49 results about "Coding artifacts" patented technology

Block-based image processing methods and apparatus that provide a reduction in block-transform image coding artifacts are described. In various embodiments, the invention is directly incorporated into a decoding process. In such embodiments, transform coefficients are modified in simple but particularly effective ways that reduce or eliminate many of the artifacts that were caused by the quantization of the transform coefficients during encoding and / or by independent block processing during encoding. In other embodiments, the invention is used on an image that has already been decoded. In such embodiments image data values are directly modified in a block-based fashion or a forward block transform is applied and then the methods of the invention for processing transform coefficient blocks are used, followed by an inverse transform operation to generate pixel values from the resulting processed transform coefficient blocks.

A method for adaptive quantization of video frames based on bit rate prediction that includes increasing quantization in sectors of a video frame where coding artifacts would be less noticeable to the human visual system and decreasing quantization in sectors where coding artifacts would be more noticeable to the human visual system. In one embodiment the method reverts to uniform quantization for video frames in which adaptive quantization would require extra bits.

A first signal representation of one or more of the multiple channels is encoded (S1) in a first encoding process, and a second signal representation of one or more of the multiple channels is encoded (S2) in a second, filter-based encoding process. Filter smoothing can be used to reduce the effects of coding artifacts. However, conventional filter smoothing generally leads to a rather large performance reduction and is therefore not widely used. It has been recognized that coding artifacts are perceived as more annoying than temporary reduction in stereo width, and that they are especially annoying when the coding filter provides a poor estimate of the target signal; the poorer the estimate, the more disturbing artifacts. Therefore, signal-adaptive filter smoothing (S3) is introduced in the second encoding process or a corresponding decoding process as a new general concept for solving the problems of the prior art.

A video quality adaptive coding artifact reduction system has a video quality analyzer, an artifact reducer, and a filter strength controller. The video quality analyzer employs input video quality analysis to control artifact reduction. The video quality analyzer accesses the video quality of the decoded video sequence to estimate the input video quality. The filter strength controller globally controls the filter strength of the artifact reducer based on the video quality estimate by the video quality analyzer. For low quality input video, the filter strength controller increases the artifact reduction filter strength to more efficiently reduce the artifact. For high quality input video, the filter strength controller decreases the artifact reduction filter strength to avoid blurring image detail.

A method for reducing or eliminating coding artifacts in video pictures processed using intra block prediction methods, for example, according to the H.264 standard. The causes of the coding artifacts are identified to be the intra prediction modes with prediction directions that are not in the direction of the raster scan. Filtering the affected blocks with a simple one-dimensional spatial filter will reduce or even eliminate these coding artifacts.

An efficient and non-iterative 3D post processing method and system is proposed for mosquito noise reduction, block localization and correction in DCT block-based decoded images. The 3D post processing is based on a simple classification that segments a picture in multiple regions such as Edge, Near Edge, Flat, Near Flat and Texture regions. The proposed technique comprises also an efficient and shape adaptive local power estimation for equivalent additive noise and provides simple noise power weighting for each above cited region. Temporal filtering configurations using Minimum Noise Variance Criterion are proposed for reducing temporally varying coding artifacts. A Minimum Mean Square Error or Minimum Mean Square Error-like noise reduction with robust and effective shape adaptive windowing is utilized for smoothing mosquito and / or random noise for the whole image, particularly for Edge regions. The proposed technique comprises also signal domain histogram analysis based Block Localization and adaptive edge based Block artifact correction. Finally, is also proposed an optional adaptive detail enhancer which can enhances the luminance signal in eight directions differently.

The present invention relates to a full-reference (FR) objective method for assessing perceptual quality of decoded video frames in the presence of packet losses and coding artifacts. A method of assessing perceptual quality is provided. First, a value indicating an amount of distortion in a corresponding portion is accessed. Then, that value is classified as packet-loss distortion or coding-artifact distortion. Next, the classified value is modified to account for visibility differences of the human visual system, based on the classification, and then the modified values are combined for the multiple portions, to form a value indicating a total amount of distortion for the multiple portions.

A video compression and decompression system has an input to receive an encoded video sequence and an output for a decoded video sequence. A video decoder is coupled to the input and decode the received encoded video sequence. A filter module is coupled to the video decoder and the output and filters the decoded video sequence from the video decoder. The filter module has a variable filter strength that is a function of detected motion activity within the video sequence. The filter module filters coding artifacts, such as mosquito artifacts and blocking artifacts from the decoded video sequence so that the displayed video is more pleasing for a viewer's eyes.

A method and circuit for processing a reconstructed picture generated from compressed data is disclosed. The method generally includes the steps of (A) estimating a magnitude of coding artifacts created by a coding process for the compressed data based upon the compressed data, (B) generating a plurality of noise samples with a probability distribution over a range, the probability distribution determined by the magnitude and (C) adding the noise samples to the reconstructed picture for concealment of the coding artifacts.

In a block-based motion compensated system, coding noises may arise due to lossy operations such as quantization. Deblocking is often used to alleviate visibility of coding artifacts by applying filtering across block boundaries adaptively. In the recent HEVC development, adaptive loop filtering (ALF) is being adopted to process deblocked reconstruction frames. Adaptive loop filtering is applied to reconstructed video data across multiple frames to reduce visibility of coding artifacts in the temporal domain. In a HEVC system, conventional ALF can be selectively turned ON or OFF for each block in a frame or a slice. The advanced ALF disclosed here allows a choice of multiple filter sets that can be applied to the reconstructed video data adaptively. Furthermore, the advanced ALF adopts a new unit for the filtering process to apply so that more flexible and / or localized processing can be provided. Furthermore, the advanced ALF allows a decoder to derive respective information for applying the filtering process without side information.

A method to reduce coding artifacts within a discrete decoded picture includes a spatial and / or temporal filtering with respective filter characteristics dependent on an image quality value (Q). Preferably, the spatial filtering includes a deblocking filtering, wherein the deblocking filter operation decreases with an increasing image quality value (Q) and / or the deblocking filtering chooses an image quality value (Q) dependent weighting function for a pixel to be filtered according to an activity of both blocks to which common border said pixel belongs.

Some embodiments of the invention encode a sequence of video images based on “visual masking” attributes of the video images and / or portions of the video images. Visual masking of an image or a portion of the image is an indication of how much coding artifacts can be tolerated in the image or image portion. To express the visual masking attribute of an image or an image portion, some embodiments compute a visual masking strength that quantifies the brightness energy of the image or the image portion. In some embodiments, the brightness energy is measured as a function of the average luma or pixel energy of the image or image portion.