Steganographic Wideband Telephony Using Narrowband Speech Codecs

We consider the transmission of wideband speech with a cut-off frequency of f
_c
= 7 kHz over a standardized digital narrowband communication link (f
_c
= 3.4 kHz). At the receiver, wideband speech is produced by artificial bandwidth extension (BWE). The BWE algorithms can be realized with or without some low bit rate side information. In this paper, we propose to communicate the side information to the receiver via a steganographic channel within the bitstream of the narrowband codec. Hence, the bitstream format is not altered and the bit rate is not increased. The following codecs are considered: mu-law PCM, ADPCM, CS-ACELP, GSM FR, and GSM EFR.