Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-07-09
2002-09-17
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S498000, C370S535000, C370S542000, C370S912000, C348S423100, C348S462000, C348S465000, C348S473000, C380S201000
Reexamination Certificate
active
06452952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital information processing system and more particularly, to a digital information processing system with a copy protection subsystem, which plays back a stream of multiplexed video, audio, and data packets of programs or services that have been packet-multiplexed in conformity with the standard given by the Moving Picture coding Experts Group (MPEG) (i.e., the MPEG standard), while preventing the programs or services from being copied illegally.
2. Description of the Prior Art
To protect the programs or services from being copied illegally in digital information processing systems of this sort, conventionally, several copy protection methods have been developed and reported.
For example, (a) some protection scheme is mixed into or added to the analog video, audio, and data signals of a program or programs to be copy-protected, (b) a specific protection code is additionally mixed into or added to the digital video, audio, and data signals of a program or programs to be copy-protected, or (c) the digital video, audio, and data signals of a program or programs to be copy-protected are scrambled.
FIG. 1
shows a conventional broadcasting receiver apparatus
161
designed for receiving toll broadcasting waves, which is disclosed in the Japanese Non-Examined Patent Publication No. 3-147490 published in 1991.
In the conventional broadcasting receiver apparatus
161
, as shown in
FIG. 1
, a demultiplexer
162
demultiplexes an audio signal and a related information signal that have been multiplexed and scrambled, thereby outputting a scrambled audio signal
163
to an audio descrambler
174
and a scrambled related information signal
164
to a decoder
165
.
The decoder
165
decodes or deencrypts the related information signal
164
thus inputted using a key signal
166
, thereby outputting an agreement signal
167
to an agreement comparator circuit
169
and an initializing signal
168
to a pseudo random-number generator
171
.
The agreement comparator circuit
169
compares the content of the agreement signal
167
to the content of the built-in agreement of the receiver apparatus
161
, and outputs a comparison result signal
170
to the pseudo random-number generator
171
and a control signal
181
to a mixer
180
.
According to the initializing signal
168
and the comparison result signal
170
thus received, the pseudo random-number generator
171
generates a sequence
172
of pseudo random numbers for audio signals and a sequence
173
of pseudo random numbers for video signals. The pseudo random-number sequence
172
for audio signals and the pseudo random-number sequence
173
for video signals are inputted into the audio descrambler
174
and a video descrambler
175
, respectively.
The control signal
181
from the agreement comparator circuit
169
is used to control the mixer
180
.
The audio descrambler
174
descrambles the scrambled audio signal
163
and outputs an analog audio signal
177
which is the same as the original audio signal. The analog audio signal
177
is then reproduced or played back by an audiovisual playback system (not shown).
The video descrambler
175
descrambles a scrambled video signal thus received and outputs an analog video signal
176
to the mixer
180
. The analog video signal
176
is the same as the original video signal.
A copy-protection signal generator
178
generates a copy protection signal
179
and supplies the signal
179
to the mixer
180
. According to the control signal
181
outputted from the agreement comparator circuit
169
, the mixer
180
performs a mixing operation of the copy protection signal
179
with the analog video signal
176
outputted from the video descrambler
175
.
Specifically, when the agreement signal
167
from the decoder
165
does not accord with the content of the built-in agreement of the receiver apparatus
161
, the mixer
180
performs the mixing operation of the copy protection signal
179
with the analog video signal
176
according to the control signal
181
. Then, the mixer
180
outputs the mixed video signal
176
to the audiovisual playback system (not shown) as a video signal
182
.
On the other hand, when the agreement signal
167
from the decoder
165
accords with the content of the built-in agreement of the receiver apparatus
161
, the mixer
180
does not perform the mixing operation of the copy protection signal
179
with the analog video signal
176
according to the control signal
181
. In this case, therefore, the mixer
180
outputs the inputted video signal
176
without any change as the video signal
182
to the audiovisual playback system (not shown).
With the conventional receiver apparatus
161
having the above-described configuration, a control or copy-protection bit to enable or disable the copy-protection function is provided in the related information signal in advance. The related information signal is encrypted in a transmitter and then transmitted by the transmitter.
In the receiver apparatus
161
shown in
FIG. 1
, the related information signal is demultiplexed by the demuliplexer
162
and then, deencrypted by the decoder
165
using the key signal
166
.
Subsequently, the content of the agreement contained in the related information signal
164
thus deencrypted is compared with the content of the built-in agreement of the receiver apparatus
161
by the agreement comparator circuit
169
. According to the result of this comparison, it is judged whether the copy protection signal
179
is mixed into the descrambled video signal
176
or not.
When the content of the agreement contained in the related information signal
164
accords with the content of the built-in agreement of the receiver
161
, the agreement comparator circuit
169
instructs the mixer
180
not to mix the copy protection signal
179
with the descrambler video signal
176
through the control signal
181
. In this case, the outputted video signal
182
from the mixer
180
can be recorded into a recording medium by using a Video Tape Recorder (VTR) or the like, and it can be normally played back for watching and listening from the medium.
On the other hand, when the content of the agreement contained in the related information signal
164
does not accord with the content of the built-in agreement of the receiver apparatus
161
, the agreement comparator circuit
169
instructs the mixer
180
to mix the copy protection signal
179
with the descrambled video signal
176
through the control signal
181
. In this case, although the video signal
182
outputted from the mixer
180
can be recorded into a recording medium, the quality of the played-back video signal
182
from the recorded medium degrades greatly so that it is difficult or unable to be watched and listened.
An example of the copy-protection signal
179
is an amplitude-varying pulse signal, which is added to or mixed with a scanning signal in the vertical blanking period of a video signal. The amplitude of the pulse signal varies at individual fields or at a longer period than the that of the fields. In this case, an Automatic Gain Control (AGC) circuit in a reproducing or play-back system such as a VTR is affected by the amplitude-varying pulse signal and as a result, the level of the played-backed video signal from the recorded medium fluctuates so that it is difficult or unable to be watched and listened.
The video and audio signals
182
and
177
can be played back normally on a TV screen independent of the existence and absence of mixing of the copy-protection signal
179
.
The above-described conventional receiver apparatus
161
shown in
FIG. 1
has the following problems.
Firstly, the control or copy-protection bit needs to be additionally provided in the related information signal to prevent illegal copy of the programs or services. Therefore, to cope with the control or copy-protection bit thus added, some subsystem is essentially provided not only at the receiver side but also at the transmitter side.
Foley & Lardner
Kizou Hassan
Logsdon Joe
LandOfFree
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