Interactive video distribution systems – Local video distribution system
Reexamination Certificate
2000-02-25
2004-08-24
Srivastava, Vivek (Department: 2611)
Interactive video distribution systems
Local video distribution system
C370S909000
Reexamination Certificate
active
06782552
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a local network having a plurality of subscribers, which are connected to one another through the use of an optical data line for transmitting audio and/or video data and control data. The subscribers, together with the optical data line, form a ring network.
Published European Patent Application EP 0 725 522 A2 describes a local network of this type, which enables audio and/or video and control data to be transmitted in a ring network between data sources and data sinks. In this case, the video data, which may be variable picture data for moving pictures or else invariable data for still frames or graphics data, are transmitted as source data in a specific format in a corresponding source data area. Separately from the video data, the control commands are transmitted in another area correspondingly reserved for control data. In this case, by way of example, items of information concerning arbitration or, channel definition are provided as control commands. In addition, arbitrary, unformatted transparent data without any reference to the formatting of the control data and without any reference, regarding content, to the individual subscribers of the network can be transmitted into the area for which the transmission of control data is intended. The content of these data has no effect on the function of the individual subscribers. In particular, it is possible for these data not to form control data or control commands for individual subscribers of the network. In order to avoid repetition of information already described, reference is made, with regard to the description of the transmission format, in particular the synchronous data transmission in a continuous data stream, to the disclosure in Published European Patent Application EP 0 725 522 A2, which forms a basis for the present invention.
This local network has control commands having a rigid, a fixedly formulated command structure. In this case, a specific control command has a defined structure and hence a defined command header sequence followed by an invariable number of parameters. The data source passes the control command via its interface to the ring data line, which forwards the control command with the associated parameters to the assigned data sink, which, with knowledge of the invariable structure of the control command, initiates specific sequences of events on the basis of the control command. This sequence of events makes it possible to integrate into the local network only data sinks which know and can process the complete set of commands of the data sources, including their structure. As a result, it is not possible for the data sinks to be configured independently of the data sources, which substantially restricts the flexibility of the local network in particular with regard to an update.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a local network having a plurality of subscribers which overcomes the above-mentioned disadvantages of the heretofore-known networks of this general type and which exhibits an increased flexibility. It is furthermore an object of the invention to provide a method for transmitting digital data in a local ring network which has a high degree of flexibility.
With the foregoing and other objects in view there is provided, in accordance with the invention, a local network, including:
an optical data line;
a plurality of subscribers connected to one another by the optical data line for forming a ring network and for transmitting control data and at least one of audio data and video data;
at least one of the subscribers constituting a data source for at least one of the audio data, video data and control data and at least another one of the subscribers constituting a data sink for at least one of the audio data, video data and control data;
the data source having a data source-control unit and a data source interface to the optical data line, the data source being configured for passing a control command, via the data source interface, to the optical data line, the control command having a length defined by the data source, having a command header sequence and having a sequence of n parameters, n being a first given number;
the data sink having a data sink control unit, a picture output unit, a data sink interface and a memory for holding and for outputting video data via the picture output unit, the data sink control unit controlling the outputting of the video data;
the data sink control unit receiving the control command, via the data sink interface, and interpreting the control command by interpreting m initial ones of the n parameters, m being a second given number; and
the data sink control unit reading video data corresponding to the m initial ones of the n parameters from the memory of the data sink and outputting the video data, corresponding to the m initial ones of the n parameters, on the picture output unit.
With the objects of the invention in view there is also provided, a method for transmitting digital data in a local ring network, the method includes the steps of:
providing a local ring network having a data source, a data sink and a ring data line;
generating, in the data source, a control command having a command header sequence and a sequence of n parameters, n being a first given number, the control command having a variable length defined by the data source;
passing the control command, via a data source interface, to the ring data line;
providing the data sink with a data sink control unit for controlling the data sink, a picture output unit, a data sink interface and a memory for holding video data to be output via the picture output unit under a control of the data sink control unit;
feeding the control command, via the data sink interface to the data sink;
interpreting, with the data sink, the control command by interpreting m initial ones of the sequence of n parameters, m being a second given number;
reading video data corresponding to the m initial ones of the n parameters from the memory of the data sink; and
outputting the video data corresponding to the m initial ones of the n parameters on the picture output unit.
In other words, the invention provides a local network having a data source which has a control unit and an interface to the ring data line and which generates a control command having a length defined solely by the data source itself and passes the control command via the interface to the ring data line. The length of the control command is produced or results from the command header sequence and an adjoining sequence of parameters whose number n is defined by the data source itself. On account of the dependence on the respective data source, the number of parameters n can be given different values for different data sources, with the result that the length of the control command is defined differently depending on the properties of the data source. Once the control command has been passed via the interface of the data source to the ring data line, the control command is read by a data sink defined by the command header sequence. In this case, the control command is fed to a control unit via the interface. In the control unit, the control command having a length defined by the data source is interpreted by evaluating a defined number of parameters m. The number of parameters m to be evaluated by the data sink is determined by the properties of the data sink and is thus independent of the data source for the control command. The first m parameters from the sequence of the n parameters of the control command are interpreted. Video data corresponding to the m parameters are read in a targeted fashion from a memory of the data sink by the control unit and fed to the picture output unit for outputting. In this case, the picture output unit may be part of the data sink, or be connected to the latter. The video data may in this case be read from the memory and output either as invariable graphics data, as still frames or as a sequen
Becker Michael
Klaus-Wagenbrenner Jochen
Schoepp Harald
Stiegler Andreas
Wietzke Joachim
Becker GmbH
Locher Ralph E.
Srivastava Vivek
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