The constants define the values for the time pitch algorithms.
In macOS, the default algorithm for all time pitch operations is
On iOS, the default algorithm for playback is
low and the default for export & other offline processing is
For scaled audio edits, i.e. when the
time of an
AVAsset is between
time of unequal duration, it is important to choose an algorithm that supports the full range of edit rates present in the source media.
spectral is often the best choice due to the highly inclusive range of rates it supports, assuming that it is desirable to maintain a constant pitch regardless of the edit rate. If it is instead desirable to allow the pitch to vary with the edit rate,
varispeed is the best choice.