GB2316828A - Compensating quantization errors of a decoded video signal by using an adaptive filter - Google Patents
Compensating quantization errors of a decoded video signal by using an adaptive filter Download PDFInfo
- Publication number
- GB2316828A GB2316828A GB9718397A GB9718397A GB2316828A GB 2316828 A GB2316828 A GB 2316828A GB 9718397 A GB9718397 A GB 9718397A GB 9718397 A GB9718397 A GB 9718397A GB 2316828 A GB2316828 A GB 2316828A
- Authority
- GB
- United Kingdom
- Prior art keywords
- discrete cosine
- cosine transform
- frame data
- transform coefficients
- current frame
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
- H04N19/86—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving reduction of coding artifacts, e.g. of blockiness
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
- H04N19/117—Filters, e.g. for pre-processing or post-processing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
- H04N19/132—Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
- H04N19/136—Incoming video signal characteristics or properties
- H04N19/14—Coding unit complexity, e.g. amount of activity or edge presence estimation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
- H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/18—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a set of transform coefficients
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
- H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/80—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Compression Or Coding Systems Of Tv Signals (AREA)
- Image Processing (AREA)
- Compression, Expansion, Code Conversion, And Decoders (AREA)
Abstract
The image quality of a decoded video signal is improved by using an adaptive filter 150. Specifically, a transmitted encoded video signal is converted to a set of discrete cosine transform coefficients corresponding to current frame data through the use of variable length decoding 130 and inverse quantization 140 techniques. High frequency components of the set of discrete cosine transform are adaptively filtered 150 based on a spatial activity of current frame data determined by utilizing previous frame data decoded prior to deriving the current frame data. Then, a set of filtered discrete cosine transform coefficients is transformed 160 into a set of inverse discrete cosine transform data. The set of inverse discrete cosine transform data and the previous frame data are used to produce a current frame data through the use of motion compensation 170-190. The current frame data serves as new previous frame data and the decoded video signal at the same time.
Description
METHOD AND APPARATUS FOR COMPENSATING QUANTIZATION ERRORS OF
A DECODED VIDEO SIGNAL BY USING AN ADAPTIVE FILTER
The present invention relates to a method and apparatus for decoding an encoded video signal; and, more particularly, to a method and apparatus capable of compensating quantization errors of a decoded video signal by adaptively filtering high frequency components of current frame data based on standard deviations of pixel values of a plurality of previous frames decoded prior to deriving the current frame data.
In digital television systems such as video-telephone, teleconference and high definition television systems, a large amount of digital data is needed to define each video frame signal since a video line signal in the video frame signal comprises a sequence of digital data referred to as pixel values. Since, however, the available frequency bandwidth of a conventional transmission channel is limited, in order to transmit the large amount of digital data therethrough, it is inevitable to compress or reduce the volume of data through the use of various data compression techniques, especially, in the case of such low bit-rate video signal encoders as videotelephone and teleconference systems.
The video signal can be normally compressed without seriously affecting its integrity because there usually exist certain correlationships or redundancies among some of the pixels in a single frame and also among those of neighboring frames. Among various video compression techniques, the socalled hybrid coding technique, which combines temporal and spatial compression techniques together with a statistical coding technique, is known to be most effective.
Most hybrid coding techniques employ an adaptive inter/intra mode coding, orthogonal transform, quantization of transform coefficients, and Variable Length Coding(VLC). The adaptive inter/intra mode coding is a process of selecting a video signal for a subsequent orthogonal transform from either
Pulse Code Modulation(PCM) data of a current frame or
Differential Pulse Code Modulation(DPCM) data adaptively, e.g., based on a variance thereof. The inter mode coding, also known as the predictive method, which is based on the concept of reducing the redundancies between neighboring frames, is a process of determining the movement of an object between a current frame and its one or two neighboring frames, predicting the current frame according to the motion flow of the object, and producing a difference signal representing the difference between the current frame and its prediction. This coding method is described, for example, in Staffan Ericsson, "Fixed and Adaptive Predictors for Hybrid Predictive/Transform
Coding", IEEE Transactions on Communications, COM-33, No.
