Towards Data Transmission Through Inaudible Sound in Ginga-NCL

Abstract

In this paper, we report our efforts to add support for data transmission through inaudible sound to the Ginga-NCL Digital TV middleware. We present an algorithm for encoding a bitstream in an inaudible audio signal, and to do so reliably on consumer-grade hardware. We also discuss two attempts to implement this algorithm in NCL, the language in which Ginga-NCL applications are written. The first attempt was to transmit prerecorded inaudible audio signals in a Ginga-NCL-compatible set-top-box. And the second attempt was to use NCLua to generate at runtime the inaudible audio signal. For the second attempt we extended NCL with a novel media object type, called SigGen, which can be used to generate arbitrary audio signals. In the paper, we describe in detail the implementation of SigGen and the result of these attempts.