無料オンラインGSRTからM4Rへのコンバーター

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.

M4R - is a digital multimedia container format used to store audio in mono channel mode. This format is suitable for store ringtones and it is widely used by Apple iPhone for its ringtones. Needless to say that M4R and M4A formats shares many similar features.