d to the AMR and AMR-WB codecs: - for the same quality, the rate is decreased; - for achieving equivalent rate, the quality is improved. The SWB-type and FB-type EVS codecs are reserved for coding music signals. 170 VoLTE and ViLTE The SDP offer relating to EVS codec must also include the AMR and AMR-WB codecs, EVS codec having priority. The rate required for reservation of resources in the 4G network is equal to 42 kbps (field b = AS: 42). The EVS codec is WB-type because the sampling frequency is 16000 Hz. The rate of WB-type EVS codec is in the range between 5.9 and 24.4 kbps. m=audio 49152 RTP/AVP 97 98 99 100 101 b=AS: 42 a=rtpmap: 97 EVS/16000/1 a=fmtp: 97 br=5.9-24.4 a=rtpmap : 98 AMR-WB/16000/1 a=rtpmap: 99 AMR-WB/16000/1 a=fmtp: 99 octet-align=1 a=rtpmap : 100 AMR/8000/1 a=rtpmap : 101 AMR/8000/1 a=fmtp: 101 octet-align=1 5.3. ViLTE profile service 5.3.1. Supplementary conversational video service The supplementary telephone service described for VoLTE service is extended for the ViLTE service, with supplements for communication hold and conference. In the case of communication hold, the IMS network can take the decision to reduce the bandwidth for audio and video streams. In the case of conference, the following configurations are possible: - a UA entity invited to the conference can only enable the audio stream and disable the video stream indicating in the SDP message, a value equal to ZERO for the port number; - a UA entity participating in a conversational video conference can disable the video stream and keep the audio stream; Service Profiles - if the UA entity responsible for the conversational video conference removes the video stream, the IMS network may decide to convert conversational video conference in an audio conference for all participants. 5.3.2. Video flow The SDP message contains the types of video codecs proposed by the caller and the codec selected by the callee, among the following codecs list: - H.264 codec, with constrained baseline profile (CBP), level 1.2; H.265 with main profi