| 摘要 |
Described herein is audio watermarking technology for inserting and detecting watermarks in audio signals. The watermark identifies the content producer, providing a signature that is embedded in the audio signal and cannot be removed. In one embodiment, a watermarking system employs chess spread-spectrum sequences to improve the balance of positive and negative chips in the watermarking sequences. The balance is not imposed in an orderly fashion, but in a pseudo-random fashion. In that way, better sequence balance is achieved while preserving its randomness for an attacker without knowledge of the keys. In another embodiment, a watermarking system employs an energy-level trigger to determine whether to skip encoding of a portion of a watermark within a given time span of an audio clip. If a large discrepancy in energy levels exists over a given time frame, then the frame is not watermarked, to avoid audible time-dispersion of artifacts. In another embodiment, a watermarking system begins encoding of a watermark at a variable position after the beginning of an audio clip. |
