Psub.mp4 Site

: MP4 files do not support bitmap-based subtitles like PGS (from Blu-ray) or VobSub (from DVD) as "soft" (toggleable) tracks.

: For toggleable subtitles in MP4, you must use text-based formats like SRT or WebVTT . Subtitles - HandBrake Documentation Psub.mp4

: To use these subtitles in an MP4, they must be hardcoded (burned directly into the video frames) using tools like HandBrake . : MP4 files do not support bitmap-based subtitles