MXPA97006586A - Co-channel communication system for video and information - Google Patents
Co-channel communication system for video and informationInfo
- Publication number
- MXPA97006586A MXPA97006586A MXPA/A/1997/006586A MX9706586A MXPA97006586A MX PA97006586 A MXPA97006586 A MX PA97006586A MX 9706586 A MX9706586 A MX 9706586A MX PA97006586 A MXPA97006586 A MX PA97006586A
- Authority
- MX
- Mexico
- Prior art keywords
- frequency
- carrier
- video signal
- signal
- auxiliary information
- Prior art date
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Abstract
In the present invention auxiliary information is modulated on a carrier frequency which is within a low energy density portion of a frequency band of a video signal, and the modulated carrier information (44) is combined with the video signal (46). ) so that the modulated carrier is either in an active video region or in an over-exploded region of the video signal. The auxiliary information is propagated over several frequencies and added to the output of the decoder to increase the readability of the auxiliary information in the decoder output. The frequency scaling can be used to add the auxiliary information to ones of a plurality of selected frequencies within the frequency band of the video signal. Then the auxiliary data can be distributed hierarchically between respective univocally specified sequential segments corresponding to many points of distribution of the vine signal
Description
COMMUNICATION SYSTEM OF CO-CHANNEL VIDEO AND INFORMATION
FIELD OF THE INVENTION The present invention relates to an apparatus and method of co-channel communication for concurrently transmitting auxiliary information with a video signal over a single communication channel, so that the auxiliary information is transmitted in an over-explored region. of the video signal and in this way, when the video signal is in the control of a receiver, the information is imperceptible to an observer. BACKGROUND OF THE INVENTION It is known to add information in the form of auxiliary signals, such as radio frequency television and / or
I radio program signals for a variety of purposes. jl For example, auxiliary signals are added to program signals in order to either monitor the broadcast or to measure audiences of those programs. These programs may include television programs, radio programs and / or the like, and the dissemination of such programs may include the transmission of those programs in the air, on a cable, via a satellite, and / or similarer. In a program monitoring system, which responds to complementary signals in the programs, the auxiliary signals, which are inserted into the signals of the program, are in the form of identification codes that identify the corresponding broadcast programs. Therefore, when the dissemination of the programs is monitored, the program's monitoring system captures the identification codes in order to verify that the coded programs are disseminated. The program monitoring system usually also determines the geographical regions in which these programs are broadcast, and the channels over which these programs are broadcast. In a program audience measurement system employing auxiliary signals, the auxiliary signal is typically added in sequence to the possible channels to which the receiver can be tuned. When the auxiliary signal appears at the tuner output of the receiver, the channel tuned by the receiver is identified, as well as the program identification codes, if any. When an auxiliary signal is added to a program signal, it must be made in such a way that the auxiliary signal is imperceptible to the audience of the program. A variety of methods have been used in attempts to achieve this imperceptibility. Most of these methods can be classified into two groups, a first group in which j the auxiliary signals are added to domains of time '| selected within the signal of the program, and? n second group in which auxiliary signals are added to frequency domains without interference of the program signal. A system of the first group, which is commonly used in the United States, is known as the "AMOL" system and is taught by Hasel Ood, and co-workers in the United States Patent Number: 4,025,851. This "AMOL" system adds an auxiliary signal, in the form of digital source identification code, for selected horizontal lines in the vertical free intervals of the program signal. The monitoring team, which locates it in selected geographic regions, verifies that the programs are disseminated by detecting the identification codes of sources (which can be digital) of the broadcast programs. The monitoring equipment stores, for later retrieval, these identification codes of detected sources together with the times at which these source identification codes were detected and the channels over which these source identification codes _J > _ detected. Another system of the first group is taught by
Greenberg in the patent of the United States of North America Number: 4,547,804, in the patent of the United States of North America Number: 4,639,779, in the patent of the United States of North America Number: 4, 805,020, and in the Patent of the United States of North America Number: 4,967,273. In this system, an auxiliary signal in the form of a source identification code is placed either in the vertical vacuum interval or an over-exploded portion of the active video signal. Even when the source identification code is placed in the over-exploded portion of the active video signal, it is still not generally present in the horizontal lines of the video signal which controls the visible part of the program and, therefore, does not It looks normally. Yet another system of the first group is taught by DeJean, and co-workers in the United States Patent Number: 5,243,423. In this system, an auxiliary signal is transmitted over active video lines previously selected from a video explorer. In order to reduce the perceptibility of the auxiliary signal, the video lines on which the auxiliary signal is transmitted are varied in a pseudo-random sequence. Alternatively, the auxiliary signal can be modulated at relatively low modulation levels by converting the auxiliary signal into an auxiliary signal of propagated spectrum. Yet another system of the first group is shown by Thomas, and collaborators in the Patent Application of the
United States of America with Series Number: 08 / 279,271,
"Which was submitted on July 22, 1994, which was allowed by the United States Patent and Trademark Office, and which is a continuation of the United States of America Patent Application with Series Number : 07 / 981,199 which has a filing date of November 25, 1992. In this system, a multi-level coding system includes a plurality of encoders each of which selectively encode information in a corresponding segment, uniquely specified, In accordance with this, the signal of the program is divided into a plurality of sequential coding segments The description of the United States of America Patent Application Serial Number: 08 / 279,271 is incorporated in the present by reference A system of the second group is shown by Hathaway in the United States of America Patent Number: 2,982,813. In this system, an auxiliary signal and a television program signal are interleaved with their frequencies so that the auxiliary signal is located in a region of the frequency spectrum of the television program signal which is substantially unoccupied. Because most of the signal components of the television programs are centered around harmonics of the horizontal line sweep rate of the television program signal, the frequency of the auxiliary signal is chosen to be unequal to any of these harmonics. In accordance with this, the auxiliary signal is intended to be imperceptible. Another system of the second group is shown by Loughlin, and co-workers in the United States of America Patent Number: 3,838,444. In this system, an auxiliary signal is added in a compatible manner and transmitted in a low energy density portion of a color television frequency spectrum. The low energy density portion of interest is located between the video carrier (i.e., luminance) and the color subcarrier (i.e., chrominance) of the television signal of the National Television Standards Committee (NTSC), and is at a frequency that is approximately 2.4 MHz above the peak of the luminance carrier in the radio frequency band of the television signal of the National Committee of Television Standards. Accordingly, this system reduces the interference between the auxiliary signal and the television program signal that may result from a system such as that shown by Hathaway. In addition, in U.S. Patent Number: 3,842,196, Loughlin describes an improved system that minimizes interference between a primary auxiliary signal and the program signal by adding a redundant auxiliary signal. The redundant auxiliary signal is transmitted with an inverted polarity compared to the primary auxiliary signal so that the visible artifacts, which may otherwise be caused by the addition of an auxiliary signal to the program signal, are canceled because the eye of the observer averages the luminance from the auxiliary signals: primary and redundant. Still another system of the second group is shown by Kramer in the Patent of the United States of North America Number: 4,931,871. In this system, a subaudible auxiliary signal is added to the program signal in a bandwidth centered around '40 Hz. Yet another system of the second group is shown by
Gerdes, and collaborators in the Patent of the United States of North Number 5,327,237. In this system, an auxiliary signal is scanned at the horizontal scanning speed and modulated on an information carrier to a non-integral multiple of the horizontal scanning speed in order to obtain frequency interleaving of the auxiliary signal and the signal of video of the program. Even moreIt is also well known to inject auxiliary signals into a television program signal within a sampled census family, which is participating in an auditory measurement investigation. Porter and Thomson signal injection systems are sampled in U.S. Patent Number: 4,044,376 and in U.S. Patent Number: 4,058,829, respectively. In these signal injection systems, the antenna input of a sampled television receiver is connected between an antenna and the output of a radio frequency oscillator. The frequency of the radio frequency oscillator is scaled through the channel frequencies of each receptive television signal. Thus, an auxiliary signal of the radio frequency oscillator is injected into each channel which carries a television signal. The auxiliary signal is injected during the vertical vacuum interval of each receptive television signal. A probe inside the television receiver determines if the auxiliary signal injected has passed through the tuner. If the auxiliary signal injected has not passed through the tuner, the frequency of the auxiliary signal injected is changed to a different channel and the process is repeated until the auxiliary signal injected is found and the tuned channel is identified by this. As in the case of these Porter and Thomson systems, the interference between the auxiliary signal and the television program signals in the signal injection systems is commonly prevented by injecting the auxiliary signal during the vertical vacuum interval of the program signal. TV. In a census family served by a cable system, however, an auxiliary signal that is injected during the vertical empty intervals of a television program signal may interfere with the view of other television sets in the census family that are tuned to other channels and that, therefore, have vertical synchronization signals phased differently. A system shown by Machnik, et al., In U.S. Patent Number: 4,605,958 addresses this problem by cycling the cable television program signals through a cable meter, through which the cable converter, and again through the cable meter before these signals from