Digital video switch for video teleconferencing

A digital video switch system comprising a smart control terminal is coupled to a digital access controller and to a multipoint control unit. The smart control terminal is provided with a plurality of function keys, each of which is designed to provide automatic interconnection of input and output ports of the digital access controller and the multipoint control unit so that a predetermined interconnection of video and audio signals from remote conferencing sites are interconnected via input/output ports of the digital access controller with each other in a desired format to provide central teleconferencing control of a plurality of sites from a central control site.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to business television and video conferencing 
systems. More particularly, the present invention relates to a 
programmable digital switch for use in controlling video teleconferencing 
systems as well as business television systems independently or 
simultaneously with a single room or studio coordinator/controller. 
2. Description of the Prior Art 
AT&T as well as MCI and U.S. Sprint now provide services referred to as 
video teleconferencing. The equipment, systems and cost may differ between 
vendors to achieve a desired result function wherein two or more groups of 
conferees at different locations are able to view each other while 
conducting a real time conference and wherein different types of 
information are exchanged. Video TeleConferencing (VTC) differs from 
Business TeleVision (BTV) in that business TV is best described as Receive 
Only Viewing (ROV) by large audiences at remote locations of a single TV 
program usually originating at a single source. When business TV is 
combined with call in telephone questions, etc. from the live audience the 
results are similar to TV talk shows that take questions via telephone 
from the viewing audience. 
Teleconferencing and business TV do not require as broad an information 
band as commercial TV. Commercial satellite TV in the United States 
employs an analog FM format requiring 36 megahertz bandwidth. Using 
digital data compression techniques it is presently possible to transmit 
sufficient data for video teleconferencing at a bandwidth of 768 kilobits 
per second with 384 kilobits per second transmission predicted for the 
future. The lower transmission rates are accompanied by lower network 
transmission cost without information degradation. 
There are presently four or five major competing transmission network 
services whose cost are constantly being reduced so that no one dedicated 
VTC/BTV system is capable of taking advantage of all of the desirable 
features of any one system over a period of time. 
Thus, it would be highly desirable to provide a teleconferencing system 
which may be used for business television and is flexible enough to accept 
input from and output to the various competitive networks so that the most 
efficient and most economical available network can be programmed for use 
with the present invention system. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to provide a most cost 
effective interactive video teleconferencing and business television 
system. 
It is a primary object of the present invention to provide a novel digital 
video switching system for teleconferencing and/or business TV. 
It is a primary object of the present invention to provide a novel digital 
video switching system which will accommodate both analog and digital 
network signals without the necessity of modifying the switching system. 
It is another object of the present invention to provide a teleconferencing 
system which is adapted to interact with different networks simultaneous. 
It is another object of the present invention to provide a video digital 
switch for a teleconferencing system that controls video teleconferencing 
and business television simultaneously. 
It is a general object of the present invention to provide a novel control 
system incorporating a novel digital switch for a hybrid video 
teleconferencing/business TV system. 
It is a general object of the present invention to provide a novel digital 
video switch for use with commercially available network communication 
lines using a mixture of dedicated and reservation-use digital circuits. 
According to these and other objects of the present invention there is 
provided a video conferencing control system for routing digital video 
signals from point-to-point or from point-to-multiple points through a 
novel programmable digital video switch (DVS) having a plurality of 
input/output ports connectable to remote teleconferencing points or sites. 
A programmable multipoint voice actuated control unit (MCU) is coupled to 
the novel digital switch for automatically interconnecting said ports 
indicative of different sites according to a predetermined program. Smart 
terminal control means are employed for programming said programmable MCU 
and DVS and/or changing said predetermined program during actual video 
teleconferencing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Before describing the preferred embodiments in detail, it should be 
understood that the equipment to be described hereinafter is for the most 
part commercially available discrete components which have been modified 
and arranged in a system configuration to be operable and compatible and 
to achieve the desired result at a minimum cost of the capital equipment 
and tariff cost of transmission lines and data links. It can be shown that 
in the present state of art that two way coders/decoders (CODEC) are 
presently capable of compressing and decompressing video data which in 
satellite transmission analog form employs 36 megahertz FM bandwidth for 
satellite uplink into compressed digital data containing approximately 1.5 
megabits per second that when decoded and decompressed permits generation 
of acceptable full motion video pictures for business TV (BTV) use. 
