WO2000060779A1

WO2000060779A1 - Method for encoding/decoding an analog television signal broadcast on a cable network enabling identification of the channel by a receiver for audience measurement

Info

Publication number: WO2000060779A1
Application number: PCT/FR2000/000811
Authority: WO
Inventors: Antoine Laures
Original assignee: Mediametrie Cabsat (Societe Anonyme)
Priority date: 1999-04-02
Filing date: 2000-03-31
Publication date: 2000-10-12
Also published as: AU3663600A; FR2791847B1; FR2791847A1; EP1166478A1

Abstract

With regard to the installations of a cabled flagship station, the inventive method comprises implementation of the following steps: a) a digital television program, i.e. a program broadcast by satellite, is received; b) the digital identifiers of the channel of said program are extracted and corresponding digital data forming the channel identifier is produced: c) the digital program is transcoded into an analog video signal; d) a digital data message comprising said channel identifier is inserted into a free line of the image signal of the video signal after transcoding; and e) the resulting analog video signal is broadcast on a cable network. The data message can also comprise: an identifier of the frequency of the carrier transporting the digital program; an identifier of the network transporting the digital program; an identifier of the program package to which the digital program belongs; and/or an identifier of the cable network broadcasting the analog video signal. In the television set, the information content of successive lines of the video signal thus received is analyzed in order to distinguish an image signal and the data identifying the chain which is associated with said image signal and which had been inserted in the flagship station into a free line of the image signal, whereby said data is utilized when the image signal is delivered onto the screen.

Description

Method for coding / decoding an analog television signal broadcast on a cable network, to allow the identification of the channel by the receiver, in particular for audimetry purposes

The present invention relates to the identification of television program channels received by a television set or a device (such as a video recorder) associated with the latter, in the case where a television signal available in digital format is transcoded to analog before replay on a domestic or public cable network.

In the following, the term “program” will be understood to mean the medium conveying the image and the sound and the term “chain” the entity which produced the content of what is conveyed by the program. The identification of a program chain is particularly useful in the field of audimetry, that is to say audience measurement. In fact, it is essential to be able to identify at any time, for statistical purposes, which channel corresponds to the program watched (or recorded) at a given time by the viewer in front of his television. This application to audimetry is not however limiting, and it will be understood that the invention may be used for other purposes, for example for viewing or storing (for example during recording) of an identifier of the channel watched at a given time, or even for the management or technical remote management of television networks using cable as a broadcasting medium.

It is known in particular to use the frame return lines, which are free of image signal, to broadcast digital data such as teletext information or service information which may in particular include a channel identifier, as provided for by various national and international standards such as Didon, Ceefax, VPS or PDC.

This service information can be detected on the television, for example by a method as described in EP-A-0 830 028 (Médiamétrie). This technique obviously assumes that all programs likely to be received by the television include such a channel identifier and, on the other hand, that this identifier is always coded in the same way, that is to say according to the same standard, from one program to the 'other. This condition is generally fulfilled in the case of analog programs broadcast over the air, directly received by the television.

On the other hand, when the television receives the programs via a cable network, the identification of the program raises a certain number of new problems. In fact, due to the very large number of programs broadcast on the same cable network, these come from very different sources. Certain programs are, or can be, a simple cable routing of radio signals locally received by the headend; in this case, if the original radio signal includes a channel identifier data, this will generally be present on the signal rebroadcast by the cable network.

However, this is not always the case. Indeed, the head end can apply to the received radio signal a transcoding, for example a color transcoding from PAL to SECAM, and this transcoding can cause the loss of the service information. Or the service information of the received signal is in a standard (for example VPS or PDC coding, on German or Italian programs, respectively) of a different type from that of the service information of the programs received and rebroadcast as such by the network (Didon coding on a French program).

More importantly, headend facilities are now increasingly receiving digital satellite programs for rebroadcast in analog on the cable network. However, a digital television signal does not include frame return lines; it only contains the video information of the image signal (approximately 560 lines in DVB 50 Hz), of the digitized sound, and a certain number of data.

These digital data of the television program, when they are PDC or Ceefax standard, certainly include a channel identifier data. But this data is often lost during the conversion of digital to analog.

