A method, an apparatus, a computer readable storage medium configured with instructions for carrying out a method, and logic encoded in one or more computer-readable tangible medium to carry out actions. The method is to decode audio data that includes N.n channels to M.m decoded audio channels, including unpacking metadata and unpacking and decoding frequency domain exponent and mantissa data; determining transform coefficients from the unpacked and decoded frequency domain exponent and mantissa data; inverse transforming the frequency domain data; and in the case M<N, downmixing according to downmixing data, the downmixing carried out efficiently.

Audio decoder and decoding method using efficient downmixing

This index covers all technical items - papers, correspondence, reviews, etc. that appeared in this periodical during 2000, and items from previous years that were commented upon or corrected in 2000. In the case of magazines, departments and other items may be also covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author’s name. The primary entry includes the coauthors’ names, the title of the paper or other item, and its location, specified by the publica tion abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author’s name, the publication abbreviation, month, and year, and inclusive pages. Subject cross-references are included to assist in find ing items of interest. Note that the item title is found only under the primary entry in the Author Index.

IEEE Signal Processing Magazine Vol. 17

High performance SIMD marching cubes isosurface extraction on commodity computers

Digital Signal Processing on MMX Technology

Software decoding of Dolby Digital (an adaptive transform-based coder using a frequency-linear, critically sampled filterbank) allows it to become a baseline capability on the personal computer (PC), with greater flexibility than a hardware approach. Intel's MMX technology provides instructions that can significantly speed up the execution of the Dolby Digital decoder, freeing up the processor to perform other tasks such as video decoding and/or audio enhancement. Intel's MMX instructions operate on 8, 16, and 32 bits. The smaller the data size, the more operations per instruction are performed. Using 16 bits of accuracy uniformly through a Dolby Digital decoder is insufficient to pass the test suite. The challenge was to obtain both good execution speed and good audio quality. Although 32-bit floating-point numbers could be used throughout the data path and only use MMX technology for bit manipulation, this would not be the most processor-efficient method. To this end, we used 16-bit SIMD (single-instruction, multiple data) operations during much of the decoder, but performed 8- and 32-bit SIMD operations on certain sections. While we discuss a particular use of MMX technology, the MMX instruction set is general purpose in nature. We provide a description of MMX technology and then describe the major functional blocks of a Dolby Digital decoder and the special techniques used that take advantage of MMX technology. We also include a description of precision enhancements that were implemented to maintain accuracy and a description of other performance enhancements that were made. We conclude with results in terms of efficient processor utilization, numerical accuracy, and audio quality.

M.A. Julier

Papers

MMX-enabled Dolby Digital decoder