Abstract: An image motion-dependent mechanism selectively inserts an image modification operator, such as a median filter, into the image signal path of a video display unit, so that loss of definition and introduction of flicker resulting from the use of a median filter in the course Of the display of a still or stationary image on an IDTV are effectively eliminated. The selectively inserted image modification operator, which responds to an index code or bit value representative of whether or not the image frame is repeated, may also serve to prevent the generation of cross-luminance and cross-color decoding artifacts, as well as reducing the amount of random noise in the image.

Abstract: A 3D nonlinear postprocessing system and method are utilized to reduce coding artifacts produced by block-based motion-compensated transform coding. In the system and method, a separable 3D filtering structure is used: space-variant FIR-Median Hybrid filtering is used in spatial domain, followed by a motion-compensated nonlinear filtering in the temporal domain. By using this structure and method, the coding artifacts in a reconstructed image sequence can be effectively reduced without blurring edges or moving objects in the image sequence. Significant improvement in the picture quality of low bit-rate coded video sequences is thereby achieved.

Abstract: A recursive noise reduction device which reduces the noise component(s) of stationary region(s) in a moving image, successively cyclically calculating the coefficient (K) times of the present image signals and (1-K) times of the previous image signal having a correlation with the present image signal. The present image signal is a signal of an image of a frame or field that is presently entered and the previous image signal is a signal of an immediately previous image of the frame or field. The recursive noise reduction device includes a calculating unit to recursively calculate a sum of the coefficient K times the present image signal and (1-K) times the previous image signal, modifying the value of the aforementioned coefficient K according to the number of times of cyclic calculation, and a movement detection unit to detect the movement of an image within the stationary region(s) of the image. The value of the coefficient K is modified according to the output signal of the movement detection unit.

Abstract: The present invention is a motion adaptive spatial filtering(MASF) method for use with a image coding apparatus, which proceeds the temporal band-limitation of the video frame signals on spatial domain along the trajectory of a moving component without temporal aliasing by using a filter having a band-limitation characteristic according to a cutoff frequency. It is well known that video signal may contain a lot of temporal aliasing components because of insufficient frame sampling rate. And it is impossible to design band-limiting temporal filter simply by convolving a sequence of frames along the temporal direction. From a signal processing point of view, the aliasing degrades filter characteristics. This filtering method takes advantage of the fact that, if motion of each pixel is known, the temporal filtering can be performed in the spatial domain filtering along its trajectory. That results in de-aliasing characteristic.

Abstract: A digital Wiener filtering method is proposed which applies motion compensation by successive approximations of increasing resolution to determine displacement vectors for two successive image frames, a vectors defining a real displacement only being applied to a block of one of the frames when the mean absolute error associated with that vector is not greater than a given fraction of the mean absolute error between that block and the corresponding block of the other frame. The current frame is then filtered block-by-block, with the blocks overlapping. In this filtering, each block is a 3D volume of pixels from the current frame and blocks selected from the preceding and succeeding frames so as to correspond according to the displacement vectors. In one embodiment, the filtering comprises applying a 3D FFT to convert to a power spectrum in the frequency domain, followed by attenuation according to a Wiener filter and conversion from the frequency domain by the inverse FFT.

Abstract: A noise reducer for outputting a noise-reduced signal by extracting noise included in an input video signal so as to produce a noise signal and by subtracting the noise signal from the input video signal is provided.

Abstract: A novel pre-processing filter apparatus for use in an image encoding system, capable of adaptively filtering an input digital video signal, comprises a circuit for delaying a current frame of the input digital video signal by one frame interval; a circuit for generating a difference signal representing the difference between averaged pixel value for N.times.N pixels of the delayed previous frame and an averaged pixel value for N.times.N pixels of the current frame, at an identical area of the previous frame and the current frame; two or more filtering circuits arranged in parallel for filtering the input digital video signal, respectively, each of the filtering circuits having different cutoff frequencies; and a control circuit for generating one of the filtered digital video signals in response to the difference signal.

Abstract: A motion signal is formed by subtracting an undelayed and a delayed video signal and by subsequently forming the absolute value. An amplitude maximum of the motion signal is initially determined within a search window and subsequently a minimum corresponding to the noise peak value is determined from the maximum values of a plurality of search windows.

Abstract: According to a presently preferred embodiment of the invention, image enhancement apparatus for digital video images comprises a two-stage filter comprising a median filter and a recursive filter. The median filter operates in one, two, and three dimensions wherein the cluster of pixels framing the center pixel are ranked, and the median value of the pixel cluster is chosen as the correct pixel value. The pixel cluster configuration is selectable, as are the planes where the pixels are located. Multiple weights may be given to the appropriate median filter inputs. A motion detector is used to prevent replacement of each pixel by its pixel cluster median value when there is excessive motion. Finally an adjustable pixel-replacement threshold is defined. Each pixel must deviate from its median value before it is replaced by that value.