12(December 1985); and in Ninomiya and Ohtsuka, "A Motion
Compensated Interframe Coding Scheme for Television Pictures",
IEEE Transactions on Communications, COM-30, No. l(January 1982), both of which are incorporated herein by reference.
The orthogonal transform, which exploits the spatial correlationships between image data such as PCM data of the current frame and motion compensated DPCM data and reduces or removes spatial redundancies therebetween, is used to convert a block of digital image data into a set of transform coefficients. This technique is described in Chen and Pratt, "Scene Adaptive Coder", IEEE Transactions on Communications,
COM-32, No. 3(March 1984). By processing such transformation coefficient data with quantization and VLC, the amount of data to be transmitted can be effectively compressed.
Specifically, in the orthogonal transform such as
Discrete Cosine Transform(DCT) or the like, the image data is divided into equal-sized blocks, for example, blocks of 8x8 pixels, and each of the blocks is transformed from the spatial domain to the frequency domain. The DC coefficient of the block reflects the average intensity of the pixels in the block. In general, the pixels in the intra mode input video signal have values ranging from 0 to 255, giving a dynamic range for the intra block DC transform coefficient from 0 to 2040 which can be represented in 11 bits; and a maximum dynamic range for any intra block AC transform coefficient from about -1000 to 1000. In case of an inter mode input video signal whose pixels have values ranging from -255 to 255, a maximum dynamic range for any AC or DC transform coefficient is about -2000 to 2000.
The orthogonal transform coefficients resulting from the orthogonal transform are then quantized. In carrying out the quantization, a smaller quantizer step size obviously entails a larger amount of data requiring a larger number of code bits for the representation thereof, whereas a larger quantizer step size results in a lower volume of data needing a fewer number of code bits for their representation. And, a larger number of code bits can represent an image more precisely than a fewer number of code bits. Accordingly, there exists a tradeoff between the amount of data or burden thrust upon a transmission channel and the quality of the image transmitted.
There are various quantization step size control schemes.
In these schemes, the quantizer step size control usually means the control of the step size employed in quantizing inter block AC and DC, and intra block AC coefficients. Such quantizer step size control is determined based on the amount of data currently stored in a buffer memory and the complexity of the input video signal. In case of the inter block AC and
DC, and intra block DC coefficient, it is quantized with a relatively small fixed step size, e.g., 16 or 8, as disclosed in the MPEG-2 standard; and in case of the intra block AC coefficients, the quantizer step size of a higher frequency is larger than that of a lower frequency.
Blocking effect is a phenomenon wherein the borderline of a block becomes visible at a receiving end. Such blocking effect occurs due to the fact that a frame is encoded in units of blocks; and may become more serious as the quantizer step size becomes larger, i.e., as the blocks undergo a coarser quantization. Accordingly, in the intra block AC coefficients, since the quantizer step size of a higher frequency is larger than that of a lower frequency, the intensity difference between a given block and its adjacent blocks may become even more pronounced, thereby resulting in a more severe blocking effect and lowering the quality of the image. Even in case of the inter mode coding with motion compensated frame prediction, while the blocking effect may not be so disturbing, it still be noticeable.
It is, therefore, a primary object of the invention to provide a video signal decoding method and apparatus for compensating quantization errors of a decoded video signal by adaptively filtering high frequency components of current frame data based on standard deviations of pixel values of a plurality of previous frames decoded prior to deriving the current frame data.
In accordance with one aspect of the present invention, there is provided a method for producing a decoded video signal by decoding an encoded video signal, wherein the decoded video signal includes a plurality of frames, comprising the steps of: (a) processing the encoded video signal by using a variable length decoding to thereby derive a set of quantized discrete cosine transform coefficients corresponding to current frame data; (b) converting the set of quantized discrete cosine transform coefficients into a set of discrete cosine transform coefficients; (c) detecting a spatial activity of the current frame data based on previous frame data decoded prior to obtaining the current frame data; (d) filtering high frequency components of the set of discrete cosine transform coefficients within a preset region based on the set of discrete cosine transform coefficients and the spatial activity of the current frame data, to thereby produce a set of filtered discrete cosine transform coefficients; (e) transforming the set of filtered discrete cosine transform coefficients into a set of inverse discrete cosine transform data; (f) generating the current frame data through the use of motion compensation based on the set of inverse discrete cosine transform data and the previous frame data; and (g) providing the current frame data as the decoded video signal.
