Detailed far-infrared spectra of the optical phonons are reported for antiferromagnetic MnO. Eigenfrequencies, phonon damping and effective plasma frequencies are studied as a function of temperature. Special attention is paid to the phonon splitting at the antiferromagnetic phase transition. The results are compared to recent experimental and theoretical studies of the spin-phonon coupling in frustrated magnets, which are explained in terms of a spin-driven Jahn-Teller effect, and to ab initio and model calculations, which predict phonon splitting induced by magnetic order. ; Comment: 5 pages, 4 figures