Video file encoded with H.264 compression, which is a popular format for high definition video; often used as the video format for AVCHD camcorders, HDTV, Blu-ray, and HD DVD; generally refers to a video file that is actually an .MP4 file. NOTE: H.264 is actually a video compression codec that requires a video container to host the encoded video. Therefore, a file with the ".h264" extension is generally a misnamed .MP4 file (or another supporting container file format such as .AVI or .MKV). Nevertheless, the ".h264" extension is still sometimes used to describe the contents of H.264 encoded video files.