In accordance with another aspect of the present invention, there is provided an apparatus for producing a decoded video signal by decoding an encoded video signal, wherein the decoded video signal includes a plurality of frames, which comprises: a frame memory for storing previous frame data decoded prior to deriving current frame data; a variable length decoder for processing the encoded video signal by using a variable length decoding to thereby derive a set of quantized discrete cosine transform coefficients; an inverse quantizer for converting the set of quantized discrete cosine transform coefficients into a set of discrete cosine transform coefficients; a filter for masking high frequency components of the set of discrete cosine transform coefficients within a preset region based on the set of discrete cosine transform coefficients and the previous frame data, to thereby produce a set of filtered discrete cosine transform coefficients;an inverse discrete cosine transformer for transforming the set of filtered discrete cosine transform coefficients into a set of inverse discrete cosine transform data; a motion compensator for generating the current frame data through the use of motion compensation based on the set of inverse discrete cosine transform data and the previous frame data; and a supplier for providing the current frame data as a new previous frame data to the frame memory and supplying the current frame data as the decoded video signal.
The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
Fig. 1 illustrates a block diagram of a video signal decoding apparatus for producing a decoded video signal in accordance with the present invention;
Fig. 2 is a detailed block diagram of the adaptive filter 150 in Fig. 1; and
Fig. 3 represents filtering regions of a 8x8 pixel block in accordance with the present invention.
Referring to Fig. 1, there is provided a block diagram of a video signal decoding apparatus 100 for producing a decoded video signal in accordance with a preferred embodiment of the present invention.
As can be seen in Fig. 1, an encoded bit stream from a corresponding conventional encoder(not shown) is coupled to a buffer 110 in the decoding apparatus 100. The buffer 110 receives the encoded bit stream and supplies it at a fixed rate to a demultiplexer(DEMUX) 120 wherein the encoded bit stream is demultiplexed to produce a decoding information signal such as an inter/intra mode signal, a quantization step size, and encoded image data, i.e., a set of variable length coded transform coefficients and coded motion vectors. The inter/intra mode signal is coupled to an inverse quantizer 140 and an adder 180 via a line L12; the quantization step size is applied to the inverse quantizer 140 via a line L10; and the set of variable length coded transform coefficients and the coded motion vectors are supplied to a variable length decoder(VLD) 130.
The variable length decoder 130 decodes the set of variable length coded transform coefficients and the coded motion vectors by using a known variable length decoding technique so as to provide a set of quantized discrete cosine transform coefficients to the inverse quantizer 140 and motion vectors to a motion compensator 170.
At the inverse quantizer 140, the set of quantized discrete cosine transform coefficients is converted into a set of discrete cosine transform coefficients in response to the quantization step size and the inter/intra mode signal coupled thereto through the lines L10 and L12, respectively, from the demultiplexer 120. The set of discrete cosine transform coefficients is provided to an adaptive filter 150 via a line
L20.
In accordance with the present invention, the adaptive filter 150 receives the set of discrete cosine transform coefficients sequentially coupled thereto via the line L20; calculates a standard deviation of current frame data which is provided from a frame memory 190 via a line L14 and stores it as a previous standard deviation; computes a spatial activity of the current frame data based on a plurality of the previous standard deviations corresponding to frame data decoded prior to obtaining the current frame; and, according to the spatial activity of the current frame, adaptively filters high frequency components of the set of discrete cosine transform coefficients to thereby provide an inverse discrete cosine transformer(IDCT) 160 with a set of filtered discrete cosine transform coefficients via a line L22. The operation of the adaptive filter 150 is described in detail with reference to
Figs. 2 to 3.
In Fig. 2, there is shown a detailed block diagram of the adaptive filter 150 including a standard deviation calculation sector 152, a control signal generation sector 154, and a filtering sector 156.
