167 results about "Adaptive loop filtering" patented technology

An apparatus and method for sample adaptive offset to restore intensity shift of processed video data are described. In a video coding system, the video data are subject to various processing such as prediction, transformation, quantization, deblocking, and adaptive loop filtering. Along the processing path in the video coding system, certain characteristics of the processed video data may be altered from the original video data due to the operations applied to video data. For example, the mean value of the processed video may be shifted. Therefore, the pixel intensity shift has to be carefully compensated or restored to alleviate the artifacts. Accordingly a sample adaptive offset scheme is disclosed that can take into consideration of the dynamic characteristics within a frame using a region partition scheme. Furthermore, the sample adaptive offset scheme also supports multiple SAO types that can be tailored to the characteristics of processed video data and achieve better quality.

A method and apparatus for processing in-loop reconstructed video using an in-loop filter is disclosed. In the recent HEVC development, adaptive loop filtering (ALF) is being adopted to process in-loop reconstruction video data, where ALF can be selectively turned ON or OFF for each block in a frame or a slice. An advanced ALF is disclosed later that allows a choice of multiple filter sets that can be applied to the reconstructed video data adaptively. In the present disclosure, pixels of the in-loop reconstructed video data are divided into a plurality of to-be-filtered regions, and an in-loop filter from a filter set is determined for each to-be-filtered region based on a rate-distortion optimization procedure. According to one embodiment of the present invention, computation of cost function associated with the rate-distortion optimization procedure is related to correlation values associated with original video data and the in-loop reconstructed video data. Furthermore, the correlation values can be shared by the multiple candidate filters during the rate-distortion optimization procedure for said each to-be-filtered region. In another embodiment, the correlation values can be shared by multiple candidate to-be-filtered regions of an area of the in-loop reconstructed video data during the rate-distortion optimization procedure for the area of the in-loop reconstructed video data.

An apparatus and method for video coding having intra-slice deblocking, intra-slice adaptive loop filter, and intra-slice adaptive offset are disclosed. In a video coding system, a picture is often divided into slices and each slice is independently processed so that errors or missing data from one slice cannot propagate to any other slice within the picture. In the recent high efficiency video coding (HEVC) development, deblock filtering (DF), adaptive loop filter (ALF) and adaptive offset (AO) may be applied to reconstructed slices. When the processing is applied across slice boundaries, it may rely on pixels outside the current slice and cause dependency of the current slice on other slice(s). Consequently, the DF / ALF / AO processing on a reconstructed slice may have to wait until the reconstructed slices that it is dependent from complete the DF / ALF / AO processing. To overcome the slice boundary issue, intra-slice DF / ALF / AO is developed that does not rely on any pixel outside the currently slice. An optional slice boundary filter may be applied to slice boundaries after all slices are processed by the intra-slice DF / ALF / AO.

The present invention relates to filtering of image data at first with a deblocking and then with an adaptive loop filter, suitable for the purpose of video coding and decoding. In order to reduce requirements to a memory on chip, used to buffer image lines necessary for filtering, the input signal for the adaptive loop filter is determined from among deblocked pixels, non-deblocked pixels and partially (horizontally only or vertically only) deblocked pixels. The adaptive loop filtering of a deblocked pixel may then apply the filter taps to already deblocked pixels and / or undeblocked pixels and / or partially deblocked pixels in accordance with the determination of the input signal. An advantage of the invention is reduction of the line memory necessary especially at the decoder for processing with both filters.

A method for in-loop filtering in a video encoder is provided that includes determining filter parameters for each filtering region of a plurality of filtering regions of a reconstructed picture, applying in-loop filtering to each filtering region according to the filter parameters determined for the filtering region, and signaling the filter parameters for each filtering region in an encoded video bit stream, wherein the filter parameters for each filtering region are signaled after encoded data of a final largest coding unit (LCU) in the filtering region, wherein the in-loop filtering is selected from a group consisting of adaptive loop filtering and sample adaptive offset filtering.

