Unexpected Duration Event
The Unexpected Duration (UD) event is reported when a tone segment of the Reference Audio file is shorter or longer than expected. In Referenced Mode, the system knows the Reference Audio file that is being played on the Source DUT and therefore knows how long a specific tone segment should last. If either a change of amplitude or frequency arrives either before or after that programmed duration, then the change is by definition unexpected. Lost or corrupted data, repeated data, faulty packet-loss-concealment algorithms, etc can cause this type of audio impairment.
The amount that a measured duration must deviate from the programmed duration of a tone segment before the system declares this event varies, depending upon the negotiated over-the-air audio stream specific parameters, but it is generally in the range of 5% to 10%. Note that this event will result in an attempt to resynchronize (see "Synchronization Lost Event" and "Synchronization") if the measured duration is greater than expected.
The info reported with the Unexpected Duration event is listed below:
- Info1: The measured duration (μs).
- Info2: The expected duration (μs).
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Msg: “UD@Lvl+, SegID=N, ixSeg=I, LastFreq=F”; where ‘N’ is the Segment ID, I is an index into the segment description in a Segment Array, and F is the measured frequency.
Note: The above “Msg” example is one of several unexpected duration cases that can occur. The exact syntax will vary.