampling frequency of the input video signal is fs.

Therefore, in the frame output block 1140, the process of performing one-dimensional low pass filtering on the image signal according to the present invention performs one-dimensional low pass filtering on each direction since the input image signal is a two-dimensional signal in the horizontal and vertical directions. This can be achieved by This process is illustrated in detail in FIG. 7 which illustrates a horizontal filtering process at (0,4) and a vertical filtering process at (3,0). That is, if the low pass filtered signal in the vertical direction at the position of (x, y) is z (x, y), this is calculated by the following equation.

[Equation 5]

In the above Equation 5, T means the order of the filter, so T = 7. Thus, the u, v values have integer values between -3 and 3. In the above Equation 5, k (u) is a filter coefficient value, and f (x, y) is a pixel value. In the above Equation 5, if the value of f (x, yu) is less than 0, the value is 0. If the value of f (x, yu) is smaller than 0, M-1 is larger than the M-1 value corresponding to the image size of one frame. Value. This is a method of setting the end value when the pixel value exists only in the area, that is, 0 to M-1, and this filtering method is a technique known in the art.

Therefore, if filtering is performed at all pixel positions as shown in [Equation 5], as shown in FIG. 7 as an example, one-dimensional filtering results in horizontal and vertical directions can be obtained. In this case, according to the present invention, in the process of performing such filtering at all pixel positions, horizontal filtering may be performed first, and vertical filtering may be performed again or the order of the horizontal filtering may be performed again.

On the other hand, the one-dimensional low-pass filtering as described above may be configured to completely remove or partially remove the high frequency components of the input video signal by using only one preset filter coefficient (or fixed), but the complexity of the input video In consideration of this, according to the size of the complexity, a plurality of filter coefficients (for example, four, etc.) may be used to adaptively (or selectively) remove high frequency components of the input image. In this case, when the input frame is adaptively filtered using a plurality of filter coefficients, the hardware implementation may be more complicated than the image filtering using one preset filter coefficient, but the image encoding block 130 of FIG. Another advantage is that in the quantization process, precise control of the quantization step size is possible. Therefore, in the case of adaptive filtering using a plurality of filter coefficients as described above, it may be selectively applied according to its application range.

On the other hand, two-dimensional low-pass filtering among the techniques for the removal of the high frequency components of the input frame is shown in Fig. 5 for each pixel of one pixel of N × M (e.g., 8 × 8 blocks). Assume that the value is f (x, y), and as an example, as shown in Fig. 8, the two-dimensional low pass filter coefficient has a 9th order having 3 orders, as shown in the following formula: Depending on the coefficient k, the value of k (0,0) is 1/2 and other values have a value of 1/16.

Accordingly, the process of performing two-dimensional low pass filtering on the input frame signal on the line L12 in the frame output block 1140 according to the present invention, for example, shows a process of performing filtering at the position of f (3,3). As shown in. In Fig. 9, the sum of the product between the filter coefficient and the overlapping pixels gives a filtered result. If the two-dimensional low pass filtered signal at (x, y) is called Z (x, y), this value is calculated by the following equation.

[Equation 6]

In the above formula, T means the order of the filter, so T = 3. Thus, the u value has an integer value between -1 and 1. Also, in the above formula, the k (u, v) value is a filter coefficient value, and the f (x, y) value is a pixel value. In this case, as in the above-described one-dimensional low pass filtering, when the values of (xu) and (yv) of f (xu, yv) are smaller than 0 in the above equation, the value is 0, or corresponds to the image size of one frame. If it becomes larger than the M-1 value, the M-1 value is used. Therefore, if the filtering is performed at the positions of all the pixels as in the above formula, as shown in FIG. 9, for example, two-dimensional filtering in the horizontal and vertical directions can be obtained.

On the other hand, when the band limiting technique using the DFT is adopted among the techniques for removing the high frequency components of the input frame, the frame output block 1140 determines the bandwidth for frequency domain division provided to the control block 1120 described above. On the basis of the output signal B to limit the high frequency components which are relatively insensitive to the time in the input image, the process can be substantially divided into two-dimensional frequency conversion process and frequency selection process, in which the discrete Fourier By using the transform (DFT), in the frequency selection process, the passband of the DFT-converted video signal is determined based on the output signal B provided from the control block 1120.

