The SMI (Synchronized Multimedia Integration Language) file format, often seen with the extension .smi or .sami, is a text-based markup language used to add subtitles or captions to multimedia content, primarily video. It's a relatively simple format that allows for the synchronization of text with audio and video streams. SMI files contain the text of the subtitles along with timing information that specifies when each line of text should appear and disappear on the screen. The timing is usually expressed in milliseconds. SMI files are typically used in conjunction with video players to display subtitles in various languages, making video content accessible to a wider audience, including those who are deaf or hard of hearing, or those who prefer to watch videos in a different language. The format supports basic text formatting, such as font styles and colors, although the extent of formatting support can vary depending on the video player or software being used. SMI is a precursor to more advanced subtitle formats like SRT and WebVTT, but it remains a widely supported format due to its simplicity and ease of creation. It's often used for encoding subtitles for DVDs and online video streaming.