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Resolving Transport Stream Errors in 10GigE Infrastructure

Tue, 08/12/2014 - 11:37pm
Ralph Bachofen, vice president of sales and marketing, Triveni Digital

To support the growing consumer demand for high-bandwidth video services, many cable operators are transitioning to a 10 Gigabit Ethernet (10GigE) networking infrastructure. However, the complexity of this new environment creates a challenge for operators trying to quickly and cost-effectively reduce, locate, and eliminate transport stream errors.

Errors in the transport stream can cause noticeable video and audio impairments, such as video tiling, lip sync errors, intermittent tuning, inconsistent loudness levels, and missing components, which lower customer satisfaction when left unaddressed.

This article offers an effective strategy for monitoring and analyzing DTV transport streams in the 10 GigE environment.

By implementing an end-to-end video monitoring and analysis solution, cable operators can proactively identify and resolve video and audio quality issues, from the 10GigE core network all the way to the edge QAM, and comply with worldwide audio loudness standards and legislation.

This ensures a superior quality of service (QoS) for television viewers and a boost in revenue streams for cable operators.

Interfacing to a 10 GigE Infrastructure

Any time cable operators make a major change to their video distribution infrastructure they introduce additional complexity and as a result can expect more issues to occur with the broadcast transmission.

With a 10GigE infrastructure, there is a much wider network that operators must monitor. Therefore, as cable operators transition from a 1GigE to 10GigE video distribution infrastructure, it becomes extremely important to be able to measure video and audio quality in real time from every area of the infrastructure and adequately filter transport stream errors so that serious issues are resolved quickly.

While the majority of cable operators today are using a real-time transport stream analysis and monitoring system to identify transmission errors, many of these systems do not support 10GigE or provide the necessary in-depth analyses. Once operators move to a 10GigE infrastructure, they’ll need a system that can interface to the 10GigE backbone while simultaneously supporting other areas on the network like ASI, QAM, and RF. Using a real-time transport stream analysis and monitoring system with a 10GigE interface, an operator can pinpoint exactly where the issue is happening and resolve it before it impacts customers’ quality of service.

While a 10GigE interface is certainly the most critical feature that operators should look for in a next-generation transport stream analysis and monitoring system, there are other important functionalities to look for as well, including sophisticated filtering techniques and tools for managing audio loudness. The following sections will take a closer look at these requirements and their associated benefits.

Intelligent Filtering: Why It’s Important

Many of today’s cable operators are migrating to a 10GigE infrastructure in order to deliver additional services, including high-bandwidth video content. However, as their transmission count increases, so does the chance of transport stream errors, making it important to employ a transport stream analysis and monitoring system with intelligent filtering.

As cable operators add additional services to their offering, being able to classify transport stream errors in an efficient manner is a growing concern. While monitoring multiple video signals, operators need to know if a transport stream error requires immediate attention, or if the error is nonthreatening to their customers’ QoS. Additionally, operator fatigue can become an issue when hundreds of errors show up on the user interface of their transport stream analysis and monitoring system, yet some of these errors don’t need to be addressed. Over time, operators become accustomed to seeing red lights on monitors, and choose to ignore them. This lack of action greatly defeats the purpose of having a monitoring system.

An advanced 10GigE monitoring system classifies and filters errors based on error severity scales defined by SCTE-142, the cable industry’s standard for transport stream error verification. This enables operators to quickly determine which errors require a timely resolution as well as those that can be ignored.

The SCTE’s Recommended Practice for Transport Stream Verification identifies transport stream issues by type, according to the following categories: PSI tables (PAT and PMT), out-of-band tables, in-band tables, PSIP tables (MGT, VCT, etc.), timing model and buffering, consistency, and general errors. Furthermore, each error type is assigned an error severity.

The five transport stream severity levels outlined in SCTE-142, listed in order of most critical to least critical are: • Transport stream off air (TOA): 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.

• Program off air (POA): A main service (virtual channel) is flawed to the point that the service is effectively off-air for conformant/ reasonable 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.

• 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.

• 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.

• 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, but do not have the urgency of higher severity errors.

An example might be a single instance of a 102 ms PAT cycle time (with the remainder of the PATs coming at less than 100 ms intervals.) After errors have been assigned a type and severity level, the monitoring system filters those errors based on rules defined by the cable operator, leaving only the most critical errors exposed. Errors that do not have an impact on QoS can be logged for later analysis.

This enables operators to be proactive about resolving severe transport stream errors in the 10GigE infrastructure.

An advanced 10GigE test and monitoring systems will continuously log DTV transport stream data and send engineers detailed real-time and historical reports.

After the key transport stream issues have been tended to, engineers can perform postmortem analyses and resolve chronic or network-wide issues.

Don’t Forget: Managing Audio Loudness Is Important Too

Today’s television viewers demand a superior TV experience, including audio quality. Inconsistent audio levels, particularly between programming and advertisements, have plagued cable operators over the last several years. Due to viewer complaints, many regulatory bodies around the world have passed standards and legislation designed to eliminate these problems.

One example of recent legislation is the U.S. Commercial Audio Loudness Mitigation (CALM) Act.

Cable operators looking to provide the best possible quality of experience for subscribers should ensure that when they are switching to a 10GigE infrastructure, their test and monitoring system can analyze DTV streams for variations in audio loudness and confirm compliance with audio loudness standards like ATSC A/85 and ITU-R BS.1770.

An advanced test and monitoring solution will log loudness levels in real time and adjust those values based on a number set by the cable operator. If signals drop above or below the recommended A complete monitoring solution provides threshold, engineers will receive an alert.

Through an intuitive, Web-based interface, engineers can remotely adjust the audio stream to eliminate inconsistencies that would be perceptible to the viewer.

The monitoring system provides the cable operator with a detailed analysis so that operators can verify where the violation occurred in the programming to eliminate future occurrences.

Final Thoughts

10GigE infrastructures appear to be the wave of the future for the cable industry, as operators try to keep up with increasing consumer demand for high-bandwidth video services.

After they’ve successfully migrated to a higher performance infrastructure, operators must determine how they can locate, reduce, and eliminate of transport stream errors in a timely and cost-effective manner.

An end-to-end monitoring and analysis solution that measures video and audio quality from the 10GigE core network all the way to the edge QAM is the best choice in this situation. Armed with an advanced monitoring system that includes a 10GigE interface, as well as intelligent filtering and audio monitoring capabilities, cable operators can efficiently address transport stream errors and deliver a superior QoS to customers. ■     

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