Similarly the same CODEC incorporated into the preferred embodiment system 
can be programmed to compress analog converted video information down to 
768 kilobits per second in digital format which may be decoded and 
decompressed to permit generation of acceptable video pictures of the type 
employed in Video TeleConferencing (VTC). Unisys Corporation has recently 
recommended 384 kilo bits per second bandwidth for video teleconferencing 
services using U.S. Sprint dedicated logical T-1 digital line service. 
The latest state of the art CODEC equipment will convert analog video 
signals into 384 Kpbs digital signal capable of being decoded and 
decompressed into analog data providing thirty full video frames per 
second. This CODEC equipment is compatible with the CCITT H.261 digital 
standard which provides 30 frames per second employing 1.544 Mbps. 
Universal acceptance of this CCITT H.261 digital standard will provide a 
format that is compatible with commercially available digital 
communication circuits in the United States and will provide an acceptable 
and viable alternative to direct FM analog uplink services which employs a 
36 Megahertz FM analog bandwidth. 
When broadcasting business TV to a large number of sites throughout the 
world it is often necessary to select satellite uplink and downlink 
transmission to be able to communicate with the most remote sites. When 
circumstances demand that a satellite data link system be employed, it is 
often possible to receive the satellite broadcast in analog format and 
display the analog signal at the receiver site or to convert the analog 
signal at or reasonably near the receiver site and employ digital 
telephone lines to the receiver site. 
Refer now to FIG. 1 showing a plan view of a preferred embodiment dual 
purpose studio/video teleconferencing (VTC) facility 10 having a VTC 
control room 11 designed and adapted to be operated by a room coordinator. 
When the facility 10 is to be employed for business TV (BTV), the BTV 
control room 12 is designed and adapted to be operated by the room 
coordinator. Prior to VTC meetings and BTV broadcast the facility 10, 
control room 11 and/or room 12 are set up by positioning front TV camera 
13, side TV camera 14, movably mounted on track 16, and rear TV camera 17 
for start of broadcast positions. People seated at conference table 18 or 
in the elevated gallery seating 19 have a clear view of the right side 
monitor 21, left side monitor 22 and large projection screen 23, usually 
used for business broadcast, but may be used together with monitors 21 and 
22 when desired. Either the control room may be set up and/or reconfigured 
while the other control room is on line. 
The three cameras 13, 14 and 17 are all mounted on high speed pan/tilt 
heads and are pre-programmable for up to 48 discrete preset camera 
positions which are accessed and controlled by keyboard controls to be 
described hereinafter at control station 15 shown having a plurality of 
monitors 24 provided for displaying different possible inputs to the 
conference room. The left side or receiver monitor 22 preferably displays 
the conference or the graphics copy or the video tape being transmitted 
from one or more active sites of a plurality of sites participating in a 
teleconference. The right side monitor 21 preferably displays the same 
information as above which originates at facility 10, thus informing the 
on-site conferees with the television picture and sound of the transmitted 
picture and sound. The receiver monitor may be controlled by the room 
coordinator or switched from site to site by voice activation as will be 
explained hereinafter. 
Refer now to FIG. 2 schematically showing a minimum site configuration 20 
for TV conferencing participation by a group of conferees. A single TV 
camera 13 is directed to display on monitor 25 the analog generated output 
on line 26. The analog information on line 26 is applied to the input side 
of coder/decoder 27 by control 30 which is programmed to produce a 
preferred digital output having at least a 384 Kpbs data rate capable of 
defining thirty frames of information per second on line 28. The digital 
information on digital duplex line 28 is applied to Unisys/Timeplex Link/2 
(TM) exchange 29 which stuffs or fills the bandwidth to produce a full T-1 
bandwidth with information having 1.5 megabits per second on dedicated 
terrestrial telephone line 31. Line 31 may be a fraction T-1 (T-1.sub.F) 
duplex line when such T-1.sub.F lines are available and capable of 
transmitting the digital video, data and voice requirements of the site. 
