US 4,797,931 AGranted

Audio frequency signal identification apparatus

AssigneesKokusai Denshin Denwa Kabushiki Kaisha, NEC Corporation

InventorsYasuo Furukawa, Katsuyuki Yamazaki, Takemi Hosaka, Akira Fukui

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Abstract

An audio frequency signal identification apparatus of the present invention has a correlator for obtaining the full band power component and autocorrelation coefficients of a digital audio frequency signal to be identified for each analysis time, a plurality of band pass filters for dividing and filtering the audio frequency signal into a plurality of bands, a plurality of integrators for full wave rectifying and integrating the outputs from the plurality of band pass filters for each analysis time so as to obtain individual power components for the respective bands, a first identification parameter calculator for calculating a maximum power component, a minimum power component, a frequency band yielding the maximum power component, a bandwidth, and a difference between the individual band power components in the respective analysis times, from the individual band power components as the outputs from the plurality of integrators, a second identification parameter calculator for calculating a difference between the autocorrelation coefficients as the output of the correlator and a difference between the autocorrelation coefficients in the respective analysis times, an identification and judgement processor for judging the signal type of the audio frequency signal to be identified in accordance with which of a plurality of predetermined judgement conditions the identification parameters obtained from the first and second identification parameter calculator and the full band power component correspond and if they satisfy a condition of continuity.

Claims4

Dependent claims

An audio frequency signal identification apparatus for identifying a signal type of an audio frequency signal presented in unit analysis times of multiplexed frames, comprising:

a correlator for calculating a full band power component first and second order autocorrelation coefficients of a digital audio frequency signal to be identified for each unit analysis time;
a plurality of band pass filters, provided for predetermined bands, for filtering the audio frequency signal to be identified in the respective bands;
a plurality of integrators, which are connected to said plurality of band pass filters in a one to one correspondence, for full wave rectifying and integrating the outputs from said band pass filters for the unit anlysis time so as to obtain individual band power components;
first identification parameter calculation means for calculating a maximum power component, a minimum power component, a frequency band F yielding the maximum power component, a bandwidth B, a difference between the individual band power component in the respective analysis times from the individual band power components output from said plurality of integrators;
second identification paramter calculation means for calculating a difference between two values of the first order autocorrelation coefficient outputted from said correlator for different unit analysis times, a difference between two values of the second order autocorrelation coefficient outputted from said correlator for the difference unit analysis times, and a difference between respective values of the first and second order autocorrelation coefficients for a same unit analysis time;
and
identification and judgement processing means for judging a signal type of the audio frequency signal to be identified in accordance with which of a plurality of predetermined judgement conditions the identication parameters obtained from said first and second identification parameter calculation means and the full band power component of the digital audio frequency signal correspond and if they satisfy a condition of continuity.

4 more elements

An audio frequency signal indentificaton apparatus comprising:

signal input control means for receiving a multiplex audio frequency signal comprising a sequence of frames for a plurality of channels and demultiplexing and outputting it as signals for the respective channels;
a plurality of signal processors, connected to the respective output channels of said signal input control means, for outputting, for each channel and frame, a plurality of identification parameters including 0th-order, first and second order autocorrelation coefficients R.sub.0, R.sub.1, and R.sub.2, a maximum band power component Pmax, a minimum band power component Pmin, a frequency band F of the maximum band power component, a bandwidth B in which the band power component continuously satisfies a predetermined condition, an interframe difference H of the first and second order, autocorrelation coefficients, and an interframe difference D of the respective maximum and minimum band power components;
and
a microprocessor for calculating a difference C between the first and second order autocorrelation coefficients and a difference S between maximum and minimum values of the band power components based on the outputs from said plurality of signal processors, and judging the type of the input signal by applying a plurality of judgement conditions in correspondence with said identification parameters Pmax, Pmin, F, B, H, D, S, and C.

1 more element

Dependencies are inferred from the claim text.