Television – Bandwidth reduction system
Reexamination Certificate
1998-01-16
2001-04-17
Marcelo, Melvin (Department: 2663)
Television
Bandwidth reduction system
C348S385100
Reexamination Certificate
active
06219100
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a communication method between N stations among which one is selected as a master station and becomes responsible for building and broadcasting at least one service information table such as the tables defined according to standards like MPEG or DVB, said master station communicating with the (N—1) other ones, called slave stations, according to a specific table management, and in a limited number of situations.
The standards MPEG and DVB have defined various service information tables describing the transport stream content. In MPEG case, these tables are referred to as PSI tables (
P
rogram
S
pecific
I
nformation), while in DVB case, they are referred to as SI tables (
S
ervice
I
nformation). They provide the minimum information to enable an automatic configuration of the receiver to demultiplex and decode the various streams of programs within a multiplexed transport stream.
In an independent broadcast system, each station transmits independently its own tables, without taking care of what the other stations broadcast and without any communication between stations. Such an independent broadcast system is the simplest one, but possible only if some constraining conditions are fulfilled (e.g. the version number and section numbers have to be independent from station to station, section interleaving shall not be possible, . . . ), which is unfortunately not always the case.
In a central broadcast system as illustrated in
FIG. 1
(that shows an emitting station
10
(ES) sending to a customer
12
(CM) a multiplexed stream MXS emitted by a multiplexor MUX
14
that receives several programs 1 to N), a station becomes responsible for building and broadcasting the tables for all the other stations, without communicating with them. The building and the transmission of these tables are relatively easy since the station
10
generating the transport stream knowns their content. Such a situation is however reserved to tables which are global (i.e. not service oriented) and for which no information is needed from the other stations.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to propose another kind of communication method, that is organised as indicated in the preamble of the description and wherein said situations are the three following ones:
a slave station wants to update the content of its tables;
a slave station wants to remove its tables;
the master station wants to refresh the tables of at least one of the slave stations; and said table management is based on transmission orders, used when the master station has to refresh a table, and stop transmission orders, used when the master station has to modify the content of a table by updating or removing it.
Such a method allows to implement a solution where all the stations receive a remultiplexed stream and one of them is responsible for building the tables.
In a particular embodiment, the table management is carried out by means of the following principle, according to which the master station is always in one of three states that are either a waiting state, or a building state, or a transferring state, the following operations corresponding to said states:
(i) in the waiting state, the master station refuses any modification of the content of any table except when one of the two following events occurs: either it is time to refresh at least one of the tables, or a slave station modifies its own contribution to one of the tables;
(ii) one of said events having occurred, the master station transmits respectively a transmission order or a stop transmission order, and the building state begins, during which said master station stores all modifications;
(iii) said modifications being stored, the transferring state begins, during which other modifications are no longer allowed and all modifications are copied, said master station finally returning to its waiting state.
Preferably, the communication rules for said operations are subdivided into rules to be respected by any slave station and rules to be respected by the master station, the former ones being the following:
(a) a slave station can transmit a modification only if it has received from the master station a transmission order concerning a table or if it wants to update its own contribution to a table;
(b) a slave station can update its own contribution to a table only if it has not received any order concerning said table since a predetermined period;
(c) when a slave station receives from the master station a transmission order concerning a table, said transmission has to be done within a predetermined period;
(d) when a slave station receives from the master station a stop transmission order concerning a table, it has to finish a pending transmission within a predetermined period and will be no longer able to begin a further transmission during a predetermined period;
while the latter ones are the following:
(e) when the master station wants to refresh a table, it has to transmit a transmission order for said table;
(f) the master station can send a transmission order only if it has not transmitted one during a predetermined previous period;
(g) when the master station receives modifications sent by a slave station wanting to update its contribution to a table, it has to transmit a stop transmission order for said table.
After the transmission of a transmission order or a stop transmission order, the master station then generally carries out the following operations:
(i) all the modifications are first stored during a first predetermined period;
(ii) after said period, all the modifications are copied during a second predetermined period.
REFERENCES:
patent: 6031577 (2000-02-01), Ozkan et al.
patent: 6064676 (2000-05-01), Slattery et al.
patent: 0374548A2 (1990-06-01), None
Lauer Ludovic
Le Maguet Yann
Le Queau Marcel
Marcelo Melvin
Piotrowski Daniel J.
U.S. Philips Corporation
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