Note: Descriptions are shown in the official language in which they were submitted.
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BROADCAST VIDEO BURST TRANSMISSION CYCLIC DISTRIBUTION APPARATUS AND METHOD
Background and Summary of the Invention
U.S. Patent Nos. 4,963,995 and 5,057,932 to Lang teach the transmission
of audio/video program information in a burst period of time that is
substantially less than the time required for real time viewing of that
audio/video program information. These prior art references teach the general
aspects of compression, storage, burst transmission, reception, decompression,
and display of audio/video program information. However, they do not address
the specific aspects of a burst transmission system for cyclic distribution of
audio/video program information. Cyclic distribution, as used herein, is
directed to a method of transmitting audio/video program information that is
commonly referred to as pay-per-view (PPV).
In a conventional PPV system, the subscriber selects an audio/video
program, such as a movie, from a predetermined broadcast schedule. This
ordering process can take place in many ways, such as calling a specified
telephone number from a touch-tone telephone, pressing the appropriate keys on
the cable converter box that is supplied by the service provider, speaking
directly with an operator over a telephone, etc. In any case, the subscriber
always selects a program from a predetermined schedule of programs that the
service provider will be broadcasting in real time. When an order is placed,
the cable converter box will automatically unscramble the program on the
selected television channel so that the subscriber may view the program as it
is being broadcast.
Video-on-demand (VOD) systems differ from PPV systems in that the
subscriber may order any audio/video program from a list of available titles
in an audio/video library. The selected audio/video program may be
transmitted or otherwise distributed in whole or in part to the subscriber in
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a number of ways, including the less than real time burst transmission
described by Lang. Regardless of the chosen transmission medium, the
subscriber selects any available audio/video program for viewing or delivery,
as opposed to tuning in to a broadcast that is on a predetermined schedule
over which the subscriber has no control.
The present invention is directed at bridging the gap between PPV and
VOD systems of the prior art. As in the VOD systems described in the prior
art patents cited above, burst transmissions are utilized as the preferred
distribution means. However, instead of providing an audio/video library that
permits the subscriber to select any program for delivery, the present
invention combines the predetermined, cyclic schedules of conventional PPV
systems with the burst transmission technique taught by Lang. This
combination results in simplified and lower cost video library equipment. It
also results in a greatly enhanced PPV system from the subscriber's viewpoint.
In a conventional PPV system, the audio/video programs are broadcast over
coaxial cable, microwave, fiber optics or any of a variety of transmission
systems in real time. That is, the programs are broadcast or literally played
back in real time to the subscribers of such systems. Thus, it is not
possible for the viewer to exercise VCR-type control during the playback, such
as stop, pause, rewind or fast-forward. In providing an audio/video program
broadcast schedule characteristic of conventional PPV systems, but using the
burst transmission technique taught by Lang, the present invention provides
enhanced user functionality over conventional PPV systems at a much lower cost
than is associated with library-based VOD systems.
The apparatus of the present invention includes a central library
storing a mulitplicity of time compressed digital audio/video programs that
may be selectively transmitted in a burst time period to corresponding storage
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at one or more remote subscriber locations, where the transmitted program may
be decompressed and viewed in accordance with the teachings of Lang. The
central library provides cyclic, predetermined broadcast transmission of the
time-compressed digital audio/video programs stored therein. A receiver at
each of the remote subscriber locations continuously monitors a communications
channel over which the sequential stream of time-compressed audio/video
programs is broadcast from the central library, but is operative for storing
only the program or programs that have been ordered by a subscriber.
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Brief Description of the Drawings
Figure 1 is a pictorial diagram illustrating the broadcast video burst
transmission system of the present invention.
Figure 2 is a pictorial diagram illustrating the way in which the
broadcast video burst transmission system of Figure 1 may be configured to
transmit portions of audio/video programs in order to reduce storage costs.
Figure 3 is a block diagram of circuitry employed in the broadcast
video burst transmission system illustrated in Figure 1.
Figure 4 is a flowchart of operation of the central library portion of
the broadcast video burst transmission apparatus and method of Figure 1 from
the time a subscriber places an order for an audio/video program to the
beginning of transmission of that audio/video program.
