FR2780228A1 - Unit for transmitting audio and video information between a broadcast center and an audio-video terminal, used in interactive TV - Google Patents

Abstract

The transmitted information includes a supplementary signal characteristic of a transmission channel, and/or a content of this channel, this supplementary signal being transmitted by the audio band of a television signal. It identifies the channel and its contents e.g. whether it is a television series. An injector inserts this signature signal which is then transformed into an audio analog signal for compatibility with PAL, NTSC etc., by a modulator. A decoder receives this signal and identifies the coded content accordingly. A return channel is used to exploit the received supplementary signal, to provide interactivity using a modem for various applications such as telephone-sales etc

Description

-1

  INFORMATION TRANSMISSION DEVICE

AUDIO AND VIDEO

  The present invention relates to a device for transmitting information between a data center

  broadcast and an audio-video terminal.

  More particularly, the invention relates to a device for identifying a television channel and / or its content, for example any program of any television channel, activated on an audio-video terminal, for example a television. No human intervention is needed to identify

the channel and / or its contents.

  The channel and its contents can indifferently be transmitted to the audio-video terminal in an analog or digital mode, by using terrestrial transmission means, for example a cable network or

  a terrestrial link, or by satellite.

  There are different standards for video broadcasting and broadcasting: - PAL, NTSC and SECAM standards are analogue television standards; - the D2-MAC standard is a digital television standard. The screen of a television set consists of several lines of pixels, which are the elementary luminous points of a screen. The electrical signal carrying a video information is structured in time: each line of the screen corresponds to an electrical signal of a determined duration. The electrical signal is most often carrying luminance and chrominance information that defines each pixel of the line. The electrical signal can also convey information signifying the end of a line, synchronization information for the different lines and frames that constitute the image ... However, during a video transmission, certain electrical signals of the video signal are not intended for the transmission of the image as such. They do not

  not necessarily useful information.

  Some electrical signals allow for example the "return frame". In addition, if the primary purpose of television systems is to transmit an image associated with sound, additional services are now also made available to viewers. For example, the Antiope system allows hearing-impaired people to access subtitling for certain television programs. For this purpose,

  certain electrical signals of the video signal,

  carriers of information intended for the definition of the image are dedicated to the transmission of the data of the Antiope system. Other services, eg teletext applications are also available

on some TVs.

  However, the use of the video signal for the transmission of new information is expensive and complicated. Indeed, such a transmission requires the establishment of a system for modulation, demodulation and decoding of the new information or the new type of information to be transmitted. The decoder used for the reception of information transmitted by the video signals is complex because of the quantity

  information to be processed. It is therefore expensive.

  In order to overcome these drawbacks, the invention proposes a device for transmitting audio and video information according to the following operation: an additional signal, called a signature signal, characteristic of a particular channel and / or of a particular transmission is transmitted by the audio band of the television signals. Thus made possible, the identification of channels and / or their content may, according to particular applications of the invention,

  offer multiple services to viewers.

  This identification can be done

  automatically by the device according to the invention.

  The device according to the invention comprises two

  main parts: an injector and a decoder.

  The injector is the part of the electronic device that injects a signature signal characteristic of a channel and / or the content of this channel. In order to be compatible with all the different standards of broadcast and audio broadcasting, (analog or digital and monaural or stereo) and video (PAL NTSC SECAM ...), the signature signal is transformed into an analog audio signal by means of a modulator converter. The signature signal is added after transformation to the audio band of the concerned channel. The decoder is the part of the device that receives and decodes the received signal. Each channel and / or each content of a channel can thus be identified in a simple and unique way by means of this signature signal. For a channel and / or the content of any channel, the signature signal may be different depending on whether the broadcast is performed in digital mode by a terrestrial or satellite means or in analog mode. Given the choice to use the audio band of any channel, the signal resulting from the encoding of the signature signal, which is embedded in the audio tape, is coded so as not to provide

hearing impairment.

