Version 0.5.9 release contains the following fixes/improvements.

New Features

• Attended call transfer implementation (Replaces support, RFC 3515).
• Major addition to support DNS SRV resolution in PJSIP:
  • Implemented generic asynchronous DNS resolution engine in PJLIB-UTIL: ​http://www.pjsip.org/pjlib-util/docs/html/group__PJ__DNS__RESOLVER.htm
  • Implemented SRV support in PJSIP: ​http://www.pjsip.org/pjsip/docs/html/group__PJSIP__RESOLVE.htm
• MP3 file recording [contributed by Toni Rutar]

Improvements

• the echo canceller seems to work and it's now enabled by default on PJSUA-API
• Speex source codes updated to their latest SVN version (version later than 1.2beta1)
• added pj_shutdown() and pj_atexit() to release internal handles allocated by libraries (important for Symbian)
• Add pjsip_regc_add_headers() APi to set headers to be added to the REGISTER request. This solves the problem where headers registered in the initial REGISTER request (such as User-Agent header) are not sent in subsequent reregistration request.
• Improve call transfer handling in PJSUA-API (not to disconnect call until call transfer completes)
• Improvements in audio device support:
  • Updated PortAudio? to latest version for Mac (OSX 10.4 compatibility)
  • PJSUA-API will try to use other sample rates when it fails to open the device
  • Better support for opening different sound devices.
• Added support for specifying IP address in PJSUA-LIB/pjsua.

Bug Fixes

• Fixed bug in SIP parser: clone_data member of message body is not set.
• Added checking for clock rate mismatch in PJMEDIA master port.
• fixed many memory and handle leaks (there is no single leak now!)
• fixed SIP message leak when transport immediately fails to send the message
• Fixed sound device ID bug: application was unable to use device ID zero because this caused pasound.c to autodetect default device
• Removed duplicated stun.o in pjlib-util Makefile
• Fixed overflow bug in conference.c causing cracking noise (thanks Norman Franke)
• Removed multiple Via headers checking in transport, as proxies will receive multiple Via headers.
• Fixed bug in log length calculation (null character was included) [thanks Klaus Darilion]
• Fixed missing pj_snd_get_info() in nullsound.c
• Changed pasound.c to handle situation when NULL is passed as input/output buffer by PortAudio?
• Fixed typos in pj_*int*_t's comments [thanks Tomasz Ostrowski]
• Removed -DNDEBUG from default CFLAGS [thanks Olivier Gournet]
• Fixed compilation errors when threading is disabled (PJ_HAS_THREADS=0) and safe ioqueue unregistration is disabled (PJ_IOQUEUE_HAS_SAFE_UNREG=0).
• Fixed compilation error in tone generator when using fixed point.
• and many others