A multimedia file and methods of generating, distributing and using the multimedia file are described. Multimedia files in accordance with embodiments of the present invention can contain multiple video tracks, multiple audio tracks, multiple subtitle tracks, a complete index that can be used to locate each data chunk in each of these tracks and an abridged index that can enable the location of a subset of the data chunks in each track, data that can be used to generate a menu interface to access the contents of the file and ‘meta data’ concerning the contents of the file. Multimedia files in accordance with several embodiments of the present invention also include references to video tracks, audio tracks, subtitle tracks and ‘meta data’ external to the file. One embodiment of a multimedia file in accordance with the present invention includes a series of encoded video frames, a first index that includes information indicative of the location within the file and characteristics of each encoded video frame and a separate second index that includes information indicative of the location within the file of a subset of the encoded video frames.

A video processing method includes determining, for a conversion between a current block of a video and a bitstream representation of the video, whether to enable a level mapping operation or a level remapping operation based on a rule, wherein the level mapping operation or the level remapping operation includes changing between a first representation of a residual coefficient of the current block and a second representation of the residual coefficient of the current block based on neighboring residual coefficients of the residual coefficient; and performing the conversion by selectively using the level mapping operation or the level remapping operation based on the determining.

A video processing method includes determining, for a conversion between a current block of a video and a bitstream representation of the video, whether to enable a level mapping operation or a level remapping operation based on a rule, wherein the level mapping operation or the level remapping operation includes changing between a first representation of a residual coefficient of the current block and a second representation of the residual coefficient of the current block based on neighboring residual coefficients of the residual coefficient; and performing the conversion by selectively using the level mapping operation or the level remapping operation based on the determining.

A method and wearable camera for encoding video captured by a wearable camera determines a centre of rotation for an image frame to be encoded. The centre of rotation relates to a rotation of the wearable camera at the time of capturing the video and the image frame comprises multiple groups of pixels. Furthermore, compression levels are set for the multiple groups of pixels of the image frame. The compression levels for the multiple groups of pixels of the image frame are set such that a level of compression increases with a radial distance from the centre of rotation. The image frame is encoded using the compression levels.

A method and apparatus for decoding a compressed video is disclosed. The method comprises scrambling the compressed video, to produce a scrambled compressed video; delivering the scrambled compressed video to a decoder, for decoding the scrambled compressed video to produce a scrambled decompressed video; receiving from the decoder the scrambled decompressed video; and descrambling the scrambled decompressed video, to produce a descrambled decompressed video.

A method and apparatus for decoding a compressed video is disclosed. The method comprises scrambling the compressed video, to produce a scrambled compressed video; delivering the scrambled compressed video to a decoder, for decoding the scrambled compressed video to produce a scrambled decompressed video; receiving from the decoder the scrambled decompressed video; and descrambling the scrambled decompressed video, to produce a descrambled decompressed video.

A method for decoding an encoded video bit stream in a video decoder is provided that includes determining a scan pattern type for a transform block to be decoded, decoding a column position X and a row position Y of a last non-zero coefficient in the transform block from the encoded video bit stream, selecting a column-row inverse transform order when the scan pattern type is a first type, selecting a row-column inverse transform order when the scan pattern type is a second type, and performing one dimensional (1D) inverse discrete cosine transformation (IDCT) computations according to the selected transform order to inversely transform the transform block to generate a residual block.

A method for decoding an encoded video bit stream in a video decoder is provided that includes determining a scan pattern type for a transform block to be decoded, decoding a column position X and a row position Y of a last non-zero coefficient in the transform block from the encoded video bit stream, selecting a column-row inverse transform order when the scan pattern type is a first type, selecting a row-column inverse transform order when the scan pattern type is a second type, and performing one dimensional (1D) inverse discrete cosine transformation (IDCT) computations according to the selected transform order to inversely transform the transform block to generate a residual block.

Sub-picture extraction is rendered less complex by providing each slice with start position information which indicates a starting position from which onwards the picture is, along a coding path, encoded into the respective slice, relative to an onset position at which the coding path starts traversing a segment the starting position is located in. Alternatively or additionally, sub-picture extraction processes are treated like choosing one layer out of a multi-layer datastream.

A method for encoding a series of symbols using several models of the arithmetic or range coder type and including steps where each model is associated with a belonging criterion, the series is run through in order to determine, for each symbol, the encoding model to which each symbol belongs, according to the criteria; then a probability of occurrence of each symbol in the corresponding model is determined; then the series is run through by encoding each symbol successively; and a file is formed from the code thus obtained.