Multiplex communications – Special services – Conferencing
Reexamination Certificate
1998-04-03
2001-12-04
Olms, Douglas (Department: 2661)
Multiplex communications
Special services
Conferencing
C370S231000
Reexamination Certificate
active
06327253
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to mechanisms for controlling the switching of connections among data processing devices, particularly video processing devices.
BACKGROUND
Analog motion video signals, such as those used in common television sets, video tape recorders and other analog video systems, are temporally continuous and synchronous signals requiring various elements in a video system to be synchronized in order to be used. In other words, analog motion video signals have a predetermined and fixed rate to which all of the elements in the video system are synchronized. Any element in the video system is designed with the assumption that there will be a constant rate for input and output of motion video information.
More recently, it has been possible to store digital motion video data in data files on a computer. There are several methods for playing back such motion video data. One method is called “pushing” or “streaming” of the motion video data. Streaming is based on an assumption that a system can provide an average data flow rate that is the same as the ultimate data flow rate needed to ensure temporally continuous output of analog motion video images to a viewer. Sufficient buffering is used to account for expected latencies in data transfer between elements. In some cases, both the temporal and spatial resolution of the motion video information may need to be reduced. Such systems typically are designed with the assumption that transfer of audio and video data from a source through several processing elements to its ultimate destination can neither be delayed nor stopped.
When a general purpose digital computer is used to process motion video information, a constant rate of flow of data generally cannot be maintained. There may be variations in data flow rates due to various latencies in the computer system due to, for example, disk or memory read latency, interrupts from other processing elements in the computer, etc. In addition, in some systems, such as editing systems, the ability to stop and restart playback is desirable. In order to overcome such problems, one method which has been used is to provide sufficient buffering in combination with an ability for data transfer to be stalled, such as shown in U.S. Pat. No. 5,045,940 (Peters, et al.) which is hereby incorporated by reference. These principles are used in a computer network as described in published European Patent Application No. 0674414A2. An extension of this combination to special effects processing is disclosed in PCT Publications WO94/24815 and WO95/26100 which are incorporated by reference. In this system, a data decompressor outputs data into a first buffer, from which it is transferred to a second buffer associated with a special effects processor. The first buffer indicates whether valid data is available. In addition, the special effects processor indicates to a controller associated with the decompressor whether it can receive data based on memory in the second buffer.
One drawback of these systems is that they use a significant amount of buffering to accommodate for delays in data transfer between elements. They also are designed for use with a single predetermined format of media. Such video processing devices also generally are designed to provide a single output stream based on a combination of inputs. In order to provide connectivity among multiple devices, such interconnections generally are provided statically by a computer network or video switcher. Such mechanisms generally do not provide a way to control data flow through the switch for multiple dynamically configured connections.
SUMMARY
Multiple data processing devices may be interconnected through a switching mechanism while simultaneously conveying flow control information over the interconnect. Mechanisms are provided to ensure that the flow of data to and from interconnected devices has completed prior to changing the configuration of the switch. The switch may be a circuit switch, such as a crossbar switch, or a packet switch or a memory. The switch may be a separate device or may be part of either an input section or an output section of a data processing device. The configuration of the switch may be defined by command data loaded from a central controller, host computer, or other device connected to the switch, such as a sending device or a receiving device with a full duplex connection to the switch. The loading of a new configuration in the switch may be controlled by command data from a sending device, receiving device, or host computer, or by a controller that is responsive to a boundary signal transmitted over the interconnect. In a packet switch, a packet is directed to an output port specified in an address field in the packet. The packet switch directs both requests for data and the data between processing devices. In a memory switch, data may be written into or read from different areas of a memory by different devices. Through a separate channel, devices communicate about the information stored into and read from the memory. Switching is performed by a device selecting a memory into which data is written or from which data is read.
Accordingly, in one aspect, a switching system dynamically configures connections between devices which control flow of data between the devices. The switching system includes an input for receiving data and a plurality of outputs to which data received through the input is directed. A switch directs data from the input to one of the plurality of outputs in response to command data. Flow control information is directed between the devices for controlling the flow of data between connected devices. The switching system ensures that flow of data between connected devices completes prior to changing connections between the devices by the switch.
In another aspect, the switching system has a plurality of inputs for receiving data and an output to which data received through the inputs is directed. A switch directs data from one of the inputs to the output in response to command data. Flow control information is directed between the devices for controlling the flow of data between connected devices. The switching system ensures that flow of data between interconnected devices completes prior to changing connections between the devices by the switch.
In one embodiment, the switch is a circuit switch. The flow control information between the devices includes a request signal from a first device, which is directed to a second device. A valid data signal may be received from the second device, which is directed to the first device. Connections between the devices are changed by the switch in response to a signal from the first device or the second device.
In another embodiment, the switch is a packet switch. Flow control information is directed between the devices by conveying a request packet from a first device to a second device for indicating a channel and an amount of data requested from the second device, and by conveying a data packet from the second device to the first device indicating an amount of valid data. Connections among the devices are established by conveying data packets with an indication of a destination device and by routing data packets among devices according to the indication of the destination device in the packet.
In another embodiment, the switch is a memory device. Flow control information is directed between the devices by using a first flow control channel connected between a first device and a second device, and a second flow control channel connected between the first device and a third device.
It should be understood that other aspects of the invention include processes for controlling switching such as performed by the switching system, and the various embodiments of the process. Systems of interconnected devices using switching systems in the various embodiments also are aspects of the invention. Another aspect of the invention is a video processing system in which different video processing devices are interconnected using a switc
Avid Technology Inc.
Gordon Peter J.
Olms Douglas
Vanderpuye Ken
LandOfFree
Method and apparatus for controlling switching of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for controlling switching of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling switching of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2575495