Patent ID: 7451093

Claim:
A method of identifying a surround sound audio technique in an encoded audio stream, the method comprising: encoding with a surround sound matrix encoder a first multi-channel audio signal into a first two-channel audio signal, the first multi-channel audio corresponding to audio for a first television commercial, the surround sound matrix encoder comprising a Circle Surround encoder; encoding with the surround sound matrix encoder a second multi-channel audio signal into a second two-channel audio signal, the second multi-channel audio corresponding to audio for a second television commercial; embedding a watermark in at least one channel of the first two-channel audio signal to produce a watermarked audio signal, the watermark configured to identify the watermarked audio signal as surround sound matrix encoded audio, the watermark comprising a pattern of data that can be detected by a watermark detector and having a bit rate of at least one bit per three seconds, the watermark being substantially inaudible; transmitting the watermarked audio signal and the second two-channel audio signal to a watermark detector, the watermark detector configured to: analyze the watermarked audio signal for a predetermined period of time lasting between approximately 1 millisecond and 3 seconds to detect the watermark; transmit a first control signal to a matrix decoder in response to detecting the presence of the watermark in the watermarked audio signal, the first control signal indicating the presence of a watermark in the watermarked audio signal; analyze the second two-channel audio signal for a predetermined period of time lasting between approximately 1 millisecond and 3 seconds to detect the watermark; and transmit a second control signal to the matrix decoder in response to detecting the presence of the watermark in the watermarked audio signal, the second control signal indicating the lack of a watermark in the second two-channel audio signal; and transmitting the watermarked audio signal and the second two-channel audio signal to the matrix detector.