Recommendation ITU-T P.863.1 provides important remarks that should be taken into account in the objective quality evaluation of speech conforming to Recommendation ITU-T P.863. Users of ITU T P.863 should understand and follow the guidance given in this Recommendation. This Recommendation is a supplementary guide for users of Recommendation ITU-T P.863, which describes a means of estimating listening speech quality by using reference and degraded speech samples. The scope of Recommendation ITU-T P.863 is clearly defined in itself. This Recommendation does not extend or narrow that scope; rather, it provides necessary and important information for obtaining stable, reliable and meaningful objective measurement results in practice.