Figure 5 is a flowchart of operation of a receiver at each subscriber's
location in the broadcast video burst transmission system of Figure 1.
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Detailed Description of the Preferred Embodiments
Referring now to Figure 1, there is shown a pictorial diagram
conceptually illustrating the broadcast video burst transmission system of the
present invention. A ring or wheel 22, rotating in a counter-clockwise
direction, provides on-line storage of a plurality of audio/video programs,
such as movies. It should be noted that the present invention does not
include a physical wheel 22. Rather, wheel 22 is illustrated simply as an aid
to understanding the concept of the present invention. The broadcast video
burst transmission system also includes an off-line storage 20, a tranmsission
line 30 that comprises a multiplicity of transmission segments 35, a receiver
40, and a monitor 45. Wheel 22, off-line storage 20, and external control
software and hardware (not illustrated) comprise a library 55. In the system
illustrated in Figure 1, sixteen predetermined programs are stored on-line on
wheel 22 of library 55 in a time-compressed format. On-line storage of
programs on wheel 22 requires the reading of information therefrom at a
sufficiently high rate to maintain a desired rate of transmission along
transmission line 30. In one embodiment, for example, transmission line 30
operates at 114 Mbits/second, thus requiring high-speed storage media to
access the stored programs. To reduce the expense associated with high-speed
storage media, less poplular programs are stored on slower, less costly, off-
line storage 20. These programs may be transferred to on-line storage on
wheel 22 when appropriate.
Conceptually, wheel 22 comprises sixteen wheel segments 25, each one of
which stor,es a program in a time-compressed format. The transmission of such
a program in a burst time period that is much less than real time may be
accomplished in accordance with the prior art teachings of the Lang patents,
supra. The rotation of wheel 22 represents the predictable cycling through
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the sixteen most requested programs stored thereon. As wheel 22 rotates in
the counter-clockwise direction illustrated, the programs stored thereon are
sequentially transferred to transmission line 30 for burst transmission to all
subscriber locations. In the system of Figure 1, a sequential stream of the
sixteen predetermined programs retrieved from on-line storage on wheel 22 is
illustrated. At the instant in time depicted in Figure 1, it may be seen that
program number 3 has just been transferred onto transmission line 30, that
program number 2 was immediately previously transferred, and that program
number 4 will be immediately next transferred.
Each of the sixteen programs stored on wheel 22 is associated with a
burst transmission time period that is much less that real time, as taught in
the prior art by Lang. Transmission segment 35 of transmission line 30 is
exemplary of such a burst transmission time period in that it represents the
block of time required to transmit the entire program number 15. Given the
transmission parameters detailed below, transmission segment 35 represents 76
seconds required to transmit the entire program number 15.
As stated previously, wheel 22 is illustrated as providing on-line
storage of sixteen programs. For example, assume that the compressed digital
video bitstream requires 1.2 Mbits/second for real-time playback, and that the
transmission line 30 is a 36-MHz satellite channel modulated at approximately
4 bits/Hz plus overhead, resulting in a 114 Mbit/second digital transmission
rate. Dividing the 114 Mbit/second transmission rate by the 1.2 Mbit/second
compressed video bit rate results in a time compression factor of 95:1. In
other words, a typical two-hour program will require a transmission time of
120 minutes divided by 95, or 76 seconds. Thus, in one hour, approximately 60
minutes divided by 1.26 minutes/program, or 47.5 programs, may be transmitted.
Transmission of the sixteen programs stored on wheel 22 at 1.26 minutes each
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requires a total of 20 minutes. Therefore, wheel 22 requires 20 minutes to
complete one revolution, with transmission of any single two-hour program
stored thereon requiring 1.26 minutes. From another prespective, a subscriber
will have to wait no longer than 1.26 minutes to begin viewing the next
transmitted one of the predetermined sixteen programs stored on wheel 22 and
will have to wait no longer than 20 minutes to begin viewing any selected
program from among the sixteen offered, resulting in an average waiting time
of 10 minutes. Of course, a different digital compressed video rate and
transmission channel bandwidth will result in different transmission rates
and, hence, different subscriber access times. For example, doubling the
compression performance to 600 Kbits/second and doubling the modulation rate
to 228 Mbits/second results in quadrupling system performance so that each
program is transmitted in 19 seconds (190 programs per hour). Increased
performance may also be obtained by multiplexing numerous channels to increase
available bandwidth.
