Research in Motion Corporation

Blackberry Corporation

Slipstream Data Inc.

Brian Lamb

Guixing Wu

En-hui Yang

Longji Wang

Michael Carmody

Brian David Randolph Lamb

Michael James Carmody

A method and system for reducing the number of mathematical operations required in the JPEG decoding process without substantially impacting the quality of the image displayed is disclosed. Embodiments provide an efficient JPEG decoding process for the purposes of displaying an image on a display smaller than the source image, for example, the screen of a handheld device. According to one aspect of the invention, this is accomplished by reducing the amount of processing required for dequantization and inverse DCT (IDCT) by effectively reducing the size of the image in the quantized, DCT domain prior to dequantization and IDCT. This can be done, for example, by discarding unnecessary DCT index rows and columns prior to dequantization and IDCT. In one embodiment, columns from the right, and rows from the bottom are discarded such that only the top left portion of the block of quantized, and DCT coefficients are processed.

Method and system for decoding encoded images and reducing the size of said images

A method of decoding data that is encoded with a set of prefix codes begins by receiving the data at a computing device, and then compiling native machine code from the prefix code set for execution by a processing unit of the computing device. The machine code implements a binary tree of prefix codes that corresponds to the prefix code set. The data is decoded by traversing the prefix code tree, which is effected by executing the machine code with the processing unit.

Method of decoding entropy-encoded data

An iterative rate-distortion optimization algorithm for MPEG I/II Layer-3 (MP3) encoding based on the method of Lagrangian multipliers. Generally, an iterative method is performed such that a global quantization step size is determined while scale factors are fixed, and thereafter the scale factors are determined while the global quantization step size is fixed. This is repeated until a calculated rate-distortion cost is within a predetermined threshold. The methods are demonstrated to be computationally efficient and the resulting bit stream is fully standard compatible.

Optimization of MP3 audio encoding by scale factors and global quantization step size

A method for optimization of rate-distortion for Advanced Audio Coding (AAC). The method provides for the identification of quantized spectral coefficient sequences for optimization of rate-distortion. The method also provides joint optimization of scale factors, Huffman codebooks and quantized spectral coefficient sequences for minimization of a rate-distortion cost. The method provides an iterative rate-distortion optimization algorithm for AAC encoding. In each iteration, the method first finds the optimal scale factors and quantized spectral coefficients when Huffman codebooks are fixed, then updates Huffman codebooks and quantized spectral coefficients given the optimized scale factors. The iterations may be applied until a predetermined threshold is attained.

Growing community of inventors

Waterloo, Canada

Guixing Wu