FR2791847A1 - Encoding method for analogue cable TV signal includes use of digital programme identifier in free image line enabling identification of programme source - Google Patents

Abstract

The system uses free space within the analogue video signal to carry programme identification data, for audience research. A digital television programme which may be broadcast by satellite is received and the digital identifiers of the programme are extracted, and corresponding digital data forming the channel identifier is produced. The digital programme is transcoded into an analogue digital signal, and a digital data message corresponding to the channel identifier is inserted into a free line of the image signal. The resulting analogue signal is broadcast on a cable network. In the receiving television, the information content of successive lines of the video signal is analyzed, enabling identification of the programme. This information can be used by the receiving screen.

Description

The present invention relates to the identification of television programs.

  received by a television or associated equipment (such as a decoder)

to the latter.

  The identification of a program - that is to say the medium conveying the

  mage et le son - is particularly useful in the field of audimetry, that is to say audience measurement. Indeed, it is essential to be able

  identify at any time, for statistical purposes, which channel that is

  tell the entity that produced the content of what is conveyed by the program-

  me - corresponds to the program watched (or recorded) at a given instant

  born by the spectator in front of his television.

  This application to audimetry is not however limiting, and we understand

  will take that the invention can be used for other purposes, for example

  for viewing or storing (for example during a recording

  record) in the clear of the program chain watched at a given time

born.

  It is known in particular to use the frame return lines, which are free of image signal, to broadcast digital data such as

  teletext or service information which may include

  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.

  sor, for example by a method as described in EP-A-0 830 028 (Médiamétrie). This technique supposes, of course, that all the programs likely to be received by the television include such a channel identifier and, on the other hand, that this identifier is always coded with the same

  way, that is to say according to the same standard, from one program to another.

  This condition is generally fulfilled in the case of programs

  analog broadcast over the air, directly picked up by TV

  viewfinder. 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

  me 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

wired network.

  However, this is not always the case. Indeed, the network head can

  apply to the received radio signal a transcoding, for example a trans-

  color coding from PAL to SECAM, and this transcoding can make

  dre service information. Or the service information for the

  general captured are 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 re-

  broadcast as is by the network (Didon coding on a French program

here).

  Most importantly, headend installations now receive

  more and more, programs broadcast by satellite in digital form

  that, to rebroadcast them in analog on the cable network.

  However, a digital television signal does not have return lines

  weft; it only includes video information of the i-signal

  mage (about 560 lines in DVB 50 Hz), digitized sound, and some

number of data.

  These digital data of the television program, when they are standard PDC or Ceefax, certainly include an identifier data

  chain. But this data is lost during the conversion of number

risk in analog.

  thus, if we consider the various programs broadcast in analog by

  a cable network, these can form a heterogeneous whole

  taking, on the one hand, main programs received on a neighboring radio network and rebroadcast as such, and for which there is a

  "signature" identifying the corresponding channel, and, on the other hand, pro-

  transcoded digital origin grams without sign

  ture. Programs in the latter category are expected to become more numerous in the near future, or even to supplant

  analog broadcast 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 pro-

  grams offered and the dispersion of viewers on a large

many of these programs.

  To overcome this drawback, instead of searching in the tele-

  vision a signature allowing to reveal the chain corresponding to

  observed program, a first solution consists in recognizing the

  carrier frequency of the program selected by the television or the

  network, and to identify the chain from a correspondence table

  dance frequencies / channels stored in the hearing instrument.

  This solution is however quite delicate to implement, because it requires an audimetric device in itself quite complex due to the fact

  of the correspondence search. In addition, programming the ta-

  ble correspondence is specific to a network at a given time, it is necessary to program as many different tables as networks and, on the other hand, to reprogram all the tables each time the

  network frequency plan, or each time new programs are added

my.

  In addition, the technique of analyzing the carrier frequency is

  a relatively intrusive technique with regard to television or decoration

  deur; it requires a certain number of internal connections

  cats, which are moreover likely to disrupt the functioning

  dull of the device visibly in the image.