Receiver 40 illustrated in Figure 1 represents the equipment located at
one or more destinations for receiving, storing, and playing back programs
transmitted as described above. A conventional user interface (not
illustrated) is utilized to request programs and communicate with the library
55. Library 55 includes the on-line storage of wheel 22, as well as the off-
line storage 20. Receiver 40 includes a VID monitor 45 that is employed to
monitor transmission line 30 for transmission segment 35 (program number 15).
When transmission segment 35 does not match the VID (a VID is data that
uniquely identifies the program, as explained ih detail below), the
transmission is ignored. Upon matching the VID, receiver 40 is then utilized
for receiving and storing transmission segment 35. Having received the
desired program, receiver 40 may be employed for decompression and playback of
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the program on display 50 at the subscriber's convenience.
A predictable transmission schedule is the major feature of the
broadcast video burst transmission system of the present invention. This is
in sharp contrast to VOD systems, which involve no schedule at all. Many
scheduling variations may be implemented in the present system without
sacrificing any of its benefits. For example, the program transmission
schedule may be determined dynamically, based upon statistical analysis of the
demand for certain programs. Wheel 22 of Figure 1 stores sixteen programs
that are cycled for transfer to transmission line 30 on a regular, predictable
schedule, resulting from rotation of wheel 22. Transmission of these same
sixteen programs, each of which is stored in one of the wheel segments 25 of
wheel 22, is repeated on each rotation of wheel 22. However, a program stored
in off-line storage 20 may be determined by industry sources or statistical
analysis, for example, to be new one of the top sixteen programs. In that
event, it may be desired to replace one of the sixteen programs currently
stored on wheel 22 with the new program previously stored in off-line storage
20. This replacement of programs associated with various ones of the wheel
segments 25 of wheel 22 may occur at regularly scheduled intervals. Of
course, such schedule changes must be communicated to each subscriber in some
manner, such as by way of a video channel that continuously displays the
current schedule of sixteen programs.
It is important to recognize that in the foregoing example in which the
programs stored-on wheel 22 and, thus, the transmission schedule for those
programs, are dynamically changing, a schedule nevertheless exists. This
predictable schedule is a factor that helps to minimize the amount of on-line
storage required, but that is transparent and not limiting to the subscriber.
Rather, the use of burst transmission of the programs stored on wheel 22
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offers such a convenient and rapid selection of programs, with only a short
queue time before a selected program is received, that the subscriber may
believe he is being served by a VOD system. The predictable schedule, even a
dynamically changing one, results in a reduction in storage costs. This
savings can be realized as long as the entirely random selection of programs
available to the subscriber in a VOD system is eliminated. Given this
requirement, the transmission schedule of the broadcast video burst
transmission system of the present invention is predictable enough to reduce
the complexity of library 55 as compared to a VOD system. By employing a
known schedule, fewer programs need to be stored on-line on wheel 22 of
library 55, without this fact being readily apparent to the subscriber.
Another major feature of the broadcast video burst transmission system
of the present invention is the use of burst transmission of programs in less
than real time, as taught in the prior art by Lang. By using this type of
transmission system, many benefits are realized. Such a system includes a
source and a destination with transmission from source to destination in less
than real time. The primary benefit is that the subscriber receives the
selected program in a digital compressed format, which is stored at the
subscriber's location for decompression and viewing at the subscriber's
convenience. Since the destination equipment processes the digital compressed
format of the program, VCR-like functions are available, such as stop, pause,
rewind, and fast forward. This unique feature of the present invention
results in a system that resembles having an electronic video rental store
accessible from the subscriber's home.
