IMF stands for Interoperable Master Format. It is a new B2B exchange format currently undergoing standardization by the Society of Motion Picture & Television Engineers (SMPTE).
IMF comes in different flavors, but IMF Application 2 (App2), like DCPs, uses JPEG 2000 for compressing images.
easyDCP Creator+ (not easyDCP Creator basic edition) supports loading and creating IMF App2 packages (abbreviated ”IMPs”).
For subtitles and captions, the “TTML Text and Image Profiles for Internet Media Subtitles and Captions 1.0” format is used.