Method of and apparatus for monitoring video-channel reception

In order to gather information on the reception of video channels in a household or other location equipped with a television receiver, partinent data such as identification and viewing time are injected into an assigned minor area of the TV picture at the receiving location. The injected data, appearing in digitized form in the assigned area where the TV picture has been blocked out, are picked up by a photosensor juxtaposed with the CRT screen of the receiver, or possibly from a video output thereof, and are fed to a processor for transmission over a telephone line with or without intermediate storage to an evaluation center. A data injector inserted between an antenna and an input terminal of the receiver blanks the incoming video signal of a selected channel during a small fraction of a frame-scanning cycle, while the CRT beam sweeps the assigned area, and replaces it with the digitized data. Alternatively, the blanking of the assigned area and insertion of channel identification may take place at the transmitting station.

FIELD OF THE INVENTION 
My present invention relates to a method of and an apparatus for monitoring 
the reception of video channels in a telecommunication system by viewers 
of television programs, e.g. for statistical or rating purposes. 
BACKGROUND OF THE INVENTION 
Systems for the evaluation of viewer preferences require the ingathering of 
various data from individual households or other locations equipped with 
television receivers, including particularly the times during which a 
given channel is turned on. Identification of the viewing locations is 
also useful in many cases. These data may be supplied to an evaluation 
center, usually via telephone lines, from monitoring units at the viewing 
locations; such units may be coupled with the respective television sets 
for the identification of the channels currently being received, e.g. by a 
system of the type disclosed in U.S. Pat. No. 4,425,578 to Haselwood et 
al. The monitoring units may further be provided with keyboards or the 
like by which viewers observing a given program may identify themselves so 
that the evaluation center can also receive information on, say, the 
number, the age and the sex of persons watching a program in a particular 
houshold. Reference in this connection may be made, for example, to German 
laid-open application No. 24 04 074, published Aug. 7, 1975, which shows 
such a keyboard in a system wherein channel-identifications and timing 
signals are fed after interim storage to a telephone for forwarding to a 
central data processor. A generally similar system is the subject matter 
of German patent No. 26 08 508, issued Feb. 28, 1980, according to which a 
channel sensor comprises a network disposed close to the television 
receiver and turned to its line-scanning frequency to determine whether 
the receiver is turned on or off; according to another arrangement 
disclosed in that German patent, a tuner connected to a TV antenna picks 
up the sounds of sequentially scanned channels and works into a comparator 
which also receives sound signals detected by a microphone juxtaposed with 
the television set, being thus able to ascertain to which channel--if 
any--the television set has been adjusted. 
OBJECTS OF THE INVENTION 
The general object of my present invention is to provide an improvement 
over these known methods and systems by virtue of which a significant 
number of demographically or statistically interesting data for the 
monitoring of television reception can be conveniently gathered for 
transmission, with or without interim storage, to an evaluation center 
and/or to a local reader. 
A more particular object is to enable the accumulation of such data not 
only during real-time TV reception but also when a program previously 
stored on a recording medium is visually reproduced on the screen of a 
television receiver. 
SUMMARY OF THE INVENTION 
In accordance with my present invention, a visually insignificant area of a 
picture displayed on a viewing screen of a TV receiver is blanked out with 
replacement of its video-signal content by the monitoring data to be 
gathered, the data so injected into the blanked area of the picture being 
sensed for processing in the manner indicated above. 
Advantageously, the sensing is carried out photoelectrically by a detector 
juxtaposed with the blanked area of the viewing screen, the detector 
preferably comprising one or a group of several photocells, photodiodes, 
phototransistors, photothyristors or the like. Alternatively, if the 
television receiver is equipped with a video output, the injected data can 
be picked up at the proper instants of a frame-scanning cycle at that 
output. In either case, with the injected data initially converted into 
digital form, their bits will produce distinct pixels (either black or 
white) on a contrasting background so as to appear consecutively during 
the scanning of the area assigned to them. That area ought to be as 
unobtrusive as possible and is preferably located at a corner of the 
viewing screen. 
In its general aspects, my invention encompasses the possibilities of 
injecting the monitoring data at the viewing location or--at least in 
part--at a transmitting station at which a given program originates. In 
the latter instance, digitized channel-identification and program codes 
inserted into the area blanked out for this purpose are radiated to all 
the receivers together with the actual picture. Even then, additional 
information (e.g. the address of the receiving location) may be introduced 
into the same area at the point of reception. 
Advantageously, the sensing of data in the manner indicated above makes it 
possible to check automatically whether the replacement of the 
video-signal content by monitoring data is performed in the correct 
channel, which is the channel that is selected at the TV receiver. If the 
result of this check should be negative, i.e. if no data and/or no blanked 
area as such is sensed at the given area of the screen or the given 
instants of the frame-scanning cycle at the receiver, this indicates that 
the monitoring data are being used in the wrong channel, i.e. a channel 
different from the channel that is chosen at the receiver. Thus, the 
video-channel may be changed automatically until the result of this check 
turns positive, i.e. until data or said blanked area as such is sensed 
correctly in the channel chosen at the receiver. 
