Remote control signaling using audio watermarks

A method for recovering data that is robustly embedded in an audio signal, comprising the steps of:

• (a) receiving a composite audio signal;
• wherein:
• at an encoder, at least a first message is embedded as a corresponding first watermark in an audio source signal to provide the composite audio signal by modifying the audio source signal so that data symbols of the first message are determined according to corresponding values of an autocorrelation function of the composite audio signal;
• the values of the autocorrelation function are determined using delays that differ for adjacent data symbols;
• and
• the first watermark is carried substantially inaudibly in the composite audio signal;
• and
• (b) recovering the first message from the composite audio signal.

A method for robustly embedding data in an audio signal, comprising the steps of:

• determining a first, candidate time segment of an audio source signal for embedding at least a first message as a corresponding first watermark to provide a composite audio signal;
• evaluating the audio source signal to determine if the first time segment is suitable for masking the first message;
• and
• if the first time segment is found to be unsuitable:
• (a) selecting another, second time segment of the audio source signal that is suitable for masking the first message;
• and
• (b) embedding the first message in the second time segment along with information indicative of a time shift between the first and second time segments.

A method for recovering embedded data from a composite audio signal, comprising the steps of:

• (a) receiving the composite audio signal;
• wherein:
• at least a first message is embedded as a corresponding first watermark in a first time segment of the composite audio signal, along with time shift information indicative of a time shift between the first time segment and another, second time segment;
• and
• an audio source signal of the composite audio signal is suitable for masking the first message during the first time segment, but is unsuitable for masking the first message during the second time segment;
• (b) recovering the first message and the time shift information from the first time segment of the composite audio signal;
• (c) determining when the time shift has elapsed in accordance with the time shift information;
• and
• (d) providing a control signal for controlling a device after the time shift has elapsed in accordance with said determining step.

A method for decoding embedded data in an audio signal, comprising the step of:

• (a) receiving a composite audio signal;
• wherein data symbols of at least a first message are embedded as a corresponding first watermark in an audio source signal to provide the composite audio signal, and the first watermark is carried substantially inaudibly in the composite audio signal;
• the audio source signal is modified so that data symbols of the first message are determined according to corresponding values of an autocorrelation function of the composite audio signal;
• and
• each autocorrelation value is calculated over a time interval of a corresponding data symbol;
• and
• (b) recovering the embedded data symbols from the received composite audio signal according to polarities of the composite audio signal.

A decoding method for improving the time resolution of the position of a message that is embedded in an audio signal, and encoded according to an error-correcting code, comprising the steps of:

• (a) receiving the audio signal;
• (b) determining an initial position in the audio signal at which the message is initially detected;
• (c) determining a bit error count for the message at each of a plurality of positions, including the initial position and at least one other position that is shifted relative to the initial position;
• (d) determining an optimum position at which it is most probable that the message is embedded in the audio signal in accordance with the bit error counts;
• and
• (e) recovering the message at the optimum position.