cable television programs pass to the television receiver. The cable meter includes video switches that are operated to momentarily disconnect signals from the cable television program of the cable converter and the television receiver. While the television program signals are disconnected from the cable converter and from the television receiver, the cable meter supplies the cable converter with an auxiliary signal injected at one of the frequencies to which the cable converter can be tuned. If the cable converter is tuned to that cable channel, the auxiliary injection signal passes through the cable converter, the auxiliary injection signal passes through the cable converter and returns to the cable meter. If the cable converter is not tuned to that cable channel, the auxiliary injection signal does not pass through the cable converter and does not return to the cable meter. Thus, by detecting when the auxiliary injection signal passes through the cable converter and back to the cable meter, the cable meter is able to determine the channel to which the cable converter is tuned. Accordingly, the auxiliary injection signal is prevented from reaching the television receiver and interfering with reception. Another signal injection system is shown in published international application Pub. No. WO 94/10799 by Mostafa et al. As shown in this published patent application, a signal generator sweeps through the possible channel frequencies to which a cable converter and a videotape recorder can be tuned. If the channel frequency has been selected by the j cable converter and / or the videotape recorder, a corresponding channel detection signal passes through the cable converter and / or videotape recorder in order to identify the tuned channel frequency. After that, an identification code at the frequency of the selected channel frequency is injected into the over-exploded region of the active video. This identification code includes the channel number of the selected channel frequency, the injection time, and the serial number of the injector device. Thus, for example, the recorded channel can be determined during playback in the recording of the videotape recorder, or during playback in another videotape recorder, which is connected to it or to a different television receiver in the measured census family. Yet another signal injection system is shown in U.S. Patent Number: 4,425,578 by Haselwood, et al. In this system, the frequencies of the auxiliary signals to be injected are selected so as to avoid erroneous readings. Haselwood et al. Specifically noted that auxiliary signals of the type shown by Hathaway are not useful for the injection of auxiliary signals because the amplitude of the signals should not be too great or the auxiliary signals would also emit the tuner causing interference in the viewed image. At the same time, the amplitude of the auxiliary signals must be large enough so that the auxiliary signal is sufficiently above the noise inherent in the video signals to be perceived. Yet another auxiliary signal injection system is shown in U.S. Patent Number: 4,216,497 and in U.S. Patent Number: 4,388,644 by Ishman et al. As described in these patents, the injection signals at the possible channel frequencies to which a receiver can be tuned are injected into a receiver until an injection signal is detected at an output of the receiver. As soon as the injection signal having the channel frequency to which the receiver is tuned at an output of the receiver is detected, the injection signals at only that channel frequency are periodically injected into the receiver.
After a failure to detect one of these signals periodically injected at an output of the receiver, three additional attempts are made. If all four attempts fail, a new search is made to find the new frequency of
I channel to which the receiver is tuned. In addition, the use of auxiliary signals that are injected into signals of television programs to be recorded on a VHS video recorder is limited due to the reduced bandwidth of the recorded signal. The VHS video recording standard allows a progressive attenuation response above two MHz with a higher frequency chrominance subcarrier in the subcarrier i. Thus, an auxiliary signal can be recorded by a VHS recorder only if the carrier frequency of the auxiliary signal is below the progressive attenuation frequency of the VHS video recorder. Also, the application of digital data compression methodologies to composite video signals has a substantial impact on the utility of auxiliary signal coding methods. Some video compression schemes erase the vertical void interval and / or reduce the normally over-exploded portions of the image. Accordingly, any auxiliary signal injected in the vertical void interval or in the over-exploded portion of a video image can be removed by this compression of the video signals. Digitization can also act to remove propagated spectrum auxiliary signal codes and other codes based on low signal amplitudes for concealment. Additionally, the auxiliary signal codes transmitted in a high frequency portion of a video signal band can be erased by compression algorithms that 'hold' the higher frequencies. Although adding an auxiliary signal to the normally visible portion of the active video signal allows the auxiliary signal to avoid removal by compression schemes in most cases, and although adding an auxiliary signal to a frequency in the density portion of the Low power of the video signal increases the probability that the auxiliary signal will be imperceptible even when the auxiliary signal is added to the active video, under certain conditions the auxiliary signal may still be noticeable. For example, if the intensity of the luminance that is modulated on the video carrier (ie, luminance), or the intensity of the color that is modulated on the chrominance subcarrier, is smaller than the auxiliary signal at the time when the signal auxiliary is modulated on a frequency between the video carrier and the chrominance subcarrier, the auxiliary signal will not be masked by the video carrier or the chrominance subcarrier of the video signal. Thus, the auxiliary signal may have sufficient relative amplitude to be perceived as noise by the program's audience.- The present invention overcomes one or more of the problems noted above. In addition, the present invention overcomes one or more of the problems noted above either by modulating the auxiliary signal on a carrier having a frequency in the low-energy density portion of a video signal and adding this modulated carrier to the over-swept region. of the video signal, or propagating the auxiliary signal over a frequency bandwidth that is greater than the frequency bandwidth of the original auxiliary signal by adding this auxiliary signal propagated to the over-swept region of the video signal.
SUMMARY OF THE INVENTION Therefore, according to one aspect of the present invention, a system for transmitting data on the same communication channel as the composite video signal, wherein the composite video signal is transmitted in a frequency band and the composite video signal has a horizontal synchronization period, comprises a selection element, a modulation element, and a combination element. The selection element selects a carrier having a carrier frequency in the frequency band at the beginning of each of a plurality of frequency stepping periods, wherein each frequency stepping period has a duration equal to, or a multiple integer
• of, the horizontal synchronization period. The element of j | modulation modulates the data on the selected carrier to 'produce a modulated data signal. The combining element combines the modulated data signal with the composite video signal. According to another aspect of the present invention, a method of adding ones of a plurality of hierarchical auxiliary signal codes to a television signal having a frequency band associated therewith, wherein each hierarchical auxiliary signal code comprises a time data and a location data, wherein each location data is uniquely associated with one of a plurality of encoders, wherein each encoder has univocally associated therewith a corresponding one of a plurality of carrier frequencies, wherein each frequency of the plurality of carrier frequencies is in the frequency band, the method comprises the steps of a) modulating each hierarchical auxiliary signal code on a carrier having a corresponding one of the plurality of carrier frequencies, and b) combining each carrier frequency modulated with the television signal. According to yet another aspect of the present invention, a system for transmitting data and a composite video signal in a common communication channel, wherein the composite video signal is transmitted in a frequency band, comprises a selection element, a modulation element, a combination element, and a demodulation element. The selection element selects a plurality of carriers, wherein each carrier has a single carrier frequency correspondingly in the frequency band. The modulation element redundantly modulates the data in each of the modulated carriers. According to yet another aspect of the present invention, a system for measuring the tuning of television programs in a sampled census family and for monitoring transmissions of television programs, wherein the television programs are transmitted by a television signal, and wherein the television signal has a bandwidth, comprises an addition element, a measuring element, and a monitoring element. The addition element adds first data to the television signal at a first frequency and adds second data to the television signal at a second frequency, wherein the first and second frequencies are within the bandwidth of the television signal . The measuring element measures the tuning of the television by detecting the first data. The monitoring element monitors transmissions of television programs detecting the second data. According to a further aspect of the present invention, an apparatus for the non-intrusive measurement of the tuning for a television signal transmitted within a sampled census family comprises a modulation element, a non-intrusive acquisition element, and an element of demodulation. The modulation element is within the fictional census family and modulates an auxiliary code that varies over time on a carrier having a carrier frequency within a video bandwidth of the transmitted television signal. The non-intrusive acquisition element is adjacent to a display of the television signal and acquires the modulated carrier in a non-intrusive manner. The demodulator element demodulates the auxiliary data that vary in time from the modulated carrier and stores the auxiliary data that vary in time for subsequent transmission to a central office. According to another aspect of the present invention, a system transmits auxiliary data on the same communication channel as the video signal. The video signal has a frequency band and an overexploited region. The system includes a selection element, a modulation element, and an element of addition. The selection element selects a carrier having a carrier frequency within a low energy density portion of the frequency band. The modulation element modulates the auxiliary data on the selected carrier to produce a modulated carrier. The addition element adds the modulated carrier to the over-swept region of the video signal. A system according to yet another aspect of the present invention transmits auxiliary data in the same communication channel as a video signal. The video signal has an over-swept region, and the auxiliary information has a first frequency bandwidth. The system comprises a data propagation element and an addition element. The data propagation element propagates the auxiliary data over a second frequency bandwidth which is wider than the first frequency bandwidth. The addition element adds the auxiliary data propagated to the over-exploded region of the video signal.