Abstract: A video signal noise reduction system is disclosed in which corresponding image pixels from a current frame and image pixels from a noise reduced previous frame are averaged to produce respective noise reduced pixel values. In the disclosed exemplary embodiment of the invention, a processed frame memory stores a noise reduced image and a motion estimator identifies a target block of pixels in this processed frame memory to be used in calculating a noise reduced video signal. A motion compensated noise reduction processor combines the block of the noise reduced image pixels stored in the processed frame memory with a current block of pixels generated from the video signal to produce a motion block of noise reduced pixels. The relative weighting applied to the stored pixel and the current pixel depends on the number of pixels that were used to generate the stored pixel.

Abstract: Motion video is represented by digital signals. The digital signals can be compressed by coding to reduce bitspace. Noise in the signal, however, reduces the efficiency of coding. The present invention is a system and method for reducing noise in video signals by filtering. The signal for the current frame is weightedly averaged with signals for a future and prior frame. The future and prior frames are given less weight as they differ more from the current frame. When motion compensation information is available, the motion compensated future and prior frames can be used for averaging, further improving filtering.

Abstract: A field recursive type noise reduction apparatus is disclosed in which the field difference is divided into a plurality of frequency components by means of the Hadamard transformation and the existence of a boundary of an oblique line in the proximity of pixels to be processed is detected from frequency components remaining by removing minimum and maximum horizontal frequency components by an oblique line detection circuit. In the location where the existence of the boundary of oblique line is detected, a feedback rate of the apparatus is reduced to avoid deterioration of the image quality by nonlinear processing means and in other locations the feedback rate is increased to improve the S/N, so that a noise reduction apparatus is realized having excellent improvement of the S/N as compared with a conventional field recursive type noise reduction apparatus.

Abstract: A coded digital video signal is obtained by dividing a digital video signal into plural pages each composed of K fields of pixel data, decomposing pixel data in each two pages into plural blocks each composed of a predetermined number of pixel data, and encoding the pixel data in each block by bit rate reduction encoding and error correction encoding. The thus obtained coded digital video signal is reproduced or transmitted and then subjected to a concealment process. The concealment process includes decoding the coded digital video signal to obtain reproduced blocks of pixel data and to detect an error block containing an error among the reproduced blocks, composing the reproduced blocks to obtain plural reproduced pages of pixel data, and concealing error pixel data contained in the error block in each two reproduced pages. Error pixel data in a first page is concealed using pixel data in a previous page, and error pixel data in a second page is concealed using pixel data in a succeeding page.

Abstract: A noise eliminating circuit comprising a noise eliminating filter for moving image part to be used when an input image is of the moving image part, a noise eliminating filter for stationary image part to be used when the input image is of the station image part, these filters being adaptively selected between according to a motion of the input image, a detecting circuit for detecting the motion of the input image, and a selecting circuit for selecting between outputs of these filters based on an output of the detecting circuit, wherein the noise eliminating circuit for stationary image part outputs an average input image of number of stationary frames n to be entered. The novel constitution effectively suppresses a noise introduced in a moving image or a stationary image, generating an output signal with a good picture quality.

Abstract: A field difference signal of a luminance signal is transformed to a plurality of frequency components by the Hadamard transformation, subsequently, nonlinear operation and inverse-transformation are applied to the frequency components and the inverse-transformed field difference signal is subtracted from the luminance signal, and thereby noise in the luminance signal is reduced, on the other hand in respect to a color difference signal, motion of a video image is detected on the basis of the level of at least one of the frequency components; and when the motion of the video image is large and the level of the frequency component is larger than a predetermined value, the level of the field difference signal to be subtracted from the color difference signal is decreased; on the contrary, when the level of the frequency component is the predetermined value and below, the level of the field difference signal to be subtracted from the color difference signal is increased.

Abstract: A device for reducing noise includes a first delay circuit for producing a first delay signal which is spacewise continuous to a current signal, a second delay circuit for producing a second delay signal which is timewise continuous to the current signal, first and second signal coincidence judging circuits for comparing the current signal with the first and second delay signals at a smapling period and judging whether or not difference in level between the current signal and the first and second delay signals is below a predetermined value continuously for a predetermined number of samples, and a conditional averaging circuit for providing, when it has been judged by the first or second signal coincidence judging circuit that the condition that difference in level between the current signal and the first or second delay signals is below the predetermined value continuously for the predetermined number of samples has been satisfied, an output signal which is an average value of one or both of the delay signal

Abstract: A noise reduction apparatus includes a frame type noise processing circuit which detects a correlation between two successive frames of a video signal and reduces noncorrelating parts of the video signal. A processed signal from the frame type circuit is mixed with a delayed video signal at a rate determined according to a degree of motion of an image represented by the video signal. A line type noise processing circuit detects a correlation between two successive lines of a mixed video signal and reduces noncorrelating parts of the mixed video signal. The line type circuit is controlled so as to change a characteristic of noise processing according to the degree of motion.

