FFMediaToolkit is a cross-platform video decoder/encoder library for .NET that uses FFmpeg native libraries. It supports video frames extraction, reading stream metadata and creating videos from bitmaps in any format supported by FFmpeg.
Sorry, I currently don't have a preview NuGet repository, but you can download the latest .nupkg file from AppVeyor artifacts and install it locally. (click the "build passing" badge in readme).
Could you hook up the develop branch to launch preview packages to NuGet or some private NuGet repository?