BRIEF DESCRIPTION OF THE DRAWING These and other features and advantages will become more apparent from the detailed consideration of the invention when taken in conjunction with the drawing in which: Figure 1 is a block diagram of a coded signal monitoring system of multiple levels according to the present invention; I Figure 2 is a graph that illustrates a format
'previously determined of a universal transmission code useful in the multi-level encoded signal system of Figure 1; Figure 3 is - a block diagram of an encoder which can be used in the system of Figure 1 to inject an auxiliary frequency interleaved signal into a schedule signal; Figure 4 is a block diagram of a decoder which can be used in the system of Figure 1; Figure 5 is a diagram. in blocks of a non-intrusive television auditory measuring system according to the present invention, - Figure 6 illustrates a non-intrusive sensor which may be used in connection with the present invention; Figure 7 illustrates the placement in a television set of the non-intrusive sensor shown in Figure 6; Y,
Figure 8 illustrates the approximate average over-swept region of television sets that receive video signals that contain television programs to be viewed.
DETAILED DESCRIPTION OF THE INVENTION As shown in Figure 1, a multi-level encoded signal monitoring system 10, which may be similar to that shown by Thomas, and co-workers in the aforementioned United States of America Patent Application. with Series Number: 08 / 279,271, includes a plurality of auxiliary signal encoders 12-1, 12-2, ..., 12-N. Each auxiliary signal encoder 12 may be located at a corresponding stage of distributing a program signal. The distribution stages are designated in Figure 1 as distribution point 1, distribution point 2, ..., distribution point N. Each auxiliary signal encoder 12 adds a corresponding auxiliary signal code in a corresponding video segment of a program signal provided by a program source 14. A plurality of decoders 16 and 18 are provided in association with selected program signal distribution points in order to decode the auxiliary signal codes that have been encoded on the video segment using the auxiliary signal encoders 12-1, 12-2, ..., 12-N. The decoder 16 is associated with the distribution point 2 so as to decode the auxiliary signal codes of the video segment of the program signal at the output of the encoder of the auxiliary signal 12-2, and the decoder 18 is associated with the distribution point N so that it decodes the codes of the auxiliary signal from the video segment of the program signal at the output of the auxiliary signal encoder 12 -N. However, more or fewer decoders can be provided to these or to other distribution points. A clock 20 for providing a date and time stamp is coupled with the first auxiliary signal encoder
12-1. However, additional clocks, such as clocks 22 and 24, can be coupled to the other encoders and decoders. These additional clocks are particularly desirable if a secondary date and time stamp is to be added to the auxiliary signal codes provided by the other auxiliary signal encoders 12-1 ... 12-N, as may be the case when a The syndicated program is initially transmitted from a central source to a plurality of local stations for retransmission. Further, if the present invention is to be operated in pseudo-random mode, to be described in greater detail here below, a clock is required for each auxiliary signal encoder 12-1, 12-2, ..., 12-N and for each decoder 16 and 18, and a synchronization clock, which may be in the form of a remote reference clock 26, may be provided in order to synchronize each of the auxiliary signal encoders 12-2 through 12 -N and each of the decoders 16 and 18 for the auxiliary signal encoder 12-1. A hierarchical auxiliary signal code, which may be similar to the universal transmission code shown by
Thomas and colleagues in the aforementioned
I Patent Application of the United States of America with
• Series Number: 08 / 279,271, includes a plurality of code segments, as shown in Figure 2. These code segments may include a network identification, a local station identification, a cable or satellite identification, a commercial identification, a program identification, a description of the program profile, for example, the content or classification of the program, and / or the like. Each of these identifications and profiles can be encoded by a separate encoder of the auxiliary signal 12-1, 12-2, ..., 12-N. Other segments, indicated by asterisks in Figure 2, are left empty during the transmission of a television program so that these "code slots" can be used for other purposes such as television audience measurements at home. Each of the segments shown in Figure 2 may include one or more video frames of a television program signal. Thus, for example, the identification of the local television station may be encoded on several video frames of the signal of the television program. Also, the segments shown in Figure 2 may represent time domains of the video signal (e.g., one or more fields or frames), or the segments shown in Figure 2 may represent frequency domains of the video signal ( for example, one or more carrier frequencies univocally located for each segment). However, it should be understood that the video segments carrying auxiliary signals may be other than those shown in Figure 2. An auxiliary signal encoder 12 is shown in more detail in Figure 3. This auxiliary signal encoder 12 can be located at a coding site 30 in the production-distribution-display chain of a television broadcast program signal. The coding site 30 receives a video signal, which is received on an input line 32 and which can be obtained as an output from a radio frequency receiver (not shown). This video signal is applied to a synchronization block 34 to provide synchronization to the incoming data, which may include an auxiliary signal code which is provided by one or more of the other auxiliary signal encoders 12-1. 12-N and which can be extended over one or more frames of the video signal. A data decoder 36 decodes the input data and couples the decoded input data to a microprocessor 38 having associated therewith a clock 40 such as the clock 22 or 24 shown in FIG. 1. In the pseudo-random mode of the invention, the microprocessor 38 receives synchronization information from the remote reference clock 26 in order to synchronize for the reference time of the monitoring system of the multi-level encoded signal 10. The auxiliary encoder 12 also includes a data encoder 42. The data encoder 42 receives an auxiliary signal to be added to the video signal, suitably encodes that auxiliary signal, and applies the coded auxiliary signal to a transport modulator 44. This auxiliary code may be the data, such as the identification of the network or the identification of the local TV station, contained in any of the segments shown in Figure 2 depending on the level of distribution. n which the auxiliary encoder 12. The carrier modulator 44, which may be controlled by the microprocessor 38 on a control line I 48 is located, modulates a carrier signal with the '| coded auxiliary and applies the modulated carrier to an inserter 46. The inserter 46 inserts the modulated carrier into the video signal. The auxiliary signal encoder 12 also includes memory as a direct access memory 50 and a read only memory 52. As shown in Figure 4, a decoder
60, which can be used for decoders 16 and 18, can include a tuneable bandpass filter 62 and a sync block 66. The tuneable bandpass filter 62 can be used in order to select a frequency of a video signal on a video input line 64. The synchronization block 66 may be used to provide synchronization to the input data as may be necessary, for example, in the case where the frequency band of the auxiliary signal propagate over a frequency bandwidth wider than the frequency bandwidth of the previously propagated auxiliary signal, or in the case where the frequency hopping is used in order to transmit the auxiliary signal. The decoder 60 also includes a data decoder 68 which couples data from
! decoded input to a microprocessor 70, and a clock 72 can be synchronized by the remote reference clock 26.
