CRITICAL GUIDELINES

Windows File Path Requirements

MANDATORY: Always Use Backslashes on Windows for File Paths

When using Edit or Write tools on Windows, you MUST use backslashes (\) in file paths, NOT forward slashes (/).

FFmpeg Karaoke & Animated Text

Use this skill for karaoke subtitles, kinetic typography, scrolling credits, animated lower thirds, typewriter text, timers, and dynamic text overlays. Keep answers practical: identify whether ASS or drawtext is the right tool, provide a copy-paste-ready command or ASS snippet, and call out timing units.

Quick Reference

When to Use This Skill

Use for animated text and karaoke:

• Music video lyrics with karaoke highlighting
• Movie-style scrolling credits
• Animated titles and lower thirds
• Typewriter text reveal
• Kinetic typography and word pops
• Countdown timers, stopwatches, frame counters, timecode overlays
• Multi-line text and textfile-driven overlays

Tool Choice: ASS vs drawtext

CRITICAL: ASS Time Unit Reference

ASS uses TWO DIFFERENT time unit systems. This is a common source of bugs. Karaoke tags use centiseconds; ASS animation tags use milliseconds; FFmpeg drawtext expressions use seconds.

Karaoke Tags = CENTISECONDS (1/100 second)

Conversion: seconds * 100 = centiseconds.

Animation Tags = MILLISECONDS (1/1000 second)

Conversion: seconds * 1000 = milliseconds.

FFmpeg drawtext = SECONDS

Common Mistake

; WRONG - mixing units:
Dialogue: 0,0:00:00.00,0:00:02.00,Style,,0,0,0,,{\k100\t(0,100,...)}Word
; {\k100} = 1 second, but \t(0,100,...) = 0.1 seconds

; CORRECT - matched duration:
Dialogue: 0,0:00:00.00,0:00:02.00,Style,,0,0,0,,{\k100\t(0,1000,...)}Word

For the full timing-unit reference, use ffmpeg-animation-timing-reference.

Karaoke Core Pattern

[Script Info]
ScriptType: v4.00+
PlayResX: 1920
PlayResY: 1080

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Karaoke,Arial,72,&H00FFFFFF,&H000000FF,&H00000000,&H80000000,1,0,0,0,100,100,0,0,1,3,2,2,10,10,50,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:05.00,Karaoke,,0,0,0,,{\k50}Twinkle {\k50}twinkle {\k50}little {\k50}star

Burn into video:

ffmpeg -i input.mp4 \
  -vf "ass=karaoke.ass" \
  -c:v libx264 -crf 18 -c:a copy \
  output_karaoke.mp4

For advanced styles, neon/gradient karaoke, per-character timing, and animated karaoke transforms, see references/karaoke-ass-patterns.md.

drawtext Core Patterns

# Fade in title over 2 seconds
ffmpeg -i input.mp4 \
  -vf "drawtext=text='Title':fontsize=100:fontcolor=white:x=(w-tw)/2:y=(h-th)/2:alpha='min(1,t/2)'" \
  output.mp4

# Vertical bounce
ffmpeg -i input.mp4 \
  -vf "drawtext=text='BOUNCE':fontsize=80:fontcolor=yellow:x=(w-tw)/2:y='(h-th)/2+50*sin(t*5)'" \
  bounce.mp4

# Scroll credits upward at 80px/sec
ffmpeg -i input.mp4 \
  -vf "drawtext=textfile=credits.txt:fontsize=48:fontcolor=white:x=(w-tw)/2:y=h-80*t" \
  -c:v libx264 -crf 18 output.mp4

For spring/elastic/wobble formulas, typewriter effects, lower thirds, countdowns, stopwatches, metadata overlays, and multi-line text, see references/drawtext-animation-recipes.md.

Workflow

1. Choose ASS or drawtext using the tool-choice table.
2. Verify timing units before writing tags or expressions.
3. Probe input when needed (ffprobe) to confirm duration, frame rate, and resolution.
4. Set output encoding explicitly when burning text (-c:v libx264 -crf 18, audio copy only when compatible).
5. Use short test renders (-ss, -t) before rendering a full music video or credit roll.
6. Check readability: karaoke should track words within ~30ms; captions need enough display time; scrolling credits should move slowly enough to read.

Reference Map

• references/karaoke-ass-patterns.md - ASS karaoke basics, \k / \kf / \ko, BPM timing, tag selection, neon/gradient styles, per-character karaoke, ASS color format, animated karaoke effects.
• references/drawtext-animation-recipes.md - Spring bounce, elastic overshoot, easing approximations, wobble/wiggle, pulse, wipes, typewriter, fades, moving text, kinetic typography, lower thirds, countdowns, stopwatches, dynamic variables, multi-line text.
• references/scrolling-credits-and-expressions.md - Music/education/credits timing, vertical credits, horizontal tickers, ASS rotation workaround, drawtext variables and expression cookbook.

Related Skills

• ffmpeg-animation-timing-reference - Timing units, caption durations, easing, sync tolerances
• ffmpeg-captions-subtitles - Subtitle fundamentals, extraction, burn-in, styling
• ffmpeg-kinetic-captions - Word-level pop/bounce/grow caption effects
• viral-video-animated-captions - Social-video caption templates
• ffmpeg-shapes-graphics - Boxes, backgrounds, graphic overlays
• ffmpeg-transitions-effects - xfade and video transitions