Natron
Support for many image formats, using OpenImageIO, including multi-layer OpenEXR. Additional image layers can be used to store several color layers, or for non-color information such as depth, optical flow, binocular disparity, or masks.
Support for reading and writing video files through the FFmpeg library, including digital intermediate formats such as DNxHD and Apple ProRes.
Full support of the OpenFX 1.4 API, enabling use of open source or commercial plug-ins.
Support for low-resolution rendering for previewing the output of computing-intensive visual effects.