The decoder 60 also includes a memory such as a direct access memory (RAM) 74 and a read-only memory (ROM) 76. The multi-level encoded signal monitoring system 10 can be operated in several modes. For example, in one embodiment of the present invention, hereinafter referred to as the single frequency mode mode, the microprocessor 38 controls the data encoder 42 so that the auxiliary signal is encoded by the data encoder 42, so that the coded auxiliary signal is modulated on a carrier by the carrier modulator 44, and so that the modulated carrier is inserted by the inserted 46 into a non-interference frequency band within the. bandwidth of the video signal. According to the teachings of Hathaway, Loughlin, Gerdes, and others, this auxiliary signal may be in the form of a signal in narrow band addition having a frequency that is a non-integral multiple of a harmonic of the horizontal synchronization frequency. This signal is usually noninterference, because most of the energy of. the video signal is nested in harmonics of the horizontal synchronization frequency. When operating in the single frequency mode, the encoder of the auxiliary signal 12 only needs a clock 40 if a date and time stamp is desired as a part of the added identification code. Moreover, in a hierarchical coding system in which different auxiliary signal encoders 12, such as auxiliary signal encoders 12-1, 12-2, ..., 12 -N, provide different parts of a code message of global auxiliary signal, such as the auxiliary signal coding message shown in Figure 2, all encoders of auxiliary signal 12 would operate with a common fixed carrier frequency. Therefore, in the single frequency mode, the microprocessor 38 would not control the frequency of the carrier modulator 44 so that the control line 48 would not be necessary. In a second mode of operation, hereinafter referred to as the fixed-frequency mode, a set of the narrow-band signal addition channels, each centered with respect to the corresponding non-interfering frequency within the bandwidth of the video signal, it would be selected for use by all the auxiliary signal encoders 12-1, 12-2, ..., 12-N. As is known, one can select a set of non-interference frequencies, f, expressed as
fj = fH (2m + l) / 2, where fjj is the horizontal synchronization frequency, and m is an integer that varies between approximately 110 and approximately 209 and between approximately 246 and I approximately 266. A first portion of low density
'energy of the bandwidth of the video signal that lies below the chrominance subcarrier frequency, as taught by Loughlin et al., corresponds to the values of the integer, m, which is between about 110 and about 209. The frequencies f i resulting from the variation of m between about 110 and about 209 cover a range from about 1.7 MHz to about 3.3 MHz above the base of the video band. A second portion of low energy density of the bandwidth of the video signal that is above the frequency of the chrominance subcarrier, as taught by Gerdes et al., Corresponds to the values of the integer, m, which remains between approximately 246 and about 266. The frequencies f i that result from the m variation between about 246 and about 266 cover a range from about 3.9 MHz to about 4.2 MHz above the base of the video band. Thus, in a fixed frequency mode, some of the one or more frequencies that do not interfere can be selected, and the television signal can be coded to each of these selected frequencies. The decoder 16 or 18 in a fixed frequency system would acquire signals at all the selected frequencies and add all these acquired signals. As is known in communication techniques, the sum of signals having both correlated and uncorrelated portions results in an improvement in the signal to noise ratio (SNR) of the correlated portion. For a signal in which the uncorrelated portion is random. this improvement is proportional to the square root of the number of signals added.
Therefore, if a correlated auxiliary signal was placed by an auxiliary signal encoder 12 in an uncorrelated co-channel video signal using four of the frequencies fj, a corresponding decoder 16 or 18 that summed the four frequencies would provide twice. the ratio of signal to noise according to a decoder 16 or 18 operating at a single fixed frequency. Thus, the fixed-frequency operation mode of the system provides a reduction in co-channel interference by allowing the auxiliary signal to be added to a video signal at a lower amplitude. • In a third mode of operation, hereinafter called "stepped frequency" mode, a sequence of carrier frequencies, fj, is selected by the auxiliary signal encoder 12 (e.g., from a table 54 of these stored frequencies) in the read-only memory 52), and sequence portions of the auxiliary signal (or sequential repetitions of the auxiliary signal) are added to the corresponding carrier frequencies fj with a predetermined time interval delta t (which can also be store in read-only memory 52). The sequence of selected carrier frequencies may or may not follow a simple sequential path from the highest to the lowest, or from the lowest to the highest. For example, the sequence of selected carrier frequencies may follow a non-linear path between any two previously selected carrier frequencies. The order of the selection of the different carrier frequencies can be chosen so as to minimize the risk of creating a fixed pattern co-channel interference with the video signal. For example, a frequency step sequence could be selected to minimize patterns of spike image interference on a monochrome screen (eg, black) where it would be more visible that the same interference pattern would be if it were displayed against a variegated background. In the stepped frequency mode, the decoder 60 necessarily includes the tuneable bandpass filter 62 in order to select the carrier frequencies fj. The bandpass filter 62 scales through the carrier frequencies f: under the control of the microprocessor 70 in synchronization with the auxiliary signal it is reading. These carrier frequencies can be selected, for example, according to a frequency table 80 and a predetermined time interval 82 in the read-only memory 76. The carrier frequencies in the frequency table 80 can be the same as the carrier frequencies. in Table 54 of the frequencies stored in the read-only memory 52. Moreover, the predetermined time interval 82 can be the same as the previously determined time interval delta t stored in the read-only memory 52. With the In order to read an auxiliary signal, the microprocessor 70 initially sets the tuneable bandpass filter 62 to pass the carrier frequency at which the initial block of an auxiliary signal is transmitted. When the synchronization block 66 and the decoder 68 encounter the start of an auxiliary signal, the microprocessor 70 waits during the predetermined time interval 82 (ie, the frequency stepping period) and then causes the pass filter to tunable band 62 steps to the next carrier frequency f, where it is expected to find information, when the decoder 60 is not receiving an auxiliary signal, sets the bandpass filter 62 to pass that carrier frequency to which it is known that all the auxiliary signals. i The time duration of a frequency step is
| j preferably fixes to be substantially longer than a period of horizontal synchronization, or line sweep time. If the frequency is shifted too quickly, the stepping operation will produce additional high-frequency components of the auxiliary signal that can interfere with the co-channel video signal. However, this interference can be minimized by configuring the system to transmit auxiliary signals only during the over-exploited portion of the active video periods and changing from one carrier frequency to another during the empty horizontal intervention intervals. In a variation of the stepped frequency mode of the system of the invention, whose variation is hereinafter referred to as the pseudo-random mode, the carrier frequency used by an auxiliary signal encoder 12 may vary in a pseudo-random manner in order to to further minimize the interference between the auxiliary signal and the video signal. Pseudo random frequency stepping, which is well known in the art of real-time communication systems, generally requires that all elements of the communication system be synchronized. The television production-distribution-viewing chain commonly incorporates recording and then playing at any point in the chain, and thus generates a signal that appears at an arbitrary later time. Therefore, forward synchronization is not possible. However, synchronization can be provided, j? '| by using a single sequence initiation input i of frequencies (eg, the date and time stamp that is recorded with the program by the initiator thereof, which may be based on the clock 20, and which may be in the segment called "NET-WORK ID" in Figure 2) and by using the remote reference clock 26 which supplies the auxiliary signal encoders 12-1, 12-2, ..., 12-N and the decoders 16 and 18 with a synchronization time value. A pseudo-random number sequence (or equivalently a pseudorandom selection of a sequence i of carrier frequencies from the set of frequencies
! carriers that do not interfere available fj) can be generated by a program that is stored in read-only memories 52 and 76 and which has the start-of-sequence entry as an input. That is, the sequence initiation input is used by the auxiliary signal encoders 12-1, 12-2, ..., 12-N and the decoders 16 and 18, in effect, to synchronously select the pseudo-random sequence of the carrier frequencies. In accordance with the foregoing, in the pseudo-random mode of the present invention, each of the auxiliary signal coders, 12-1, 12-2, ..., 12-N and the decoders 16 and 18 could use the same algorithm for generating pseudo-random numbers (for example, which can be stored in read-only memories 52 and 76) that have as input the sequence initiation input in order to select the appropriate sequence of carrier frequencies to be used to encode and decode the auxiliary code signal. The previously determined time interval delta t as stored in the Queens 52 and 76 is used to set the time interval between the passages of the carrier frequencies in the pseudo-random carrier frequency sequence. The foregoing describes the means for staggering all the elements of the multi-level encoded signal monitoring system 10 in pseudo-random synchronization, but i, leaves unresolved the question of how the process begins, ie, how the decoder is going to discover the initiation entry of the sequence. This start-up problem can be solved by having the initial part of the auxiliary signal, the
which includes the sequence initiation input, always transmitted to a single predetermined start frequency, which may preferably be a frequency found to provide a minimum value of channel interference. According to this. In this method, each of the decoders 16 and 18, when they do not receive the code, sets their tuneable bandpass filter 62 to pass the previously determined start carrier frequency, and waits in this state until the start input is received. sequence. Thus, the system of the present invention provides means for minimizing co-channel interference in a system having a minimally interfering carrier frequency and a plurality of possibly more interference-carrying frequencies but pseudo-randomly distributed.