Referring now to Figure 2, there is illustrated a second embodiment of
the present invention. This embodiment includes a wheel 100 having a
plurality of wheel subsegments 110a-llOd, an off-line storage 120, a
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transmission line 130, transmission line segments 140a-140d, a receiver 150,
VID monitor segments 160a-160d, and a display 170. Wheel 100, off-line
storage 120, and external control hardware and software (not shown) comprise a
library 180. Similar in concept to the embodiment of Figure 1, the embodiment
of Figure 2 burst transmits portions of a movie or other audio/video program
rather than the entire movie. The wheel 100 of Figure 2 includes a number of
arcuate sectors, each of which is divided into four radially extending
segments. As illustrated, for example, the wheel sector containing program
number 15 is divided into four program segments 15a, 15b, 15c, and 15d,
labeled as wheel subsegments 110a-d. Consequently, wheel subsegment 110a
stores a portion of program 15, wheel subsegment 110b stores another portion
of program 15, etc. As in the embodiment of the invention illustrated in
Figure 1, off-line storage 120 is employed to store less popular programs on
slower, less costly storage media.
As wheel 100 rotates counter-clockwise, one of the wheel segments
representing one portion of a program, is burst transmitted. The transmission
of an entire program, such as program number 15, for example, invoves the
separate burst transmissions of program segments 15a, 15b, 15c, and 15d.
While Figure 2 illustrates four radially extending storage segments
comprising each of the 16 arcuate sectors of wheel 100, the actual number of
radially extending segments may vary and would most likely be evenly
distributed over the entire length of a transmission cycle in order to
minimize the amount of storage required for each program segment. In the
example illustrated in which each program is divided.i~to four segments, each
segment represents 30 minutes of real time viewing. Using the same
transmission parameters as described above in connection with the system of
Figure 1 (114 Mbit/second transmission rate and 1.2 Mbits/second compressed
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video rate), one wheel segment is burst transmitted in 19 seconds. That 19-
second burst transmission, received and stored by receiver 150, represents 30
minutes of viewing when decompressed and played back in real time. In the
present example, the two-hour program 15 is burst transmitted by burst
transmitting four separate program segments 15a, 15b, 15c, and 15d, each
program segment requiring 19 secQnds for transmission and representing 30
minutes of viewing time.`
The use of a system such as that illustrated in Figure 2 for receiving
and viewing a program, for example, is as follows. As wheel 100 rotates such
that it becomes time to transmit program number 3, which is divided into
segments 3a-3d, segment 3a is first transmitted. If the subscriber has
ordered program number 3 through the user interface of receiver 150, then VID
monitor 160 monitors transmission line 130 for the YID which identifies
ordered program number 3. Note that VID monitor 160 is divided into VID
monitor segments 160a-160d. This corresponds with the fact that VID monitor
160 must monitor transmission line 10 for each appropriate transmitted segment
140a-140d. Consequently, VID monitor 160 will receive transmitted segments
and enable storage of these segments four separate times for transmitted
segments 140a-140d. In this manner, each transmitted segment 140a-140d for
the program that has been ordered is received and stored within receiver 150.
In the present example, when the first 19-second transmitted segment is
received and stored, playback of that program segment by the subscriber may
begin. At that point-in time, the subscriber has full VCR-like control over a
30-minute segment of the program. To maintain the real time decompression and
playback of the program, receiver 150 must receive and store the next
transmitted segment before playback of the previously stored segment has been
completed. In order to provide a seamless, uninterrupted playback of the
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program, receiver 150 should begin receiving the next segment 19 seconds
before playback of the previously received segment has been completed. In
doing so, the next segment overwrites the prior segment in storage within
receiver 150 as playback of the previously stored segment is completed. This
incoming segment then becomes the current segment and receiver 150 then
continues a seamless playback by beginning the decompression and playback of
the newly received segment.
Such an embodiment reduces the cost of the receiver 150 at the
subscriber's location by reducing the amount of storage required. In the
example described immediately above, one-fourth the usual storage capacity is
required in receiver 150. Different levels of segmentation may be used,
depending on marketing, economic, and strategic considerations.
The requirement to transmit the next program segment in time, i.e.
before the segment previously stored within receiver 150 is completely
decompressed and viewed in real time, results in some increased complexity.
Timing and control of the transmission of the next segment of the program is
managed by the library 180. Having only a portion of the program stored in
receiver 150 also imposes some operational limitations. For example, the
subscriber would not be able to rewind or fast-forward beyond the beginning or
end of the portion of the program that is currently stored in receiver 150.
