35 results about "Context-adaptive variable-length coding" patented technology

A method for efficient and fast implementation of context-based adaptive binary arithmetic encoding in H.264/AVC video encoders is disclosed. The H.264/AVC video standard supports two entropy coding mechanisms. These include Context Adaptive Binary Arithmetic Coding (CABAC) and Context Adaptive Variable Length Coding (CAVLC). The entropy coding efficiency of CABAC exceeds that of CAVLC by a clear margin. The method further provides techniques that make the implementation of CABAC on digital signal processors (DSPs) and other processing devices significantly faster. In one aspect, the method increases decoupling between the binarization process and the arithmetic encoding process from bit level to single or multiple syntax element(s) level. The binarized data is provided to the arithmetic encoding engine in bulk, thereby significantly reducing the overhead due to procedure calls. In another aspect, a CABAC arithmetic encoding engine format is provided which decreases data writing overhead and better exploits parallelism in the encoding process. This aspect is particularly advantageous to, for example, very long instruction word (VLIW) DSPs and media processors. In yet another aspect, the method discloses efficient CABAC binarization schemes for syntax elements.

Various embodiments of decoding systems and methods are disclosed. One system embodiment, among others, comprises a software programmable core processing unit having a context-adaptive variable length coding (CAVLC) unit configured to execute a shader, the shader configured to implement CAVLC decoding of a video stream and provide a decoded data output.

The invention relates to a method of adaptive variable length coding in which a set of data symbols comprising a certain first number of data symbols having a first value and a certain second number of data symbols having values other than the first value are represented by variable length codewords. According to the invention, at least one characteristic of the variable length coding applied to the data symbols is adapted according to the second number of data symbols which have values other than the first value. The invention also relates to a corresponding method of variable length decoding, as well as an encoder and decoder which implement the variable length coding and decoding methods according to the invention.

A method encoding successive input data values includes: selecting one of plural complementary sub-ranges of a set of code values according to a current input data value, proportions of the sub-ranges relative to the set of code values defined by a context variable associated with that input data value; assigning the current input data value to a code value within the selected sub-range; modifying the set of code values based on the assigned code value and a size of the selected sub-range; detecting whether the set of code values is less than a predetermined minimum size and if so, successively increasing it until reaching the predetermined minimum size; outputting an encoded data bit in response to each size-increasing operation; modifying the context variable to increase the proportion of the set of code values in the sub-range selected; after encoding a group of input data values, terminating the output data.

Methods and systems for processing an encoded video stream are disclosed. Aspects of the method may comprise generating a plurality of temporal or spatial prediction pixels based on mode information within the encoded video stream. A plurality of prediction errors may be generated from a plurality of quantized frequency coefficients generated from the encoded video stream. At least one current macroblock may be generated using the generated plurality of temporal or spatial prediction pixels based on the generated plurality of prediction errors. The encoded video stream may be symbol interpreted using context adaptive variable length coding and/or context adaptive binary arithmetic coding. The encoded video stream may be buffered prior to the symbol interpretation. The plurality of quantized frequency coefficients may be generated from the encoded video stream. If the encoded video stream comprises temporal prediction mode information, the plurality of temporal prediction pixels may be generated.

A context-adaptive variable length coding (VLC) apparatus includes a coefficient information generation unit configured to generate coefficient information used for coding variable-length-code coefficients for a selected block of a selected macroblock of image data that is read out in response to an information generation control signal, a bit data generation unit configured to operate in response to a bit generation control signal, and to code coefficients of a previous block, which is read out just before the selected block, using coefficient information of the previous block, and a control unit configured to generate the information generation control signal and the bit generation control signal, and to cause the coefficient information generation unit and the bit data generation unit to operate at in parallel using the information generation control signal and the bit generation control signal. A method of variable-length coding coefficients of image data is also provided.

An effective H.264/AVC CAVLC decoding method is disclosed. In accordance with the method a VLC code is classified into groups according to a correlation thereof, an arithmetic equation is defined for each of the groups, and a decoding is carried out according to the arithmetic equation in order to minimize a memory access by a table look-up and reduce a decoding time and a power consumption.

