Möller, S., Raake, A., Kitawaki, N., Takahashi, A., and Wältermann, M.
Impairment Factor Framework for Wideband Speech Codecs
IEEE Trans. Audio, Speech and Language Proc., 14(6), 1969-1976.
A new method is described for quantifying the
quality degradation introduced by wideband speech codecs via
a one-dimensional impairment factor. The method is based on
auditory listening-only tests, but the resulting impairment factors
may be used for predicting speech quality in an instrumental
way, e.g. for network planning purposes. Following the method,
auditory test results are first transformed to an overall quality
rating scale, and then adjusted to rule out test-specific effects.
The derived impairment factors fit into the common framework
which is defined by the E-model for narrow-band telephone
networks, and which is hereby extended towards wideband
speech transmission. The paper presents the necessary auditory
test data, describes the derivation and adjustment methodology,
and provides numerical values for a range of wideband speech
codecs. The values are tested for their robustness in case of codec
tandems and adjusted to represent the effects of packet loss.