However, it will be obvious to one skilled in the art that these tradeoffs may
be designed into the system of the present invention based on strategic and
economic considerations. For example, market analysis may show that
subscribers are willing to have limited VCR-like control in order to reduce
the cost of receiver 150. Perhaps the analysis would show that a 15-minute
buffer, during which the subscriber would have full VCR-like control, is
acceptable.
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Many other benefits are realized in the embodiment of Figure 2. The
communications channel used for the transmission is not occupied for the
entire viewing time of the program, as it is in real-time broadcast systems.
This results in the ability to use the communications channel more
efficiently. In one example, if a burst transmission of a two-hour program
occupies a few minutes of transmission time, and the scheduling process has
resulted in a two-minute gap between burst transmissions of consecutive
program transmissions, then that gap may be used for any purpose, such as data
transmission, voice communications, a burst transmission of a segment from
another program, a burst transmission of an entire program, or transmission of
the schedule information of the present invention. This benefit cannot be
realized by real-time systems since the bandwidth is used in a real-time mode.
Another benefit that results from the broadcast video burst
transmission system of the present invention is the lowered susceptibility to
loss of signal. In a real-time, channelized distribution system, any loss of
signal results in the loss of some viewing time. In the present invention,
the time during which the system is susceptible to loss of signal is lowered
dramatically. For example, while a real-time system signal might be
interrupted anywhere in its two-hour program transmission, a burst
transmission in accordance with the present invention may be susceptible for
only a few minutes. Of course, the actual time required for a burst
transmission is dependent on several factors, including the level of the
digital video compression, communications channel bandwidth, and the
performance of the storage systems.
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A loss of signal in the system of the present invention would at first
seem to affect the system more adversely than a real-time system. In a real-
time system, a five-minute loss is literally a loss of five minutes of viewing
of transmitted program. In the present system, a five-minute loss could
result in loss of the entire program. However, the present invention actually
offers benefits in this area as well. Real-time systems are limited by the
time domain. If a five-second or even a five-minute loss occurs, there is no
possibility for recovering the lost material since the time-frame for the
missed viewing has passed. On the other hand, the present system, due to its
use of the Lang prior art burst transmission technique, is not limited by the
time domain. If a loss occurs during transmission, digital error-correcting
techniques may be used to detect the loss. When a loss occurs, the system may
automatically retransmit the corrupt or missing data. In an embodiment in
which viewing by the subscriber does not take place until an entire program or
portion of a program is received, this retransmission may occur an indefinite
number of times and is transparent to the subscriber. Full recovery is
therefore virtually guaranteed.
The present invention is operative via a variety of digital
transmission means. In one embodiment, the transmission means is an ATM
(Asynchronous Transfer Mode) network, such as those currently being deployed
by telephone companies, cable companies, and for use in computer networks. In
such a network, the digital data is packetized, and time-dependent data such
as audio/video data is guaranteed to arrive at the destination at the
appropriate time. Therefore, real-time compressed video transmissions are
likely to occur on such networks. The present invention, with its use of
burst transmission, can coexist in a given bandwidth on an ATM network with
other burst audio/video transmissions, real-time audio/video transmissions,
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and any other digital data. The packetized, time-guaranteed nature of such a
network ensures that these disparate transmission methods can coexist.
Referring now to Figure 3, there is shown a hardware block diagram of
the broadcast video burst transmission system of the present invention. A
library 210 is connected to a receiving unit 220 via transmission line 230.
Library 210 comprises a storage unit 240, a controller 250, a CPU 260, a
memory 270, a bus 280, and a transceiver 290. Receiving unit 220 comprises a
storage unit 300, a controller 310, a bus 320, a memory 30, a receiver 340, a
CPU 60, a decompressor 370, and an optional compressor 90.
Compressed digital audio/video programs, such as movies, may be entered
into storage unit 240 in several ways. First, storage unit 240 may comprise
any of a number of different types of storage media, including, but not
limited to, magnetic disk, optical disk, random access memory or combinations
thereof. Furthermore, storage unit 240 may utilize a removable storage
medium, such as an optical disk, a removable magnetic disk, digital tape or a
floppy disk. In such a case, the physical media itself, such as an optical
disk, is inserted into the storage mechanism for reading or possible transfer
to another media type. It is anticipated that different embodiments of the
present invention will utilize different types of medial for storage unit 240,
with some embodiments using several types of storage media.
