IMSDroid 是 Android 上的一个高质量的视频 SIP/IMS 客户端。值得关注的特性：
SIP(RFC 3261, 3GPP TS 24.229 Rel-9)
TCP and UDP over IPv4 or IPv6
Signaling Compression, SigComp(RFC 3320, 3485, 4077, 4464, 4465, 4896, 5049, 5112 and 1951)
Enhanced Address Book (XCAP storage, authorizations, presence, …)
Partial supports for GSMA Rich Communication Suite release 3
Partial supports for One Voice Profile V1.0.0 (GSMA VoLTE)
Partial supports for MMTel UNI (used by GSMA RCS and GSMA VoLTE)
IMS-AKA registration (both AKA-v1 and AKA-v2), Digest MD5, Basic
3GPP Early IMS Security (3GPP TS 33.978)
Proxy-CSCF discovery using DNS NAPTR+SRV
Private extension headers for 3GPP
Service Route discovery
Subscription to reg event package (Honoring network initiated (re/de/un)-registration events)
3GPP SMS Over IP (3GPP TS 23.038, 24.040, 24.011, 24.341 and 24.451)
Voice Call (G729AB1, AMR-NB, iLBC, GSM, PCMA, PCMU, Speex-NB)
Video Call (VP8, H264, MP4V-ES, Theora, H.263, H.263-1998, H.261)
DTMF (RFC 4733)
QoS negotiation using Preconditions (RFC 3312, 4032 and 5027)
SIP Session Timers (RFC 4028)
Provisional Response Acknowledgments (PRACK)
Communication Hold (3GPP TS 24.610)
Message Waiting Indication (3GPP TS 24.606)
Calling E.164 numbers by using ENUM protocol (RFC 3761)
NAT Traversal using STUN2 (RFC 5389) with possibilities to automatically discover the server by using DNS SRV (TURN already implemented and ICE is under tests)
