Returns a list of two vectors: pitch_upsampled (the upsampled version
of the input) and gc_upsampled (new indices of glottal cycles on an
upsampled scale)
Arguments
pitch_per_gc
a vector of fundamental frequencies per glottal cycle
samplingRate
target sampling rate after upsampling, in Hz
Details
Upsamples a pitch contour to samplingRate through linear interpolation
between successive glottal cycles.