The invention discloses a decoding method of adaptive variable length coding based on a context and a system of the adaptive variable length coding, wherein the method comprises the steps of obtaining a code stream needing to be decoded; determining the non-zero coefficient number predicted value nC in the code stream; according to the predicated value nC, finding a preset first decoding code table to obtain the number of the non-zero coefficients and the number of the trailing ones in the code stream; if the number of the non-zero coefficients is more than 0 and the number of the tailing ones is more than 0, decoding the symbol of the tailing with 1 coefficients; if the number of the non-zero coefficients is less than the maximum number value of the non-zero coefficients, finding a preset second decoding code table according to the number of the non-zero coefficients, obtaining the number of total zeros before the last non-zero coefficient in the code stream; according to the number of total zeros before the last non-zero coefficient and the number of the non-zero coefficients, decoding the numbers of zeros before other non-zero coefficients in the code stream. By adoption the decoding method and the system disclosed by the invention, the storage space of the code table can be saved and the decoding efficiency can be improved.

A pattern-search based method and apparatus for context-adaptive variable length coding/decoding (CAVLC/CAVLD) is provided. The method analyzes the correlation between bit patterns and blocks. Before CAVLD, a step of bit-stream pattern search is conducted. If a pattern is matched in a look-up table, this invention skips the CAVLD procedure and reconstructs a block directly. Before CAVLC, a step of zig-zag ordered coefficients search is conducted. If a sequence of zig-zag ordered coefficients is matched in a look-up table, a corresponding coded bit-stream can be obtained directly. Compared with the standard CAVLD procedures, this invention improves about 10% performance in memory access speed.

A system and method that process encoded data, wherein the encoded data is an encoded video stream. The encoded data may be buffered and the characteristics of the buffered encoded data may be determined and used to select a decoding table from a plurality of decoding tables. An encoded word may then be decoded using the selected decoding table. The output of the decoding table may be the corresponding decoded word and the size of the encoded word. The size of the encoded word may be utilized to shift the buffered encoded data. The decoded word may be sent to the appropriate portion of the system.

The invention relates to a dual-coefficient scanning method for CAVLC (context-based adaptive variable length coding). The dual-coefficient scanning method includes: converting a coefficient block to be coded into a one-dimensional coefficient array, acquiring the number of non-zero coefficients in the one-dimensional coefficient; under the condition that the number of the non-zero coefficients in the one-dimensional coefficient array is not zero, acquiring two adjacent coefficients in the one-dimensional coefficient array within every clock period, and coding the two adjacent coefficients.

Unified binarization for CABAC/CAVLC entropy coding. Scalable entropy coding is implemented in accordance with any desired degree of complexity (e.g., entropy encoding and/or decoding). For example, appropriately implemented context-adaptive variable-length coding (CAVLC) and context-adaptive binary arithmetic coding (CABAC) allow for selective entropy coding in accordance with a number of different degrees of complexity. A given device may operate in accordance with a first level complexity a first time, a second level complexity of the second time, and so on. Appropriate coordination and signaling between an encoder/transmitter device and a decoder/receiver device allows for appropriate coordination along a desired degree of complexity. For example, a variable length binarization module and an arithmetic encoding module may be implemented within an encoder/transmitter device and a corresponding arithmetic decoding module and a variable length bin decoding module may be implemented within a decoder/receiver device allowing for entropy coding along various degrees of complexity.

The invention provides a context-adaptive variable-length coding (CAVLC) method and an apparatus thereof. The method comprises the following steps that: a code list corresponded to nonzero coefficients of all encoding blocks except trailing coefficients is determined; the number of nonzero coefficients in the code list is calculated, wherein the nonzero coefficients are corresponded to all levels; and all the levels in the code list are arranged again in a descending order according to the number of the nonzero coefficients; coding is carried out on the number of the nonzero coefficients and the number of the trailing coefficients; coding is carried out on amplitudes of the nonzero coefficients except the trailing coefficients according to the rearranged code list; and coding is carried out on the number of zeroes before the last nonzero coefficient and the number of continuous zeros before each of the nonzero coefficient. According to the embodiment of the invention, a problem of low compression efficiency in CAVLC in the prior art can be solved; and thus the compression efficiency is improved.

Provided are an apparatus for decoding a minimum memory access-based context adaptive variable length code (CAVLC) of the moving picture compression standard, H.264, and a table search method for decoding a context adaptive variable length code using the same. The apparatus for decoding a context adaptive variable length code may be useful to improve an overall decoding speed since the repeated memory accesses may be reduced to 2 cycles of memory accesses by reconstructing a context adaptive variable length code table of first decoding information (TrailingOnes) and second decoding information (TotalCoefficient) into 2-step tables and storing the reconstructed 2-step tables in advance and performing a table search to decode the first decoding information and the second decoding information, by using the information stored in the 2-step tables, depending on whether the remaining bits except for the number of leading zero are present in the inputted bit stream.