Digital video converter box for subscriber/home with multiple television sets

A digital video conversion system housing multiple converter chains of units in a single main box chassis. A preferred embodiment uses only a single conditional access unit to authorize decryption of premium channels in response to a smartcard. The conversion system allows a single converter box sharing consolidated decryption (access control) circuitry and a single remote control receiver to provide video output for multiple television sets on the subscriber's premises. In addition to reducing the subscriber's hardware costs per television set, a common access control allows the video service provider to grant a multiple-set discount on a single smartcard.

BACKGROUND OF THE INVENTION 
The present invention relates to digital video conversion systems, in 
particular, a system for use with multiple television sets at the home of 
a single subscriber. 
Subscription and pay-per-view video services are delivered to a 
subscriber's premises via both satellite and cable transmission systems. 
In cable systems, 6 MHZ analog video and/or digital QAM channels are 
frequency division multiplexed (FDM) across the 500-1000 MHZ cable 
bandwidth. In typical satellite systems, several compressed digital video 
programs are time division multiplexed (TDM) into a single 10-40 Mbit/s 
QPSK or BPSK modulated C- or K- band carrier. Several carriers may be 
available to subscribers over several transponders in the satellite. 
In order to select and view a program, the received broadcast signal must 
be tuned, demodulated, and decompressed. Additionally, in the case of 
premium or pay-per-view programming, authorization must be obtained for 
the digital data to be decrypted. In traditional systems, these functions 
are placed in a set-top converter box, which RF modulates the decompressed 
video for viewing on channel 3 or 4 of a standard television. 
The tuning and demodulation functions of the conversion process for cable 
and satellite systems differ because of their transmission methods. The 
decompression and RF modulation of the digital video data are similar to 
both systems. In cable systems, the appropriate 6 MHZ channel is tuned by 
mixing the received FDM signal to bring the desired channel to an 
intermediate frequency (IF). The IF QAM signal is then demodulated into 
the compressed digital video data. For satellite systems, the set-top 
converter box does not receive the K- or C- band carrier directly, but is 
fed an amplified signal translated to the L-band. The converter box then 
tunes the desired channel to an IF frequency. In both systems, the digital 
video data is decompressed according to pre-defined algorithms (e.g., as 
an MPEG-2 program), then is modulated as an analog signal for viewing on a 
television set or monitor. 
Because of advantages of digital video broadcast systems over analog 
systems in the quality, density, and versatility of services, digital 
systems are projected to soon replace analog transmission systems. 
However, by their nature, digital set-top converter boxes are more complex 
and expensive than analog set-tops. Additionally, digital video systems 
currently require one set-top box for each independently operating 
television, whereas many televisions are simply split off the cable drop 
to a household subscribed to an analog system. A television can usually be 
directly split off an analog system because many sets come equipped with 
"cable-ready" tuners. "Cable-ready" tuners are relatively inexpensive 
since they are mere extensions of terrestrial broadcast tuners. Further, 
premium channels are often authorized by simply removing a notch filter on 
the cable drop entering the premises of an analog system subscriber. Thus, 
although digital video transmission systems offer more and better services 
than analog systems, they suffer a higher cost per television set for a 
given subscriber. 
Controlling the ability to view programming by only authorized subscribers 
or purchasers is of primary importance in a satellite or cable broadcast 
system. Unlike free terrestrial broadcasts which are paid by advertising 
sponsors, satellite and cable systems charge viewers directly for 
programming. Many access control systems have been deployed and were 
subsequently defeated. Because of arguments that any access control system 
can eventually be dissected and defeated, the state-of-the-art system 
features a "replaceable security" element such as a "smartcard". The 
smartcard is credit-card sized, and contains an integrated circuit chip 
for authorizing a unique subscriber. The smartcard is inserted into the 
set-top box to decrypt premium programming. A smartcard may be used on a 
pre-paid basis, or can be inexpensively replaced in the event the existing 
access control system is defeated. 
In addition to the cost disadvantage of requiring an individual set-top box 
for each television in a household, problems also arise in managing access 
control for a household. For example, additional televisions in the home 
of an analog cable subscriber are often charged only a nominal fee, based 
on a multiple-license discount. However, in a digital transmission system 
with individual set-top boxes per television, a system operator could not 
offer such a discount since the smartcards could be moved to other homes. 
At the time of this invention, this necessity to pay for each individually 
operating set in a household remains a disadvantage of digital systems 
compared to analog systems. 
SUMMARY OF THE INVENTION 
Embodiments of the present invention provide a more efficient, single 
digital video converter box for a subscriber's premises (household) to 
eliminate the need to use an individual set-top converter for each 
television in the premises. 
According to an embodiment of the present invention, a household converter 
box accepts a frequency division multiplexed signal containing many 
channels of modulated digital video programming from either a cable drop 
or a satellite LNB amplifier. The converter box employs an independent 
tuning, demodulation, and video decompression chain for each independently 
operating television set in the house, but shares a common conditional 
access circuit, remote control receiver, power supply and chassis. 
In further accordance with an embodiment of the present invention, each 
individual tuning, demodulation, and video decompression chain may be 
housed as a modular unit which plugs into the main chassis. The individual 
modules provide a digital output to the conditional access unit for 
decryption, and a digital input for decompression of the decrypted data 
stream. Where television sets contain built-in decompression ability 
(e.g., MPEG-2 decoding ability) and accept digital inputs, a form of the 
present invention does not decompress and RF modulate the digital program 
data, but outputs the digital data directly. 
In further accordance with an embodiment of the present invention, the 
household video decoder box will contain a single remote control receiver 
which accepts commands from the various remote control transmitters 
associated with each television on the subscriber's premises. A single 
remote control receiver, as opposed to individual receivers in individual 
set-top boxes reduces costs per television set on a subscriber's premises. 
Since the remote control receiver can be separated from each transmitter 
by one or more walls, infrared or other line-of-sight modulation schemes 
cannot be used, but an RF band is used in the present invention. 
In further accordance with an embodiment of the present invention, the 
output of the conversion box to the individually operating television sets 
can be over a number of media, including a wireless RF link. For example, 
an RF modulated analog video signal on channel 3 or 4 may be carried from 
the household conversion box to the individual television sets over 
separate coax links. Similarly, direct baseband digital data from the 
converter box may be carried to the individual sets over twisted wire pair 
links. Additionally, the selected video program may be transmitted to the 
individual television sets over a local, low-power wireless RF link, in 
analog or digital form. 
The present invention is advantageously able to operate multiple 
televisions in a subscriber's premises through the same conditional access 
device. Prior to this invention, each television subscribed to a digital 
video transmission system required its own set-top box, and because of 
replaceable security, it's own smartcard. This arrangement makes it 
difficult for a digital video service to allow a household multiple-set 
discount, common in analog cable services, because smartcards could be 
easily moved to other households. The present invention allows the use of 
a single smartcard for a subscriber, and enables a digital video service 
provider to competitively offer a multiple set household discount. 
The following benefits are obtained from the present invention: (1) a 
reduced cost per television set in a household viewing digital video 
transmissions, (2) a secure method of identifying all of a subscriber's 
digital video television decoders through a single conditional access 
unit, and (3) a simpler method of decoding digital television 
transmissions for a single subscriber premises, or household.

