FFMPEG - Apply Hardsubs To Video

Hardsubs are simply subtitles baked into the video imagery. E.g. you cannot turn them off/on, they are part of the image. Because of this, usually they are undesirable. However, if you are watching something that needs subtitles, with a tool that does not support subtitle tracks or having separate subtitle files, this may prove to be a workaround solution.

Steps

Assuming you have a subtitles SRT file to hand for the video, you can apply them as hardsubs to the video with:

#!/bin/bash
INPUT_FILENAME="someFileWithoutHardsubs.mp4"
OUTPUT_FILENAME="someVideo.hardsubbed.mp4"
SUBTITLES_FILE="subtitles.srt"

ffmpeg \
  -i $INPUT_FILENAME \
  -vf subtitles=$SUBTITLES_FILE \
  $OUTPUT_FILENAME

Unfortunately this will perform a video re-conversion, so video quality is likely to be lost unless you specify your own CRF/bitrate parameters. You may wish to perform this step with CRF 0, and perform a 2-pass encoding on the finished result. E.g.

#!/bin/bash
INPUT_FILENAME="someFileWithoutHardsubs.mp4"
OUTPUT_FILENAME="someVideo.hardsubbed.mp4"
SUBTITLES_FILE="subtitles.srt"

ffmpeg \
  -i $INPUT_FILENAME \
  -c:v libx264 \
  -crf 0 \
  -vf subtitles=$SUBTITLES_FILE \
  $OUTPUT_FILENAME

References

• trac.ffmpeg.org - HowToBurnSubtitlesIntoVideo