As shown in Figure 5, a home television auditorium measuring system 100 includes a source 102 of radio frequency television signal. The source 102, for example, can be a cable television, an antenna, a satellite, and / or the like. The radiofrequency television signal is divided into a divider 104 and the channels present in the radio frequency television signals are sequentially tuned by a tuner 106 that is part of the home meter 108. A hierarchical auxiliary signal that is present in the tuned signal at the output of the tuner 106 may have a code at home (eg, a printed date and time designation of the channel on which the auxiliary signal is received) added thereto on the radio frequency television signal. In a version of the home meter 108 for use in recording families having a videotape recorder 110, a dual frequency encoder 112 can be used to simultaneously and redundantly sum the same code at home at both a first frequency, which is in the low-density density portion of the frequency spectrum of the television signal and that is below the
I frequency of progressive attenuation of a tape recorder? Of video, and to a second frequency, which is in the portion i of low energy density of the frequency spectrum of the television signal and which is above the attenuation frequency progressive of the video tape recorder. This home code in the first and second frequencies is added to the radio frequency television signal by means of an upward converter 114 and an address coupler 116., and is supplied to the video tape recorder 110 and an associated television 118. In addition, the first frequency may instead be a group of frequencies that is in the low energy density portion of the frequency spectrum of the television signal and that is below the frequency of progressive attenuation of a video cassette recorder. This group of frequencies can be chosen by appropriate selection of the integer m. Also, this second frequency may instead be a frequency group that is in the low energy density portion of the frequency spectrum of the television signal and which is above the progressive attenuation frequency of the television recorder. Video tapes. This group of frequencies can also be chosen through the appropriate selection of the integer m. A non-intrusive sensor 120, which may be a video probe (ie, an antenna tuned to a video baseband frequency) or a frequency antenna
Intermediate I (e.g., tuned to the commonly used IF I and B to 44 MHz) acquires the modulated carrier of the I 'auxiliary signal from the radio frequency television signal from a position that is adjacent to the television 118. The auxiliary signal, which it is present in the radiofrequency television signal at the time the radio frequency television signal is received in the home television auditorium measurement system 100, and the home code, which is inserted in the television signal by means of the home television auditorium measuring system 100, they are demodulated by a dual frequency decoder at home 122 and stored in a home controller 124 for subsequent transmission by, for example, a public telephone network 126 to a central information collection office 128. An example of the non-intrusive sensor 120 is shown in Figure 6. The non-intrusive sensor 120 includes a support 120a, e Which one can be used in the form of a cardboard bottom, a sheet 120b, a terminating resistor 120c, a connector I20d, and a coaxial cable 120e. The sheet 120b has a groove 120f which forms the leaf 120b in the form of a cycle. The connector 120d has an internal connector 120g connected to the blade 120b on one side of the groove 120f, and an external connector 120h connected to the blade 120b on the other side of the groove 120f. The coaxial cable 120e has internal and external conductors connected with the corresponding internal connector 120g and the external connector 120h. The non-intrusive sensor 120, therefore, is configured as a tuned coil, and can be co-tapped, as shown in Figure 7, on the back of the television of a census family so that it picks up the video signal radiated by the rear end of an image tube of a television set. If the non-intrusive sensor 120 does not adequately capture the horizontal and vertical synchronization pulses, a magnetic picker 121 can be placed in the television housing near the deflection coils that control the image tube. Tape recorders of the VHS type will not record the second frequency of the code at home because this second frequency is above the two MHz progressive attenuation frequency of these video tape recorders. Thus, if a radio frequency television signal is seen at the same time it is received, the dual frequency decoder at home 122 will detect a home channel code on both frequencies, but if a signal reproduced from the 110 video tape recorder, the dual frequency decoder at home 122 will read only the lowest frequency code. Thus, the home television auditorium measurement system 100 can distinguish between time change and non-change of view time in a television auditorium measurement. After decoding the home code that was added to the first and second frequencies, the home controller 124 can compare the home code associated with the second frequency to the home code associated with the first frequency in order to provide security of that the code at home was added and decoded properly. In another embodiment of the present invention, the auxiliary signal added in this first frequency can be used by a home measurement system to determine the tuning of a television, and the auxiliary signal added to this second frequency can be used by a television system. monitoring to verify the transmission of television programs. In addition, instead of setting the first frequency below the progressive attenuation frequency of a video tape recorder and the second frequency above the progressive attenuation frequency of the video tape recorder, the first frequency can be set below of the chrominance subcarrier frequency of a television signal or even below the progressive attenuation frequency of a video tape recorder and the second frequency can be set above the chrominance subcarrier frequency of the television signal. Even more, first information can be added to the television signal at the first frequency which is below the progressive attenuation frequency of a video tape recorder, a second information can be added to the television signal at a second frequency which is above the progressive attenuation frequency of a video tape recorder but below the chrominance subcarrier frequency of the television signal, and a third information can be added to the television signal at a third frequency of the signal of TV. Any of the first, second, and third frequencies can be used for television measurement and any of the remaining frequencies can be used for program monitoring and verification. Other combinations are possible. Also, the segments of the hierarchical auxiliary signal shown in Figure 2 can be added using these three frequencies in any combination. In addition, the first information can be added using a first group of frequencies that fall in the low-energy density portion of the frequency spectrum of the television signal and that are below the frequency of progressive attenuation of a tape recorder. video, the second information can be added by using a second group of frequencies that lie in the low-energy density portion of the frequency spectrum of the television signal, which is above the f-frequency of progressive attenuation of the tape recorder of video, and that is below the chrominance subcarrier and the third information can be added using a third group of frequencies that are in the low-energy density portion of the frequency spectrum of the television signal and that are above the chrominance subcarrier. Additionally, instead of associating the decoder 16 with the distribution point 2 by associating the decoder 18 with the distribution point N as shown in Figure 1, a plurality of decoders 16 can be placed in statistically selected census families where they are measuring the spectator habits of a panel of spectators and a plurality of decoders 18 can be placed on central monitoring sites in the television markets in which the transmission of television programs will be monitored. In accordance with the foregoing, in the television display measurement application, the decoders 16 decode the codes of the auxiliary signal from the programs that are being viewed in television sets in the statistically selected census families. The auxiliary signal codes may be in the form of program identification codes that are inserted by the encoders 12-1, 12-2, ..., and / or 12-N in the video segments of the possible programs visible in the corresponding television sets. In accordance with this, the panel's viewing habits can be checked in statistically selected census families. Moreover, in the application of program monitoring, the decoders 18 decode the codes of the auxiliary signals in the form of program identification codes that are inserted by the encoders 12-1, 12-2 ... and / or 12 -N within the video segments of selected programs. Accordingly, in the detection of an identification code in the programs selected by a decoder 18, the broadcast of the selected programs in the market in which the decoder 18 is located can be verified. Similarly, the decoders can be used. 16 and 18 at the same time to measure the
I viewing habits of an audience and to monitor the diffusion of selected programs. In this case, the program identification codes detected by the decoders 16 and 18 may be the same, or they may be inserted in different formats or at different frequencies.