In addition, any of several different types of transceivers may be
employed as transceiver 290. These include, but are not limited to,
transceivers for fiber optic lines, microwave, satellite, coaxial cable,
broadcast television, and telephone lines. In some embodiments, the
transceiver employed for burst transmission of programs to receiving unit 220
will differ from the transceiver used for updating storage unit 240 of library
210. In other embodiments, a separate transceiver (not shown) may be used for
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updating storage unit 240. For example, one embodiment is envisioned that
uses coaxial cable for distribution of programs to subscribers, each of whom
would have an embodiment of receiving unit 220 at his location, while fiber
optic lines or satellite links may be used for very rapid updating of storage
unit 240.
In any event, storage unit 240 may be updated with new material
whenever appropriate. This can mean offloading the less-popular programs to
cheaper off-line storage devices for storage unit 240, such as magnetic tape.
This off-loading helps to reduce the cost of the storage required for library
210. Higher performance storage devices, on the other hand, may be used for
the programs that comprise the current schedule of programs beng broadcast by
the broadcast video burst transmission system of the present invention.
Higher performance storage devices can be required to maintain a bit rate in
reading the data to keep up with the required transmission rate of transceiver
290.
Storage unit 20 of library 210 is operative for retrieving and
transmitting the stored time compressed programs according to a predetermined
schedule. The timing of this schedule and the selection of the programs from
storage unit 20 occur under control of CPU 260. This operation is
accomplished in accordance with the flow chart of Figure 4, which is described
in detail below.
As CPU 260 initiates the burst transmission of scheduled programs, it
interfaces to storage unit 240 for reading program information into-buffer
memory 270. The purpose for reading into a buffer memory 270 is~t~ aid in the
interface to transceiver 290, which transmits the program information over
transmission line 230. In transmitting via transmission line 230, the
protocol of the transmission line must be adhered to. For example, in an
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embodiment where transmission line 230 comprises a fiber optic line, some type
of protocol, such as SONET, is used. In most cases, the data format as stored
in storage unit 240 is incompatible with the format required for transmission
by the protocol of transmission line 230. Therefore, the data is read from
storage unit 240 into memory 270 via controller 250, and properly reformatted
and timed for adherence to the protocol defined by transmission line 230. All
of the foregoing operations are performed under control of CPU 260, with data
moving between the components illustrated in Figure 3 via bus 280.
Receiving unit 220 is connected to transmission line 230 via receiver
340 and may be operative for continuously monitoring the incoming data from
transmission line 230. The incoming data is transferred to memory 330 via bus
320 and examined by CPU 360 for data to indicate that the incoming program has
been ordered. If it has not been ordered, the data is ignored. When the
enabling data is found, CPU 360 enables the system to store the incoming data
in storage unit 300, as described below. This process is depicted in the
flowchart of Figure 5, which is also described in detail below.
Receiver 340 transfers the incoming data to memory 330. Under control
of CPU 360, the data is stripped of any protocol header information, resulting
in the same data that had been stored in storage unit 240 of library 210. The
data is transferred via bus 320 to controller 310. Controller 310 writes the
time compressed data to storage 300. All of the foregoing operations are
performed under control of CPU 360. When viewing is initiated by a user
interface (not illustrated~ of receiving unit 220, controller 310 reads the
data from storage unit 30~ and transfers the data to decompressor 370.
Decompressor 370 decodes the compressed data and, in one embodiment, converts
the digital data to an analog signal for viewing that is available at a video
out terminal 380. In another embodiment, the display device is digital.
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Consequently, analog-to-digital conversion is not required. Video out
terminal 380 is connected to an appropriate display device (not shown), such
as a conventional television or computer monitor. Consequently, the foregoing
decompression may include format conversion for the display device. The
decompression process also has memory 330 available for the decoding process
when the compression a1gorithm may require such memory.
