Auxiliary data subband samples representing an auxiliary data signal are transported in a subband-coded compressed digital audio signal without decompressing the data. A pre-existing packetized data stream is provided to an input of a encoder. Subband audio samples are extracted from the packet stream and normalized if required. The data to be transported modulates data carrier subbands including, for example, a pseudo-noise (PN) spread spectrum signal, each subband of which has a bandwidth corresponding to those of the digital audio signal. The data carrier sequence can also include a sparse PN sequence, sample twiddle sequence, or a bit twiddle sequence. The modulated data carrier sequence is combined with the audio subband samples to form a combined signal in which the auxiliary data subband samples are carried. The combined signal is then multiplexed into the pre-existing packet stream. In a decoder, the combined signal is demodulated to recover the auxiliary data signal. The recovered auxiliary data signal is carried substantially inaudibly in the audio signal and is spectrally shaped according to the audio signal to enhance concealment.