Patent ID: 8014741

Claim:
An Second Audio Programming (SAP) signal quality estimation and control system for controlling an SAP signal having noise, the system comprising: a signal quality estimation system having an input configured to receive the SAP signal and an output configured to output a quality signal indicative of the quality of the received signal, wherein the signal quality estimation system includes, a signal strength determination system having an input configured to receive the SAP signal and an output configured to output a SAP strength signal indicative of the strength of the SAP signal, wherein the signal strength determination system includes (i) an envelope extraction system having an input configured to receive the SAP signal and an output configured to output a SAP magnitude signal indicative of the magnitude of the envelope of the SAP signal, and (ii) an averaging system having an input configured to receive the SAP magnitude signal from the envelope extraction system and an output configured to output an average SAP signal indicative of an average of the SAP magnitude signal; a noise strength determination system having an input configured to receive the SAP signal and an output configured to output a SAP noise strength signal indicative of the strength of the noise in the SAP signal, the noise strength determination system including a subtracting system having an input configured to receive the SAP magnitude signal from the envelope extraction system, an input configured to receive the average SAP signal from the averaging system, and an output configured to output a difference signal indicative of the difference between the SAP magnitude signal and the average SAP signal from the averaging system, and wherein the noise strength determination system is configured to receive the difference signal from the output of the subtracting system; a signal quality evaluation system having an input configured to receive the SAP strength signal from the output of the signal strength determination system, an input configured to receive the SAP noise strength signal from the noise strength determination system, and an output configured to output a SAP quality signal indicative of the quality of the SAP signal based on the SAP strength signal from the signal strength determination system and the SAP noise strength signal from the noise strength determination system; and a signal control system having an input configured to receive the quality signal from the signal quality estimation system and to provide a switching function relating to the SAP signal.