The current frame data fed to the adaptive filter 150 via the line L14 is coupled to the standard deviation calculation sector 152. The standard deviation calculation sector 152 ciphers a standard deviation of frame data, e.g., the current frame data, coupled thereto from the frame memory 190 to thereby represent a statistical characteristic of the frame data by using the standard deviation thereof.
For instance, in case of frame data containing, e.g., MxN pixel values, M and N being positive integers, respectively, a mean value and a standard deviation thereof are determined as follows:
EQ. 1
EQ. 2 wherein NIp represents the mean value; Ip(x,y) is a pixel value positioned at coordinates (x,y) of a frame; and ACT depicts the standard deviation.
In the above, a comparatively large value of the calculated standard deviation means that a video image of a corresponding frame data is complicated.
The standard deviation determined as above is provided to the control signal generation sector 154 and stored at a memory(not shown) therein as a previous standard deviation.
The control signal generation sector 154 produces a spatial activity of the current frame based on a plurality of previous standard deviations stored in the memory therein, wherein the previous standard deviations correspond to respective previous frame data decoded prior to deriving the current frame data. In particular, the spatial activity of the current frame data is determined by averaging the standard deviations of, e.g., 30 number of previous frames which are processed in a second.
Once the average standard deviation is computed as the spatial activity of the current frame, the control signal generation sector 154 provides a filtering control signal FC1 to the filtering sector 156, wherein the filtering control signal FC1 is determined by comparing the spatial activity with a predetermined threshold value TH1.
In accordance with an embodiment of the present invention, the control signal generation sector 154 produces the filtering control signal FC1 as follows: FC1 = 1 if MACT < TH1 + O.5xSe
2 if TH1 + O.5xSe < MACT c TH1 + lxSe
3 if TH1 + lxSe < MACT < TH1 + l.5xSe 4 if MACT > TH1 + l.5xSe EQ. 3 wherein MACT represents the spatial activity of the current frame; TH1 is a predetermined threshold value; and Se depicts an adaptive filtering parameter.
According to EQ. 3, the filtering control signal FC1 is determined by considering relevance among the spatial activity, the predetermined threshold value TH1, and the adaptive filtering parameter Se. The adaptive filtering parameter Se is an experimental value giving a weight to determine the different values of the filtering control signal. The generated filtering control signal FC1 is provided to the filtering sector 156.
In response to the filtering control signal FC1, the filtering sector 156 selects a region to be filtered and masks the discrete cosine transform coefficients within the selected region.
Referring to Fig. 3, there are shown the filtering regions for the discrete cosine transform coefficients in the frequency domain, wherein Z(u,v) is a discrete cosine transform coefficient in the frequency domain, u, v being 1 to
K, e.g., 8; Z(0,0) represents a DC component; and a frequency of Z(u,v) increases as u or v is getting larger. If the filtering control signal FC1 has a digit "1", the filtering sector 156 does not perform the filtering operation for the set of discrete cosine transform coefficients; if it has a digit "2", high frequency components in the region below a dotted line B1 are set to a digit value "0"; if it has a digit "3", high frequency components below a dotted line B2 are set to a digit value "0"; and if it has a digit "4", high frequency components below a dotted line B3 are set to a digit value "0". The set of filtered discrete cosine transform coefficients determined as above is inputted to the inverse discrete cosine transformer 160.
In the above processes, the filtering regions and the filtering control signal FC1 can be adjusted in accordance with another embodiment of the present invention.
Referring back to Fig. 1, the inverse discrete cosine transformer 160 converts the set of filtered discrete cosine transform coefficients fed from the adaptive filter 150 via the line L22 into a set of inverse discrete cosine transform data and then provides the set of inverse discrete cosine transform data to the adder 180.
Meanwhile, the motion compensator 170 extracts corresponding pixel data from previous frame data stored in a frame memory 190 based on the motion vectors transferred from the variable length decoder 130 and provides the extracted pixel data as motion compensated data to the adder 180.
At the adder 180, the set of inverse discrete cosine transform data from the inverse discrete cosine transformer 160 is added/or not added to the motion compensated data from the motion compensator 170 in response to the inter/intra mode signal on the line L12, to thereby generate a decoded image.
