The VUE Out-of-Band Multiplexer (OOBM) processes down stream SCTE 55-1 streams. Each OOB Multiplexer runs in a VUE OOBM Pipe container. This container does not count against the standard maximum number of pipe containers as these containers processes only DS SCTE 55-1 streams. The VUE OOB Multiplexer supports bare metal deployment and VM environment deployment.
The VUE OOB Multiplexer input interface IP should be unique as it is used to identify an VUE OOB Multiplexer uniquely in the network. The VUE Out-of-Band Multiplexer (OOBM) receives control data stream as its input and multiplexes the data. The OOBM links the digital headend with the distribution system by combining the out-of-band (OOB) data stream of a digital Cable television (CATV) system. This signal is sent from the headend to the set-top boxes installed in subscriber homes. The OOB data stream acts as a control link through which the headend transmits the commands and authorization messages. These commands and messages control the set-tops distributed throughout the CATV system.
The VUE OOB Multiplexer routes PIDs up to 14 different input UDP streams and combines to a single output transport stream as shown in the image.
This illustration shows how the packet multiplexer uses a destination queue to create an output multiplex. In this example, the OOBM routes three different input packet streams labeled A, B, and C to the output queue. As a packet from stream A enters the queue, the multiplexer transfers it to its associated buffer in the destination queue. The multiplexer handles packets from streams B and C in the same way.
The multiplexer builds the output multiplex by extracting packets from each buffer in the queue in sequence (that is, one packet from the A buffer, one from the B buffer, one from the C buffer, and so on). Because of the number of possible input sources, the OOBM relies on PID (Packet Identifier) maps to support the proper multiplexing and routing of data through the packet multiplexer. One set of PID maps is defined for each input port to control how the multiplexer handles packets from those streams. Within the set for a port, a single PID map controls the handling of one packet stream. Each set includes a default PID map to control the handling of packet streams having no explicit PID mapping.
The multiplexer uses a queuing scheme to transfer packets from input ports to output buffer. Each destination has a dedicated queue composed of multiple data buffers setup to handle packets from particular input packet streams. As an input packet enters a given input port, the packet multiplexer reads the stream PID map and transfers the packet to the correct output queue. To generate the output multiplex for a given destination, the multiplexer extracts packets from the destination s queue by taking one packet from each buffer in a round-robin fashion.
The output stream from the OOBM is sent to an R-PHY device, which modulates the data using QPSK. The primary functions of OOBM are:
- Receives MPEG packets over UDP on Ethernet interface.
- Combines multiple sources of data into MPEG-2 output transport stream.
- Transmits an MPEG-2 data stream to cable terminals individually or on a broadcast. Transmission of the MPEG-2 data stream includes, authorization information, Electronic Program Guide (EPG) data, code downloads, interactive data, and Emergency Alert Messages (EAS).
- Triggers Proxy Serial Contact Closure for EAS when a valid MPEG packet is received from EAS ENDEC.
PID remapping/filtering
The VUE OOB Multiplexer supports PID mapping and PID filtering. For any given input UDP stream, the VUE OOB Multiplexer supports configuring up to 28 PIDs entries for each input where the total across all inputs cannot exceed 100 PID entries. There are 16 logical ports available to configure input and output interfaces. The first two ports are not available for user configuration. First port is assigned for TS output that sends the data to a modulator. This is the only one output port in OOBM. The second port is assigned for PID generator. The PID generator sends EAS data when there is a proxy contact closure. The remaining 3 to 16 ports are available for input interface configuration.
PID remapping or filtering is configured per logical port. You can configure the multiplexer to:
- Drop all PIDs in the input. PID map table shall be empty. No PID mappings.