It should be noted that, in an entirely different context, coded messages 
without demographic significance are flashed onto a selected area of a 
television screen by an apparatus disclosed in U.S. Pat. No. 3,737,566 to 
Baer et al. 
An apparatus for reception-point data injection is interposed between a 
source of incoming video signals modulated upon different carrier 
frequencies--i.e. an antenna or a cable--and a signal input of a 
television set served thereby. The apparatus includes a tuner for the 
selection of an incoming video channel, working into a demodulator which 
controls a synchronizer in response to incoming line- and 
frame-synchronizing signals. The synchronizer, in turn, activates a 
blanking and insertion circuit for the suppression of the incoming video 
signals of the selected channel and their replacement by the locally 
generated data pulses at the instants reserved for them, e.g. at the 
beginnings of the first few line scans of a frame. A processor in the 
apparatus, to which these data pulses are fed back via a photosensor or a 
video output as discussed above, has a memory which stores the data to be 
injected and which may also temporarily register the data pulses picked 
up, together with such ancillary information as time of day and personalia 
of the viewers, for subsequent transmission to an evaluation center during 
periods of low and possibly cheaper telephone traffic. Thus, an output of 
the processor may be connected to a modem, interfacing it with a telephone 
line, and/or to some other peripheral unit such as a printer, a long-term 
recorder or a display device. 
Advantageously, the apparatus provided according to the main aspect of my 
invention may further comprise automatic channel-selection means including 
a tuner and a tuner control system, which are controlled by said processor 
and which are controlling said synchronizer. By way of this tuner and 
tuning control system being controlled by the processor a specific 
video-channel may be selected automatically. upon feed-back of the 
information from the photosensor or the video output of the receiver said 
tuner and tuning control system will change said channel step by step 
until said processor in fact detects the monitoring data or the blanked 
area as such. Thus automatically the selected channel of said apparatus is 
made identical with the channel selected at the receiver set by 
push-button selection. Of course the tuner provided according to this 
aspect of my invention must comprise a heterodyne-oscillator as usual to 
obtain the necessary beat-frequency. As this is standard-technique 
additional information is not necessary with regard to the tuner's 
construction. 
According to a further aspect of my invention care is taken of the case 
that two different channels should carry programs that accidentally are 
totally coincident in frame and line timing. Of course, in this case the 
automatic channel identification and feed-back operation indicated above 
will fail. To take care of this problem an adjustable oscillator is 
provided, the frequency of which is equal to the frequency of the tuner, 
which itself is the expected frequency of the channel to be chosen at the 
receiver set. In case of a coincidence of frequencies of tuner and 
receiver set a black spot is produced by the oscillator as long as data 
injection takes place. This black spot indicates that the correct channel 
of both otherwise identical channels is chosen.

SPECIFIC DESCRIPTION 
FIG. 1 shows a conventioal television receiver 3 with a viewing screen 4, 
forming part of a cathode-ray tube, to which incoming video signals 
modulated upon different carriers originating at respective transmitting 
stations are fed by an antenna 1. Interposed between this antenna and a 
signal input of receiver 3 is a data injector 5 to which monitoring data 
displayed along with a TV picture--as more fully described 
hereinafter--are fed back by a photosensor 9 closely juxtaposed with a 
small, unobtrusive area of screen 4 at the upper left-hand corner thereof. 
Data injector 5, which represents an apparatus embodying my present 
invention, works into a peripheral unit 6 designed as a modem through 
which information accumulated therein can be transmitted to a telephone 
line for delivery to a centralized evaluator. Receiver 3 and data injector 
5 are energized by a cable 2 plugged into a nonillustrated wall socket. 
The receiving set 3 is further provided with the usual knobs or 
pushbottons, not shown, for on/off control and channel selection. Antenna 
1 could be replaced by another source of incoming carrier waves, such as a 
cable extending from a transmitting station (as shown at 22 in FIG. 3) or 
from a master antenna serving a number of receiving stations. 
Details of the data injector 5 are illustrated in FIG. 2 which shows it as 
including a data-output state 7 and a data-input stage 8, the latter 
working directly into a processor 15 which contains a data memory and 
feeds accumulated monitoring data to the modem 6. Antenna 1 is connected 
to a tuner 13 comprising an adjustable oscillator 13' as usual, which is 
adjustable by an automatic tuning control system 14 to extract an 
intermediate frequency from a particular channel chosen automatically by 
the tuning control system 14. The extracted IF signal for the chosen 
channel is fed to a demodulator 16 delivering frame-synchronizing and 
line-synchronizing pulses from the selected channel to a synchronizer 17 
for frame and line controlling a blanking and insertion circuit 10 
connected to antenna 1 as well as to data-output stage 7. At instants 
determined by synchronizer 17, occuring during a period which is a small 
fraction of a frame-scanning cycle corresponding to the time, the beam of 
the CRT would dwell on the area on screen 4 overlain by photosensor 9, the 
incoming radiofrequency signals normally transmitted directly to the input 
of receiver 3 are blanked by the blanking and insertion circuit 10 and are 
replaced by pulses representing digitized data stored in the memory of 
processor 15 and delivered by way of system 14 and stage 7 to circuit 10. 
