Disclosed are an intra prediction method of a chrominance block using a luminance sample and an apparatus using the same. An image decoding method comprises the steps of: calculating an intra prediction mode of a chrominance block on the basis of an LM mapping table when the chrominance block uses an LM; and generating a prediction block for the chrominance block on the basis of the calculated intra prediction mode of the chrominance block. When intra prediction mode information of chrominance blocks are decoded, mutually different tables are used depending on whether or not an LM is used, so that encoding and decoding can be performed without an unnecessary waste of bits.

This application relates to video encoding and decoding, and specifically to tools and techniques for using and providing supplemental enhancement information in bitstreams. Among other things, the detailed description presents innovations for bitstreams having supplemental enhancement information (SEI). In particular embodiments, the SEI message includes picture source data (e.g., data indicating whether the associated picture is a progressive scan picture or an interlaced scan picture and/or data indicating whether the associated picture is a duplicate picture). The SEI message can also express a confidence level of the encoder's relative confidence in the accuracy of this picture source data. A decoder can use the confidence level indication to determine whether the decoder should separately identify the picture as progressive or interlaced and/or a duplicate picture or honor the picture source scanning information in the SEI as it is.

This application relates to video encoding and decoding, and specifically to tools and techniques for using and providing supplemental enhancement information in bitstreams. Among other things, the detailed description presents innovations for bitstreams having supplemental enhancement information (SEI). In particular embodiments, the SEI message includes picture source data (e.g., data indicating whether the associated picture is a progressive scan picture or an interlaced scan picture and/or data indicating whether the associated picture is a duplicate picture). The SEI message can also express a confidence level of the encoder's relative confidence in the accuracy of this picture source data. A decoder can use the confidence level indication to determine whether the decoder should separately identify the picture as progressive or interlaced and/or a duplicate picture or honor the picture source scanning information in the SEI as it is.

360-degree video content may be coded. A sampling position in a projection format may be determined to code 360-degree video content. For example, a sampling position in a target projection format and a sampling position in a reference projection format may be identified. The sample position in the target projection format may be related to the corresponding sample position in the reference projection format via a transform function. A parameter weight (e.g., a reference parameter weight) for the sampling position in the reference projection format may be identified. An adjustment factor associated with the parameter weight for the sampling position in the reference projection format may be determined. The parameter weight (e.g., adjusted parameter weight) for the sampling position in the target projection format may be calculated. The calculated adjusted parameter weight may be applied to the sampling position in the target projection format when coding the 360-degree video content.

A video decoding device, in the case where a video of the progressive format is inputted, processes a frame as a picture, in the case where a video of the interlace format is inputted, processes a field as a picture. A video decoding device performs display control corresponding to a format of the both video by analyzing display control information in display control information analyzer. The display control information includes sequence unit display control information which is commonly used in a display process of all pictures that belong to a sequence to be decoded and picture unit display control information which is individually used in a display process of a picture to be decoded. A second code string analyzer acquires each of the sequence unit display control information and the picture unit display control information from an extended information area in units of pictures.

A video decoding device, in the case where a video of the progressive format is inputted, processes a frame as a picture, in the case where a video of the interlace format is inputted, processes a field as a picture. A video decoding device performs display control corresponding to a format of the both video by analyzing display control information in display control information analyzer. The display control information includes sequence unit display control information which is commonly used in a display process of all pictures that belong to a sequence to be decoded and picture unit display control information which is individually used in a display process of a picture to be decoded. A second code string analyzer acquires each of the sequence unit display control information and the picture unit display control information from an extended information area in units of pictures.

The present invention discloses a video encoding and decoding method, apparatus and system, where the video encoding method includes: determining an independently decodable view in a to-be-encoded picture according to a configuration file corresponding to the video; dividing the picture into at least two tiles, where an area corresponding to one or more tiles that cover the independently decodable view is an independently decodable area; generating an auxiliary message corresponding to the picture, where the auxiliary message includes a location identifier of the independently decodable area; and encoding all tiles included in the picture to form an encoded video bitstream, where the encoded video bitstream includes the auxiliary message. Decoding this encoded video bitstream can lower a requirement for performance of a decoder and improve decoding efficiency.

An example method includes the steps of receiving an encoded video packet including a packet header and generating a modified packet header. The modified packet header is generated by setting a first value in the packet header to indicate zero reference frames, and by setting a second value in the packet header designating an i-frame as unused for reference. The i-frame is decoded in response to the modified packet header to extract the i-frame without caching the i-frame in a decoded picture buffer. A thumbnail image is generated and includes an image from the i-frame. The thumbnail image is stored directly in memory.

An example method includes the steps of receiving an encoded video packet including a packet header and generating a modified packet header. The modified packet header is generated by setting a first value in the packet header to indicate zero reference frames, and by setting a second value in the packet header designating an i-frame as unused for reference. The i-frame is decoded in response to the modified packet header to extract the i-frame without caching the i-frame in a decoded picture buffer. A thumbnail image is generated and includes an image from the i-frame. The thumbnail image is stored directly in memory.

An image decoding method of decoding, on a block-by-block basis, image data included in a coded stream includes: deriving candidates for an intra prediction mode to be used for intra prediction for a decoding target block, the number of the candidates constantly being a plural number; obtaining, from the coded stream, an index for identifying one of the derived candidates for the intra prediction mode; and determining, based on the obtained index, one of the derived candidates for the intra prediction mode as the intra prediction mode to be used for intra prediction for the decoding target block.