  The acoustic constraints to be applied to the coding of the signature signal in order to transform it into a sound signal are as follows: The central part of the auricle and the external auditory canal have a resonance frequency around 2.5 kHZ, and the part The center of the auricular horn alone has a resonant frequency around 5.5 kHZ. Any frequency transmission between 2 and 7 kHZ occurs with a gain of 10 to 20 decibels compared to the extreme frequencies, that is to say less than 0.5 kHZ and greater than 10 kHZ. Thus, the sounds emitted above 10 kHZ require a physical level expressed in pascal 14 times higher to create the same physiological level expressed in a phone. The frequency band 10 kHz and 15 kHz is therefore naturally preferred for the transmission of the signal

signature.

  Moreover, the study of sounds and sounds of short duration called "click", shows that the subjective intensity of their perception depends on their duration. In fact, the subjective intensity is first and foremost an increasing function of time up to a maximum value. Then the subjective intensity decreases slowly. The maximum

  is of a duration close to 0.2 seconds.

  In addition, you should know that the hearing of certain sounds is masked by ambient noise. This phenomenon, called "mask effect", has the following characteristics: The mask effect is maximum for the frequencies close to the masking sound. High frequencies are the most disturbed by this masking effect. The mask effect grows faster than the level of masking sounds. Also in response to these acoustic comfort constraints, the signature signal has the following properties: The resulting sound signal is emitted periodically several times per minute at a variable frequency so as to avoid any remanence phenomenon. The maximum repetition frequency depends on the length of the signature signal. The minimum frequency of the signature signal may vary depending on the external constraints that depend on the use and operation of the signature signal. The invention therefore relates to a device for transmitting audio and video information in analog or digital form in a wired or wireless manner

  between a broadcast center and an audio terminal

  video, characterized in that the transmitted information contains an additional signal characteristic of a transmission channel and / or a content of this transmission channel, the additional signal being combined with the audio information

initially transmitted.

  In the rest of the description, the signal

  additional is designated as a signal of

signature.

  In addition, the signature signal is reliably detected by a decoder, even in a large noise environment. The spectrum of the encoded signature signal must be contained in the audio frequency band. The sound signal resulting from a modulation of the signature signal in the soundtrack shall not create an audible gene. Finally, the coding of the signature signal must be compatible with the various modulations that may occur. The coding of the signature signal must also be compatible with the existing sound qualities (right and left channel) in stereo-phonic transmission, monophonic channel, hi-fi sound. Finally, the coding of the signature signal must not be disturbed by pre-distortions resulting from quantification noises for the digital signals, as well as pre-accentuations of the signal.

  made of a DOLBY encoding type sound encoding.

  The different aspects and advantages of the invention

  will appear in the following description in

  reference to figures which are given only

  indicative and not limiting of the invention.

  The figures show: FIG. 1 shows an exemplary embodiment of an information transmission device according to the invention of a broadcast center and an audio-video terminal; FIG. 2 shows the structure of a signal of

signature according to the invention.

  FIG. 3 is a timing diagram illustrating an exemplary coding of the signature signal according to the invention. - Figure 4 is a block diagram of the injector involved in the transmission system according to the invention. FIG. 5 is a block diagram of the injector intervening in the transmission system according to the invention. FIG. 1 represents a preferred embodiment of an information transmission system

according to the invention.

  A television 100 receives, via a first antenna 102, information in the form of radio signals 104. The radio signals 104 are derived from a second

  antenna 106 of a broadcast center 108.

  A signature signal 110 is generated by a signature signal generation system 112. The signature signals 112 are converted into analog audio signals 113 by means of a converter / modulator 122. The converter / modulator 122 associated with the signature generation system constitutes an injector 115. The broadcasting center 108 diffuses signals which are the combination of a conventional television signal and signature signals 112 transformed into signals

analog audio.

  A decoder 114 makes it possible to identify the signature signal 112 received by the television set 100. A video recorder 116, which can also be controlled by the decoder 114, can also be used in an exemplary embodiment of a transmission device according to FIG. invention. The signature signals 112, once decoded by the decoder 114, may possibly be retransmitted by any feedback channel 118. A reception unit 120 of the re-transmitted signatures allows authentication of the channels and / or

  contents of the displayed channels.