Dedicated line 31 is connected to an inter-exchange point of presence 
(POP) 32 provided by a carrier such as U.S. Sprint. The carrier 
interconnect line 33 is shown as a full T-1 bandwidth line for purposes of 
illustration only but could be a fractional line T-1.sub.F as explained 
above. At the time of this application, Sprint half T-1 meeting channel 
lines (T-1.sub.F) could be obtained on short notice for coast to coast 
transmission for approximately $225.00 per hour. The same service using a 
Virtual Private Network line was available for approximately $60.00 per 
hour, thus providing teleconferencing users with one of the lowest cost 
means of network communication. Like common voice telephone lines, T-1 
digital lines are bi-directional and digital voice and video data received 
at site 20 via line 33 is applied to decoder (CODEC) 27 where it is 
decoded into analog signals for display on right side monitor 34 via line 
35. 
Refer now to FIG. 3 showing a schematic diagram of a preferred embodiment 
site 40 connected by a Video Satellite disk 36 which is preferably 
transmitting and receiving digital data compatible with the aforementioned 
T-1 digital lines. Hughes Network Systems installs such video satellite 
equipment (VSATS) 37 which is connected via full or fractional T-1.sub.F 
analog lines 38 to 2.4 meter Ku- band satellite antennas 36 for 
transmission to and reception from Hughes owned Satellite Business 
Systems, Inc. (SBS) satellites (not shown). Other satellite network 
services, such as AT&T Sky Net Satellite Services, are available and could 
be substituted for elements 36 to 38 and could be provided with a 
compatible and proper signal on line 39 from CODEC 41. In the preferred 
embodiment of the present invention the signals on line 39 are digital and 
compatible with CCITT H.261 digital standard format as well as full or 
fractional T-1 network line employing 1.544 Mbps for a full T-1 line. 
Digital systems reduce the cost of conversion equipment when standardized 
and are preferred. 
Commercially available CODEC equipment may be purchased with a plurality of 
digital conversion options, however, a prior art CODEC equipment is not 
selectably switchable to a plurality of fractional T-1 bandwidths and/or 
analog frequencies for compatibility with different manufacturers 
equipment. 
The VSAT disk 37 is capable of transmitting digital or analog signals to an 
SBS satellite having a bandwidth capable of supporting a large number of 
T-1 digital channels. Recent developments in digital transmission 
techniques have more than doubled the number of T-1 channel supported by 
one satellite transducer channel, thus, the trend and the preferred 
embodiment shown in FIG. 3 is preferably fully digital, but is adapted to 
operated in a hybrid analog mode in remote areas where full digital mode 
is commercially uneconomical or virtually unobtainable. 
The digital side of CODEC 41 on line 39 may be 384 Kbps or 768 Kbps with 
the trend toward lower frequencies as better data compression techniques 
become available. The analog side of CODEC 41 is connected to the left 
side receiver monitor 42 via line 43 for displaying the received video 
signal. The right side monitor 44 is connected to transmit line 45 under 
control of control console 46 which is provided with a plurality of 
control monitors 47, one for each source of video information. One of the 
two video cameras 48 shown is directed toward the conferees and the people 
in the gallery. A graphics display video camera 49 is mounted vertically 
at the control console 46 to permit a room coordinator/operator to display 
indicia such as text, slides, computer graphics, charts, etc. In addition, 
to the graphic camera 49, a video tape player/recorder 51 is provided at 
the preferred embodiment site 40. The control console 46 is preferably 
provided with a high speed full frame grabber (or freeze control) 52 for 
holding, recording on transmitting selected full frames of video 
information from any of the aforementioned analog sources. Thus, a frame 
of video information available at console 46 may be loaded in CODEC 41 and 
transmitted on the video channel as a frame of 256,000 bits while the 
operator is changing the graphics displayed on one of the console monitors 
prior to subsequent transmission. 
