Browse Prior Art Database

SPREAD SPECTRUM COPYRIGHT PROTECTION FOR MULTIMEDIA

IP.com Disclosure Number: IPCOM000008024D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-13
Document File: 2 page(s) / 132K

Publishing Venue

Motorola

Related People

Philip C. Blum: AUTHOR [+2]

Abstract

We describe a digital copyright protection method for use in multimedia data such as audio, still-frame imagery and video. The method provides a virtually undetectable means of modifying the original data in an imperceptible manner for copy- right enforcement and tracking of copyrighted material. The copyright provides a means to track reproduction (authorized or unauthorized) and retransmission of digital multimedia information. The original audio, still-image, or video can be nearly perfectly reconstructed, if desired. The method is robust to signal distortions and degrada- tion, common signal processing operations (e.g., fil- tering, resampling, requantization, and redigitiza- tion), noise forgery, and attack.

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MOTOROLA Technical Developments

SPREAD SPECTRUM COPYRIGHT PROTECTION FOR MULTIMEDIA

by Philip C. Blum and Mark S. Nowak

ABSTRACT

  We describe a digital copyright protection method for use in multimedia data such as audio, still-frame imagery and video. The method provides a virtually undetectable means of modifying the original data in an imperceptible manner for copy- right enforcement and tracking of copyrighted material. The copyright provides a means to track reproduction (authorized or unauthorized) and retransmission of digital multimedia information. The original audio, still-image, or video can be nearly perfectly reconstructed, if desired. The method is robust to signal distortions and degrada- tion, common signal processing operations (e.g., fil- tering, resampling, requantization, and redigitiza- tion), noise forgery, and attack.

DESCRIPTION

  The basic idea is to embed the copyright infor- mation as a relatively low bit rate narrow band information channel in a wide band signal that is the data using direct sequence spread spectrum techniques. The multimedia data has a wide band spectrum (relative to the copyright) and accepts the copyright by allowing the spectral components of the audio or video to be directly modified. The degradation to the multimedia information is mini- mized by spreading the power of the copyright sig- nal across the substantially broader spectrum of the multimedia data.

The accompanying figures illustrate the inven-

tion. At the transmitter, the narrow band informa- tion signal s(r), with a data rate of R bits/second, is interpolated and multiplied by a spreading signal, g(r), with symbol or chip rate of % chips/second. g(t) is known in advance at both the transmitter and receiver, and is chosen to have bandwidth compara- ble to that of the multimedia signal. Multiplication in the time domain corresponds to convolution in the frequency domain:

s(f) g(t) * S(w) @ G(w)

  So, if the information signal is narrow band compared to the spreading signal, the resulting product signal s(r) g(t) will have approximately the same bandwidth of the spreading signal. The band- width of the spreading signal is chosen to be no larger than the bandwidth of the audio or video sig- nal chosen to carry the narrow band information signal s(t). The product signal is then scaled by a possibly time-varying parameter o(t), which is based on the estimated power of the audio or video signal, x(r) and then added to x(t) as the composite signal:

x'(t) = x(t) + o(t) s(t) g(t)

o(r) is chosen small enough to render the composite perceptually inaudible or invisible, yet large enough to provide robustness to common manipulations of and attacks on the composite signal. The composite signal, x(t), in this form is suitable for mass distrib- ution and use. It suffers from no perceptible degra- dation in quality from the original.

Pulse Shape

Fillei

Fig. 1 Copyright...