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Cue Point Alignment (Station Manager)
Triton Digital's ad insertion technology relies on the reception of metadata cues (cue points) provided by publishers to determine when to replace or insert commercial content. For the best listener experience, these cue points need to be as close as possible to the perceivable audio transition. This allows for the advertising content's start and end to be defined precisely enough to minimize the listener's perception that a new piece of content is replacing the underlying original one.
When cue points are perfectly aligned, the experience is seamless; the listener perceives inserted ads as if they were part of the original broadcast content, without noticeable interruptions and without hearing a portion of the underlying original content.
This alignment is important at both the beginning of an ad pod and on the return-to-content marker (which we call the ENDBREAK cue point) since the ENDBREAK determines where to reconnect the original content after the replacement content has been played.
General Information about Cue Point Alignment
Whenever a system is playing out audio, it is not guaranteed that the metadata associated with it is perfectly timed to the first frame of the played-out audio. Many factors, such as crossfade position and the audio infrastructure, can affect the alignment between metadata and audio. Misalignment is called "cue point offset."
Cue point offset can have many properties with regard to the beginning of an audio piece. It can be:
Ahead of the audio;
Late with regard to the audio (i.e., behind);
Constant, where the totality of programming has always the same offset (or at least within an acceptable range);
Variable, where different crossfades define the transitions as different times;
Altered by audio delays, profanity filter delays, or other tools affecting the path of metadata.
Note: a small variability within 1 to 30ms is barely perceivable and thus should be considered as “close enough to constant.”
Why are Cue Point Offsets So Different from Station to Station?
There are many reasons why this can happen, such as:
Audio being fed through an audio delay system.
Audio routed through an audio processor before, or on, the streaming computer.
Automation system configuration set to delay the metadata in the configuration.
Metadata being sent through a bad network path, such as:
Sending the data over the internet instead of direct peer-to-peer internally.
Data routed through multiple networks/firewalls or packet scanners.
Metadata being fed through multiple third-party systems.
Automation system computer not up-to-date (hardware) so it processes the output of the metadata slowly or at variable rate because of a lack of resources on the computer.
Variable delays are sometimes caused by profanity delays that need to reconstruct their buffer often without properly realigning the metadata feed. These cases are very difficult to correct and might require help from your profanity delay provider.
How Does Triton Digital Help Achieve Cue Point Alignment?
Triton Digital's Station Manager application, and the Triton Digital Services component in the Telos Z/IPStream R/2, include a tool that apply its own offset, essentially correcting or adjusting the incoming cue point offset. But this cue point alignment correction is only possible in the following addressable cases:
Incoming cue point offset is constant, and
Late or ahead by a range within +5000 to -5000 milliseconds.
Cue points that vary or are altered beyond the range described above cannot be corrected using this method. However, it is possible that the cause of variability can be isolated and removed from the audio chain, thus making cue point offset fall within the addressable cases. Note that even within this range, the farther away from zero offset the more difficult it might be to obtain a stable solution.
For example: a system is constantly sending metadata 500 ms ahead of the beginning of an audio segment; Station Manager can set a cue point alignment value of “-500” making the cue point corrected to 0 ms. The outgoing cue point is then considered to be aligned to 0ms.
Whenever the cue point offset is constant and within a -5000 to 5000 ms range, you can use the cue points alignment tool and attain very acceptable results.
In other situations, you might want to investigate where any variability to extreme offset (more than 5000 ms) is coming from, as the Station Manager/Triton Services cue point alignment tool will not be able to correct those situations.
To determine the cue point offset needed to correct alignment:
You might be able to "guesstimate" (based on your experience with audio technology) and come close enough to the correction value for your adjustment to be successful.
Otherwise, Triton Digital can provide a tool that helps measure this value.
Suggested Areas to Investigate based on Cue Point Offset
0ms – 450ms ahead or early: This is typical and should be regarded as normal. Use the Station Manager cue point correction to adjust. You likely will NOT want to change anything else, since other systems are possibly already taking this offset into account (such as RDS encoders and HD Radio Exporters).
450ms – 800ms: This is usually found in systems that read the metadata off of a filesystem in order to understand the cue point to send. You can reduce this by avoiding writing files over network drives (network drives can be a source of variability). There might be other ways (for example XML over TCP) to send the data that your automation supports; you should look into this if you have too much variability on the cue point offsets. Otherwise, this is well handled by the Station Manager cue point alignment setting.
800ms – 5000ms: This is still within the range that Station Manager can attempt to correct. This often happens when using certain audio processing settings. Be careful; when you change audio processing settings your delay might also change. The typical 1800ms is often a sign that you are feeding your encoder “POST” an existing On-air processor, which is generally not recommended as it is better to have a specific audio stream processing chain.
Over 5000ms: Look at your audio chain and reduce any audio delays and other likely culprits mentioned above. If the offset remains constant and can be reduced to under 5000ms, then the methods described above can be used to finish the alignment.
Maintaining Alignment
Maintaining cue point alignment requires some basic maintenance. Here are some tips that will help in maintaining alignment for as long as possible.
Synchronize the clocks on all of the computers that are involved in the delivery of content, including your automation system, using Network Time Protocol (NTP). Achieve this by making sure you use the same time server for your clock synchronization. In Windows 10, for example, use the “Set the time automatically” feature in Date and Time settings. This prevents having one machine “drift away” slightly every day.
Measure and verify the alignment by listening to the stream at least once every three months. A scheduled reboot at night might help realign things, or you might find that adding or retracting a few milliseconds from the “Cue Point Alignment Setting” in Station Manager could help.