Abstract: A method of measuring the noise in an active video image. During a given processing period, for each pixel of a video image considered to be stationary, the difference f.sub.d between the video signal corresponding to this pixel and the video signal corresponding t the pixel at the same spatial position in a preceding image is calculated. The square of the absolute value of the difference is calculated so as to obtain a value .vertline.f.sub.d .vertline..sup.2, and the value .vertline.f.sub.d .vertline..sup.2 is added to previously obtained values so as to form a sum value .SIGMA..vertline.f.sub.d .vertline..sup.2. The above operations are repeated until the number of pixels processed is equal to a given threshold value N.sub.0, or until the end of the processing period. At the end of the processing period, if the number of pixels processed is equal to the threshold value, the value .SIGMA..vertline.f.sub.d .vertline..sup.2 is used to determine a reference point giving a new noise-reduction coefficient k.sub.

Abstract: A frame image signal which is output cyclically is converted to a digital signal and input to a first multiplier in a digital filter. The first multiplier multiplies a digital image signal Y.sub.i of each frame by (1-a), and supplies the product (1-a).multidot.Y.sub.i to a first input terminal of an adder. The coefficient a is a negative coefficient whose absolute value is not more than 1, so that (1-a) becomes a positive coefficient of not less than 1. An output of the adder serves as an output Y.sub.i ' of the digital filter from which the residual image has been erased, and is supplied to a subsequent unit, e.g., a display unit (not shown) connected to the output of the adder. The output Y.sub.i ' of the adder is also supplied to a frame memory and is delayed by one frame period. Therefore, an output Y.sub.i-1 ' of the frame memory is a one-frame preceding image output. The signal Y.sub.i-1 ' is input to a second multiplier and is multiplied by the coefficient a.

Abstract: A median filter is modified for temporal suppression of image grain in a time-varying sequence of images. Successive sets of samples are produced by operation of a sample producer (20), each set including a current sample, a sample delayed by a framestore (50), and a sample derived from a recursive component generator (60). A median selector (80) operates upon each set to select the median sample value. Either the median value or the current sample is selected for the filter output, dependent upon an interframe magnitude generated by an adaptive component generator (30). Evaluation of interframe magnitude minimizes artifacts in the reproduction of picture information that is temporarily impulsive, while including the recursive component in the median sample set increases the level of grain suppression.

Abstract: A signal from an input terminal (1) is supplied to a video signal processing circuit (2) which derives a carrier chrominance signal. The carrier chrominance signal is supplied through a low-pass filter (3) to an A/D converter circuit (4). A signal converted by the A/D converter circuit (4) is supplied to a bandpass filter (5) which limits the band of the chrominance signal. A signal from the bandpass filter (5) is supplied to a decoder circuit (6) which alternately derives color difference signals (R-Y) and (B-Y). The signal from the decoder circuit (6) is supplied to a decimation filter (7) which effects a decimation. The signal thus decimated is supplied to a multiplexer (8) and thereby generated as 2-bit series data. A signal from the multiplexer (8) is supplied to a CNR (chroma noise reducer) circuit (9). Thus, the number of bits can be reduced without reducing the number of lines of a chroma signal and data gradation.

Abstract: An image motion-dependent mechanism selectively inserts an image modification operator, such as a median filter, into the image signal path of a video display unit, so that loss of definition and introduction of flicker resulting from the use of a median filter in the course of the display of a still or stationary image on an IDTV are effectively eliminated. The selectively inserted image modification operator, which responds to an index code or bit value representative of whether or not the image frame is repeated, may also serve to prevent the generation of cross-luminance and cross-color decoding artifacts, as well as reducing the amount of random noise in the image.

Abstract: An image signal processing apparatus according to the present invention is configured so that a new image signal is formed using an input image signal and an image signal which has previously been stored, and either one of the input image signal and the newly formed image signal is selectively stored again. It becomes thereby possible to instantaneously store the input image signal whenever necessary.

Abstract: A motion adaptive vertical filter is used to filter an interlaced video signal on a frame basis in areas of the image that are not in motion and on a field basis in areas that are in motion. A soft switch mixes the field filtered data and the frame filtered data in areas where there is relatively little motion to prevent artifacts which may be caused by abruptly switching between the two vertical filtering schemes. The frame vertical filter reduces the vertical resolution of still NTSC images to 180 cycles per picture height (CPH) while the field filter reduces the vertical resolution to 90 CPH.