I started my first digital voice project for amateur radio in 1982 together with Hartmut, DC2BI. May be this was the first digital voice project worldwide. Unfortunately processors were too slow at these times, and there was a part- success only. We stopped the project 2 years later.
That is the reason, that I am interested in digital voice all the time.
You will find something about my digital voice activities and my experience
My experience with the ard9800 (AOR)
Something about windrm and drmdv (free)
You will find a (german) lecture about digital voice in general here
For SSTV I use EasyPal and have translated the Helppages to german