« Last post by cannam on January 17, 2017, 09:46:20 »
It's true that there has never been a 64-bit Windows build of the QM Vamp Plugins. Making one is a priority for us once SV v3.0 is out.
There are various reasons why few Vamp plugins are available in 64-bit builds for Windows.
The proximate reason is that none of the most widely-used Vamp hosts (Sonic Visualiser, Sonic Annotator, Audacity) exists in a 64-bit Windows version. Since 32-bit hosts can't load 64-bit plugins, there's no pressing reason to produce 64-bit plugins. This will change with Sonic Visualiser v3.0, which for the first time will have a 64-bit Windows build, as well as an adapter that allows it to load 32-bit plugins (out-of-process). So SV v3.0 can continue to use the 32-bit Windows plugins, but also provides more of an incentive to produce 64-bit ones.
In a way this can be attributed to Microsoft's success at providing excellent 32-bit compatibility in 64-bit Windows. On both Linux and OSX we have already had to face the issue of requiring all existing plugins to be rebuilt in 64-bit versions because the underlying platform standard changed. This has never been forced on anyone in the Windows world.
Finally there are various practical reasons, such as that many of the 32-bit Windows plugin builds have been produced using the MinGW compiler which until recently was not readily available in a stable 64-bit version. (I think until fairly recently the 64-bit Visual C++ compiler wasn't included in the free version of Visual Studio either?) So it's not just a question of using the same native platform compiler on the newer platform and getting a new build for the new architecture, as it has been on both Linux and OSX.
The QM plugin set is relatively tricky to rebuild as well, because of its use of LAPACK and BLAS.
Anyway, that's the explanation -- the short answer is that a 64-bit version is "planned soon".