Thus, if we consider the various programs broadcast in analog by a cable network, these can form a heterogeneous whole comprising, on the one hand, main programs received on a neighboring wireless network and rebroadcast as such, and for which there is a "signature" identifying the corresponding channel, and, on the other hand, transcoded programs of digital origin that do not have a signature. Programs in the latter category are expected in the near future to become more and more numerous, or even to supplant repetitive analog radio programs.

An audimetric device connected to the television will thus only be able to identify part of the programs watched by the viewer, which constitutes a major drawback at the time of the multiplication of the programs offered and the dispersion of viewers over a large number of these programs.

US-A-5 850 249 proposes a workaround consisting in inserting, at the level of the household receiving and distributing the emissions by means of a local brewing system, a code identifying the input of the brewing circuit from which the program viewed.

In this way, all the programs viewed are provided with a code usable for audimetric purposes: some already include the channel identifier introduced upstream (by the broadcaster) and kept throughout the transmission channel; for the others, this identifier is replaced by a local code introduced downstream (at the household level) indicating the physical input from which the watched television signal comes.

But this previous proposition does not solve the difficulty linked to the identification of the chain looked at from the local code, since the significant data (the identity of the chain) is absent or has been lost upstream. A first solution consists in recognizing the carrier frequency of the program selected by the television set or the network decoder, and in identifying the channel from a frequency / channel correspondence table stored in the hearing instrument. This solution is however quite delicate to implement, because it requires an audimetric device in itself quite complex because of the correspondence search. In addition, the programming of the correspondence table is specific to a network at a given time, it is necessary to program as many different tables as there are networks and, on the other hand, to reprogram all the tables each time the plan changes. network frequencies, or each time new programs are added.

In addition, the technique of analyzing the carrier frequency is a relatively intrusive technique with respect to the television set or the decoder; it requires a certain number of delicate internal connections, which are moreover likely to disturb the internal functioning of the device in a visible manner on the image.

Another technique for identifying the channel consists of deferred and indirect processing, by recording samples of the sound and / or image of the television program watched by the viewer, as well as time tracking information. of the sampling instant. This various information is stored locally and then transmitted and analyzed to the computing center of the audiometry operator, by correlating it with recordings made at the same times of the programs of the various channels, so as to thereby identify the channel. corresponding to this program.

This technique is not very intrusive with regard to the television (it suffices to record the signal delivered by the video stages of the television), on the other hand it is extremely cumbersome to implement, requires significant computing powers and requires local memory. or frequent connection of the meter to its collection system. Finally, the correlation is never obtained at 100%, so there is always a fraction of samples for which it is not possible to identify the channel watched. One of the aims of the invention is to propose a particular coding mode making it possible, in the particular case described above of a cable network broadcasting analog programs originating from digital sources, to mark and identify the chain corresponding to each program, and this in a way that is both exhaustive (all the programs will be identified) and homogeneous (the programs will all be identified in the same way), so as to guarantee an effective and significant audimetry. The invention will thus make it possible to have a new auditorium meter particularly suitable for audience measurement of program channels broadcast by digital channels and transcoded at the head of the network in analog format (typically PAL or SECAM) for broadcasting on a broadcaster. wired bucket.

Another object of the invention is to allow this implementation in a simple manner from the point of view of the necessary technical means: it will be seen in particular that, thanks to the coding of the invention, it is possible to use audio devices at the same time simple and effective, for example the apparatus described in the aforementioned EP-A-0 830 028.

On the other hand, as will be seen, the particular coding according to the invention advantageously provides for including the binary fields necessary for the good synchronization of the receiver as well as for bringing it into conformity with existing standard signature signals for other analog program channels, broadcast simultaneously on the same cable network, but obtained by reception and demodulation of a local or regional hertzian broadcast.