In addition, to measure the viewing habits of an audience, you can add identification codes of t programs in the low energy density portion of the frequency spectrum of the television signal, and both below and above the frequency of attenuation progressive of a video tape recorder. Also, each identification code can be added by using multiple frequencies in one or more frequency bands. The convenience of non-intrusive measurement methods (ie, those that do not require even the partial disassembly of the amusement electronic device measured for the purpose of installing sensors) is well established in the technique of television audience measurement. Prior art systems that employ a time division multiplex code (e.g., a code written on lines previously determined in the video frame) have generally required an intrusive connection to television (e.g., soldering a probe in a point, video test on a television circuit board) in order to acquire a signal that can be decoded. The system of the present invention, on the other hand, provides a non-intrusive connection due to the use of the non-intrusive sensor 120. Thus, the system of the present invention provides non-intrusive detection and decoding of both the auxiliary signal, which is present in the radiofrequency television signal at the time that the radio frequency television signal is received by the television audience measurement system in the home 100 and which is transmitted with a television signal in a co-channel mode , such as the home code that is inserted into the radio frequency television signal by means of the home television audience measurement system 100. In order to further ensure the imperceptibility of the auxiliary signal, the auxiliary signal can be added to the overexploited region of the video signal. Consequently, the auxiliary signal is not only added to the interfering frequency domains of a video signal of a program (ie, the auxiliary signal is modulated in one or more carriers in the low energy density portion of the signal of video), but the modulated carrier of the auxiliary signal is added within the time domains without interference of the video signal of the program (that is, the auxiliary signal is added to the over-exploded region of the video signal). Therefore, the imperceptibility of the auxiliary signal is also ensured when a program is displayed on a television monitor. Figure 8 represents, in general, an area 200 that is occupied by the frame of a frame of the video signal interlaced as it is transmitted to television sets and which includes all the horizontal scan lines except the scan lines in the vertical vacuum interval. Area 200, as is widely known in the television arts, includes a visible region 202 and an overexploited region 204 of demonstrated average size. The visible region 202 is the region of the area 200 that is normally visible on a television monitor. The overexploited region 204 is the region of the area 200 that is generally not visible on the television monitor. Although area 200, as shown in Figure 8, covers a complete video frame, it should be understood that a complete video frame comprises two video fields. By convention, the standard of the National Television Standards Committee for television signals requires that each frame comprise 525 horizontal scan lines. These 525 scan lines are divided into 262.5 horizontal scan lines per video field. The 262.5 scan lines of the two fields are interleaved to form a complete video frame of 525 horizontal scan lines. Some of these 525 horizontal scan lines are generally considered to be at vertical empty intervals. For example, the scan lines
I horizontal 1-21 is generally considered to be in the empty interval i. As noted above, the signals in the vertical vacuum interval can be emptied during information compression. Consequently, if an auxiliary signal is placed in the vertical vacuum interval, and if the vertical vacuum interval becomes empty during compression of the signal, it is likely that the auxiliary signal is lost. The overexplored region I 204 includes (i) the horizontal scan lines that are not in the vertical vacuum range and that are not in the visible region 202 (i.e., those horizontal scan lines are masked by the upper and lower parts of the frames of conventional television equipment). Thus the mask established by a television set's box affects the four sides of the video signal that is framed. Accordingly, the over-swept region 204 includes an over-swept upper sub-region 206, an over-swept lower sub-region 208, a left over-swept sub-region 210, and a right over-swept sub-region 212. In general terms, the auxiliary signal added to the time domains without interference from a video signal of a program represented by one or more of the over-exploited sub-regions 206, 208, 210 or 212 is generally invisible to the viewer of a program encompassed by the signal of
'I video of the program. Also an auxiliary signal added to the
! domains of the frequency without interference of a video signal of the program represented by the low-energy density portions of the video signal is also generally unnoticeable to the viewer of a program encompassed by the video signal of the program. By adding an auxiliary signal to both the non-interference time domain and the non-interference frequency domain of a program video signal, the confidence that the auxiliary signal will be imperceptible to the program viewer covered by the program signal will substantially increase. video of the program. This confidence can be further increased if the auxiliary signal is added to one or more unexplored subregions of the corners 214, 216, 218 and 220. Thus, although the over exploded sub-regions 206, 208, 210 and 212 may vary in size of the television to television set, the possibility that the over-exploited sub-regions 206, 208, 210 and 212 vary in size in such a way as to reveal an auxiliary code in one or more of the over-explored sub-regions of the corners 214, 216, 218 and 220, It is less likely. For example, if an auxiliary code is inserted into a program video signal, so that the auxiliary signal is confined to the overexploited subregion of the corner 214, both overdrawn sub-regions 206 and 210 must be less than average to result that the auxiliary code is in the visible region 202. Therefore, the probability of a code au. The signal in the program is increased by placing the auxiliary code in one or more of the over-exploded sub-regions of the corners 214, 216, 218, and 220. Accordingly, as the video signal of the program receives on the input line 32 of the auxiliary signal encoder 12 shown in Figure 3, the synchronization block 34 detects the horizontal and vertical synchronization pulses in the incoming video signal. F? data encoder 42 counts the horizontal synchronization pulses and is controlled by the microprocessor 38 to encode the auxiliary signal and to supply the coded auxiliary signal to the carrier modulator 44 during one or more of the over exploded subregions, preferably the over exploded regions 206 and 208, of the video signal of the received program. The carrier modulator 44 modulates the coded auxiliary signal on one or more carriers having frequencies in the low-energy density portions of the program's video signal, and supplies the modulated carrier to the inserter 46. The inserter 46 thus inserts the modulated carrier during one or more of the over exploded sub-regions 206 and 208 of the video signal of the program. Furthermore, the received video signal can also be processed by the encoder 12 in order to determine the signal level of the video signal received at the input 32 so that the amplitude of the auxiliary signal coded, modulated on a carrier it can be set by the carrier modulator 44 to a level below the signal level of the received video signal i. In this way, the video signal can be used to mask the frequency of the auxiliary signal. In addition, by counting the horizontal synchronization pulses appropriately and resetting a clock after the occurrence of each horizontal synchronization pulse, the data encoder 42 can encode the auxiliary signal and supply the coded auxiliary signal to the carrier modulator 44 during one or more of the over-exploded sub-regions 210 and 212 of the video signal dq of the received program. As above, the carrier modulator 44 modulates the coded auxiliary signal on one or more carriers having frequencies in the low-energy density portions of the video signal of the program and supplies the modulated carrier to the inserter 46. The inserter 46 inserts this mode the modulated bearer during one or more of the over exploded sub-regions 210 and 212 of the program video signal. Also, by appropriately counting the horizontal synchronization pulses and by resetting a clock at the occurrence of each horizontal synchronization pulse, the information encoder 42 can encode the auxiliary signal and supply the coded auxiliary signal to the carrier modulator 44 during one or more of the over-scanned sub-regions at corner 214, 216, 218 and 220 of the video signal of the received program. As before, the carrier modulator 44 modulates the coded auxiliary signal in one or more carriers having frequencies in the low-energy density portions of the video signal of the program and supplies the modulated carrier j to the inserter 46. The inserter 46 thus inserts the modulated bearer during one or more of the over-exploded sub-regions at corner 214, 216, 218, and 220 of the video signal of the program. Accordingly, the auxiliary signal may be added to the video signal during any of one or more of the over exploded sub-regions 206, 208, 210, 212, 214, 216, 218, and 220. The auxiliary signal may be modulated on a carrier so that a bit of information "zero" is modulated on one or more of the first carriers and a bit of information "one" is modulated on one or more of the second carriers. Both the first and second carriers have corresponding frequencies in the low-energy portion of the program's video signal. Also each bit of the auxiliary signal may be added to one or more of the over-exploded regions of a field or frame such that a horizontal scan line carries a single bit of information. For example, because there are approximately twelve lines in the upper overdraught sub-region 206 and about twelve lines in the lower-sub-sub-sub region 208 of the over-swept 204 region of a field, one byte of information can be added per field of the video signal adding a single bit of information to each of the four horizontal scanning lines in the upper over-explored sub-region 206 and a single bit of information to each of the four horizontal scanning lines in the lower over-explored sub-region
, 208. By repeating each byte in several fields (like six fields), j it is possible to increase the probability that the auxiliary signal I will survive compression. The encoded video signal is received on the video input line 64 of the decoder 60. The video signal passes through the tuneable bandpass filter 62 and the synchronization block 66 to the data decoder 68. The microprocessor 70 controls the synchronization block 66 and the tuneable bandpass filter 62 in order to synchronize the auxiliary signal immersed in the video signal. For example, if the auxiliary signal was transmitted using a frequency hopping algorithm, the microprocessor 70 controls the tuneable bandpass filter 62 and the sync block 66 in order to synchronize the decoder 60 for the incoming data. After synchronization, the data decoder o8 decodes the I data and supplies the decoded data to the microprocessor j 70 for storage and subsequent processing. In addition, a synchronization pulse detector 240 detects the vertical and horizontal synchronization pulses in the video signal on the video input line 64 in order to facilitate the decoding of data by the decoder 60. That is, the microprocessor 70. , in response to the vertical and horizontal synchronization pulses, controls the tuneable bandpass filter 62 and the synchronization block so that the tuneable bandpass filter 62 and the sync block 66 synchronize to only the information that it is in the horizontal scanning lines in the overexploited region 204 of the video signal received in the video input line 64. Although the present invention has been described with respect to several preferred embodiments, many modifications and alterations can be made without departing of the invention. For example, instead of transmitting the sequence indicating the input together with the auxiliary code signal, as described above, the sequence initiating the input can be stored in each encoder and in each decoder. Also, the auxiliary signal can contain any type of auxiliary information. For example, the auxiliary information may be an identification code or an injection code. Moreover, the microprocessor 38 can be accommodated to control the carrier modulator 44 on the line 48 so that the coded auxiliary information is
I propagates over a frequency bandwidth that is more
Boat that information frequency bandwidth
Auxiliary previously propagated. The propagated auxiliary information can be added to the video signal so that the propagated auxiliary information is in the over-explored region
204 of the video signal. Egta auxiliary information can be disseminated by using known techniques, such as by the use of frequency hopping, by the use of direct sequence propagation codes, and the like. In addition, the present invention can be used as a monitoring and / or measurement system that is alone, or can be used in combination with signature extraction. As taught in the joint pending application with Serial No. 08 / 144,289 filed on October 27, 1993, these signatures can be used when the auxiliary signal codes are not included in the program being measured or monitored. Signature extraction is also taught in the United States of America Patent Number: 4,677,466. Additionally, the number of overexploited regions can be effectively increased by increasing the number of carrier frequencies added thereto. For example, if only one carrier frequency is used in the upper and lower subregions, there are effectively only two subregions. However, if two carrier frequencies are used in the upper and lower subregions, there are effectively four subregionsif three carrier frequencies are used in the upper and lower subregions, there are effectively six subregions, and so on. A first byte of data can then be transmitted in a field using a first carrier frequency, a second byte of data can be transmitted in the same field using a second carrier frequency, a third byte of data can be transmitted in the same field using a third carrier frequency, etc. Accordingly, it is intended that all such modifications and alterations be considered within the spirit and scope of the invention as defined in the appended claims.
