Log Message:
Import sptk-3.4 as audio/sptk.
Based on PR#44556 by ISHIHARA Takanori.

The Speech Signal Processing Toolkit (SPTK) is a suite of speech
signal processing tools for UNIX environments, e.g., LPC
analysis, PARCOR analysis, LSP analysis, PARCOR synthesis
filter, LSP synthesis filter, vector quantization techniques,
and other extended versions of them.