Koninklijke Philips Corporation N.V.

Nxp B.v.

Adrianus Wilhelmus Maria Van Den Enden

Marc Victor Arends

Eric Kathmann

Rutgerus Elisabertus Eduardus Franciscus Suermondt

A time discrete filter comprises a sampling rate converter provided with an input and an output, and a down-sampler having a down-sampling factor nd. The time discrete filter further comprises an up-sampler having an up-sampling factor nu, whereby the up-sampler is coupled to the converter input, and the converter output is coupled to the down-sampler. It has been found that if a sampling rate conversion operation is preceded by an up-sampling operation and only after the conversion is followed by a down-sampling operation to a wanted sampling frequency, that then the complexity in terms of the ultimate number of calculations, in particular multiplications and additions, is reduced. This leads to a decrease of the number of instructions per second which is a measure for the complexity of a Digital Signal Processing (DSP) algorithm. In addition this leads to an associated decrease of power consumed by a DSP, such as applied in for example audio, video, and (tele)communication devices, as well as radio and television apparatus.

Time discrete filter comprising upsampling, sampling rate conversion and downsampling stages

Sample rate converters () for converting input sample rates (F) of signals into output sample rates (F) are provided with sample rate adapters () for adapting (basic idea) intermediate sample rates (F) such that output sample rates (F) are larger (upsampling) or smaller (downsampling) than input sample rates (F), to reduce their complexity and to avoid bookkeeping and structure switching problems. Sample rate adapters () in the form of variable sample rate decreasers () allow the sample rate converters () to be used in video applications requiring DC-out being equal to DC-in. Sample rate adapters () in the form of variable sample rate increasers () allow the sample rate converters () to be used in audio applications. By locating the sample rate adapter () between a fixed sample rate increaser () for increasing with a factor K and a fixed sample rate decreaser () for decreasing with a factor M, filters () in between can be designed independently from the varying factor L as long as K and M are fixed and-K.

Up and down sample rate converter

In a method of encoding a source signal by determining Line Spectral Frequencies (LSFs) for representing Linear Predictive Coding (LPC) filter coefficients, real zeros are determined in associated polynomials P&Prime; and Q&Prime; in cos(m&ohgr;), with each polynomial being a series of Chebyshev polynomials, a search for real zeroes being performed by evaluating the associated polynomials in a series of steps of a real variable u, an approximation of cos(m&ohgr;) as a function of the real variable u being employed.

Method of calculating line spectral frequencies

Sample rate converters are known, and are used to convert a signal with a first sample rate (sampling frequency) into a signal with a second sample rate (sampling frequency). To obtain a flexible sample rate converter with sampling frequencies that are not known beforehand, until now only sample rate converters with very high intermediate sampling frequencies are known. The invention provides a flexible sample rate converter, which is able to handle unknown input and output sampling frequencies. This is achieved by using polyphase decomposition filter means in combination with interpolation means.

Growing community of inventors

Eindhoven, Netherlands

Adrianus Wilhelmus Maria Van Den Enden