Dropout Event

The purpose of the Dropout event is to report the detection of an unusual brief silence period where the brief silence is preceded and followed by “normal” audio levels. A typical definition of Dropout is the short dramatic loss of volume typically caused by lost digital information. Root causes include transmission system errors resulting in lost data packets, transmission channel reconfigurations, bad sections of memory, processor overloads that temporarily interrupt the flow of information, and so on. The challenge is to detect real dropout events while at the same time honoring natural silence. For music, there are natural musical “rests” that occur. Speech includes natural inter-syllable, inter-word, and pause silence.

Dropout events are reported when the average audio level (RMS) is initially above the Measurement Threshold, then falls below the Silence Threshold, and then quickly rises above the Measurement Threshold again (see " Measurement And Silence Threshold"). This approach largely disqualifies the natural inter-syllable silence and pauses that occur in natural speech, but will detect gaps caused by dropped data. Note that the system does not report dropouts that begin at very low energy levels.

Shown in " Dropout Examples" are examples to illustrate the Dropout event.

The two events of 2.5 ms and 25 ms are reported as Dropout events, while the 57 ms interval at the center is not. Although 57 ms interval is of sufficient duration, and the level remains below Silence Threshold for the duration, the interval is not immediately preceded by sustained energy above the Measurement Threshold.

The info reported with the Dropout event is listed below:

• Info1: The number of samples over which the dropout persisted. The value can be converted to time duration (sec) by dividing by sample rate. Likewise the Start Time of the dropout can be calculate by subtracting the duration from the event’s sample number (time stamp) parameter and converting to time.
• Info2: Not used.
• Msg: Not used.