Subtitles

FFmpeg supports extracting, burning-in, and converting subtitles between formats.

Extract Subtitles

# Extract SRT from MP4
ffmpeg -i input.mp4 -map 0:s:0 output.srt

# Extract all subtitle tracks
ffmpeg -i input.mkv -map 0:s output_%d.srt

# Extract with language filter
ffmpeg -i input.mkv -map 0:s:m:language:eng output_eng.srt

Convert Subtitles

# SRT to ASS (with style)
ffmpeg -i input.srt output.ass

# ASS to SRT (strip formatting)
ffmpeg -i input.ass output.srt

# Convert to WebVTT (for HTML5)
ffmpeg -i input.srt output.vtt

Burn Subtitles into Video

# Burn SRT into video
ffmpeg -i input.mp4 -vf "subtitles=input.srt" \
  -c:v libx264 -crf 22 -c:a aac output.mp4

# Burn ASS with custom styles
ffmpeg -i input.mp4 -vf "subtitles=input.ass" \
  -c:v libx264 -crf 22 -c:a aac output.mp4

# Burn subtitles from embedded track
ffmpeg -i input.mkv -vf "subtitles=input.mkv" \
  -c:v libx264 -crf 22 -c:a aac output.mp4

# Burn subtitle at specific time offset
ffmpeg -i input.mp4 -vf "subtitles=input.srt:force_style='FontSize=24,PrimaryColour=&H00FFFF&'" \
  -c:v libx264 -crf 22 output.mp4

Hardcoded Subtitles (Image-based)

# Convert text subtitles to image-based (for players without subtitle support)
ffmpeg -i input.mp4 -vf "subtitles=input.srt:stream_index=0" \
  -c:v libx264 -crf 22 output_hardsub.mp4

Add Soft Subtitles (Track)

# Copy subtitles without burning in (player chooses to show)
ffmpeg -i input.mp4 -i subs.srt -c:v copy -c:a copy \
  -c:s srt -metadata:s:s:0 language=eng \
  output_with_subs.mp4

# Add multiple subtitle tracks
ffmpeg -i input.mp4 -i eng.srt -i spa.srt -i fra.srt \
  -c:v copy -c:a copy \
  -c:s srt \
  -metadata:s:s:0 language=eng \
  -metadata:s:s:1 language=spa \
  -metadata:s:s:2 language=fra \
  output_multilang.mp4

Subtitle Bitstream Filters

# Convert ASS subtitles for MP4 (mov_text codec)
ffmpeg -i input.mp4 -i subs.ass \
  -c:v copy -c:a copy \
  -c:s mov_text \
  -bss:v filter_codec_tags -metadata:s:s:0 codec_tag=0x0000 \
  output_mp4.mp4

Common Subtitle Formats

Format	FFmpeg Codec	Description
SRT	subrip	Plain text, most compatible
ASS/SSA	ass	Advanced styling, animated
WebVTT	webvtt	HTML5 web standard
VOBSub	dvdsub	Image-based (DVD subtitles)
MovText	mov_text	MP4 soft subtitles
HDMV PGS	hdmv_pgs_subtitle	Blu-ray image subtitles

Subtitle Filters

# Adjust subtitle position
ffmpeg -i input.mp4 -vf "subtitles=input.srt:force_style='MarginV=50'" \
  -c:v libx264 output.mp4

# Change subtitle appearance
ffmpeg -i input.mp4 -vf "subtitles=input.srt:force_style='FontName=Arial,FontSize=18,PrimaryColour=&H00FFFFFF&,OutlineColour=&H00000000&,Bold=1'" \
  -c:v libx264 output.mp4

# Scale subtitle font
ffmpeg -i input.mp4 -vf "subtitles=input.srt:force_style='FontSize=36'" \
  -c:v libx264 output.mp4