ANSI SCTE 142 pdf free download
ANSI SCTE 142 pdf free download.Recommended Practice for Transport Stream Verification.
The distinctions between these are important and should be taken into account both by equipment manufacturers of SCTE TS monitoring equipment and the users ol that equipment.
6. 1 Regarding “Technically Non-Conformant” error handling
Considering these classes of errors, particular attention needs to be paid to the “TNC” or “Technically Non-Conformant” class. In Standards as complex as MPEG-2 and those from the SCTE, situations arise where two “shall” statements collide. At such junctures, the Transport Stream (TS) may be momentarily non-conformant. An example of this might be “PAT repetition error” (see Section 7. 1 ). If the multiplexer is faced with a choice of outputting a packet carrying a PTS on a video PID on the schedule required by Section 1 1.2 or a repetition of the PAT within the requirements of Section 7. 1 , an implementer may choose to output the PTS sample rather than the PAT. Either way, the TS is for a moment non-conformant. Neither choice of non-conlormance will affect any real-world receivers. Neither will result in disruption of service. Either will be non-conformant. There is no avoiding these conflicts, and they arise periodically in real-world equipment.
Should a manufacturer of MPEG analysis equipment choose to make either of these errors the cause of an operator alarm, after multiple false alarms the operator may ignore all
alarms. That is not desirable.
A number of the possible errors within this Section fall into these categories. While a
continuous occurrence of any should constitute an operator alarm, a single occurrence of any should (as indicated by the table) be treated merely as a minor problem, which, unless re-occurring, is not significant.
6.2 Discussion of Error Classification
An explanation of the error classification scheme is as follows:
1 . Transport Stream Off Air (TOA): The transport is effectively off-air as the Transport Stream errors are severe enough that transport level logical constructs are damaged beyond utility. Receivers will not be able to tune and decode anything within the transport. The complete or repeated absence of sync bytes would be an example of this level of error.
2. Program Off Air (POA): A main service (virtual channel) is flawed to the point that that service is effectively off air for conformant/reasonahie receiver designs. This could involve all of the program elements being improperly constructed or incorrect/missing signaling about elements. The absence of a PMT instance for a service would be an example of this type of error.
3. Component missing (CM): One of the program components that is signaled by PSIP or PSI as present is either not present or cannot be found and decoded. One example would be a mismatch between the video PID signaled in the PMT and the actual PID used for the video elementary stream.
4. Quality of Service (QOS): Parameters are out of specification by such a margin that a significant fraction of the receivers can be expected to produce flawed outputs. In many cases, the broadcast is viewable, but may exhibit some form of degradation to the viewer. An example might be the PAT cycle time being somewhat longer than the specification, which would cause slower than normal tuning.
5. Technically Non-Conformant (TNC): Violates the letter of the standard, but in practice will have little effect on the viewing experience. Errors of this type should be corrected, hut do not have the urgency of higher severity errors. An example might he a single instance of a 102 rns PAT cycle time (with the remainder of the PATs coming at less than 100 ms intervals).
In most cases the error threshold for what may appear to he escalating categorization is
based on: I) the official metric to twice the metric, 2) twice the official metric to 5 times the metric, and 3) over five times the metric.ANSI SCTE 142 pdf download.
