Reversible and Robust Audio Watermarking Based on Quantization Index Modulation and Amplitude Expansion

Existing techniques for reversible hiding of data in audio signals are so fragile that no data can be extracted from a modified stego audio signal. The present study proposes a reversible and robust technique for hiding data in audio. A robust payload is embedded based on quantization index modulation (QIM) at the averaged root mean square levels of the segmented stego waveforms. Simultaneously, a reversible payload is embedded into the apertures in the amplitude histogram created by amplitude expansion in QIM. Computer simulation was conducted to evaluate the robustness and size of the reversible payload for 20 music pieces. MP3, tandem MP3 coding, MPEG4AAC, and bandpass filtering of the stego signals revealed a maximum bit error rate of less than 16 % in 6-bits per second robust payload. Objective measurement of the stego audio quality using the perceptual evaluation of audio quality method revealed that the mean objective difference grade was higher than ‘perceptible, but not annoying’. The amount of reversible payload was above several kilobits per second.