High-performance tone detection using a digital signal processor (DSP) having multiple arithmetic logic units (ALUs)

摘要

In one embodiment, a DSP having four arithmetic logic units (ALUs) and able to have two read/write operations per clock cycle performs silence detection and tone detection for data frames containing samples of an audio signal. The ALUs are used together in parallel to process the samples in the data frames received by the DSP. A received data frame is filtered by the silence detection so that substantially silent frames are dropped and non-silent frames are further processed. In the tone detection, a filtered data frame is processed, four samples at a time, to determine the power of the signal at a given frequency, where the power determination is used to determine whether a given tone (i.e., a signal at a given frequency) is present in the data frame.

主权项

1. A digital signal processor (DSP) comprising a plurality of D arithmetic logic units (ALUs), wherein the DSP is adapted to:
receive an N-sample data frame comprising digital samples corresponding to an audio signal; and perform tone detection for the data frame using the ALUs of the plurality of D ALUs in parallel, wherein the tone detection comprises:
(i) determining a power P(F) of a frequency F for the data frame by performing the following operations on the N-sample data frame:
(a) generate Va(n) where Va(n)=M·xnD+a, for a=1, . . . , D and n=0, . . . , [N/D−1], wherein the DSP is adapted to perform operation (a) in one clock cycle for at least one value of n by using all of the ALUs of the plurality of D ALUs in parallel;(b)⁢⁢generate⁢⁢Rea⁡(n+1)⁢where⁢⁢Rea⁡(n+1)=Rea⁡(n)+Va⁡(n)·cos⁡(2⁢π⁢⁢FFs⁢(n-Dn-a)), for a=1, . . . , D and n=0, . . . , [N/D−1], wherein the DSP is adapted to perform operation (b) in one clock cycle for at least one value of n by using all of the ALUs of the plurality of D ALUs in parallel; and(c)⁢⁢generate⁢⁢Ima⁡(n+1)⁢where⁢⁢Ima⁡(n+1)=Ima⁡(n)+Va⁡(n)·sin⁡(2⁢π⁢⁢FFs⁢(n-Dn-a)), for a=1, . . . , D and n=0, . . . , [N/D−1], wherein the DSP is adapted to perform operation (c) in one clock cycle for at least one value of n by using all of the ALUs of the plurality of D ALUs in parallel, wherein Va(k), Rea(k), and Ima(k) are storage variables, Fs is a sampling frequency for the data frame, xi is the ith sample of the data frame, a, k, and n are counting variables, and M is a normalization factor; and
(ii) thresholding the determined power P(F) to determine whether a tone corresponding to the frequency F is present in the audio signal.