Claims (51)
- CLAIMS 1. A system for transmitting data in the same communication channel as a composite video signal, where the composite video signal is transmitted in a frequency band and the composite video signal has a period of horizontal synchronization, the system comprises: a selection element for selecting a carrier having a carrier frequency within the frequency band at the start of each of a plurality of frequency stepping periods, each frequency stepping period having a duration equal to, or an integer multiple of, the horizontal synchronization period; a modulation element for modulating the information in the selected carrier to produce a modulated information signal; and., a combining element for combining the modulated information signal with the composite video signal. The system mentioned in claim 1 wherein: the selection element comprises an element for selecting a carrier having a plurality of carrier frequencies; and each of the carrier frequencies is within the frequency band and is selected at the beginning of the corresponding one of the frequency stepping periods. The system mentioned in claim 1 wherein: the composite video signal has a horizontal synchronization frequency; and, each of the carrier frequencies is substantially centered with respect to a non corresponding multiple of half the horizontal synchronization frequency. The system mentioned in claim 1 wherein the composite video signal has a frame period, and wherein each frequency stepping period is I equal to, or greater than, the frame period. The system mentioned in claim 1 wherein: the composite video signal has a horizontal synchronization frequency; the selection element comprises an element for selecting a carrier having a plurality of carrier frequencies; each one of the carrier frequencies is within the frequency band and is selected at the beginning of the corresponding of the frequency stepping periods; and, each of the carrier frequencies is substantially centered with respect to a non corresponding multiple of half the horizontal synchronization frequency. The system mentioned in claim 1 wherein the selection element comprises a control element for controlling the modulation element so that the data is transmitted only during a period of active video of the composite video signal. The system mentioned in claim 1 wherein: the composite video signal has a horizontal synchronization frequency; the selection element comprises an element for selecting a carrier having a plurality of carrier frequencies; each of the carrier frequencies is within the frequency band and is selected at the beginning of the corresponding frequency scaling periods; and, each of the carrier frequencies is substantially centered with respect to a non corresponding multiple of half the sync frequency i horizontal. 8. The system mentioned in the Avindication 6 wherein the composite video signal has a frame period, and wherein each frequency stepping period is equal to, or greater than, the frame period. 9. The system mentioned in claim 1 wherein: the information comprises a time variation code; the selection element, the modulation element, and the combining element comprise a plurality of encoders; a first encoder of the plurality of encoders combines a first segment of the time variation code with a first predetermined carrier frequency; the first segment comprises a sequence initiation input, - a second encoder of the plurality of encoders comprises a clock having a current time value as output, - the second encoder of the plurality of encoders further comprises a memory that has been stored in the same the periods of staggering frequencies, a plurality of values of the carrier frequency, and a pseudo-random sequence; and, the second encoder of the plurality of encoders reads the first segment of the code and selects, by means of "1 use of the pseudo-random sequence at the beginning of a period of frequency staggering, the values of the carrier frequency. to add ones of a plurality of hierarchical auxiliary codes to a television signal having a frequency band associated therewith, wherein each hierarchical auxiliary code comprises a time data and a place data, wherein each place data is univocally associated with one of a plurality of encoders, wherein each encoder has univocally associated therewith the corresponding one of a plurality of carrier frequencies, wherein each carrier frequency of the plurality of carrier frequencies is in the frequency band, the method comprises the steps of: a) modulate each code au:; hiar hierarchical carrier that has the corresponding of the fr carrier sequences; and, b) combining each modulated carrier frequency with the television signal. The method of claim 10, wherein each carrier frequency of the plurality of carrier frequencies is in a low energy density portion of the frequency band. 12. The method of claim 10, wherein the television signal has a horizontal synchronization frequency associated therewith, and wherein each carrier frequency of the plurality of carrier frequencies is substantially centered with respect to a multiple non of the half of the horizontal synchronization frequency. The method of claim 10, wherein the television signal comprises an active video period and an empty period, and wherein each encoder combines a corresponding modulated carrier with the television signal only during the active video period. 14. A system for transmitting information and a composite video signal in a common communication channel, wherein the composite video signal is transmitted in a frequency band, the system comprising: a selection element for selecting a plurality of carriers, wherein each carrier has a correspondingly unique carrier frequency within the frequency band, - a modulation element for redundantly modulating the information on each of the selected carriers, - combination elements for combining the carriers modulated redundantly with the signal of composite video; and, a demodulation element to demodulate the information from the redundantly modulated carriers. The system of claim 14, wherein the demodulation element comprises sum elements for summing the demodulated information from the first of the carriers redundantly modulated with the data demodulated from a second of the redundantly modulated carriers. The system of claim 14, wherein the demodulation element comprises comparison elements for comparing demodulated data from a first of the modulated carriers. redundantly with the data demodulated from a second of the redundantly modulated carriers. 17. A system to measure the tuning of television programs in a sampled census family and to monitor the broadcasting of television programs, where television programs are transmitted by means of a television signal, and where the signal of television has a bandwidth, the system comprising: an addition element for adding the first information to the television signal at a first frequency , and for adding the second information to the television signal at a second frequency, wherein the first and second frequencies are within the bandwidth of the television signal; a measuring element for measuring television tuning by detecting the first information; and, a monitoring element to monitor transmissions of television programs detecting the second information. The system of claim 17, wherein the first frequency is below a frequency of progressive attenuation of a video tape recorder, and wherein the second frequency is above the frequency of progressive attenuation of the tape recorder Of video. The system of claim 18, wherein each of the first and second frequencies is within the low energy density portion of the frequency spectrum of the television signal. The system to claim 17, wherein the television signal has a chrominance frequency, wherein the first frequency is below the chrominance frequency, and wherein the second frequency is above the chrominance frequency. 21. The system of claim 20, wherein one of the first and second frequencies is within the low energy density portion of the frequency spectrum of the television signal. 22. The system of claim 17, wherein the addition element adds a third information to the television signal at a third frequency. 23. The system of claim 22, wherein the first, second and third frequencies are within the low energy density portions of the television signal. The system of claim 23, wherein the first frequency is below a frequency of progressive attenuation of a video tape recorder, wherein the third frequency is on top of the video tape recorder but below a carrier frequency. of chrominance of the television signal and where the second frequency is above the chrominance carrier frequency of the television signal. 25. An apparatus for the non-intrusive measurement of the tuning to a television signal transmitted within a recorded census family, the apparatus comprising: a modulation element within the census family shown, to modulate an auxiliary code that varies! over time on a carrier having a carrier frequency within a video bandwidth of the transmitted television signal, a non-intrusive acquisition element adjacent to a visual display of the television signal to acquire non-intrusively the modulated carrier, - and, a demodulator element for demodulating auxiliary information that varies over time from the modulated carrier and for storing auxiliary information that varies with time for subsequent transmission to a central office. 26. A system for transmitting auxiliary information on the same communication channel as a video signal, wherein the video signal has a frequency band and an over-swept region, the system comprising: a selection element for selecting a carrier that has a carrier frequency within a low-energy density portion of the frequency band, - a modulation element for modulating the auxiliary information in the selected carrier to produce a modulated carrier; and, an addition element for adding the modulated carrier to the over-swept region of the video signal. 