Portable players do not "search" for subtitles. They require identity. If your video file is named: Prison.Break.S01E01.Pilot.720p.BluRay.YIFY.mp4

, having accurate subtitles is crucial. Technical jargon regarding structural engineering, legal maneuvers, and prison slang can be easily lost if the subtitle file is poorly synced or translated. How to Watch Legally (with Subtitles)

The gold standard for subtitles. They have a massive database.