In another embodiment of the present invention, receiving unit 220 also
includes compressor 390 for reciving an input audio/video signal at a video in
terminal 395. Under control of CPU 360 and with access to bus 320 and memory
330, incoming audio/video signals may be compressed and written to storage
unit 300 via controller 310. In providing such a feature, the present
invention may be used as a digital ~CR for use in recording programs or other
program information from standard broadcast sources such as cable television,
network television, satellite, cameras, etc. The stored time compressed
programs may be decompressed and viewed with VCR-like control in like manner
to that described above for viewing a stored program that was burst
transmitted to a subscriber.
In another embodiment of the present invention, receiving unit 220 may
include a transceiver (not shown), in addition to or in place of receiver 340
for both real-time and burst transmissions of any stored time compressed
program or other audio/video program information.
Referring now to Figure 4, there is shown a flow chart of the process
for burst transmitting programs from library 210 from the time that a
subscriber orders a program until transmission of that program is completed.
Included is a step 470 as a gray action step to indicate that ordering does
not affect the process as a whole. That is, this step is not part of the
process at library 210 that results in transmission of a program. It is
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depicted in the flow chart of Figure 4 to delineate a sample time frame in
which the subscriber places a program order, relative to the process as a
whole.
The process begins with a play list being communicated to the
subscriber in some manner, as indicated by step 420. This play list would
most likely contain information such as a list of available program titles and
queue times, and may be provided in any number of ways, such as devoting a
television channel to text denoting the play list. Based on the play list,
the subscriber may order a program at any time. This is accomplished through
any convenient means well known in the PPV art, such as by way of a touch-tone
telephone or by interface to a cable converter box.
Next, the library 210 must determine if the next program in the play
list is stored in on-line or off-line storage unit 430. This part of the
process is optional, but allows for programs to be stored on off-line storage
media such as magnetic tape, optical disk, etc. Typically, off-line storage
is less costly than on-line storage, but has insufficient read speed to
interface to the transmission line at the desired bit rate. For this reason,
off-line storage is brought on line by reading the data from the slower off-
line storage to faster on-line storage such as RAM, magnetic disk, etc. Thus,
the process illustrates a determination by the system as to whether an
upcoming scheduled program must first be brought on line.
Once the next program is on line and ready for transmission, the system
simply waits for the appropriate time, as indicated by process bLock 450, and
then begins transmission, as indicated by process block 460. ,During this idle
period while the system waits for a transmission, the system may be used for
other purposes, such as communicating an updated schedule. In such an
embodiment, care must be take to ensure that the system continues to monitor
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the time so that transmission of the next scheduled program may begin when
appropriate. This process of bringing off-line programs into on-line storage
for transmission may be distinguished from a VOD system in that it is
automated. The off-line storage and change to on-line storage is determined
by the system based upon a predetermined, although sometimes dynamic,
schedule. In any case, it is the broadcast video burst transmission system of
the present invention that determines the schedule, not a selection by a
subscriber from a virtually unlimited video library. This distinction
provides many of the benefits of a VOD system without the expense of
maintaining a large video library.
Referring now to Figure 5, there is shown a flow chart of the process
performed by receiver 340. This process includes the steps of receiving data
520, transferring data to memory 50, determining if a VID is included 540,
determining if storing is enabled 550, determining if the program has been
ordered 560, enabling storing 570, transferring data to the controller 580,
and writing to storage 590. With additional reference to Figure 3, the
process illustrated in Figure 5 begins by receiving data at receiver 340, as
indicated by process step 520. This data is transferred, as indicated by
process step 530, to memory 330 via bus 320. The incoming data is received in
blocks, with the block size being determined by the protocol used for
transmission over transmission line 230 and the desired performance of the
system. During the process of transferring the data block to memory 330, the
data block may be reformdtted by CPU 360 to remove protocol information, as
previously described.
The receiving equipment of the present invention must monitor the
system for the programs that have been ordered or the receiver must be
addressable in some manner. In one embodiment, CPU 360 examines the data
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block to determine if it contains a video identification (VID), as indicated
by process step 540. VIDs are defined as a system implementation dependent
string of data that identifies the program being transmitted. In one
embodiment, VIDs are transmitted only at the beginning of a program, with the
data that follows representing the compressed digital video data of the
program. In the preferred embodiment, VIDs are interspersed at regular
intervals throughout the compressed digital video data. VIDs must be defined
to be easily distinguishable from compressed digital video data, and are
dependent to some degree on the selected compression algorithm. Such a design
choice is well within the capability of one of ordinary skill in the art.