Next, the frame output block 1140 performs a two-dimensional DFT conversion on the input frame on the line L12 and selects a frequency of the two-dimensional DFT-converted video signal based on the output signal B for bandwidth determination. Explain.

First, the frame output block 1140 utilizes the similarity of the spatial domain of the input image signal. The frame output block 1140 uses the Fourier function to convert the image signal (pixel data) of the spatial domain using a Fourier function. For example, two-dimensional DFT transform coefficients of a frequency domain of 8x8 units are converted.

[Formula 7]

In the above formula, f (u, v) denotes the value of each pixel, u denotes the position in the horizontal direction, and v denotes the position of the pixel in the vertical direction. Therefore, the value for each fill cell of the N × N block has the following value. That is, when N = 8 u and v have a value between 0 and 7. At this time, each value has an integer value between 0 and 255. In addition, in the above formula, Z (k, l) means a converted signal, and k, l means frequency components in the horizontal and vertical directions, respectively. Therefore, when N = 8, an 8x8 DEF block, that is, a signal in the spatial domain is converted into a signal in the frequency domain.

More specifically, in the frame output block 1140, the DEF conversion coefficients obtained through the process described above are passed based on the output signal B for bandwidth determination provided from the control block 1120 through the line L14. Determine the frequency band to be In this case, as shown in Equation 5, the output signal B for bandwidth determination may be set to an integer value between 1 and 4, and the selected frequency is as follows.

That is, the frame output block 1140 selects a specific frequency from the converted frequency Z (k.l). Here, k, l is an integer value between 0 and N-1. Therefore, the value output from the frame output block 1140 becomes a signal from which a specific frequency component (ie, a high frequency component) is removed. For example, in the case of N = 8, as shown in FIG. 4 as an example, the pass frequency band will be determined.

Therefore, as shown in FIG. 4, the frequencies below the dotted line corresponding to each are all zero according to the output signal B for determining the bandwidth provided from the control block 1120 to the frame output block 1140 via the line L14. Do not choose. That is, in the case where the B value is 4 in FIG. 4, frequencies below the dotted line such as Z (1,7), Z (2,6), etc. are all mapped to 0. FIG. Alternatively, a predetermined filter coefficient may be used to limit the high frequency components of the predetermined level or more (replace the high frequency components of the fixed level or more with 0, etc.) in response to the output signal B from the control block 1120. In this case, the implementation would be rather easy compared to the adaptive (or optional) band limit.

Next, as described above, the DFT transform coefficients (signals in the frequency domain) from which the frequency (high frequency component) of the specific region is removed according to the output signal B value for determining the bandwidth determined based on the complexity of the image are expressed as follows. The inverse is transformed into the original spatial signal.

Equation 8

In the above formula, f (u, v) denotes the value of each pixel, u and v denote the position of the pixel in the horizontal and vertical directions, Z (k, l) denotes the converted signal, and k denotes frequency components in the horizontal and vertical directions, respectively. Therefore, when N = 8, 8x8 DFT blocks in the frequency domain are converted into signals in the spatial domain (pixel data).

As a result, the frame output block 1140 is calculated based on the complexity of the input image, that is, the frequency of the specific region selectively removed according to the complexity of the image when the input image is the scene change portion on the line L15. According to the output signal B for bandwidth determination, a frame signal in which a high frequency component of the image is selected (or adaptively) is removed (an image signal in which a high frequency component of a specific region is replaced with a zero value). A frame signal in which a high frequency component which is relatively insensitive to human visual characteristics is selectively removed) is a video encoding block via a c-a-d line and a forced intra coding mode line L17 of the first switching block 114 of FIG. 130 will be provided.

On the other hand, when the band limiting technique using DCT is adopted among the techniques for removing high frequency components of the input frame, the frame output block 1140 determines the bandwidth for frequency domain division provided to the control block 1120 described above. On the basis of the output signal B to limit the high frequency components which are relatively insensitive to the time in the input image, the process can be substantially divided into a two-dimensional frequency conversion process and a frequency selection process, where discrete cosine is used in the two-dimensional frequency conversion process. In the frequency selection process, the passband of the DCT-converted video signal is determined based on the output signal B provided from the control block 1120.

