Provided is an inter-layer video decoding method including obtaining a disparity vector of a current block included in a first layer image; determining a block of a second layer image corresponding to the current block by using the obtained disparity vector; determining a reference block including a sample that contacts a boundary of the block; obtaining a motion vector of the reference block; and determining a motion vector of the current block included in the first layer image by using the obtained motion vector.

A general entropy coding method for source symbols is disclosed. This method determines a prefix part and any suffix part for the current symbol. The method divides prefix of the source symbol into at least two parts by comparing a test value related to the prefix part against a threshold. If the test value is greater than or equal to the threshold, the method derives a first binary string by binarizing a first prefix part related to the prefix part using a first variable length code. If the test value related to the prefix part is less than the threshold, the method derives a second binary string by binarizing a second prefix part related to the prefix part using a second variable length code or a first fixed-length code. The method then encodes at least one of the first binary string and the second binary string using a CABAC mode.

An encoding target region in an image can be partitioned into a plurality of prediction regions. Based on prediction information of a neighboring region neighboring a target region, the number of previously-encoded prediction regions in the target region, and previously-encoded prediction information of the target region, a candidate for motion information to be used in generation of a predicted signal of the target prediction region as a next prediction region is selected from previously-encoded motion information of regions neighboring the target prediction region. According to the number of candidates for motion information selected, merging block information to indicate generation of the predicted signal of the target prediction region using the selected candidate for motion information and motion information detected by prediction information estimation means, or either one of the merging block information or the motion information is encoded.

A method of encoding an image in a merge mode, the method including determining motion information of a current prediction unit, and generating a prediction block using the motion information; generating a residual block using an original block and the prediction block, transforming the residual block to generating a transformed block, quantizing the transformed block using a quantization parameter to generate a quantized block, and scanning the quantized block to entropy-code the quantized block; and encoding the motion information using effective spatial and temporal merge candidates of the current prediction unit. In addition, a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate within a temporal merge candidate picture, and the quantization parameter is encoded using an average of two effective quantization parameters among a left quantization parameter, an upper quantization parameter and a previous quantization parameter of a current coding unit, also when the quantized block is larger than a predetermined size, the quantized block is divided into a plurality of subblocks to be scanned, and a scan pattern for scanning the plurality of subblocks is the same as a scan pattern for scanning quantized coefficients within each subblock. Further, a scanning scheme for scanning the quantized coefficients is determined according to an intra-prediction mode and a size of a transform unit.

A method of encoding an image in a merge mode, the method including determining motion information of a current prediction unit, and generating a prediction block using the motion information; generating a residual block using an original block and the prediction block, transforming the residual block to generating a transformed block, quantizing the transformed block using a quantization parameter to generate a quantized block, and scanning the quantized block to entropy-code the quantized block; and encoding the motion information using effective spatial and temporal merge candidates of the current prediction unit. In addition, a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate within a temporal merge candidate picture, and the quantization parameter is encoded using an average of two effective quantization parameters among a left quantization parameter, an upper quantization parameter and a previous quantization parameter of a current coding unit, also when the quantized block is larger than a predetermined size, the quantized block is divided into a plurality of subblocks to be scanned, and a scan pattern for scanning the plurality of subblocks is the same as a scan pattern for scanning quantized coefficients within each subblock. Further, a scanning scheme for scanning the quantized coefficients is determined according to an intra-prediction mode and a size of a transform unit.

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.

Different implementations are described for determining one or more illumination compensation parameters for a current block being encoded by a video encoder or decoded by a video decoder, based on the selection of one or more neighboring samples. The selection of the one or more neighboring samples is based on information used to reconstruct a plurality of neighboring reconstructed blocks. The selection may be based on the motion information, such as motion vector and reference picture information. In one example, only samples from neighboring reconstructed blocks that have (1) the same reference picture index and/or (2) a motion vector close to the motion vector of the current block is selected. In another example, if the current block derives or inherits some motion information from a top or left neighboring block, then only the top or left neighboring samples are selected for IC parameter calculation.

Different implementations are described for determining one or more illumination compensation parameters for a current block being encoded by a video encoder or decoded by a video decoder, based on the selection of one or more neighboring samples. The selection of the one or more neighboring samples is based on information used to reconstruct a plurality of neighboring reconstructed blocks. The selection may be based on the motion information, such as motion vector and reference picture information. In one example, only samples from neighboring reconstructed blocks that have (1) the same reference picture index and/or (2) a motion vector close to the motion vector of the current block is selected. In another example, if the current block derives or inherits some motion information from a top or left neighboring block, then only the top or left neighboring samples are selected for IC parameter calculation.

An index, indicating a vector representing a spatial relationship between a block to be encoded and at least one block spatially at the periphery of the block to be encoded, is encoded in a case where an coding mode to encode the block to be encoded is a first coding mode, and an index, indicating a vector representing a spatial relationship between the block to be encoded and at least one block spatially at the periphery of the block to be encoded, and a vector correlated with a block within an image that is different from the image to be encoded, is encoded in a case where the coding mode to encode the block to be encoded is a second coding mode.

An index, indicating a vector representing a spatial relationship between a block to be encoded and at least one block spatially at the periphery of the block to be encoded, is encoded in a case where an coding mode to encode the block to be encoded is a first coding mode, and an index, indicating a vector representing a spatial relationship between the block to be encoded and at least one block spatially at the periphery of the block to be encoded, and a vector correlated with a block within an image that is different from the image to be encoded, is encoded in a case where the coding mode to encode the block to be encoded is a second coding mode.