Are All Patents Fleeting?

 
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The reasoning of the Court of Appeals for the Federal

Circuit in its recent decision in In Re Nuijten and

its subsequent denial of a petition for rehearing en banc has

the potential effect of invalidating thousands of issued

patents that may fall into newly un-legislated exceptions from

patentable subject matter In Re Nuijten, 500 F.3d 1346

(Fed. Cir. 2007), rehearing denied, 515 F.3d 1361 (Fed. Cir.

2008). The Federal Circuit in In Re Nuijten held that

a transitory propagating signal is not patentable subject

matter under 35 U.S.C. § 101.

Background:

Nuijten's patent application discloses a technique for

reducing distortion induced by the introduction of

"watermarks" into signals. In the context of signal

processing, watermarking is a technique by which an original

signal is manipulated so as to embed within it additional data.

The additional data is preferably imperceptible to someone who

views or listens to the signal-for instance, a listener who

plays back a watermarked digital audio file would, if the

watermark is sufficiently unobtrusive, not be able to

distinguish between the watermarked and unwatermarked versions.

An analysis of the file by software capable of detecting the

watermark, however, will reveal the mark's contents.

Publishers of sound and video recordings, for example, find

watermarks useful to embed in the media they distribute

information intended to protect that media against unauthorized

copying. For these publishers and others, watermarking

represents a trade-off: the desired additional data is encoded

directly into the signal, but like any change to a signal, the

watermark introduces some level of distortion. Thus, a key goal

of watermarking techniques is to minimize the distortion so

that the resulting diminution in signal quality is as minimal

as possible.

Nuijten's technique improves existing watermark

technology by further modifying the watermarked signal in a way

that partially compensates for distortion introduced by the

watermark.

Figure 2 from the Nuijten application, illustrated above,

demonstrates a relatively simple form of digital audio encoding

called "delta modulation." The smooth line in the

upper graph (labeled 'x') represents a very small slice

of the sound wave to be encoded. The lower graph represents a

digital encoding of that signal. It takes on only two values to

illustrate the signal. These are labeled here as '1'

and '-1,' rather than the usual labeling of these

binary values as one and zero. The sound wave is reconstructed

from the digital signal one step at a time, left to right. If

the digital signal has value '1,' then the

reconstructed sound wave's value is increased slightly. If,

on the other hand, the digital signal has value '-1,'

then the sound wave is decreased by the same amount. Therefore,

the recording is represented by the change (or

"delta") over a very small increment of time, either

'1' for an increase or '-1' for a decrease.

Hence, the encoding scheme is known as "delta

modulation." The result is a close but imperfect

approximation of the original sound wave, illustrated on the

upper graph by 'x' with a caret above it. The fidelity

of the reconstructed sound wave to the original will depend in

large part on the "sample rate"-the length of the

time interval represented by each discrete value in the digital

signal. Representing all of the nuances of the original sound

wave in order to produce a rich, clear recording may require

tens or hundreds of thousands of samples per second.

The watermark of Nuijten is imposed on the signal by

altering, if necessary, every hundredth value of the digital

signal. A reader seeking to extract the watermark from the

digital signal would therefore view only every hundredth value,

disregarding the other 99 along the way; by stringing together

all such values, the watermarked data may be discerned. Every

point where a portion of the watermark is found represents a

possibility that the signal may be distorted. If the watermark

value designated for a certain position and the original value

at that same position happen to coincide, there is no need to

modify the original and hence no distortion. About half of the

time, though, those values will not coincide and the digital

signal will be altered. The result is shown below in Figure 3

from the Nuijten application: the digital value at the point

labeled '21' and illustrated by a vertical dashed line

has been changed from '1' in the original to

'-1.' The reconstructed signal is thus decreased where

it should be increased, and the encoded signal departs from the

original in a pronounced manner.

Nuijten's application teaches that the above illustrated

departure may be minimized by making an additional change to

the watermarked digital signal, as shown below in Figure 4:

Here, the value preceding the one that was modified by the

watermark has also been modified: it was '-1' in the

original signal, but is now '1.'...

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