Double embedding in the quantization index modulation framework

Quantization index modulation (QIM) is a commonly used data hiding technique where a single bit is embedded per coefficient. Here, we propose the use of double embedding in the QIM framework where a single coefficient is modified twice, using two quantizers, to embed two bits. The motivation behind substituting single embedding with double embedding in the QIM framework for a certain steganographic scheme is to increase its hiding rate without significantly increasing the embedding distortion and the stego scheme´s detectability against steganalysis. We empirically determine the best way to couple the double embedding framework with a repeat accumulate code based error correction scheme. For moderate noise levels, the use of double embedding is seen to be significantly advantageous over single embedding.