  The embodiment of the transmission device as described in Figure 1 is only one particular example among the possible embodiments of the invention. Indeed, the transmission of information between the broadcast center 108 and the television 100 can also be performed via cables or satellites. In addition, the mode of transmission of the signals can be an analog mode

or a digital mode.

  The signature generation system 112 transmits signature signals 110 that are specific to a television channel and / or the content of that television channel. The content of the channel may be a television program or a type of television program. The signature signals are compatible with all the different standards of broadcast and broadcast analog or digital audio and monaural or stereo. On the other hand, the signature signals do not disturb video signals either, regardless of the broadcast and transmission standards. The signature signals are compatible with the set

different video standards.

  The signature signal may also include a different characteristic depending on whether the broadcast is performed in digital mode by a terrestrial means or

  well satellite, or in analog mode.

  The signature signal is a short message. FIG. 2 shows an exemplary structure of a signature signal according to the invention. The signature signal is in a preferred application consisting of a succession of bits constituting a bit stream. The bitstream is composed of a synchronization header 200 of a few bits, a message

  useful 202 of several bits and integrity bits 204.

  The integrity bits 204 serve to verify that the transmission of the signature signal is carried out without

fault.

  In a preferred example of the invention such as that shown in Figure 2, the synchronization header 200 has 32 bits; the useful message 202 which allows the identification of a channel and / or the content of this channel comprises 48 bits. Finally, the bits

  of integrity 204 are 16 in number.

  The integrity bits 204 of a signature signal are determined, according to a known method, by performing a polynomial division of the useful message 202 to be transmitted from 48 bits by a polynomial P (x) whose

  the expression is P (x) = x16 + x12 + x5 + 1.

  The coding of the bit stream which constitutes the signature signal is, in a preferred application of the invention, a differential coding of the phase e of a carrier frequency Fp. The carrier frequency Fp makes it possible to transmit a succession of messages

coded elementary bits.

  An elementary bit message consists of two bits. There are thus four possible elementary bit messages: 01, 10, 11, and 00. Each elementary bit message is characterized by the duration of the signal of the carrier frequency Fp between two phase changes. In an example proposed in Table 1 below, the binary message 01 is coded by a phase difference equal to f after a time

  equivalent to two elementary time units.

  The elementary time unit may for example be the period of the carrier frequency Fp. Table 1 shows an example of correspondence between the elementary bit message to be transmitted and the duration of the signal of the carrier frequency Fp between two changes of

  phase 4 of the carrier frequency Fp.

Table 1

  Information Value of the phase Duration of the signal between bits to be transmitted before after 2 phase changes 01 if 4> + r 2 idem 4 11 idem 6 00 idem 8 Figure 3 shows an example of coding of the signature signal according to the invention. The carrier frequency

  Fp is assigned a differential phase coding.

  The abscissa of the curve having the carrier frequency Fp carries a time scale. Seven time intervals 300, 302, 304, 306, 308, 310 and 312 are shown. The time interval 300 is

  equivalent to 4 periods of the carrier frequency Fp.

  According to the correspondences presented in table 1, it is the elementary bit message "10" which is here coded. The time intervals 302, 304, 306, 308 and 310 are equivalent to 2 periods of the carrier frequency Fp. It is therefore the elementary bit message "01" which is each time coded. The time interval 312, which is equivalent to 6 periods of the carrier frequency Fp, codes according to the example shown in Table 1 the elementary bit message "11". A phase shift of 7T is observable at the end of each of the time intervals 300, 302, 304, 306, 308, 310 and 312, in agreement with the

  differential coding principle previously described.

  FIG. 4 is a block diagram of the decoder 114 involved in the transmission device according to the invention. The decoder is the device that receives the channel displayed by the terminal. The block diagram of Figure 4 consists of 4 main blocks

  respectively 400, 402, 404 and 406.

  the first block 400 constitutes the reception block for the sound signals, the second block 402 constitutes the extraction block of various signals, the third block 404 constitutes a block for decoding and extraction of the signature signals; fourth block 406 constitutes a logical block of interpretation for a possible exploitation of

signature signals.