If the data block includes a VID, CPU 360 must also determine if the
program is one that the subscriber has ordered, as indicated by process step
560. If it has not been ordered, the data is ignored, and the system is
operative for receiving the next block of data, as indicated by process step
520. If the data contains a VID of a program that has been ordered, storage
is enabled, as indicated by process step 570, and the data is transferred to
controller 310, as indicated by process step 580, which in turn writes the
data to storage unit 300, as indicated by process step 590. Prior to writing
the data to storage unit 300, CPU 360 may further reformat the data, such as
by removing the VIDS from it so that a pure compressed digital video may be
stored for later decompression and viewing. Upon storing the data, the system
is ready for the next block of incoming data. Enabling storage may consist of
setting a few bits within memory 330 or enabling specific circuitry (not
shown) in receiving unit 220. With a VID having been found and storage
enabled because the program had been ordered, all future data blocks which
represent compressed digital video portions of the program will be written to
storage unit 300. By not requiring every data block to have a VID, the
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transmission of a significant amount of redundant data is avoided.
If no VID is found in the data block, the process then includes
determination of whether storing has been enabled, as indicated by process
step 550. When store has been enabled from a previous data block, the data
does not contain a VID because the entire data block represents compressed
digital video of a program that has been ordered. Consequently, the data is
transferred to controller 310 and written to storage unit 300. If the data
does not contain a VID and store has not been enabled, the data may be
ignored.
In any case, when a proper VID has been identified, the burst
transmission of that program is captured and stored for viewing.
Consequently, billing may take place for the ordered program. In one
embodiment, the receiver equipment communicates back to the system library
that the selected program has been received, so the subscriber may be
appropriately billed. However, the present invention does not require such
back-channel communication. Since the system cycles through burst
transmissions, no back channel to the system library is required for ordering.
Rather, the receiver equipment simply captures the appropriate incoming burst
transmission. Similarly, for billing, a back channel is not required. In one
embodiment, billing may take place by updating system software at the local
receiving equipment. The receiving equipment may be polled periodically by
the system for billing purposes. For example, the receiving equipment may be
connected to a telephone line, via modem in most cases, in addition to the
network connection for the burst transmissions. Once per month, billing
software running on a computer system located at the library may connect to
the receiving equipment to obtain usage information for the past month. This
type of polling may happen in any desired period, perhaps even nightly.
22
2155~B3
The additional telephone line connection (not shown) also provides the
present invention with a remote diagnostic feature. Through this connection,
computer hardware at a remote site may diagnose the system by sending test
data and commands and monitoring the results. In this manner, system faults
may be identified to a level such that a technician may bring replacement
components to the receiver for repair, without moving the receiver to a repair
center.
An important use of the broadcast video burst transmission system of
the present invention is to implement it on multiple channels and incorporate
a theme for each channel. As an example, a operator of such a system can
offer a comedy channel, as well as channels that concentrate on drama, action,
science fiction, etc. In this manner, the subscriber can have any one of a
very large number of the top films of a certain category available in a very
short time frame. On the other hand, with a single channel, the play list may
include 100 various burst transmissions before a particular horror film is
transmitted, for example. This limitation may be avoided by implementing
theme broadcasting.
It is also important to note that the digitization and compression of a
program for entering into a video library may be reduced in time. This
building of a time compressed video library does not need to take place in
real time. If the selected vendor's equipment supports it, a program may be
captured and compressed at an accelerated rate that is less than real time.
For example, for the compression process, a program that would normally be
viewed at a rate of 30 frames per second may be played back at 300 frames per
second from the source. Such an embodiment would reduce the time required to
compress a one-hour program to only six minutes. This embodiment offers a
time savings which would directly affect the marketability of such a system,
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as it has the unique ability to quickly update a video library by compressing
and then distributing programs in less than real time. For example, a one-
hour live event that had just been broadcast over conventional television
could be compressed and distributed to broadcast video burst transmission
libraries, available for burst transmission to subscribers, in just minutes.
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