Next, in the frame output block 1140, the process of selecting the frequency of the 2D DCT transformed video signal based on the 2D DCT transformed input signal and the output signal B for determining the bandwidth for frequency domain division. It will be described in detail with reference to the accompanying Figure 10.

First, in the frame output block 1140, two-dimensional DCT conversion is performed on an input image. As is well known in the art, the DCT conversion process is well known to reflect spatial similarity of an image signal. The conversion technique is widely applied in the process of encoding an image signal. Therefore, detailed description is omitted here. Therefore, in the present embodiment, when the input image is a scene change part, DCT transform having such characteristics (reflecting spatial similarity) is used as an effective frequency selection technique according to the complexity of the image signal. The frequency selection process according to the present invention returns to the frequency domain by better reflecting the characteristics of the image signal than the simple frequency conversion technique, and as a result, it is possible to increase the efficiency when selecting a frequency for the input image.

FIG. 10 shows a detailed block diagram of the frame output block 1140 according to the present invention shown in FIG. As shown in the figure, the frame output block 1140 includes a DCT block 1141, a quantization block 1143, a frequency selector 1145, an inverse quantization block 1147, and an IDCT block 1149.

In Fig. 10, the DCT block 1141 uses the similarity of the spatial domain of the video signal, and according to the following equation, the DCT block 1141 uses the cosine function to convert the video signal (pixel data) of the spatial domain into N × N units, for example. For example, two-dimensional DCT transform coefficients of a frequency domain of 8x8 units are converted and provided to the next quantization block 1143.

[Equation 9]

In the above equation, F (u, v) means the transformed DCT coefficient and f (x, y) means the input video signal. Here, x, y means the horizontal and vertical position of the pixel data, u, v means the frequency in the horizontal and vertical direction in the transformed DCT coefficients. The quantization block 1143 then quantizes the two-dimensional transformed DCT coefficients using the above-described equation, for example, using a nonlinear operation to a finite number of values. In this case, the QP value is used in the quantization process of the DCT transform coefficient. When the transformed DCT coefficient is F (u, v), an operation of performing an integer value by performing F (u, v) / (2 * QP) is performed. This is an example of a representative quantization process.

On the other hand, the frequency selector 1145 uses the output signal B for bandwidth determination provided from the control block 1120 of FIG. 2 through the line L14 for the DCT transform coefficients quantized through the above-described process. Determine the frequency passed. In this case, as shown in Equation 5, the output signal B for bandwidth determination may be set to an integer value between 1 and 4, and the selected frequency is as follows.

That is, the frequency selector 1145 selects a specific frequency from the converted frequency Z (k, l). Here, k, l is an integer value between 0 and N-1. Therefore, the value output from the frequency selector 1145 becomes a signal from which a specific frequency component (ie, a high frequency component) is removed. For example, when N = 8, its pass frequency will be determined as shown in FIG.

Therefore, as shown in FIG. 4, the frequency below the dotted line corresponding to each of the frequencies according to the output signal B for determining the bandwidth provided from the control block 1120 to the frequency selector 1145 through the line L14 is all zero. Do not choose. That is, when the B value is 4 in FIG. 4, frequencies below the dotted line such as Z (1,7), Z (2,6), etc., are all mapped to 0. FIG. Alternatively, a predetermined filter coefficient may be used to limit the high frequency components of the predetermined level or more (replace the high frequency components of the fixed level or more with 0, etc.) in response to the output signal B from the control block 1120. In this case the implementation would be rather easy compared to the adaptive (or selective) band limit.

Next, as described above, when the input image is a scene change part, the quantized DCT from which the frequency (high frequency component) of the specific region is removed according to the output signal B value for bandwidth determination determined based on the complexity of the input image. The transform coefficients are restored to the original signal (pixel data) through the next inverse quantization block 1147 and IDCT 1149. At this time, the inverse transformation process of the inverse quantized DCT transformation coefficient in the IDCT block 1149 is as shown in the following equation.

Equation 10

In the above formula, f (x, y) means inversely transformed video signal (pixel data), and F (u, v) means transformed DCT coefficient. Here, u and v mean horizontal and vertical frequencies in the converted DCT coefficients, and x and y mean horizontal and vertical positions of the pixel data.