In this way, the coding according to the invention can be applied only to certain of the programs broadcast on the cable network (the programs originating from digital programs after transcoding), which makes it possible to distribute the analog radio programs by receiving and retransmitting these as is, without the need to modify the coding of the channel identifier, already present in the signal of the latter. To this end, the invention proposes to code the television signal by the installation of the cable headend, or of the domestic distribution network, by implementing the steps consisting in: a) receiving a digital television program, in particular a program broadcast by satellite; b) extract the available digital identifiers from the chain of this program and produce a corresponding digital data item forming a chain identifier; c) transcode this program into an analog video signal; d) after transcoding, inserting a data message including said channel identifier into a free image signal line of this video signal; and e) broadcasting the resulting analog video signal over a cable or home distribution network. On the television receiver side, the decoding of the television signal according to the invention includes the steps of: a) receiving an analog video signal from a cable network or a home distribution network; b) analyzing the information content of the successive lines of this video signal to distinguish, on the one hand, an image signal and, on the other hand, digital data messages conveyed by free lines of image signal; c) extract from these messages a chain identifier data associated with said image signal, data inserted at the head of the network in a free line of image signal by the coding process referred to above; and d) deliver the image signal on a screen and, at the same time, use the chain identifier thus extracted.

The analog video television signal according to the invention is an analog video signal broadcast on a cable network or a home distribution network, formed of successive lines comprising, on the one hand, an image signal and, on the other hand, digital data messages conveyed by free image signal lines, signal characterized in that the image signal comes from a digital television program transcoded at the head of the network and in that one of said messages of data comprises a chain identifier data of this digital program associated with said image signal, this data being inserted at the head of the network in a free line of image signal, and of all other data, by the coding method referred to above. According to various advantageous subsidiary characteristics: the data message also includes an identifier of the frequency of the carrier for transporting the digital program; - the data message also includes: a digital program transport network identifier; an identifier of a bouquet of programs to which the digital program belongs; and / or an identifier of the cable network broadcasting the analog video signal; - the data message is preceded by a preamble comprising a synchronization bit pattern; the data message is preceded by a prefix comprising service information including: information relating to the availability of the received program; information relating to the quality of the program received; function information indicating the pro- origin, digital transcoded or not, of the analog video signal broadcast; and / or information relating to the encrypted state or not of the received program.

0

We will now give an example of detailed implementation of the invention, of course without limitation.

In this example, the channel identifier corresponds to a Didon type signature, according to the VS-16 specification (service channel located on line 16 of SECAM signals from the radio network) of Télédiffusion de France. Analog radio programs received by the headend and bearing this signature are rebroadcast as is on the cable network. On the other hand, digital television programs, in particular programs broadcast by satellite, must be transcoded before they can be broadcast in analog, in particular by adding field return lines to the image signal conveyed by the program. digital.

To implement the invention, a data message will be inserted into one of these frame return lines free of any video signal or service signal (teletext, color identifier in SECAM, etc.).

By default, line 16 will be used, which is the same row as the service channel VS-16 of the wireless network.

If this line is not free, it is possible to choose another one by coding an "offset", for example an offset on 8 bits making it possible to cover a range of ± 127 lines on either side of the line 16. This offset value will be stored in a local table with the identification of the channel, given at the transcoder level by all or part of the DVB triad "ServiceJD + Transport_stream_ID + NetworkJD". The actual message (useful message) is preceded by a preamble including:

- a bit synchronization pattern comprising 2 bytes ($ 55, $ 55);

- a synchronization byte ($ E7).

This pattern allows in particular, by good synchronization at the level of the remote receiver, an implementation of an audimetric device such as that described in the aforementioned EP-A-0 830 028, which is precisely a- gencé so as to analyze the signal delivered by the video stage of the receiver before its display on the screen by searching for a synchronization pattern and by setting its clock on this pattern so as to be able to read the subsequent channel identifier. The useful message is also preceded by a prefix of nine bytes of service information, namely:

- three bytes coding the "channel number": $ 64, $ 02, $ 15;

- a byte equal to $ 15;

- a byte equal to $ D0; - two bytes indicating an image number ($ 02, $ 38);

- a byte coding the "insertion point", $ 02; and

- a byte coding the state of the satellite receiver / decoder receiving the digital program, the four states being: 0 = normal, 1 = non-existent HF reception, 2 = encrypted program and 3 = local image (HMI of the receiver / decoder, etc.).

This service information is particularly useful for revealing at the level of the receiver, and therefore of the hearing instrument, a certain number of information such as: availability or not of the program (for example in the event of a transmitter or antenna failure disconnected, etc.), clear or encrypted state of the program, etc., which also makes it possible to easily implement a certain number of technical network management functions.