  Another technique for identifying the chain is to carry out a deferred and indirect way, by recording samples of the sound.

  and / or the image of the television program watched by the televiewer

  as well as time tracking information of the sample instant

  tillonnage. This various information is stored locally and

  then transmitted and analyzed to the data center of the audio operator

  metrics, correlating them to recordings made at the same

  programs of the various channels, so as to identify

  if 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 power 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

  samples for which it is not possible to identify the chain

guarded.

  One of the aims of the invention is to propose a particular coding mode.

  link allowing, in the particular case described above for a cable network broadcasting analog programs from digital sources, to mark and identify the channel corresponding to each program, and

  this in an exhaustive way (all the programs will be identified

  consistent) and homogeneous (the programs will all be identified in the same way

  lesson), so as to guarantee an effective and significant audimetry.

  The invention will thus make it possible to have a new particular audimeter.

  particularly suitable for audience measurement of broadcast program channels

  digital channels and transcoded at the head of the network

  analog mast (typically PAL or SECAM) for broadcasting on a

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

  simple and efficient hearing aids, for example

  reil 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 pro chains

  analog grams, broadcast simultaneously on the same cable network, but obtained by reception and demodulation of a hertzian broadcast

local or regional.

  In this way, the coding according to the invention can only be applied 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 their signal.

  To this end, the invention proposes to code the television signal by means of the

  installation of a cable headend by implementing the steps consisting in: a) receiving a digital television program, in particular a program broadcast by satellite; b) extract the digital identifiers

  available from the chain of this program and generate a numerical data

  corresponding risk forming chain identifier; c) transcode this pro-

  gram to an analog video signal; d) after transcoding, insert into a free image signal line of this video signal a data message including said channel identifier; and e) broadcast the video signal

  analog resulting on a cable network.

  On the television receiver side, the decoding of the television signal according to

  the invention comprises the steps consisting in: a) receiving from a cable network

  wheat an analog video signal; b) analyze the information content of the successive lines of this video signal in order to distinguish, on the one hand, an image signal and, on the other hand, digital data messages

  conveyed by free image signal lines; c) extract from these mes-

  a string 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 method 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 a video signal.

  analog deo broadcast on a cable network, formed of successive lines comprising, on the one hand, an image signal and, on the other hand, digital data messages conveyed by free lines of image signal, signal characterized by that the image signal comes from a digital television program transcoded at the head of the network and that one of said data messages comprises a channel identifier data of this digital program associated with said image signal, given debt being inserted at the head of the network in a free image signal line, and

  any other data, by the coding process referred to above.

  According to various advantageous subsidiary characteristics: - the data message also includes an identifier of the frequency of the transport carrier of the digital program;

  - the data message also includes: an identification identifier

  digital program transport bucket; an identifier of a

  bouquet of programs to which the digital program belongs

  than; 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 program received; quality information

  the program received; function information indicating the pro-

  source, digital transcoded or not, of the analog video signal

  as broadcast; and / or information relating to the encrypted state or not of the

program received.

  We will now give an example of a detailed implementation of the information.

  vention, of course without limitation.

  In this example, the chain identifier corresponds to a Didon type signature, according to the VS-16 specification (service channel located online

  16 SECAM signals from the wireless network) of Télédiffusion de France.

  Analog radio programs received by the head end and

  with 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

  to be able to be broadcast in analog, in particular by adding li-

  frame return genes to the image signal conveyed by the digital program. To implement the invention, a data message will be inserted in 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

  wireless service channel VS-16.

  If this line is not free, it is possible to choose another by co-

  in an "offset", for example an 8-bit offset making it possible to cover a range of 127 lines on either side of line 16. This offset value will be stored in a local table with the identification of the chain , given at the transcoder level by all or part of the DVB triad "Service_lD + Transport_stream_lD + Network_lD". The actual message (useful message) is preceded by a preamble comprising: - a bit synchronization pattern comprising 2 bytes ($ AA, $ AA online, $ 55, $ 55 in the output register);

  - a synchronization byte ($ E7).

  This pattern allows in particular, by good synchronization at the remote receiver, an implementation of an audimetric device such as that described in the aforementioned EP-A-0 830 028, which is precisely

  arranged to analyze the signal delivered by the video stage of the

  sensor before it is displayed on the screen, looking for a pattern of syn-

  chronization and setting its clock on this pattern so that you can

  read the subsequent channel identifier.