An apparatus and method for coding unit-synchronous adaptive loop filtering (ALF) for an image area that is partitioned into a plurality of coding units are disclosed. In a conventional approach, the slice-level bitstream cannot be generated until all coding units in a slice are processed since the ALF filter coefficients are determined based on reconstructed pixels and original pixels of a slice. According to one embodiment, the method processes the coding units in the image area one after the other to generate a CU-level bitstream. The method also reconstructs the coding units to from reconstructed coding units which are subject to adaptive loop filtering. Upon the availability of reconstructed coding units for the image area, the method derives filter coefficients for the ALF filter based on the reconstructed pixels and original pixels in the image area. The designed ALF filter is then tested for each coding unit to determine whether the ALF filter should be applied to the coding unit and the decision is indicated by an ALF flag. After all ALF flags are determined, an image area header is created by incorporating the filter coefficients and ALF flags in the header. The header and the CU-level data previously created are combined into an image area level bitstream. An apparatus to perform the steps recited in the method is also disclosed.

The present invention relates to a simplified pipeline for Sample Adaptive Offset (SAO) and Adaptive Loop Filtering (ALF) in the in-loop decoding of a video encoder and a video decoder. According to the present invention, filter parameter setting regions and filtering processing windows are aligned, to reduce the required amount of memory for parameter sets necessary for delayed filtering. This is preferably achieved by a displacement of the filter parameter setting regions with respect to LCU boundaries in at least one (preferably: vertical) or both vertical and horizontal directions.

The invention discloses a boundary treatment method and device for adaptive loop filter. The method comprises the steps of determining a filter area according to an upper boundary and a lower boundary of the current maximum coding unit in a sequence; determining whether pixels at the outsides of the left boundary and the right boundary of the filter area are usable; replacing the unusable pixel samples by the closest pixel samples within the filter area during loop filter ALF process. With the adoption of the method, the problem of boundary treatment of ALF filter process can be solved, the correlation of pixels is fully utilized, the cost is tiny loss on coding performance, and the hardware cost during achieving the adaptive loop filter can be decreased.

The application relates to a loop filtering method, a loop filtering device, a piece of electronic equipment and a readable medium. The loop filtering method includes the following steps: setting a virtual boundary outside the actual boundary of a coding tree unit according to the size and shape of a filter; filling the gap between the actual boundary and the virtual boundary with virtual pixel samples; and using the virtual pixel samples instead of the pixels beyond the actual boundary of the coding tree unit to carry out loop filtering on the multiple pixels in the coding tree unit. According to the method, a virtual boundary is set outside the actual boundary, and virtual pixel samples are set between the virtual boundary and the actual boundary, so that virtual pixel samples can be used in adaptive loop filtering, and the problem of data dependence between coding tree units is solved.

Adaptive loop filter (ALF) padding in accordance with video coding. Various types of video processing are performed including performing virtual padding. When a filter coefficients collocated pixel is not available, that pixel may be replaced using an available pixel within a given location within a filter to process a number of pixels. For example, an available pixel located within the center of such a filter (e.g., which may be a cross shaped filter including a predetermined number of pixels, such as 18 pixels in one instance) may be used to replace those pixel locations which are not available in accordance with such virtual padding. With respect to the implementation of such an adaptive loop filter (ALF), such an ALF may be implemented to process a signal output from a de-blocking filter, from a sample adaptive offset (SAO) filter, and / or from a combined de-blocking / SAO filter in various implementations.

A method for image decoding, according to the present invention, includes the following steps: receiving image information including a plurality of filter coefficients; generating a restored block for a current block on the basis of the image information; and applying an adaptive loop filter to the restored block on the basis of the plurality of filter coefficients. According to the present invention, image encoding efficiency may be improved, and complexity may be reduced.

A method and apparatus for loop filter processing of video data are disclosed. Embodiments according to the present invention eliminate data dependency associated with loop processing across tile boundaries. According to one embodiment, loop processing is reconfigured to eliminate data dependency across tile boundaries if cross-tile loop processing is disabled. The loop filter processing corresponds to DF (deblocking filter), SAO (Sample Adaptive Offset) processing or ALF (Adaptive Loop Filter) processing. The processing can be skipped for at least one tile boundary. In another embodiment, data padding based on the pixels of the current tile or modifying pixel classification footprint are used to eliminate data dependency across the tile boundary. Whether cross-tile loop processing is disabled can be indicated by a flag coded at sequence, picture, or slice level to indicate whether the data dependency across said at least one tile boundary is allowed.