As a result, in the IDCT block 1149, when the input image is the scene change portion on the line L15, the bandwidth calculated based on the complexity of the input image, that is, the image signal from which the frequency of a specific region is selectively removed according to the complexity of the image. According to the output signal B for the determination, a frame signal in which the high frequency component of the image is selectively (or adaptively) removed (an image signal in which the high frequency component of a specific region is replaced with a value of 0) is generated. The frame signal in which the high frequency component, which is relatively insensitive to the visual characteristics, of the frame signal is selectively removed) is obtained by using the image encoding block (c-a-d line of the first switching block 114 of FIG. 1 and the forced intra coding mode line L17). 130).

Accordingly, in the image encoding block 130 of FIG. 1, the preprocessing block 110 in the image encoding system according to the present invention uses a filtering technique for removing high frequency components (band using one-dimensional or two-dimensional low pass filtering, DFT or DCT). (Restriction), if the input image is a complex scene change part, the frame signal itself or the frame from which the high frequency component is removed through the forced intra coding mode line L17 connected to the output d of the first switching block 114 is removed. Forcible intra-mode coding such as DCT and quantization taking into account the correlation on the spatial axis is performed on the signal (the signal from which the high frequency component relatively insensitive to human visual characteristics) is removed. Efficient coding of images as well as low quantization error for low frequency signals It can be done.

As described above, according to the present invention, short-time statistics and current inputs based on averages and standard deviations of a plurality of frames for a predetermined time period for an input image input to an image encoding system for encoding a desired bit rate. It is determined whether the video input for current encoding is a complex scene change part by using the average and standard deviation of the video frames. If the input image is a complex scene change part, the frame signal itself or a filtering technique is used. By performing forced intra mode coding including DCT, quantization, etc. on a frame signal from which high frequency components are insensitive to human visual characteristics, the motion estimation technique is performed even if a scene change situation with a large complexity occurs in the input image. Via forced intra-mode encoding Both to an improved coding efficiency, but also it can effectively control the amount of bits generated after coding without increasing the excessive quantization step size of the quantization step. Therefore, according to the present invention, it is possible to effectively suppress deterioration in image quality due to quantization error inevitably present in the reproduced image when the encoded image is displayed on the receiving side.

Claims (14)

Discrete cosine transform, quantization, and entropy encoding are performed on an intra encoding mode for performing discrete cosine transform, quantization, and entropy encoding on the input current frame itself, and a differential signal between the current frame and a prediction frame obtained through motion estimation and compensation. In an image encoding system including encoding means having an inter encoding mode, an average MIp and a standard deviation ACT of pixels representing statistical characteristics of the frames sequentially input for encoding through frequency analysis thereof. Statistical characteristic calculation block for extracting each; A memory block for sequentially storing an average Mp and a standard deviation ACT for each of the extracted frames for a predetermined time period; Computing the predetermined average by calculating the total average (MMIp, MACT) and the total standard deviation (SMIp, SACT) for each of the average (MIp) and the standard deviation (ACT) for each of the plurality of frames corresponding to the stored predetermined time Calculating short-time statistics for a time, wherein the current inputted for the encoding is based on a comparison result between the statistical characteristics of the current input frame present later in time than the frames used for calculating the short-time statistics and the calculated short-time statistics A control block for generating a control signal for determining an encoding mode of the input frame; And an adaptive encoding path for adaptively performing the intra mode encoding and the inter mode encoding and a forced intra encoding path only for the intra mode encoding, wherein the short-time statistics provided from the control block and statistical characteristics of the current input frame. And a switching means for providing the current input frame to the encoding means through the forced intra encoding path in response to a switching control signal generated based on a comparison result between the two. system. The method of claim 1, wherein the plurality of frames during the predetermined time period is the previous 30 frames immediately adjacent in time to the frame input for the encoding. Video encoding system. Intra coding mode for performing discrete cosine transform, quantization and entropy encoding on the input current frame itself, and discrete cosine transform, quantization, and entropy encoding for differential signals between the current frame and prediction frames obtained through motion estimation and compensation. In an image encoding system including encoding means having an inter encoding mode, the average MIp and the standard deviation ACT of pixels representing a statistical property through frequency analysis of each frame sequentially input for encoding are performed. A statistical characteristic calculation block for extracting a); A memory block for sequentially storing an average Mp and a standard deviation ACT for each of the extracted frames for a predetermined time period; The predetermined average is calculated by calculating the total mean MMIp and MACT and the standard standard deviation SMIp and SACT for the average Mp and the standard deviation ACT for each of the plurality of frames corresponding to the stored predetermined time. Calculating short-time statistics for a time, wherein the current inputted for the encoding is based on a comparison result between the statistical characteristics of the current input frame present later in time than the frames used for calculating the short-time statistics and the calculated short-time statistics A control block for generating a filtering control signal of the input frame; Band limiting means for generating a frame from which a high frequency component is removed by filtering the current input frame and restricting a pass band based on a filter coefficient determined according to the generated filtering control signal; And an adaptive encoding path for adaptively performing the intra mode encoding and the inter mode encoding and a forced intra encoding path only for the intra mode encoding, wherein the short-time statistics provided from the control block and statistical characteristics of the current input frame. And a switching means for providing the coding means with a frame signal from which the high frequency component has been removed through the forced intra coding path in response to a switching control signal generated based on a comparison result between the two. Improved Image Coding System. [4] The improved encoding method of claim 3, wherein the plurality of frames during the predetermined predetermined time period is the previous 30 frames immediately adjacent in time to the frame input for the encoding. Video encoding system. The method of claim 5, wherein the band limiting means selectively removes the high frequency component level of the current input frame through one-dimensional band filtering using one of a plurality of filter coefficients having different values. An Improved Image Coding System with Adaptive Coding Mode Determination. 11. The improved method of claim 10, wherein the one-dimensional low pass filtering is performed sequentially in the horizontal-vertical or vertical-horizontal direction of each pixel position in the 8x8 block. Video encoding system. 6. The improved video encoding system of claim 5, wherein the band limiting means removes high frequency components of the current input frame through two-dimensional low pass filtering. 14. The method of claim 13, wherein the band limiting means selectively removes a high frequency component level of the current input frame by using one of a plurality of filter coefficients having different values. An improved video encoding system with functionality. 6. The method of claim 5, wherein the band limiting means converts the video signal in the spatial domain for the current input frame into DFT transform coefficients in the frequency domain in M × N block units using discrete Fourier transform. Determine a high frequency pass band for the converted DFT transform coefficient blocks based on a filtering control signal for band limitation, limit the high pass band of each converted DFT transform coefficient block to the determined bandwidth, And a frame signal from which the high frequency component is removed by reconstructing the original signal through an inverse discrete Fourier transform for each limited DFT block. 19. The method of claim 18, wherein the bandwidth limitation of the current input frame is adaptively performed to any one of a plurality of levels preset according to the complexity of the input frame. Improved image coding system. 21. The adaptive encoding mode of claim 18 or 20, wherein the bandwidth limit maps high frequency components below the determined bandwidth to zero values for each of the transformed DFT transform coefficient blocks. Improved picture coding system with decision function. The method of claim 5, wherein the band limiting means comprises: a discrete cosine for converting an image signal in a spatial domain with respect to the current input frame signal into a two-dimensional DCT transform coefficients in a frequency domain in M × N block units using a cosine Conversion means; Quantization means for quantizing two-dimensional DCT transform coefficient blocks in units of M × N using a quantization parameter value to a finite number of values; based on the filtering control signal provided from the control block, the quantized DCT transform Frequency selecting means for determining a high frequency pass band for coefficient blocks and for limiting the high frequency pass band of each quantized DCT transform coefficient block to the determined bandwidth; And performing inverse quantization and inverse discrete cosine transform on each of the bandwidth-limited quantized DCT blocks to reconstruct the original signal before encoding to generate a band-limited frame, wherein the band-limited frame is removed from the high frequency component. An improved image encoding system having an adaptive encoding mode determining function, characterized in that it comprises image restoring means provided to said switching means as a signal. 24. The adaptive encoding mode determination function of claim 23, wherein the bandwidth limitation of the current input frame is adaptively performed at any one of a plurality of levels preset according to the complexity of the input frame. An improved image encoding system with 27. The adaptive encoding mode of claim 23 or 25, wherein the bandwidth limit maps high frequency components below the determined bandwidth to zero values for each of the transformed DCT transform coefficient blocks. Improved picture coding system with decision function.