Hardsubs don’t come with timestamps. When you extract them, you not only need the text but also the and out-time for each line. Most extraction tools attempt to detect scene changes or subtitle blocks automatically.
# Convert to grayscale and apply heavy contrast mogrify -grayscale Rec709Luma -contrast-stretch 2% -threshold 50% *.png extract hardsub from video
If the video is 480p or lower, OCR accuracy drops significantly. You may need to manually correct typos (SubtitleEdit has a built-in spellcheck for this). Hardsubs don’t come with timestamps
For large files or privacy, local tools are often faster and more accurate. SubExtractor: Extract Hardcoded Subtitles to SRT/VTT Online extract hardsub from video