DETAILED DISCUSSION OF THE PRESENTLY PREFERRED EMBODIMENTS 
In the prior art, a single household could use an individual digital video 
decoder settop box 10 for each independently operating television set 12, 
as in FIG. 1. As used herein, a television set may be any video signal 
display device including conventional televisions and computer monitors. 
Each set-top box 10 has a remote control 14 associated with it. The 
signals into the household are split by splitter 16 for delivery to each 
of the set-top boxes 10. In addition to a constant cost per television in 
the household, each set-top would probably be authorized as an individual 
subscriber, independent of one another. Each set-top 10 would have it's 
own conditional access unit, and as systems often use such replaceable 
security elements, it's own smartcard. 
The present invention allows the use of a single converter box for cable or 
satellite pay-per-view and/or subscription digital video system, using a 
single conditional access unit (smartcard). A typical example of this 
single household digital video converter box 100 is shown in FIG. 2, for 
three television sets 12 in the home. Each television set has a remote 
control 18 associated with it for communication with the converter box 
100. 
A block diagram of the household digital video converter box 100 is shown 
in FIG. 3. For serving a plurality of television sets, the converter box 
includes a plurality of chains, each including a tuner 102, a demodulator 
104, a decompression unit 110 and an RF video modulation unit 108. The 
chains share a single conditional access unit 110 and one or more remote 
control receivers 112 for all household sets, and a single power supply 
114 and chassis. The input to the converter box provides the television 
signals. Current examples of such inputs include a cable drop with 6 MHZ 
QAM channels FDM'ed (frequency division multiplexed) over the 500-1000 MHZ 
bandwidth, or an L-band FDM signal of a number of 10-40 MHZ QPSK/BPSK 
satellite channels from an LNB. The conditional access unit 110 operates 
with a single smartcard 116. 
The FDM signal from the cable drop or LNB is power split in the converter 
box, and fed to the individual tuner/demodulator/decompression/modulator 
units. The individual converter units are modularly inserted into the main 
chassis in the preferred embodiment. This modularity allows the subscriber 
to purchase only the amount of hardware required for his household. In 
other embodiments, a fixed number of 
tuner/demodulator/decompression/modulator units may be configured. The 
converter units accept commands from the remote control receiver 112 to 
tune a desired FDM channel. The selected channel is demodulated from the 
QAM or QPSK/BPSK signals in a cable or satellite converter box, 
respectively, into digital data to be decrypted by the conditional access 
unit 110. The conditional access unit outputs the decrypted digital data 
on a baseband video signal. The decrypted digital data is then input back 
into the units to be decompressed according to predetermined algorithms 
(e.g., as an MPEG-2 stream). The decompressed video is then modulated into 
an RF analog signal viewed on a standard television set typically on 
channel 3 or 4. The RF signals from the decoder box to the individual 
television sets are carried on separate coaxial cable segments. In 
configurations where television sets have built-in decompression ability 
and accept direct digital video data, the modular units contain only tuner 
and demodulation functions, and baseband digital data is output from the 
converter to the televisions in the subscriber's home. In the latter 
embodiment, the baseband digital data may be carried from the converter 
box to the individual television sets over twisted wire pair, coax, or 
wireless RF means. 
In the preferred embodiment, a single RF remote control receiver services 
individual remote control transmitters associated with the independently 
operating televisions in the household. The remote control transmitters 18 
use the RF band, as opposed to infrared, because a (reflected) 
line-of-sight is not always available to the single decoder box. 
Of course, it should be understood that various changes and modifications 
to the preferred embodiments described above will be apparent to those 
skilled in the art. For example, a less efficient implementation of the 
invention may be configured with a plurality of remote control receivers, 
one for each chain of converter units. Also, the system of the invention 
is applicable regardless of the content of the signals being processed. 
The signals may include broadcast television programs, cable programs, 
interactive games, computer data, etc. for display on a television or 
monitor. These and other changes can be made without departing from the 
spirit and scope of the invention and without diminishing its attendant 
advantages. It is therefore intended that such changes and modifications 
be covered by the following claims.