  Steganography comprises the mechanics of hiding data in a host media that may
be publicly available. While previous works focused on unimodal setups (e.g.,
hiding images in images, or hiding audio in audio), PixInWav targets the
multimodal case of hiding images in audio. To this end, we propose a novel
residual architecture operating on top of short-time discrete cosine transform
(STDCT) audio spectrograms. Among our results, we find that the residual audio
steganography setup we propose allows independent encoding of the hidden image
from the host audio without compromising quality. Accordingly, while previous
works require both host and hidden signals to hide a signal, PixInWav can
encode images offline -- which can be later hidden, in a residual fashion, into
any audio signal. Finally, we test our scheme in a lab setting to transmit
images over airwaves from a loudspeaker to a microphone verifying our
theoretical insights and obtaining promising results.

Multimedia;Sound;Audio and Speech Processing