  The decoder 114 receives from the first block 400 the audio signals from the television, for example by means of pins of a SCART connector or a scart socket available on the television. A filter 408 filters the received audio signal so as to extract from the soundtrack received by the reception block 400 a filtered audio signal 409 located in a predetermined frequency band. In order to best meet the criteria of no hearing impairment, the 10 kHz - 15 kHz frequency band is preferred for

  transmit the signature signals.

  The filtered audio signal 409 is transmitted to the second block 402. In the extraction block 402, the filtered audio signal 409 is compared in a logic circuit 413 to the signal of a voltage controlled local oscillator 410. The phase difference between the output of the local oscillator 410 and the filtered audio signal 409 gives an error signal 411. The error signal 411 is used to adjust by means of a feedback circuit 412 the phase of the local oscillator 410. The phase and the frequency of the local oscillator 410 are thus

  enslaved by the frequency of the filtered audio signal 409.

  Once the error signal is close to 0, the local oscillator 410 is said to be "hooked" by the filtered audio signal 409. The local oscillator 410 is then locked. The logic circuit 413 then transmits to the decoding block 404 a coherent signal 415 carrying phase variation information encoding the signal.

signature.

  The role of the synchronization header 200 which precedes the start of the useful message 202 of the signature signal is to enable the local oscillator 410 to be servocontrolled and locked. The synchronization header therefore does not include information to identify a transmission channel and / or its contents. This phase-locked device makes it possible to extract from the filtered audio signal 409 received the phase variation information, which identifies the

  receiving an elementary bit message.

  In the decoding block 404, a clock H delivers a clock signal Hs which arrives at the input of a clock pulse counter 414. The clock pulse counter 414 receives at a second input the coherent signal 415 carrying information from

  phase variation encoding the signature signal.

  When a phase variation is detected, the pulse counter of the clock signal 414 counts the number of pulses of the received clock signal Hs to the next phase change. The output of the clock pulse counter 414 is connected to an internal decoder 416 operating with a PROM 418 (acronym for "Programmable Road Only Memory"). This decoder makes it possible to establish the pre-established correspondence between the duration of the phase variation expressed in pulses.

  clock Hs, and the corresponding binary information.

  An example of these correspondences was previously

given in Table 1.

  When the counter 414 does not detect phase variations after 30 clock pulses, the counter 414 then commands in the logic block 406 a controller 420 which terminates, by a signal transmitted on a link 419 connecting it to the local oscillator 410, servocontrolling the local oscillator 410 and locking its phase. The automaton 420 also signals, by a signal transmitted on a link 421, the receipt of a message to a microprocessor 422. The microprocessor 422 controls an automaton 424 for checking the coherence of the received message. The automaton 424 is connected to the internal decoder 416. The coherence verification automaton 424 of the received message can thus verify whether the bit stream of the received signature signal is correct by means of the integrity bits 204. Integral bits 204, the decoding is not coherent, then the message is rejected and the decoder 114 is again waiting for carrier detection. If the coding is coherent, then the signature signal is processed and exploited: It may be, in certain applications of the invention retransmitted, for example by means of a modem

426 connected to the decoder 414.

  FIG. 5 shows a block diagram of the injector intervening in the transmission system according to the invention. The injector 115 is the device that codes and

  introduces the signature signal into the sound channel.

  The block diagram of the injector can be divided into

  three separate blocks 500, 502 and 504.

  The first block 500 is a logical unit for selecting coding and adding headers of

  synchronization and calculation of integrity bits 204.

  The useful message 202 is determined by the channel

  transmitter and / or the contents of this channel.

  The second block 502 contains the elements necessary for converting the bit stream into phase variation on the carrier frequency Fp. A

  sinusoidal converter is necessary.

  The third block 504 contains the elements necessary for the injection of the signature signal into

the audio tape.

  The electrical level of the signature signal can be adjusted with respect to the level of the signal present in the soundtrack by an amplification device

  counter-reaction present in block 304.

