ANSI SCTE 137-6:2017 pdf free download – Modular Headend Architecture Part 6: Edge QAM Video Stream Interface
1.1 Introduction and Purpose
This specification is a component of the Modular Headend Architecture. In particular, it defines the data plane requirements for receiving, processing, and transmitting MPEG transport streams in EQAMs, compliant with the Video EQAM or Universal EQAM profiles described in the Architectural Overview of the Modular Headend Architecture X [SCTE 137-7] X It should be noted that this document refers to “MPEG video” support as a short-hand to designate support for the delivery of X [ISO/IEC 13818-1] X compliant MPEG transport streams that may carry audio material, video material, data, or a combination. The EQAM supporting MPEG video has one or more IP network interfaces (e.g., Gigabit Ethernet) for receipt of IP- encapsulated MPEG transport stream packets that may arrive from a VOD or streaming server. The EQAM can be configured either statically (via X [SCTE 137-5] X ) or dynamically (via ERMI-2, as defined in [SCTE 137-4]) to process the incoming MPEG transport streams, generate a Multiple Program Transport Stream (MPTS), and then, from that MPTS, generate a QAM modulated RF waveform that is transmitted at a particular frequency on an RF output of the device.
This word means that the item is an absolute requirement of this specification. This phrase means that the item is an absolute prohibition of this specification. This word means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications should be understood and the case carefully weighed before choosing a different course. This phrase means that there may exist valid reasons in particular circumstances when the listed behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label. This word means that this item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because it enhances the product, for example; . another vendor may omit the same item.
In support of dynamic sessions, a QAM channel provides two modes: multiplexing mode and passthrough mode. In multiplexing mode, the QAM channel can simultaneously support several dynamic sessions (and potentially even a mix of static and dynamic sessions). In passthrough mode, the QAM channel only supports a single dynamic session. When there are no sessions active on a particular QAM channel, the channel is considered to be in an “idle” state, and only MPEG null packets and PAT are produced on the output. The first session to be created brings the QAM channel out of the idle state and selects which mode it will operate in. When in multiplexing mode, dynamic multiplexing sessions can be created that map one or all of the programs from an input transport stream into an output multiplex. The output multiplex will generally contain multiple programs associated with multiple sessions. In many cases, each session will require the EQAM to remap the PIDs from the input program(s) to new PID values in order to prevent conflicts between the various sessions. For multiplexing sessions, only the MPEG packets corresponding to the elementary streams described in the PMT for each program will be multiplexed into the output transport stream. Any other MPEG packets arriving in the input transport stream will be discarded. At regular intervals, the EQAM will generate output PMTs and a PAT for the output multiplex, based on the PATs and PMTs that it receives on the input transport streams.