Title page for ETD etd-52298-163159


Type of Document Master's Thesis
Author Tilki, John F.
Author's Email Address tilki@vt.edu
URN etd-52298-163159
Title Encoding a Hidden Digital Signature Using Psychoacoustic Masking
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Beex, A. A. Louis Committee Chair
Abbott, A. Lynn Committee Member
Bay, John S. Committee Member
Keywords
  • Psychoacoustics
  • Hidden Audio Coding
  • Inaudible Audio Coding
  • Interactive Television
Date of Defense 1998-06-09
Availability unrestricted
Abstract
The Interactive Video Data System (IVDS) project began with an

initial abstract concept of achieving interactive television by

transmitting hidden digital information in the audio of commercials.

Over the course of three years such a communication method was

successfully developed, the hardware systems to realize the application

were designed and built, and several full-scale field tests were

conducted.

The novel coding scheme satisfies all of the design constraints

imposed by the project sponsors. By taking advantage of psychoacoustic

properties, the hidden digital signature is inaudible to most human

observers yet is detectable by the hardware decoder. The communication

method is also robust against most extraneous room noise as well as the

wow and flutter of videotape machines.

The hardware systems designed for the application have been tested

and work as intended. A triple-stage audio amplifier buffers the input

signal, eliminates low frequency interference such as human voices, and

boosts the filtered result to an appropriate level. A codec samples the

filtered and amplified audio, and feeds it into the digital signal

processor. The DSP, after applying a pre-emphasis and compensation

filter, performs the data extraction by calculating FFTs, compensating

for frequency shifts, estimating the digital signature, and verifying

the result via a cyclic redundancy check. It then takes action

appropriate for the command specified in the digital signature. If

necessary it will verbally prompt and provide information to the user,

and will decode infrared signals from a remote control. The results of

interactions are transmitted by radio frequency spread spectrum to a

cell cite, where they are then forwarded to the host computer.

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