Provided are an encoding device using predictive coding in a screen and a method thereof, and a decoding device and a method thereof. The encoding device is capable of generating a prediction block of a current block according to one of methods for generating a plurality of predetermined prediction blocks, and outputting at least one of encoding information and differential blocks as bitstream by entropy encoding according to whether differential blocks are encoded or not.

Methods for decoding of a video bitstream by a video decoding circuit are provided. In one implementation, a method receives coded data for a 2N×2N coding unit (CU) from the video bitstream, selects one or more first codewords according to whether asymmetric motion partition is disabled or enabled when a size of said 2N×2N CU is not equal to a smallest CU size, wherein none of the first codewords corresponds to INTER N×N partition, selects one or more second codewords when the size of said 2N×2N CU is equal to the smallest CU size, wherein none of the second codewords corresponds to the INTER N×N partition when N is 4, determines a CU structure for said 2N×2N CU from the video bitstream using said one or more first codewords or said one or more second codewords, and decodes the video bitstream using the CU structure.

Various innovations in media encoding are presented herein. In particular, the innovations can reduce the computational complexity of encoding by selectively skipping certain evaluation stages during encoding. For example, based on analysis of decisions made earlier in encoding or based on analysis of media to be encoded, an encoder can selectively skip evaluation of certain coding tools (such as residual coding or rate-distortion-optimized quantization), skip evaluation of certain values for parameters or settings (such as candidate unit sizes or transform sizes, or candidate partition patterns for motion compensation), and/or skip evaluation of certain coding modes (such as frequency transform skip mode) that are not expected to improve rate-distortion performance during encoding.

Disclosed are a method for encoding a video signal and a device therefor. Specifically, a method for decoding an image based on an inter prediction mode comprises: generating a merging candidate list by using a spatial merge candidate and a temporal merge candidate of a current block; obtaining a merge index indicating a certain merge candidate in the merging candidate list; and generating a prediction block of the current block by using motion information of the certain merge candidate, wherein the generating of the merging candidate list may include adding a first merge candidate indicating a collocated block specified by motion information of the spatial merge candidate to the merging candidate list if a reference picture of the spatial merge candidate is same as a predetermined picture.

A method of adaptive chroma downsampling is presented. The method comprises converting a source image to a converted image in an output color format, applying a plurality of downsample filters to the converted image and estimating a distortion for each filter chose the filter that produces the minimum distortion. The distortion estimation includes applying an upsample filter, and a pixel is output based on the chosen filter. Methods for closed loop conversions are also presented.

A method of adaptive chroma downsampling is presented. The method comprises converting a source image to a converted image in an output color format, applying a plurality of downsample filters to the converted image and estimating a distortion for each filter chose the filter that produces the minimum distortion. The distortion estimation includes applying an upsample filter, and a pixel is output based on the chosen filter. Methods for closed loop conversions are also presented.

Provided is a method for decoding a video signal based on a reduced transform, which includes: checking whether a transform skip is applied to a current block; obtaining a transform index indicating a transform kernel of the current block from the video signal when the transform skip is not applied to the current block; determining a region where a primary transform is applied to the current block based on the transform kernel indicated by the transform index and a size of the current block; and performing an inverse primary transform on the region to which the primary transform is applied by using the transform kernel indicated by the transform index.

A method includes receiving transform coefficients corresponding to a scaled video input signal, the scaled video input signal including a plurality of spatial layers that include a base layer. The method also includes determining a spatial rate factor based on a sample of frames from the scaled video input signal. The spatial rate factor defines a factor for bit rate allocation at each spatial layer of an encoded bit stream formed from the scaled video input signal. The spatial rate factor is represented by a difference between a rate of bits per transform coefficient of the base layer and an average rate of bits per transform coefficient. The method also includes reducing a distortion for the plurality of spatial layers by allocating a bit rate to each spatial layer based on the spatial rate factor and the sample of frames.

A method includes receiving transform coefficients corresponding to a scaled video input signal, the scaled video input signal including a plurality of spatial layers that include a base layer. The method also includes determining a spatial rate factor based on a sample of frames from the scaled video input signal. The spatial rate factor defines a factor for bit rate allocation at each spatial layer of an encoded bit stream formed from the scaled video input signal. The spatial rate factor is represented by a difference between a rate of bits per transform coefficient of the base layer and an average rate of bits per transform coefficient. The method also includes reducing a distortion for the plurality of spatial layers by allocating a bit rate to each spatial layer based on the spatial rate factor and the sample of frames.

Disclosed herein are an image encoding method and an image decoding method. The image decoding method includes determining an initial motion vector of a current block using a motion vector of a reconstructed region, searching for the motion vector of the current block based on the initial motion vector, and generating a prediction sample of the current block using the motion vector. The initial motion vector includes a motion vector in a past direction and a motion vector in a future direction.