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This chapter provides physical and functional overviews of the Cisco 6920. It contains physical descriptions of the unit's hardware and functional descriptions of hardware and software components.
The Cisco 6920 is a real-time bandwidth management solution for digital cable operators and digital video service providers. Available in a compact four-rack unit (4RU) rack-mounted system, the RateMux uses high-speed programmable DSPs to dynamically perform real-time rate conversion and bitstream manipulation on encoded MPEG-2 streams. This maximizes audio, video, and data signal throughput, and effectively widens bandwidth capability, while ensuring quality transmission at full transponder link rates.
The Cisco 6920 accepts up to 15 MP&ML MPEG-2 input signals through DHEI or DVB-ASI compliant interfaces. The unit's programmable statistical remultiplexing engine then performs real-time Variable Bit Rate (VBR) and Constant Bit Rate (CBR) rate conversion and bitstream manipulation processing to the input streams.
Using a proprietary statistical model, the processed streams are then recombined into a highly efficient, multiplexed program transport stream while maintaining video quality. The Cisco 6920's processing engine, aside from performing static and dynamic grooming, also supports PID filtering and PCR jitter removal.
The Cisco 6920 is a four-rack unit (4RU) high, rack-mountable device. Each basic unit comes equipped with the following components:
Based on input requirements and selected features, you will also install one or more of the following components:
The PowerPC card is a powerful "PC on a card" that controls the operation of the Cisco 6920. An Ethernet cable connects the PowerPC card in the Cisco 6920 either to a network or directly to a PC equipped with a web browser (Netscape Communicator 4.08 or higher). The RateMux Manager graphical user interface software runs on your PC's web browser to start up and configure the
Cisco 6920.
Each DVB-ASI and DHEI input/output card is equipped with three input connectors. The DVB-ASI I/O card is equipped with two output connectors with identical output streams. The DHEI I/O card is equipped with one output connector.
For DVB-ASI video input: If you have only one video input stream, you can use any of the three input connectors on the DVB-ASI I/O card.
For DHEI I/O video input: If you have only one video input stream, you must use the first/top input connector (Input0) on the DHEI I/O card. Clock timing is only received through the first or top DHEI input connector, so if no input source is connected to this connector, the DHEI I/O card will not work properly.
Each DVB-ASI input card is equipped with four input connectors and each DHEI Input card has three input connectors.
The DSP card is the powerful video processor of the Cisco 6920. Each DSP card has three DSP processors that perform digital grooming, rate conversion, and all other video processing functions. Each Cisco 6920 will support from one to six DSP cards. The number of DSP cards required depends upon your application and features implemented.
The Cisco 6920 is compatible with the defined PAT and PMT tables of the ISO/IEC 13818-1 MPEG-2 standard. The Cisco 6920 reads the PAT and PMT tables of all input sources, and faithfully displays these tables and generates an accurate PAT and set of PMTs for the output channels. The generated table will reflect your program selections and any remapping of the PID or program values. The ECM value remains constant, equal to the value at input.
Posted: Fri Jul 21 10:22:55 PDT 2000
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