The data may include, besides an identification of the selected channel, 
the address of the location equipped with television set 3 and additional 
information stored in the memory of processor 15, such as the number and 
personalia of viewers currently observing the TV-program. In case that the 
channel automatically chosen by system 14 coincides with the channel 
selected at the set 3 these data pulses appear at the assigned area of the 
screen 4 and are picked up by the photosensor 9 for feedback via 
data-input stage 8 to processor 15 which accumulates them over a 
predetermined number of frame cycles before delivering them to modem 6 or 
to its memory for temporary storage. The accumulated data can be 
accompanied by timing signals from a clock forming part of or connected to 
the processor 15. 
If the set 3 is not tuned to the channel chosen by system 14, the timing 
signals emitted by synchronizer 17 will generally not coincide with the 
illumination of the assigned area of screen 4 by the CRT beam so that 
photosensor 9 will not pick them up. In this case, since this information 
is received by the processor 15 as well, the processor 15 will make tuning 
control system 14 step to the next channel and so forth until the tuning 
of the data injector 5 correlates automatically with the tuning of set 3, 
i.e. the channel chosen by data injector 5 becomes identical to the 
channel chosen at set 3. Such automatic step-technique is widely known 
with car-radio receivers as "channel-searching" and needs no detailed 
description, here(see BROCKHAUS "Naturwissenschaften und Technik", Volume 
4, NI-SN, F. A. Brockhaus, Wiesbaden, 1983, page 298 "Sendersuchlauf"). 
Also shown in FIG. 2 is a video processor 12 connected to a video output 11 
of TV set 3 and controlled by synchronizer 17 in parallel with circuit 10. 
A switch 24 may connect the data input of data-input stage 8 to video 
processor 12, instead of photosensor 9, if the associated set 3 does in 
fact have a video-output 11; photosensor 9 may be removed in that case 
from the screen 4. 
A further switch 25 shown in FIG. 2 enables the transmission of the output 
signals of circuit 10, i.e. of the incoming RF signals and injected data 
pulses, to a video-recording deck 26. The video-recording deck 26 may be 
connected to circuit 10 instead of set 3 or in parallel thereto. Anyway 
the video-tape of deck 26 carries the data pulses. The deck 26 is 
connected to the video processor 12 via output 35 for initial check of the 
data pulses. Moreover, upon playback of a recorded program via screen 4 
the data pulses from the tape are recognized automatically by photosensor 
9 or via video output 11. The described feedback of data can therefore 
also take place upon subsequent reproduction of a recorded program on 
screen 4. 
An adjustable oscillator 27 shown in FIG. 2 as an optional equipment in 
dashed lines serves its purpose in case that two different channels should 
carry programs that accidentally are totally coincident in frame and line 
timing. In this case the automatic channel identification and follow 
operation of system 14 would normally fail. Now the frequency of the 
oscillator 27 is set equal to the frequency of the tuner 13, which is the 
expected frequency of the channel chosen at set 3. In case of coincidence 
of frequencies of tuner 13 and set 3, a black spot is produced by 
oscillator 27 as long as data injection takes place. Thus even for this 
exceptional case the oscillator 27 guarantees the correct tuning of the 
system 5 with respect to set 3. 
Reference will now be made to FIG. 3 where I have shown a modified 
telecommunication system in which a transmitting station 31 sends out 
video-modulated carrier waves, via a cable 22 or an antenna 23 energized 
by an output amplifier 21, to a receiving station 32 generally similar to 
that of FIG. 2. Transmitting station 31 comprises a signal generator 18 
connected to a nonillustrated video camera or any other video signal 
source and to a synchronizer 17' controlling an ancillary modulator 19 
through an output stage 7' for the injection of monitoring data, such as a 
channel-identification code and a program code, into the signal flow 
passing from generator 18 via an RF converter 20 to amplifier 21. 
Modulator 19 operates in a manner analogous to that of blanking and 
insertion circuit 10 described with reference to FIG. 2. However, the 
monitoring data referred to could also be directly delivered to the video 
camera for insertion into a blanked area of the viewing field. 
In this instance, an apparatus 5' assiciated with TV set 3 in receiving 
station 32 no longer need insert locally stored information in the form of 
digital pulses in the area assigned therefor, provided that the data 
injected at transmitting station 31 are the only ones of interest. Thus, 
apparatus 5'--of which only the data-input stage 8, the video processor 12 
and the processor 15 of FIG. 2 have been illustrated for simplicity's 
sake--need not include components 7, 10, 13, 14, 16, 17 of FIG. 2. If, 
however, additional data are to be injected locally, apparatus 5' may have 
the same structure as its counterpart in FIG. 2 except that circuit 10 no 
longer will have to carry out any signal-suppressing function as long as 
enough blanked area to accomodate the additional data pulses has been 
spaced out at the transmitting station.