US 2019/0200071 A1 · INAUDIBLE SIGNALING TONE

Abstract

A method of encoding, and decoding, a human-inaudible acoustic signal 240 embedded within audio content, suitable for use within the processor of an encoding and broadcasting system or a decoding and receiving system 200, 202. A binary message is encoded into a sequence 1000, 2000 of symbols selected from a group of four or eight symbols, each symbol encoding two or three binary bits with an associated frequency. The human-inaudible acoustic signal may have a variable length, with the length of the signal encoded in a header 1002-1008, 2002-2009. The encoding uses both forward error correction and cyclic redundancy coding to increase the robustness of the transmission. Furthermore, the binary bits encoded by the symbols are selected such that a Hamming distance of a single bit transformation exists between symbols associated with adjacent frequencies, so that a frequency error creates only a single bit error.

Claims37

Dependent claims

A method of decoding a human-inaudible acoustic signal embedded within audio content in the processor of a decoding device, comprising:

a. receiving samples of a digitized version of the audio content including the human-inaudible acoustic signal into the processor of a decoding device;
b. correlating the audio content within said samples with a prefix template for a prefix of the human-inaudible acoustic signal to identify candidate samples potentially associated with the start of said human-inaudible acoustic signal;
c. repeatedly performing a frequency domain transformation of samples of the candidate samples and comparing frequency domain transformations thereof to frequency characteristics associated with two or more candidate symbols to generate a symbol sequence;
d. performing an error correction decoding upon the symbol sequence to determine the validity of the symbol sequence;
and
e. upon identifying a valid symbol sequence, transmitting the symbol sequence as the decoded equivalent of the human-inaudible acoustic signal.

3 more elements

Dependencies are inferred from the claim text.

Inaudible signaling tone

Life of this patent

Inaudible signaling tone

Life of this patent

Abstract

Claims37