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United States Patent [w]
Bourcet et al.
US006151578A [ii] Patent Number: 6,151,578  Date of Patent: Nov. 21,2000
 SYSTEM FOR BROADCAST OF DATA IN AN AUDIO SIGNAL BY SUBSTITUTION OF IMPERCEPTIBLE AUDIO BAND WITH DATA
 Inventors: Patrice Bourcet, Mey; Denis Masse, Rosselange; Bruno Jahan, Montigny les Metz, all ol France
 Assignee: Telediffusion de France, Paris, France  Appl. No.: 08/952,998  PCT Filed: Jun. 3, 1996  PCT No.: PCT/FR96/00833
§ 371 Date: Nov. 21, 1997
§ 102(e) Date: Nov. 21, 1997  PCT Pub. No.: W096/38927
PCT Pub. Date: Dec. 5, 1996
 Foreign Application Priority Data
Jun. 2, 1995 [FR] France 95 06727
 Int. C I. II04II 9 00
 U.S. CI 704/500; 380/253
 Field of Search 704/501, 229,
704/230, 500; 370/214; 380/253; 455/2
 References Cited
U.S. PATENT DOCUMENTS
5,319,735 6/1994 Prass et al 704/205
A system for broadcasting data (D) that can transmit information in the passband ol a broadcast audio-frequency signal (S). The system can determine at least one frequency band (F'13, . . . , F'24) and the amplitude (A'13, . . . , A'24) ol the audio-frequency signal (S). The system compares this amplitude with an auditory masking level (Nm(13), . . . , Nm(24)) associated with this frequency band and eliminates the frequency components ol the audio-frequency signal in the frequency band il the amplitude ol the signal is lower than the auditory masking level ol the band. The system can insert the data in this frequency band at a level lower than or equal to the auditory masking level ol the frequency band.
8 Claims, 2 Drawing Sheets
SYSTEM FOR BROADCAST OF DATA IN AN
AUDIO SIGNAL BY SUBSTITUTION OF IMPERCEPTIBLE AUDIO BAND WITH DATA
BACKGROUND OF THE INVENTION 5
1. Field of the Invention
The invention concerns the signal broadcasting field for signals including an audio-frequency component. More especially, it concerns a data broadcasting system. 10
2. Description of the Related Art
The broadcasting field (broadcasting of TV or radio programmes, radiotelephony, etc.) is well known.
A current tendency is to transmit, in addition to the programmes (or sound in the telephony field), data useful for 15 the broadcasting companies, for control organisations, or for listeners or viewers. This data can concern for example: help in selecting a radio or TV programme (example: automatic tuning aids, search for a radio station by 2Q name, search by type of programme, search by menu, etc.),
information on the programme being broadcast or replayed after recording (for example the name of the company which created a programme, the title of a film 25 broadcast by a TV channel, the record reference of a song broadcast by a radio station, etc.),
service data in the analogue radiotelephone field.
We also remark the development of so-called interactive broadcasting systems which allow the viewers or listeners to 30 dialogue in a more or less efficient manner with the programme source. These means are used either to act on the content of the broadcast programme, or to play, bet or communicate on the subject of this same programme. Thus, a form of interactivity, via small devices simulating 35 pseudodialogue with a programme designed for this purpose, recently appeared. A remote-sized unit gives the illusion of interactivity as it allows, for instance, to reply to a televised question/reply game as and when the questions are asked. Or again, an electronic device dissimulated in a 40 fluffy toy allows the toy to react to a broadcast programme or a programme played back on a video cassette recorder. In fact, the interactivity is not real as the string of good replies or the reactions of the toy follows preestablished sequences, common to the memory of the interactive device and the 45 broadcast or played back programme. As the audiovisual sequence was prerecorded in accordance with a selected code, its execution is predictable and therefore the only information to be transmitted to the interactive device is the start signal and the exact timing of the questions/replies or 50 the various possible reactions in the case of a toy.
There is also a demand for the automatic identification of a sound sequence, accompanied by an image or not. For the broadcasters, this is used to check that a given programme is correctly broadcast on the frequency allocated to it; this 55 can become fairly complex when a national programme is affected by regional or local disconnectings. This also allows the controlling bodies to count the broadcasting of works protected by copyrights or to check the conformity of the broadcasting of commercials. Finally, for sample survey or 60 audience evaluation organisations, it is used to rapidly identify that which is actually listened to or seen by a listener or a viewer. Today, to assess a radio audience, the only solution available is to conduct a sample survey by interviewing the consumers. 65
All these applications are easy to incorporate when designing new radio or TV broadcasting systems, especially
digital systems. However, existing systems and equipment populations do not in general easily lend themselves well to this development and experience proves that, from a sales engineering viewpoint, the compatibility and the relative cost of the processes and devices to be implemented are critical factors when introducing a new service.
For the transmission of data concerning a broadcast programme, two techniques are currently used.
The first technique consists in transmitting these data outside of the passband occupied by the signal of the transmitted programme (sound and possibly image). A solution exists, for instance, in sound broadcasting by multiplex frequency modulation, in using the upper part of the multiplex, between 54 and 76 kilohertz. Another example consists in using the lines available during frame retrace for TV broadcasting. These techniques have drawbacks. The saturation of the frequency resources available for broadcasting limits the number of users of these resources. Also, receivers adapted to the passbands used to transmit the emitted information are required.
Another technique consists in transmitting the data in the passband of the signal of the transmitted programme; this technique does not require the use of dedicated frequency bands. It is therefore not necessary to use transmitters and receivers with a frequency adapted to transmit these dedicated frequency bands. Typically, the original signal (corresponding to the programme to be transmitted) is filtered at origin to eliminate the frequency components in a given frequency band and the data is inserted in this band. The original signal is therefore deformed which may be unpleasant for a viewer or a listener not interested in the data. Therefore, the time dedicated to transmitting the information is limited by the broadcasters to the strict minimum which reduces the data flow rate accordingly. Thus, for interactive devices in the television field, the data is loaded globally, in one go, at the start of a given application. It is then impossible to adapt the data subsequent to a modification in the programme which must be run according to scheduled timing and without unexpected interruptions. Filtering means can of course be used at the receivers so as not to systematically pass on the sound or visual data received, this data then being transparent to the listener or the viewer. Nevertheless, we cannot ensure that the signal seen or heard by the viewer or listener will be the same as the original signal that he would have perceived before the insertion of the data.
OBJECTS AND SUMMARY OF THE
In view of the above, the purpose of the invention is to propose a system to allow transmission of data in the passband of a signal including an audio-frequency component, without modifying, in relation to the original audio-frequency signal, the signal perceived by the listener. The invention proposes to insert these data in the so-called masked frequency bands of the original audio-frequency signal, if these bands exist, that is at a level lower than the instantaneous auditory threshold due to the auditory masking phenomena induced by the original audio-frequency signal itself. The data transmitted are then inaudible, do not alter the original audio-frequency signal from a subjective viewpoint and do not require the use of frequency components located outside of the spectral band occupied by the original signal. The invention therefore proposes data transmission adapted to the use of existing receivers and transmitters and subjectively not disturbing for the listener.
The invention thus concerns a data broadcasting system, this information being transmitted in the passband of a