  The useful message is also preceded by a prefix of nine bytes of information.

  service training, namely: - three bytes coding the "channel number": $ 64, $ 02, $ 15; - a byte equal to $ 15 (Ic = 0); - a byte equal to $ D0 (Ft = 20); - 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 pro-

  digital gram, the four states being: 0 = normal, I = reception

  HF does not exist, 2 = encrypted program and 3 = local image (HMI of the

receiver / decoder, etc.).

  This service information is particularly useful in revealing to the

  level of the receiver, and therefore of the hearing instrument, a certain name-

  bre of information such as: availability or not of the program (for example in case of transmitter failure, antenna disconnected, etc.), clear or encrypted status of the program, etc. The actual message (useful "source identification" message), which

  follows this preamble and this prefix, contains the signature allowing identification

  proud the chain. It is made up as follows: - a byte "F" function identifier ($ 02 to designate the type of

  data "program channel from DVB"), used to recognize

  be born, among all the analog programs diffused by the cable network, those which result from a transcoded digital program;

  - a "LF" byte giving the length of the data field ($ 0C, mes-

  useful sage of length 12 bytes); - a chain identifier, broken down as follows:

  - 4 bytes code the program string ("Service_lD" coded Ham-

  ming 4/8 in the case of DVB); - 4 bytes encode the digital multiplex, i.e. allow

  identify the frequency of the upstream carrier ("Trans-

  port_stream_lD "Hamming coded 4/8 in the case of DVB);

  - 4 bytes possibly code the upstream transport network of

  gine ("Network_lD" 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 information from er-

  transmission errors (this code will be checked at reception).

  The message thus formed is sent repeatedly, if possible at least twice a second so as to minimize the time

  latency of the hearing device at each change of pro-

gram.

  Regarding the electrical characteristics (signal level, se-

  time sequence, etc.), these are chosen to be identical to the specification

cation VS-16 above.

  If necessary, to allow a finer auditimetric 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 channel belongs, or an identifier of the

  wired bucket carrying the analog signal downstream, etc.

Claims (11)

  1. A method of coding a television signal, characterized in that it comprises the implementation, by a cable headend installation, of 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   program and produce corresponding numerical data for- mant chain identifier;   c) transcode this digital program into an analog video signal   than; d) after transcoding, inserting a digital data message including said channel identifier into a free image signal line of this video signal; and   e) broadcast the resulting analog video signal over a cable network.   2. The coding method of claim 1, wherein the message   inserted in step d) also includes an identifier of the   carrier frequency of the digital program.   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 identi-   proud of the cable network broadcasting the analog video signal.   4. The coding method of claim 1, in which, in step d),   before the data message, a preamble including a mo- tif of synchronization bits.   5. The coding method of claim 1, in which, in step d),   a prefix with information is inserted before the data message   service locations including: information relating to the availability of   program received; information relating to the quality of the program   perceived; function information indicating the provenance, digital   transcoded or not, of the analog video signal broadcast; and / or information   mation relating to the encrypted state or not of the received program.   6. A method of decoding a television signal, characterized in that   that it includes the implementation, by a television receiver, of the   pes consisting in: - receiving an analog video signal from a cable network;   - analyze the information content of the successive lines of this si-   general video 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 an associated chain identifier data   ciée to said image signal, data inserted at the head of the network in   a free image signal line by the method of one of the res dication 1 to 5;   - deliver the image signal on a screen and, concomitantly, operate   ter the chain identifier thus extracted.   7. A television signal broadcast over a cable 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   risks conveyed by free lines of image signal, characteristic signal   that the image signal is from a digital television program   meric transcoded at the head of the network and in that one of said data messages comprises a data of chain identifier of this program   digital associated with said image signal, given debt being inserted at head   network te in a free image signal line by the method of one of claims I to 5.   8. The television signal of claim 7, wherein the message   also includes an identifier for the frequency of the gate   digital program transport.   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 bucket 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 message   is preceded by a prefix with service information   defect including: information relating to the availability of the program   received; information relating to the quality of the program received; an information   function indication indicating the source, digital transcoded or not, of the analog video signal broadcast; and / or information relating to   the encrypted state or not of the received program.