Is a the most popular media container format on phones without the support of 3G, which is currently somewhat outdated. Its main advantage is a compactness. Video data here gets stored in h.263 or MPEG-4 formats. AAAC-LC or AMR-NB are available for audio.
Grandstream ring-tone files. Whilst this file format can contain A-Law, μ-law, GSM, G.722, G.723, G.726, G.728, or iLBC encoded audio, SoX supports reading and writing only A-Law and μ-law.