Mozilla Corporation

Xiph.org Foundation

Timothy B Terriberry

Jean-Marc Valin

Nathan E Egge

Content to be encoded may be defined by a sequence of values chosen from a set of possible values. Individual values of the set of possible values may have a probability of occurrence in the sequence of values. The set of possible values may have a total probability value. The content may be encoded based on a reduced complexity entropy coding and an interval. The reduced complexity entropy coding may partition the interval into sub-intervals based the probability of individual values that appears in the sequence of values and a reduced complexity partition function. The reduced complexity partition function may have an interval size value reduced by a reduction value less than the total probability value.

Systems and methods for reduced complexity entropy coding

Systems and methods are described for removing ringing artifacts from a coded image. For each block of coded image data, a direction is identified by selecting a directional block divided into a plurality of pixel lines in one predetermined direction of a set of at least four predetermined directions. The directional block may have a constant value across each pixel line. A parameter related to a sum of a mean-square difference between a pixel value and the pixel average of pixels falling on a pixel line in the directional block that includes the location of the pixel may be calculated for each direction of the set. The direction of the set having a minimum summed mean-square difference is selected as the direction for the block based on the calculated parameter values. A non-linear filter is then applied to each block based on the identified direction for the block.

Directional deringing filters

Systems and methods are described for predicting a mode value of a block of an image. Mode values are received for a predetermined number of neighboring blocks of the image. Each mode value may within a predetermined range of integer values. Using a probability table, a probability of each mode value in the range of integers being selected may be computed. The probability table may have a first axis that includes every integer value within the range of integer values, and second axis that includes combinations of the neighboring blocks, each combination of the neighboring blocks representing a binary determination whether or not each neighboring block is equal to a corresponding integer value on the first axis. Based on the computed probabilities, a mode value for the block may be selected and coded by an entropy coder.

Probability modeling of intra prediction modes

An apparatus and method for lossless encoding of video data is provided, including a reversible transform, connected to a plurality of inputs, having a same plurality of orthonormal outputs, wherein the reversible transform comprises rotations combined with internally cancelled scalings that are connected to said orthonormal outputs.

Encoding video data using reversible integer approximations of orthonormal transforms

An apparatus and corresponding method are provided for pyramid vector quantization of video data, including receiving the video data in the frequency domain; and pyramid vector quantizing at least one group of pictures (GOP) from the received video data in accordance with a potentially varying bandwidth, the GOP comprising key frames and predicted frames.

Pyramid vector quantization for video coding

Systems and methods are described for encoding quantized vector parameters in a bitstream are described. An exemplary method may include receiving a vector of integers used in a data compression codebook, the sum of the integers equaling a pulse sum. An initial expected magnitude may be determined for a first integer, the initial expected magnitude being based on the pulse sum, a distribution parameter, and a value corresponding to a number of integers in the vector. The actual magnitude of the first integer may be encoded based on the initial expected magnitude of the first integer. The pulse sum may be adjusted using the encoded actual magnitude. Also, the value corresponding to the number of integers in the vector may be reduced by one. Expected magnitudes for each of the remaining integers of the vector may then be calculated recursively.

Vector quantization with non-uniform distributions

Embodiments are described of a multi-block coding scheme for an audio signal to prevent partial collapse conditions from causing pre-echo compression artifacts. An audio codec includes a segmentation component partitioning the audio signal into a plurality of tiles, wherein each tile comprises data from a particular segment of time and a particular set of frequencies of the audio signal; a band energy component determining an energy value for each tile corresponding to a signal component in a respective tile; an encoder flag tracking component marking a tile as not collapsed or collapsed based on the energy value in that tile; and a decoder flag tracking component filling all tiles marked as collapsed with pseudorandom noise at an estimated energy level.

Methods and systems for avoiding partial collapse in multi-block audio coding

Embodiments are described for a system and method for implementing an adaptive time-frequency resolution in audio and video coding systems. A method of adaptively transforming the time-frequency resolution for a defined spectrum comprises dividing the spectrum of the input signal into a into plurality of bands; determining, for each band of the plurality of bands, a characteristic of the content (e.g., tonal or transient content); modifying the time-frequency resolution value to one or more bands of the plurality of bands to increase either a time resolution of the band or a frequency resolution of the band depending on the characteristic of the content; determining a cost associated with modifying the time-frequency resolution value of the one more bands based on an entropy measure of the bands, and altering the modified time-frequency resolution values in a manner that accounts for the coding cost.

Methods and systems for adaptive time-frequency resolution in digital data coding

Embodiments are generally directed to systems and methods for bit allocation and band partitioning for gain-shape vector quantization in an audio codec. An audio codec implements a method that uses an implicit, dynamic scheme to allow an encoder and decoder to recreate a series of bit allocation decisions for gain and shape without transmitting additional side information for each decision, based on the number of bits that are left remaining and available in a given packet. For implementation in practical codecs, the band comprising the allocation of bits for the shape is recursively split into equal partitions until the number of bits allocated to each partition is less than the maximum codebook size.

Methods and systems for bit allocation and partitioning in gain-shape vector quantization for audio coding

Embodiments are directed to an audio coding scheme implemented in a codec that eliminates birdie artifacts generated by transform coding methods. A frequency coefficient spreading method invertibly rotates a spectrum of coefficient values based on a defined rotation angle, The rotated spectrum is then quantized, and the rotation operation is then reversed so that a previously sparse spectrum (i.e., one with few non-zero values) becomes one that has many non-zero values. The method arranges the coefficients for a particular partition into a linear array and computes a gain factor for the partition. A rotation angle of between 0 and &#x3c0;/4 for successive pairs of coefficients of the linear array based on the gain factor is then derived. One or more rotation operations are then applied to successive pairs of coefficients in the linear array using a specific rotation angle and a stride length for each rotation operation.

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Mountain View, CA, United States of America

Timothy B Terriberry