In case of the inter mode, the set of inverse discrete cosine transform data is added to the motion compensated data; and in case of the intra mode, the set of inverse discrete cosine transform data is provided through the adder 180 to the frame memory 190 without any adding operation.
The decoded image is stored in the frame memory 190 as previous frame data, and is provided as a decoded video signal to a digital to analog(D/A) converter 200. And also the decoded image is transferred as the current frame data to the adaptive filter 150 via the line L14 so as to be used to produce a standard deviation thereof.
The digital to analog converter 200 converts the decoded video signal to an analog video signal to thereby provide same to a display unit(not shown) for the visualization thereof.
In accordance with the present invention, the complexity of the current frame data is determined by averaging the standard deviations of pixel values of a multiplicity of previous frames decoded prior to obtaining the current frame data. That is, it is determined according to the average standard deviation that the current frame data is complex and high frequency components of the current frame data which is insensitive to human visual characteristic is filtered, thereby depreciation of the image quality due to a quantization error being efficiently reduced.
While the present invention has been described with respect to certain preferred embodiments only, other modifications and variations may be made without departing from the scope of the present invention as set forth in the following claims.
Claims (16)
1. A method for producing a decoded video signal by decoding an encoded video signal, wherein the decoded video signal includes a plurality of frames, comprising the steps of:
(a) processing the encoded video signal by using a variable length decoding to thereby derive a set of quantized discrete cosine transform coefficients corresponding to current frame data;
(b) converting the set of quantized discrete cosine transform coefficients into a set of discrete cosine transform coefficients;
(c) detecting a spatial activity of the current frame data based on previous frame data decoded prior to deriving the current frame data;
(d) filtering high frequency components of the set of discrete cosine transform coefficients within a preset region based on the set of discrete cosine transform coefficients and the spatial activity of the current frame data, to thereby produce a set of filtered discrete cosine transform coefficients;
(e) transforming the set of filtered discrete cosine transform coefficients into a set of inverse discrete cosine transform data; and
(f) generating the current frame data through the use of motion compensation based on the set of inverse discrete cosine transform data and the previous frame data, and providing the current frame data as the decoded video signal.
2. The method as recited in claim 1, wherein the step (c) includes the steps of:
(cl) calculating a standard deviation of the previous frame data;
(c2) averaging the standard deviations which correspond to a multiplicity of previous frames processed prior to obtaining the current frame; and
(c3) providing the average standard deviation as the spatial activity of the current frame data.
3. The method as recited in claim 2, wherein the step (d) includes the steps of:
(dl) producing a filtering control signal by comparing the spatial activity with a predetermined threshold value; and
(d2) filtering, in response to the filtering control signal, the high frequency components of the set of discrete cosine transform coefficients within the preset region in order to generate the set of filtered discrete cosine transform coefficients.
4. The method as recited in claim 3, wherein the high frequency components of the set of discrete cosine transform coefficients within the preset region are set to a digit value "0".
5. The method as recited in claim 4, wherein the filtering control signal has more than two logic levels in order to adaptively filter the high frequency components of the set of discrete cosine transform coefficients.
6. The method as recited in claim 5, wherein the filtering control signal is determined as: FC1 = 1 if MACT < TH1 + O.5xSe
2 if TH1 + O.5xSe < MACT s TH1 + lxSe
3 if TH1 + lxSe < MACT # THl + 1.5xSe 4 if MACT > TH1 + 1.5xSe wherein FC1 is the filtering control signal; MACT represents the spatial activity of the current frame data; TH1 is the predetermined threshold value; and Se depicts an adaptive filtering parameter which is used as a weight to determine the different values of the filtering control signal.
7. The method as recited in claim 6, wherein the preset region is changed in response to the filtering control signal, the width of the preset region becoming larger as the value of the filtering control signal increases.