The present disclosure provides various techniques related to adaptive loop filtering (ALF), and particular to geometry transformation-based ALF (GALF). In an aspect, a method for decoding video dataincludes receiving an encoded bitstream having coded video data from which reconstructed video units are generated, identifying multiple filter supports for the reconstructed video units, and filtering the reconstructed video units using the respective multiple filter supports to produce a decoded video output. Another method includes enabling block-level control of ALF of chroma components for the reconstructed video units, performing, for the reconstructed video units, the block-level ALF for the chroma components when ALF is enabled for one video block and skip performing the block-level ALF for the chroma components when ALF is disabled for another video block, and generating, based on the enabled block-level control of ALF, a decoded video output. Related devices, means, and computer-readable medium are also described.

In a block-based motion compensated system, coding noises may arise due to lossy operations. Adaptive loop filter (ALF) is a technique used to improve the quality. A pixel adaptive (PA) ALF method was developed that uses the Sum-modified Laplacian Measure (SLM) to classify pixels and applies a respective ALF filter to each pixel according to the SLM. While the PA ALF achieves better performance over a conventional single filter (SF) based ALF, the PA ALF causes higher complexity and consumes more power due to the high complexity and per-pixel filter switching. Accordingly region based ALF scheme is disclosed which allows adaptive filter selection on a region by region basis and does not require per-pixel filter switching. In one embodiment according to the present invention, a picture is divided into M×N regions. The region based ALF also allows region merging for the M×N regions to improve performance. In another aspect of the present invention, the optimal ALF design also takes into consideration of the system complexity by using rate-distortion-complexity optimization (RDCO). The RDCO technique is also applied to sample adaptive offset (SAO) design.

The embodiment of the invention provides an adaptive loop filter method in video coding and decoding. The method comprises: image block division is carried out on an inputted reconstruction video image, a similar block matrix is formed based on the image blocks, and singular value decomposition is carried out on the similar block matrix to obtain a singular value of the similar block matrix; a standard difference of the reconstruction video image is calculated, a shrinkage filter threshold value of the similar block matrix is determined according to the standard different, a coding mode, and a quantization parameter of the reconstruction video image, and shrinkage filtering is carried out on the singular value of the similar block matrix based on the shrinkage filter threshold value; and the image blocks in the similar block matrix are reconstructed by using the shrunk singular value to obtain an adaptive loop filter video image. According to the embodiment of the invention, an adaptive filter control parameter estimation method is put forward by using non-local similarity inside a video image and high-efficiency adaptive loop filtering in video coding and decoding is realized, so that the video compression performance is improved effectively.

The present invention provides an improved video encoding and decoding method, which maintains the advantages of LCU-based filter parameter signaling as compared to frame-based filter parameter signaling, but considerably reduces signaling overhead. Therefore, signaling syntax is modified by grouping LCUs (Largest Coding Units) together for signaling employing a mapping function. Consequently, filter parameters no longer need to be signaled for each single LCU, but for a group of several LCUs. The syntax structure of the invention avoids redundancies present in the state of the art as far as possible and thus increases the information content of the syntax elements. At the decoder side, the mapping function is applied to infer information about the filter parameters to be applied to a current LCU from information encoded in different syntax structures.

Adaptive loop filtering in accordance with video coding. An adaptive loop filter (ALF) and / or other in-loop filters (e.g., sample adaptive offset (SAO) filter, etc.) may be implemented within various video coding architectures (e.g., encoding and / or decoding architectures) to perform both offset and scaling processing, only scaling processing, and / or only offset processing. Operation of such an ALF may be selective in accordance with any of multiple respective operational modes at any given time and may be adaptive based upon various consideration(s) (e.g., desired complexity level, processing type, local and / or remote operational conditions, etc.). For example, an ALF may be applied to a decoded picture before it is stored in a picture buffer (or digital teacher buffer (DPB)). An ALF can provide for coding noise reduction of a decoded picture, and the filtering operations performed thereby may be selective (e.g., on a slice by slice basis, block by block basis, etc.).