The actual message (useful "source identification" message), which follows this preamble and prefix, contains the signature used to identify the chain. It is made up as follows:

- a byte "F" function identifier ($ 06 to designate the data type "program channel from DVB"), allowing to recognize, among all the analog programs broadcast by the cable network, those which come from a program transcoded digital; - a "LF" byte giving the length of the data field ($ 0C, useful message of length 12 bytes);

- a chain identifier, broken down as follows:

- 4 bytes code the program chain ("ServiceJD" coded Hamming 4/8 in the case of DVB); - 4 bytes encode the digital multiplex, i.e. allow identify the frequency of the upstream transport carrier ("Transport_stream_ID" coded Hamming 4/8 in the case of DVB); - 4 bytes possibly coding the original upstream transport network ("NetworkJD" coded Hamming 4/8 in the case of DVB); - an error correcting code, for example two bytes of CRC-16, can be added to the message to protect the information from transmission errors (this code will be checked on reception). The message thus formed is transmitted repeatedly, if possible at least twice per second so as to minimize the latency time of the audio device at each program change.

With regard to the electrical characteristics (signal level, time sequencing, etc.), these are chosen to be identical to the above-mentioned specification VS-16. If necessary, to allow a finer auditory study, it is possible to supplement the identification message with additional information such as, for example, an identifier of a bouquet of programs to which the chain belongs, or even an identifier of the cable network. carrying the analog signal downstream, etc.

Claims

1. A method of coding a television signal, characterized in that it comprises the implementation, by a cable headend installation or a home distribution network, of the steps consisting in: a) receiving a program digital television, including a program broadcast by satellite; b) extract the available digital identifiers from the chain of this program and produce corresponding digital data forming the chain identifier; c) transcode this digital program into an analog video signal; d) after transcoding, inserting a digital data message including said channel identifier into a free image signal line of this video signal; and e) broadcasting the resulting analog video signal over a cable or home distribution network.

2. The coding method of claim 1, wherein the data message inserted in step d) also includes an identifier of the frequency of the digital program transport carrier.

The coding method of claim 1, wherein the data message inserted in step d) also includes: a digital program transport network identifier; an identifier of a bouquet of programs to which the digital program belongs; and / or an identifier of the cable network broadcasting the analog video signal.

4. The coding method of claim 1, in which, in step d), a preamble comprising a synchronization bit pattern is inserted before the data message.

5. The coding method of claim 1, in which, in step d), a prefix comprising service information is inserted before the data message including: information relating to the availability of the program received; information relating to the quality of the program received; function information indicating the origin, digital transcoded or not, of the analog video signal broadcast; and / or information relating to the encrypted state or not of the received program.

6. A method of decoding a television signal, characterized in that it comprises the implementation, by a television receiver, of the steps consisting in: receiving from a cable network or from a domestic distribution network - an analog video signal; analyze the information content of the successive lines of this video signal to distinguish, on the one hand, an image signal and, on the other hand, digital data messages conveyed by free lines of image signal; - Extract from these messages a data of chain identifier associated with said image signal, data inserted at the head of the network in a free line of image signal by the method of one of claims 1 to 5; output the image signal on a screen and, at the same time, use the channel identifier thus extracted.

7. A television signal broadcast on a cable network or a home distribution network, this signal being an analog video signal formed by successive lines comprising, on the one hand, an image signal and, on the other hand, digital data messages conveyed by free image signal lines, signal characterized in that the image signal comes from a digital television program transcoded at the head of the network and in that one of said data messages comprises a data item of channel identifier of this digital program associated with said image signal, this data being inserted at the head of the network in a free image signal line by the method of one of claims 1 to 5 .

8. The television signal of claim 7, wherein the data message also includes an identifier of the carrier frequency of the digital program.

The television signal of claim 7, wherein the data message also includes: a digital program transport network identifier; an identifier of a bouquet of programs to which the digital program belongs; and / or an identifier of the cable network broadcasting the analog video signal.

The television signal of claim 7, wherein the data message is preceded by a preamble including a pattern of synchronization bits.

11. The television signal of claim 7, wherein the data message is preceded by a prefix comprising service information including: information relating to the availability of the received program; information relating to the quality of the program received; function information indicating the origin, digital transcoded or not, of the analog video signal broadcast; and / or information relating to the encrypted state or not of the received program.