8. An apparatus for producing a decoded video signal by decoding an encoded video signal, wherein the decoded video signal includes a plurality of frames, which comprises:
means for storing previous frame data decoded prior to deriving current frame data;
means for processing the encoded video signal by using a variable length decoding to thereby derive a set of quantized discrete cosine transform coefficients;
means for converting the set of quantized discrete cosine transform coefficients into a set of discrete cosine transform coefficients;
means for filtering high frequency components of the set of discrete cosine transform coefficients within a preset region based on the set of discrete cosine transform coefficients and the previous frame data, to thereby produce a set of filtered discrete cosine transform coefficients;
means for transforming the set of filtered discrete cosine transform coefficients into a set of inverse discrete cosine transform data;
means for generating the current frame data through the use of motion compensation based on the set of inverse discrete cosine transform data and the previous frame data; and
means for providing the current frame data as a new previous frame data to the storing means and supplying the current frame data as the decoded video signal.
9. The apparatus according to claim 8, wherein the filtering means includes:
means for detecting a spatial activity representing complexity of the current frame data based on the previous frame data;
means for producing a filtering control signal by comparing the spatial activity with a predetermined threshold value; and
means for filtering, in response to the filtering control signal, the high frequency components of the set of discrete cosine transform coefficients within the preset region in order to generate the set of filtered discrete cosine transform coefficients.
10. The apparatus according to claim 9, wherein the detecting means includes:
means for calculating a standard deviation of the previous frame data;
a memory means for storing the standard deviation;
means for averaging the standard deviations stored in the memory means, wherein the standard deviations correspond to a multiplicity of previous frames processed prior to obtaining the current frame; and
means for providing the average standard deviation as the spatial activity of the current frame data.
11. The apparatus according to claim 10, wherein the high frequency components of the set of discrete cosine transform coefficients within the preset region are set to a digit value "0".
12. The apparatus according to claim 11, wherein the filtering control signal has more than two logic levels in order to adaptively filter the high frequency components of the set of discrete cosine transform coefficients.
13. The apparatus according to claim 12, wherein the filtering control signal is determined as: FC1 = 1 if MACT s TH1 + O.5xSe
2 if TH1 + O.5xSe < MACT s TH1 + lxSe
3 if TH1 + lxSe < MACT s TH1 + 1.5xSe
4 if MACT > TH1 + 1.5xSe wherein FC1 is the filtering control signal; MACT represents the spatial activity of the current frame data; TH1 is the predetermined threshold value; and Se depicts an adaptive filtering parameter which is used as a weight to determine the different values of the filtering control signal.
14. The apparatus according to claim 13, wherein the preset region is changed in response to the filtering control signal, the width of the preset region becoming larger as the value of the filtering control signal increases.
15. A method substantially as described herein with reference to any one of Figures 1 to 3.
16. An apparatus substantially as described herein with reference to any one of Figures 1 to 3.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019960036970A KR100229533B1 (en) | 1996-08-30 | 1996-08-30 | Improved image decoding system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9718397D0 GB9718397D0 (en) | 1997-11-05 |
| GB2316828A true GB2316828A (en) | 1998-03-04 |
Family
ID=19471849
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9718397A Withdrawn GB2316828A (en) | 1996-08-30 | 1997-08-29 | Compensating quantization errors of a decoded video signal by using an adaptive filter |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH1098727A (en) |
| KR (1) | KR100229533B1 (en) |
| CN (1) | CN1175855A (en) |
| GB (1) | GB2316828A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1927951A3 (en) * | 2006-11-28 | 2009-05-27 | NTT DoCoMo, Inc. | Image adjustment amount determination device, method and program |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5087368B2 (en) * | 2007-10-30 | 2012-12-05 | 株式会社エヌ・ティ・ティ・ドコモ | Image processing apparatus, image processing method, and image processing program |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0526885A2 (en) * | 1991-08-05 | 1993-02-10 | Eastman Kodak Company | A method of reducing block artifacts created by block transform compression algorithms |
