Audio protection with removable watermarking

A perceptible removable watermark can be used to add copyright owner´s identification to media or lower the value of the digital contents. The application scenario for perceptible watermarks is to give the protected contents available freely for download as a preview. For a fee, the watermark can be removed to restore the media quality to the original level. We present a scheme to protect the audio data by embedding high capacity robust watermark to it. The watermark can be removed using a secret watermarking key with only minimal remaining distortion. The protection watermark embedding and detection is done in the spectral domain. The watermark is embedded into selected FFT coefficients´ magnitudes of the cover audio using frequency hopping method. The method proposed is media format independent and it can be used with lossy compression. The objective and subjective quality evaluations indicate that the audio quality after watermark removal is excellent.