- Pass all PIDs in the input, no remapping (inputPidNumber = -1 & outputPidNumber = -1)
- Pass specific PIDs and no remapping (inputPidNumber = X & outputPidNumber = X)
- Pass specific PIDs with remap (inputPidNumber = X & outputPidNumber = Y: Pass PID X, remapping it to PID Y)
- Drop specific PIDs (inputPidNumber = X & outputPidNumber = -1)
- Pass all the PIDs except specific
PIDs:
(inputPidNumber = X & outputPidNumber = -1: Drop PID X and inputPidNumber = -1 & outputPidNumber = -1 to pass all other PIDs)
- Pass specific PIDs with remap and
remaining passthrough:
(inputPidNumber = X & outputPidNumber = Y: Pass PID X,remapping it to PID Y and inputPidNumber = -1 & outputPidNumber = -1 to pass all other PIDs)
Priority based queuing
The VUE OOB Multiplexer supports priority-based queuing based on input port priority or PID based priority. Priority-based queuing minimizes the latency of traffic through the OOB Multiplexer by processing higher-priority packets before lower-priority packets in the priority queue buffers. The other purpose of the PBQ is to assign an input source which may be dropped in favor of other data sources when the overall input data goes beyond 2 Mbps. The VUE OOB Multiplexer supports three priority queues to prioritize input MPEG packets: High, Medium, and Low. Each priority queue can cache up to 256 MPEG packets.
When processing MPEG packets assigned to different priority levels, the VUE OOB Multiplexer manages the output buffer such that MPEG packets assigned to a High priority level is processed before MPEG packets assigned to either a Medium or Low priority level which are already in the buffer. Moreover, the VUE OOB Multiplexer manages the output buffer such that MPEG packets assigned to a Medium priority level is processed before MPEG packets assigned to a Low priority level which are already in the buffer. VUE allows you to assign the priority of each input UDP stream. The default priority is Medium.
In Port-based priority queuing, the priority can be configured on the input logical port.
In PID-based priority queuing, the priority can be assigned from on the data streams. You can enable priority-based queuing on a per-PID basis for up to 10 PIDs.
Message-level multiplexing
Message-level multiplexing (MLM) enables the OOB Multiplexer to merge packet streams from multiple sources that are carried on the same PID. Without MLM, the OOBM multiplexes the input elementary streams onto an output port without modifying the MPEG continuity count. If the same PIDs are carried on multiple inputs, the resulting output stream that contain packets with discrepant continuity counters. These may be discarded at the receiver. MLM ensures that the MLM PIDs have a unique continuity count on the output stream, and that transport stream MPEG packets that contain payload fragments maintain continuity. MLM supports up to eight PIDs in the output queue.
The VUE OOB Multiplexer allows you to designate up to eight PIDs for MLM.
PID Generator
The VUE OOB Multiplexer supports an internal message store. It can periodically insert MPEG packets from its internal message store to the output transport stream. The VUE OOB Multiplexer receives special cable terminal control messages from the DAC and stores them. These messages are input to the internal MPEG message generator. They include PID streams (TS Packets), and commands that specifies how often the generator should insert the packets into the multiplexer. You can disable PID generator if it is not used.
Emergency Alert System
The VUE OOBM monitors the input from the Emergency Alert System (EAS) message generator. If a valid MPEG packet is received from the EAS message generator on the configured proxy EAS input port, the VUE OOB Multiplexer simulates a contact closure. When a contact closure is simulated, and if PID blocking is enabled, OOB Multiplexer drops the PIDs to be blocked from the designated input port. The input port from which the PIDs to blocked are sent by Digital Addressable Controller (DAC) while OOB Multiplexer initially communicates with DAC. If DAC is not accessible then PID block data is considered from the persistence storage, which contains previously used data. If no persistence data available, then it considers the user configured data. Then the OOB Multiplexer triggers the PID generator to send the stored special cable terminal control messages, if PID generator is enabled.
It is assumed that ENDEC never sends traffic on the port, other than EAS messages. In addition, we assume that any traffic sent on that port always consists of properly formatted MPEG-2 transport stream packets, carrying SCTE-18 messages.