| US5475434A (en) * | 1993-08-17 | 1995-12-12 | Goldstar Co. Ltd. | Blocking effect attenuation apparatus for high definition television receiver |
| US5610729A (en) * | 1994-02-22 | 1997-03-11 | Kokusai Denshin Denwa Kabushiki Kaisha | Noise reduction apparatus for reducing noise in decoding of moving picture sequence |
| EP0796011A2 (en) * | 1996-03-15 | 1997-09-17 | International Business Machines Corporation | Video decoder including polyphase fir horizontal filter |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4170283B2 (en) * | 2004-11-01 | 2008-10-22 | 株式会社ソニー・コンピュータエンタテインメント | Drawing processing apparatus and drawing processing method |
-
1996
- 1996-08-30 KR KR1019960036970A patent/KR100229533B1/en not_active IP Right Cessation
-
1997
- 1997-08-29 GB GB9718397A patent/GB2316828A/en not_active Withdrawn
- 1997-09-01 JP JP23557497A patent/JPH1098727A/en active Pending
- 1997-09-01 CN CN97116864A patent/CN1175855A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0526885A2 (en) * | 1991-08-05 | 1993-02-10 | Eastman Kodak Company | A method of reducing block artifacts created by block transform compression algorithms |
| US5475434A (en) * | 1993-08-17 | 1995-12-12 | Goldstar Co. Ltd. | Blocking effect attenuation apparatus for high definition television receiver |
| US5610729A (en) * | 1994-02-22 | 1997-03-11 | Kokusai Denshin Denwa Kabushiki Kaisha | Noise reduction apparatus for reducing noise in decoding of moving picture sequence |
| EP0796011A2 (en) * | 1996-03-15 | 1997-09-17 | International Business Machines Corporation | Video decoder including polyphase fir horizontal filter |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1927951A3 (en) * | 2006-11-28 | 2009-05-27 | NTT DoCoMo, Inc. | Image adjustment amount determination device, method and program |
| US8150194B2 (en) | 2006-11-28 | 2012-04-03 | Ntt Docomo, Inc. | Image adjustment amount determination device, image adjustment amount determination method, image adjustment amount determination program, and image processing device |
Also Published As
| Publication number | Publication date |
|---|---|
| KR100229533B1 (en) | 1999-11-15 |
| GB9718397D0 (en) | 1997-11-05 |
| JPH1098727A (en) | 1998-04-14 |
| KR19980017211A (en) | 1998-06-05 |
| CN1175855A (en) | 1998-03-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5473377A (en) | Method for quantizing intra-block DC transform coefficients using the human visual characteristics | |
| US5852682A (en) | Post-processing method and apparatus for use in a video signal decoding apparatus | |
| US6445739B1 (en) | Quantization matrix for still and moving picture coding | |
| JP3678481B2 (en) | Video data post-processing method | |
| US5786856A (en) | Method for adaptive quantization by multiplication of luminance pixel blocks by a modified, frequency ordered hadamard matrix | |
| US20030185303A1 (en) | Macroblock coding technique with biasing towards skip macroblock coding | |
| EP0680219B1 (en) | Improved post-processing method for use in an image signal decoding system | |
| US5606372A (en) | Video signal decoding apparatus capable of reducing blocking effects | |
| US6865229B1 (en) | Method and apparatus for reducing the “blocky picture” effect in MPEG decoded images | |
| US5787210A (en) | Post-processing method for use in an image signal decoding system | |
| US5844607A (en) | Method and apparatus for scene change detection in digital video compression | |
| US5946421A (en) | Method and apparatus for compensating quantization errors of a decoded video image by using an adaptive filter | |
| JP3316157B2 (en) | Post-filtering method and apparatus | |
| US6016365A (en) | Decoder having adaptive function of eliminating block effect | |
| JP3437901B2 (en) | Video encoding method and apparatus | |
| US5614953A (en) | Image signal decoding apparatus having an encoding error compensation | |
| US6061401A (en) | Method and apparatus for selectively encoding/decoding a video signal | |
| GB2316828A (en) | Compensating quantization errors of a decoded video signal by using an adaptive filter | |
| KR0181033B1 (en) | Apparatus for selectively encoding error signals | |
| Choi et al. | Adaptive image quantization using total variation classification | |
| Salari et al. | Low-bit-rate segmentation-based image sequence coding | |
| Zheng et al. | A novel video coding scheme with frequency-domain-based conditional frame replenishment algorithm | |
| JPH03124184A (en) | Cell abort compensation picture decoding system | |
| JPH08181997A (en) | Image coder and image decoder | |
| JPH06350988A (en) | Method of intra-block dc transformation coefficient quantization |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |