This dot release replaces 5.8.0 that was missing a couple CMake files in the tarball and the multicore detection did not compile on MacOS and other BSDs. Because the Windows executables were not affected I will not be updating them.
Much of the development for this release stemmed from the discovery of situations where the quantization noise introduced with the hybrid mode was higher than expected, in particular with very low bitrates (e.g., < 3 bps) and high sample rates. This was traced to feedback in the decorrelation loop and has been addressed. Also, audio samples were discovered where the DNS (dynamic noise shaping) algorithm produced sub-optimal shaping, and this has been addressed with an all-new DNS algorithm. Finally, some issues were fixed that caused the "extra" mode performance to degrade with multithreading and also with the hybrid mode.
The other major change is that multithreading is now turned on by default for the command-line programs, assuming that a multicore CPU is detected. This can be disabled with a new option --no-threads.
MinGW is now used to build all official Windows binaries, both the command-line programs and the .DLL library. The multi-threading feature uses condition variables which are not supported on Windows XP, so the regular Windows binaries (-x64 and -x86) will not work there. However, I created builds that have the threading feature disabled and these work fine on XP and are available below (-WinXP). The WinXP versions can also be used on newer Windows in situations where default multi-threading is not desirable, such as when multi-threading is already implemented at a higher level (e.g., with Foobar2000 or EAC).
For the remaining minor fixes and improvements, see the official NEWS file.
The DirectShow filter installers for Windows have been updated to 1.6.0 and are available here.
Note that I am no longer able to generate binaries for macOS. These should probably be obtained from HomeBrew anyway, so check there for an update to 5.8.1.