Refer now to FIG. 4 showing a schematic drawing of a preferred 
teleconferencing site 50 having all of the same facilities and on-site 
equipment as shown in FIG. 3. In addition computer 52 may be coupled 
through control console 46 having data output line 53 coupled directly to 
a Timeplex digital mini link 54 which is capable of managing both digital 
video on line 55 and/or generating loss less compressed data on duplex 
line 55 for transmission to the central studio/control via fractional 
T-1.sub.F line 56. When T-1.sub.F line 56 is not fully utilized with video 
or data information the mini link 54 stuffs bits during transmission and 
removes bits during reception automatically. The numbers of elements and 
components which are the same as those used in site 40 and FIG. 3 are 
numbered the same as in FIG. 4 and do not require additional explanation 
for this full digital transmission/reception site. 
In the preferred mode of operation the graphics camera 49 or the computer 
52 may generate a frame of data to be transmitted to the other sites. The 
most economical way to transmit this frame of data is to provide a 
graphics card in the CODEC 41. Such cards are available from Compression 
Labs, Inc. for use with Rembrandt video CODECs. The frame of data may be 
stored in the CODEC data portion as one megabit of digital data. The video 
picture is interrupted for less than one second and the uncompressed 
digital data frame is transmitted to a CODEC at the receiving end having a 
similar graphics card capable of storing the transmitted frame of data. 
The frame of data is then available at the output of the receiving CODEC 
under the control of the room coordinator at the receiving end as will be 
explained hereinafter. 
The compressed video data on line 55 may be presented as the transmitted 
signal or the freeze frame data may be presented as the transmitted signal 
to the receiver. When a Timeplex link (L2) is inserted into the circuit as 
element 54, it can be used to manage the transmission of other forms of 
data that can be received and routed to a data center. Thus, data on line 
53 could use a fractional T-1.sub.F line or the video line 56 when not in 
active use. 
Refer now to FIG. 5 showing a schematic diagram of the central control site 
hub 60 which comprises a FIG. 4 type site 50 and the preferred embodiment 
digital video switch (DVS) 57. The DVS comprises three main elements 
including a smart control terminal 58, a plurality of port interchange 
switches 59 and a multipoint (channel) control unit (MCU) 61. 
The preferred embodiment smart terminal 58 around which other components 
were designed is a C-88GX central processor manufactured by Video 
Teleconferencing Systems, Inc. (VSI) and this processor actively controls 
peripheral audio, video and subsystem control devices using single 
keystroke of function keys on a special keyboard operable by a single 
coordinator/operator. 
The system 57 and DVS terminal 58 enables the operator to control the 
inputs and outputs connected to a multichannel control unit (MCU) 61. MCU 
61 was designed to be controlled by a dumb terminal (not shown) which is 
preferably removed, but could be bypassed. MCU 61 was modified for the 
present invention application to provide remote programming and remote 
control via smart terminal 58 which is coupled to MCU control terminal 61 
via a standard interface 61 I. 
A plurality of Phoenix Model 1505 small digital access controls (Micro 
DAC's) 59 are chained together to provide sixteen T-1 digital ports P1 to 
P16 that were designed to be controlled by a dumb terminal (not shown) 
which is preferably removed, but could be bypassed. Micro DAC 59 was 
modified for the present invention application to provide remote 
programming and remote control via smart terminal 58 which is coupled to 
Micro Dac 59 via a standard interface 62. The present invention will be 
explained using sixteen DAC input/output ports and a Compression Labs, Inc 
MCU 61. Such multipoint control units are available from several 
manufacturers. The MCU 61 and the CODEC's employed at the the remote 
sites, (used in the preferred embodiment) and shown in FIG. 5 have been 
modified to be voice actuated and to select one of the video signals on 
one of the lines 63 to 66 and to couple it to any or all of the output 
lines 67 to 70. It will be recognized that the output on lines 67 to 70 
are input to ports P9 to P12 of the port interconnection means 59 and that 
these ports P9 to P12 may be connected to any one of the output ports P13 
to P16 which are coupled to video conferencing sites via lines 71 to 74 or 
back through the bidirectional input lines. 
