Embedding side information into a speech codec residual

We introduce a technique for embedding side information into a speech codec residual. While conserving the backward compatibility with existing decoders, it is described how it is possible to hide information into the speech long-term residual signal when it is encoded using a uniform or quasi-uniform quantiser. The method consists of embedding multiple parity bits at the quantiser level in a configuration that minimises the distortion over the whole subframe. The system has been evaluated quantitatively in terms of MOS and subjectively using “double blind” listening tests using the GSM-FR speech codec. It has been found that data can be embedded without severe perceptual degradation of the signal quality. Beyond this particular application to speech coding, it is shown how simple parity-check techniques can be developed to transparently transmit any binary data alongside the main encoded signal by using such joint quantisation and embedding scheme.