  Before the injection of the signature signal into the audio band accompanying the image, the energy level of the signal present in the audio band is measured after a filtering which passes only the frequency band capable of transmitting the signature signal. (typically the frequency band 10 kHz and kHz). This energy level then controls the emission level of the signature signal so that the ratio of the voluntarily transmitted signal with respect to the noise level is 2. The ratio

  Useful signal / noise is then 3 decibels.

  By way of a numerical example, with a 96-bit signature signal such as that presented in FIG. 2 and with a modulator converter having an average transmission capacity of 3129 bits per second, the total duration of the transmission of a sound signal resulting from the emission of a signature signal is close to 0.03 seconds. This choice is thus compatible with the criteria of non-auditory genes

previously stated.

  Multiple particular applications of the invention may provide various services to viewers. The transmission device according to the invention can be, as has been described

  previously, used with or without a return path.

  Firstly, if we consider the case of a transmission device according to the invention without return path, the decoder can for example determine when a program must be recorded by a VCR. For this, it is sufficient that the emitted signature signal includes the necessary information: part of the useful message of the signature signal can be reserved for the identification of the channel. Another part of this useful signal can characterize a type of emission, for example a film. A third part of the useful message may indicate the beginning of the film, another the end of the film ... The decoder can trigger the recording of the coveted film from the beginning of the film with a particular signature signal issued and recognized by the decoder. Commercials that sometimes cut the film may not be recorded in the same way. All these operations can be

  managed by the microprocessor 422 of the decoder.

  Another example of application of a transmission device according to the invention without a return path is the protection of children facing certain types of transmission: it is sufficient that the useful message of the signature signal includes information relating to a program not suitable for children so that the decoder acts on the television, for example by changing

channel.

  Another example of application of a transmission device according to the invention without a return path is the dissemination of information of an advertising nature and / or commercial or not incrustation on the display screen, such as weather information , bursaries, lotto results or other games, or the beginning of a movie on a competing channel or not. The useful message of the signature signal includes information which, interpreted by the internal decoder 416 and the microprocessor 422, causes the display of appropriate characters by means of display functions previously integrated in the

decoder 114.

  Numerous examples of applications of the transmission device according to the invention with a

  return can also be considered.

  A return channel, dedicated to the operation of the received signature signal, may be a modem connected to the decoder of the device according to the invention and connected to any communication network, for example a telephone network. Another way back can be

  the television antenna itself.

  A transmission device, according to the invention, associated with a return path, can make it possible to develop many applications: games, teleshopping, instantaneous audience ... The decoder can also be associated with an authentication device, a card to chip for example, and a

keyboard or a joystick.

  Messaging services can be set up via a television made more interactive by the transmission device according to

the invention.

Claims (8)

R E V E N D I C A T IO N S   1. Device for transmitting audio and video information in analog or digital form in a wired or wireless manner between a broadcast center (108) and an audio-video terminal (100), characterized in that the transmitted information contains an additional signal characteristic of a transmission channel and / or a content of this transmission channel, the additional signal being combined   to the audio information originally transmitted.   2. Transmission device according to claim 1, characterized in that it comprises a   injector (115) and a decoder (114).   3. Transmission device according to one   any of the preceding claims characterized   in that it comprises a return path (118) dedicated to   the exploitation of the additional signal received.   4. Device according to claim 3 characterized in that the return path (118) consists of a   modem associated with any communication network.   5. Transmission device according to one   any of the preceding claims characterized   in that the additional signal is transmitted in a frequency band of 10 Khz to 15 Khz in such a way that   periodic at a variable frequency.   6. Transmission device according to one   any of the preceding claims characterized   in that the additional signal is a succession of bits composed of a synchronization header (200),   a useful message (202) and integrity bits (204).   7 Transmission device according to one of the   Claims 2 to 6, characterized in that the decoder   (114) is associated with an authentication device.   8. Transmission device according to one of   preceding claims characterized in that the   additional signal is coded by a coding   phase differential of a carrier frequency (Fp).