| abstract |
A system for using a watermark embedded in an audio signal to remotely control a device. Various devices such as toys, computers, and appliances, equipped with an appropriate detector, detect the hidden signals, which can trigger an action, or change a state of the device. The watermarks can be used with a “time gate” device, where detection of the watermark opens a time interval within which a user is allowed to perform an action, such as pressing a button, typing in an answer, turning a key in a lock, etc. To prevent fraudulent activation of a time gate, the time gate device can be configured to react only to watermarks coming from live broadcasts, and not from replays from tapes or other storage devices. In another feature, robustness of the watermark is improved, e.g., for acoustic propagation channels, by shifting the detection time of the watermark based on a measured bit error count of the watermark. Furthermore, the watermark may be inserted before the desired action along with corresponding offset information if the audio signal is not suitable at the time of the action. |