The various input elements to Micro-DAC 59 are all adapted to produce 
standard 1.5 Megabit per sec. data in T-1 format. FIG. 5 is designed to 
show the input of different forms of data. The video data on line 75 is 
illustrated as being in analog format and could originate from a camera, a 
monitor input or a video satellite dish. CODEC 76 converts the analog 
information to a preferred 1.5 Mbps format and if the digital output to 
port P1 is in a fractional T-1.sub.F format a Phoenix Model 1564 
fractional multiplexer bit stuffer (not shown) is employed to produce a 
proper T-1 format input to DAC 59. 
Line 77 is illustrated as being in digital T-1 format and could originate 
from a nearby conferencing site as the output of the remote site CODECSs. 
When the distance to such nearly sites exceeds approximately 1500 feet, 
Phoenix Model 1544 line repeaters (amplifiers) 78 are installed to boost 
the signal input to DAC 59 at port P2. 
Line 79 is illustrated as being a T-1 line from anywhere in the USA. 
However, T-1 fiber optic cable and data links now reach most of North 
America and parts of Europe. As an example fractional T-1.sub.F lines 81 
and 82 could comprise T-1 line 79 coupled to a Sprint Channel Server Unit 
(CSU) 80 which serves as an interface adapter into port P3. Lines 81, 82 
are shown as separate lines to illustrate that line 79 may muxed in CSU 80 
and the two fractional T-1.sub.F lines of video data signal separated and 
recovered. Since DAC 59 is formatted for T-1 input the digital video data 
at port P3 is muxed and bit stuffed at CSU 80 to produce two distinct 
signal shown as being produced at two ports P3A and P3B each of which when 
stuffed to a T-1 format is separately connectable to an output port such 
as port P5. The two lines 81 and 82 could just as well be connected to a 
major site in England and a domestic USA site with the same result. 
Line 83 illustrates a fractional T-1.sub.F dedicated lease line coupled to 
a fiber optic cable. The signal on line 83 is bit stuffed to provide a 
full T-1 format at a site bit suffer 84 before being transmitted to micro 
DAC 59 via T-1 line 85. 
Having explained a preferred embodiment of the present invention it should 
be understood that the control hub 60 is designed to accept different 
types of digital video information and relay or transmit the received 
information to a plurality of remote sites. When used in the 
teleconferencing mode it is preferred to have available the equipment 
shown in FIGS. 2 to 4, however, the digital video switch 58 can make 
connection to rollabout systems of the type sold by Vidicom-Picture Tel, 
Oki America, Inc. and Mitsubishi Electronics America, Inc. When such 
integrated type systems are to be employed it is preferred to use a CLI or 
compatible CODEC system modified to generate the aforementioned voice 
activation signals for use with the programmable voice activated MCU 61 so 
that the whole system is two way compatible. When the remote site is used 
only for business conferencing in a receive only mode it is not necessary 
to modify the CODEC receiver which acts as a one way digital to analog 
converter. 
The novel digital video switch shown in FIG. 5 may be used for business 
broadcast of TV presentation using the site 50 connected to micro DAC 59, 
however, it will be understood that in the teleconferencing mode there 
will always be video and/or data transmitted from a teleconferencing site 
as well as the active local video on one of the local monitors in addition 
to the received video teleconferencing signal from the central site or one 
of the local sites. 
The same transmitting/receiving equipment shown in the FIG. 2 to 4 remote 
sites is used at the central hub site 60 shown in FIG. 5 to convert 
transmitted signals to a format convertible to T-1 format for use in the 
digital video switch 57. The system is adapted for use with any video 
signal that can be converted to a digital T-1 format. 
It will now be understood that smart terminal 58 may be pre-programmed for 
various conditions so as to connect any input line 63 to 66 to any or all 
of the output lines 67 to 70 to set up a predetermined teleconferencing 
interconnection. 
Since the outgoing video signal is to be transmitted to all 
teleconferencing sites being interconnected it is possible to select all 
predetermined sites and select one of the sites received video signal as 
the transmitted signal. Further it is possible to employ a voice activated 
signal generated at the CODEC of any teleconferencing site and use that 
signal on input lines 63 to 66 to automatically select the video signal 
for transmittal to all sites. When voice activation is employed, the 
switching may be prioritized by source or delayed to avoid rapid switching 
or even manually overridden while observing the incoming signals on the 
control console monitors 47.