A method for adaptive loop filtering of a reconstructed picture in a video encoder is provided that includes determining whether or not sample adaptive offset (SAO) filtering is applied to the reconstructed picture, and using adaptive loop filtering with no offset for the reconstructed picture when the SAO filtering is determined to be applied to the reconstructed picture.

The invention relates to a method and device for carrying out adaptive loop filtering during video coding and decoding and a corresponding video coding and decoding system. The method includes the steps of solving filtering coefficients of a current image at the coding end, filtering color components of the current image according to the filtering coefficients, and obtaining frame-level filtering control switches and LCU-level filtering control switches of the color components; reconstructing the filtering coefficients at the decoding end according to the frame-level filtering control switches of the color components and the corresponding filtering coefficients, and filtering pixels in an LCU selectively through the reconstructed filtering coefficients according to the obtained LCU-level filtering control switches. By means of the method and device and the video coding and decoding system, the coding efficiency is effectively improved; meanwhile, the calculation complexity and the hardware achievement complexity are reduced to be within acceptable ranges, the practical application requirement is met, the errors between distortion signals and original signals are reduced, the quality of the current image is improved, and then the high-quality reference forecasting image is provided.

Provided are a method and apparatus for encoding and decoding images based on constrained offset compensation and a loop filter. The image decoding apparatus: receives, from an encoder, a first indicator indicating whether a sequence, a picture, a frame, a slice, a coding unit (CU), a prediction unit (PU), and / or a transform unit (TU) supports constrained offset compensation; receives, from the encoder, a second indicator indicating whether constrained sample adaptive offset (SAO) compensation or an adaptive loop filter (ALF) is applied; receives a parameter from the encoder; and applies the SAO compensation or the ALF to pixels of a restored image on the basis of the second indicator and the parameter.

Techniques are described for adaptation parameter sets (APS) for adaptive loop filter (ALF) parameters. One example involves obtaining an APS ID value and an APS type value associated with a NAL unit from a bitstream. A first APS associated with at least a portion of at least one picture is identified, with the first APS being uniquely identified by a combination of the APS type value and the APS identifier value, and the APS identifier value of the first APS is in a range based on the APS type value. The portion of the at least one picture is then reconstructed using an adaptive loop filter with parameters defined by the first APS uniquely identified by the APS type value and the APS identifier value.

An extension of an adaptive loop filter includes, in the sequence parameter set, a bit is added to signal whether the “default” or fixed adaptive loop filters are to be updated for this sequence. If yes, then the new set of default filters are explicitly coded. In the picture parameter set, a flag is used to determine whether to update the default filters at the picture level. If yes, filter coefficients are transmitted. In the Slice Header, a flag is added to show whether the online filter and the fixed filters are both available for block-level switching or not. Block-level filter switching is also referred to as ALF's CU control parameters. In the LCU Header, the maximum depth (minimum block-size) for the ALF's CU control parameters (block-level filter switchings) is explicitly signaled.

An adaptive loop filter classifies a decoded image from a deblocking filter into a smooth region class and an edge / texture region class, in accordance with results of edge detection from an edge detecting unit. The adaptive loop filter performs filter coefficient calculation for each of classified classes such that the residual difference between an original image from a screen rearranging buffer and an image from the deblocking filter is smallest. The adaptive loop filter performs filter processing using filter coefficients calculated for each classified class, and outputs an image after filter processing to frame memory. The filter may be applied to an image encoding device for performing encoding with the H.264 / AVC format as a basis, for example.

Disclosed are adaptive loop filtering techniques for video encoding and / or decoding. For a video unit, the encoder selects a set of predefined filters or generates a set of new filters, and places into the bitstream information identifying the set of predefined filters, or information defining the set of new filters. The set of filters may be used for loop filtering of at least one of the reconstructed samples of the video unit. At the decoder, a set of filters may be obtained by, decoding an index that identifies a set of predefined filters, or by decoding information related to a set of new filters. The obtained set of filters may be used for loop filtering of at least one decoded and reconstructed sample of the video unit.