A method, device and medium for determining a coding format are provided. The method includes: receiving one or more data packets forwarded by a call center during a VoLTE communication, in which the one or more data packets carry a first coding format; detecting whether the first coding format is same with a negotiated second coding format; and modifying the coding format used during the VoLTE communication from the second coding format to the first coding format, if the first coding format is not same with the negotiated second coding format.