A Novel Virtual Pulse-Based Steganography Schemefor Low-Bitrate AMR-WB Speech

This paper proposes a novel virtual pulse-based steganography technique for concealing data within the 8.85 kbits/s mode of the Adaptive Multi-Rate Wideband (AMR-WB) speech codec. The scheme introduces the concept of a virtual pulse within each track of the algebraic codebook, enabling data embedding across all tracks even at the lowest bitrate mode which normally contains only a single pulse per track. An embedding process based on Gray code modulation is devised to manipulate the virtual pulse positions according to the secret message bits. The proposed approach facilitates adjustable embedding capacities by varying the payload, defined as the proportion of subframes utilized for data embedding versus standard coding. Evaluations on a speech corpus demonstrate the method's ability to achieve covert communication with minimal distortion to speech quality when operating at moderate payloads. Furthermore, an analysis of statistical steganalysis detection indicates favorable resistance against unveiling the presence of hidden data. The virtual pulse steganography scheme offers a viable solution for secure communication over low-bitrate AMR-WB channels while preserving a configurable trade-off between embedding rate and speech quality degradation.