27. The system mentioned in claim 26, wherein: the carrier frequency is a first carrier frequency; the modulated frequency is a first modulated carrier; the selection element selects a second carrier having a second carrier frequency within the low-energy density portion of the frequency band; and, the modulator element modulates the first auxiliary information in the first carrier to produce the first modulated carrier and the second auxiliary information in the second carrier to produce a second modulated carrier. The system mentioned in claim 27, wherein: the video signal includes at least the first and second horizontal scanning lines in the over-scanned region; the first auxiliary information is at least a first bit of auxiliary information; the second auxiliary information is at least a second bit of auxiliary information; the modulation element modulates the first auxiliary information bit in the first carrier to produce the first modulated carrier and the second auxiliary information bit in the second carrier to produce the second modulated carrier; the addition element adds the first modulated carrier to the video signal so that the first auxiliary information bit is on the first horizontal scan line; and, the addition element adds the second modulated carrier to the video signal so that the second auxiliary information bit is on the second horizontal scan line. 29. The system mentioned in claim 26, wherein: the video signal includes at least the first and second horizontal scanning lines in the over-scanned region; the addition element adds the modulated carrier to the video signal so that the first horizontal scanning line of the video signal carries a single bit of auxiliary information; and, the addition element adds the modulated carrier to the video signal so that the second horizontal scanning line of the video signal carries a single bit of auxiliary information. 30. The system mentioned in claim 1U > , where: the video signal includes eight horizontal scanning lines in the over-explored region; and, the eD, adding element adds the modulated carrier to the video signal so that each of the eight horizontal scanning lines of the video signal carries a single corresponding information bit. The system mentioned in claim 26, wherein: the video signal has a horizontal synchronization period; the selection element selects the carrier having a carrier frequency within the frequency band at the beginning of each of a plurality of staggered periods; and, each stepped frequency period has a duration equal to, or an integral multiple of, the horizontal synchronization period. 32. The system mentioned in claim 31, wherein: the selection element comprises an element for selecting a carrier having a plurality of carrier frequencies; and, each of the carrier frequencies is within the frequency band and is selected at the beginning of the corresponding of the frequency stepping periods. 33. The system mentioned in claim 32, wherein: the video signal has a horizontal synchronization frequency; and 34. The system mentioned in claim 31, wherein the video signal has a frame period, and wherein each frequency stepping period is equal to, or greater than, the frame period. 35. The system mentioned in claim 34, wherein: the video signal has a frequency of I horizontal synchronization; 'the selection element comprises a selection element a carrier having a plurality of carrier frequencies; each of the carrier frequencies is within the frequency band and is selected at the beginning of a corresponding one of the frequency stepping periods; and, each of the carrier frequencies is substantially centered around the corresponding multiple non of half the horizontal synchronization frequency. 36. The system mentioned in claim 31, wherein: the auxiliary information includes a code that varies in time; the selection element, the modulator element, and the addition element comprise a plurality of encoders; a first encoder of the plurality of encoders adds a first segment of the time variation code having a first carrier frequency previously determined; the first segment comprises a sequence initiation entry; a second encoder of the plurality of encoders comprises a clock having a current time value as an output; the second encoder of the plurality of encoders reads the first segment of the code and selects, by using the pseudo-random sequence at the beginning of a stepped frequency period, the values of the carrier frequency. 37. The system mentioned in claim 26, wherein: the selection element selects a plurality of carriers; each carrier has an exclusive carrier frequency within the frequency band, - the modulator element redundantly modulates the auxiliary information in each of the selected carriers i; the addition element adds the redundantly modulated carriers to the video signal; and, the system further comprises a demodulator element for demodulating the auxiliary information of the redundantly modulated carriers. 38. The system mentioned in claim 37, wherein the demodulator element comprises summing elements for adding the auxiliary information demodulated from a first one of the carriers modulated and redundantly with the auxiliary information demodulated from a second of the carriers. modulated redundantly. 39. The seventh mentioned in claim 37, wherein the demodulator element comprises comparison element for comparing the demodulated auxiliary information from a first of the modulative carriers redundantly with the auxiliary information demodulated from a second one. of the redundantly modulated carriers. 40. The system mentioned in claim 26, wherein: the system is a measurement and monitoring system for measuring the tuning of television programs in a sampled census family and for monitoring the broadcasting of television programs; the television programs are transmitted by means of the video signal, - the carrier is a first carrier; the carrier frequency is a first carrier frequency; the selection element selects a second carrier having a second carrier frequency within the low energy density portion of the frequency band; the modulator element modulates the first auxiliary information in the first carrier and modulates the second auxiliary information in the second carrier, - the first and second carrier frequencies are within the frequency band of the video signal, - the seventh measurement and monitoring it also includes a measuring element to measure the tuning of the television by detecting the first auxiliary information; and, the seventh measurement and monitoring also includes a monitoring element to monitor the broadcast of the television programs by detecting the second auxiliary information. 41. The system mentioned in claim 40, wherein: the first carrier frequency is below the progressive attenuation frequency of a video tape recorder; and, the second carrier frequency is above the frequency of progressive attenuation of a tape recorder of; ideo. 42. The system mentioned in claim 40, wherein: the first carrier frequency includes a first group of carrier frequencies; the second carrier frequency includes a second group of carrier frequencies; the first group of carrier frequencies is below a frequency of progressive attenuation of a video tape recorder, and, the second group of carrier frequencies is above a frequency of progressive attenuation of the video tape recorder. 43. The seventh mentioned in claim 40, wherein the video signal has a chrominance subcarrier frequency, wherein the first carrier frequency is below the chrominance subcarrier frequency, and in? where the second carrier frequency is above the chrominance subcarrier frequency. 44. The system mentioned in claim 40, wherein: the selection element selects a third carrier having a third carrier frequency within the low-energy density portion of the frequency band; and, the modulation element modulates a third auxiliary information in the third carrier. 45. The system mentioned in claim 44, wherein: the first carrier frequency is below the progressive attenuation frequency of a video tape recorder; the second carrier frequency is above the progressive attenuation frequency of a video tape recorder, but below a chrominance subcarrier frequency of the video signal; and, the third carrier frequency is above the chrominance subcarrier frequency of the video signal. 46. The seventh mentioned in claim 44, wherein: the first carrier frequency includes a first group of carrier frequencies, - the second carrier frequency includes a second group of carrier frequencies; the third carrier frequency includes a third group of carrier frequencies; the first group of carrier frequencies is below the progressive attenuation frequency of a video tape recorder, - the second group of carrier frequencies is above the frequency of progressive attenuation of a , video tape recorder, but below a frequency and subcarrier of chrominance of the video signal; and, the third group of carrier frequencies is above the chrominance subcarrier frequency of the video signal. 47. The system mentioned in claim 26, wherein: the auxiliary information includes a code that varies in time, - the modulation element is placed within a sampled census family and modulates the auxiliary code that varies over time in the carrier, - the seventh further includes a non-intrusive acquisition element adjacent to a visual display of the video signal for non-intrusively acquiring the modulated carrier; and, the seventh additionally includes an element of the modulator to demodulate the auxiliary information that varies over time from the modulated carrier. 48. The system mentioned in claim 26, wherein the addition element modulates the auxiliary information in the selected carrier so that the auxiliary information is confined to an over-scanned region in a corner of the video signal. 49. A system for transmitting auxiliary information on the same communication channel as a video signal, wherein the video signal has an over-exploded region, and wherein the auxiliary information has a first frequency bandwidth, the seventh comprises: an auxiliary information broadcasting element for broadcasting the auxiliary information on a second frequency bandwidth, wherein the second frequency bandwidth is wider than the first frequency width, - y, i the addition element for add the auxiliary information diffused to the over-explored region of the 1 video signal. 50. The system mentioned in claim 49, wherein the addition element includes: an element, modulating to modulate the auxiliary information in a carrier, wherein the carrier has a carrier frequency selected so as not to interfere with the subcarrier frequency of chrominance and the luminance carrier frequency of the video signal; and, an insertion element for inserting the modulated carrier into the video signal. 51. The seventh mentioned in claim 49, wherein: the overexplored region comprises n over-explored regions; n is an integer; and, n is effectively increased by a number of carrier frequencies added to the unexplored regions.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/395,789 US5737025A (en) | 1995-02-28 | 1995-02-28 | Co-channel transmission of program signals and ancillary signals |
| US08395789 | 1995-02-28 | ||
| US08/482,820 US5737026A (en) | 1995-02-28 | 1995-06-07 | Video and data co-channel communication system |
| US08482820 | 1995-06-07 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| MX9706586A MX9706586A (en) | 1998-06-28 |
| MXPA97006586A true MXPA97006586A (en) | 1998-10-30 |
Family
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