RLE

Run-length encoding (RLE) is a process where a single value repeated several times is encoded as that value, its starting point and its duration. For example, the string ``ABBBBBBCCCCCAAAAA'' might be encoded as A1B6C5A5 (which implicitly encodes starting time, since the string is in order). RLE is the generalisation of the LoudRun metafeature. RLE instantiated features consist of the following tuple:

• value: The value that is repeated.
• start: The frame at which that sequence of repetitions begins.
• duration: The number of frames that the value remains the same as the starting value.

It operates on a single channel. It accepts the following settings:

• channel: Which channel to extract runs from. Default value is the first channel defined in the domain description file.

• minrun: The minimum run of identical values for a run to be of interest. Default value is 2 (i.e. runs of length 1 don't count).

• limitvalues: In some cases, we are not interested in runs of all possible values of a channel. For instance, in the Tech Support domain, we were only interested in runs of high-volume conversation, not low volume ones. Hence we can constrain our interest to only some possible values and not all of them.