Video and audio processing with FFmpeg

FFmpeg for Video Production

FFmpeg is the essential tool for video/audio processing. This skill covers common operations for Remotion video projects.

Quick Reference

GIF to MP4 (Remotion-compatible)

ffmpeg -i input.gif -movflags faststart -pix_fmt yuv420p \
  -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" output.mp4

Why these flags:

• -movflags faststart - Moves metadata to start for web streaming
• -pix_fmt yuv420p - Ensures compatibility with most players
• scale=trunc(...) - Forces even dimensions (required by most codecs)

Resize Video

# To 1920x1080 (maintain aspect ratio, add black bars)
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" output.mp4

# To 1920x1080 (crop to fill)
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=increase,crop=1920:1080" output.mp4

# Scale to width, auto height
ffmpeg -i input.mp4 -vf "scale=1280:-2" output.mp4

Compress Video

# Good quality, smaller file (CRF 23 is default, lower = better quality)
ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4

# Aggressive compression for web preview
ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset fast -c:a aac -b:a 96k output.mp4

# Target file size (e.g., ~10MB for 60s video = ~1.3Mbps)
ffmpeg -i input.mp4 -c:v libx264 -b:v 1300k -c:a aac -b:a 128k output.mp4

Extract Audio

# Extract to MP3
ffmpeg -i input.mp4 -vn -acodec libmp3lame -q:a 2 output.mp3

# Extract to AAC
ffmpeg -i input.mp4 -vn -acodec aac -b:a 192k output.m4a

# Extract to WAV (uncompressed)
ffmpeg -i input.mp4 -vn output.wav

Convert Audio Formats

# M4A to MP3 (for ElevenLabs voice samples)
ffmpeg -i input.m4a -codec:a libmp3lame -qscale:a 2 output.mp3

# WAV to MP3
ffmpeg -i input.wav -codec:a libmp3lame -b:a 192k output.mp3

# Adjust volume
ffmpeg -i input.mp3 -filter:a "volume=1.5" output.mp3

Trim/Cut Video

# Cut from timestamp to duration (recommended - reliable)
ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c:v libx264 -c:a aac output.mp4

# Cut from timestamp to timestamp
ffmpeg -i input.mp4 -ss 00:00:30 -to 00:00:45 -c:v libx264 -c:a aac output.mp4

# Stream copy (faster but may lose frames at cut points)
# Only use when source has frequent keyframes
ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c copy output.mp4

Note: Re-encoding is recommended for trimming. Stream copy (-c copy) can silently drop video if the seek point doesn't align with a keyframe.

Speed Up / Slow Down

# 2x speed (video and audio)
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

# 0.5x speed (slow motion)
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" output.mp4

# Video only (no audio)
ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" -an output.mp4

Concatenate Videos

# Create file list
echo "file 'clip1.mp4'" > list.txt
echo "file 'clip2.mp4'" >> list.txt
echo "file 'clip3.mp4'" >> list.txt

# Concatenate (same codec/resolution)
ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp4

# Concatenate with re-encoding (different sources)
ffmpeg -f concat -safe 0 -i list.txt -c:v libx264 -c:a aac output.mp4

Add Fade In/Out

# Fade in first 1 second, fade out last 1 second (30fps video)
ffmpeg -i input.mp4 -vf "fade=t=in:st=0:d=1,fade=t=out:st=9:d=1" -c:a copy output.mp4

# Audio fade
ffmpeg -i input.mp4 -af "afade=t=in:st=0:d=1,afade=t=out:st=9:d=1" -c:v copy output.mp4

Get Video Info

# Duration, resolution, codec info
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 input.mp4

# Full info
ffprobe -v quiet -print_format json -show_format -show_streams input.mp4

Remotion-Specific Patterns

Video Speed Adjustment for Remotion

When to use FFmpeg vs Remotion playbackRate:

Scenario	Use FFmpeg	Use Remotion
Constant speed (1.5x, 2x)	Either works	✅ Simpler
Extreme speeds (>4x or <0.25x)	✅ More reliable	May have issues
Variable speed (accelerate over time)	✅ Pre-process	Complex workaround needed
Need perfect audio sync	✅ Guaranteed	Usually fine
Demo needs to fit voiceover timing	✅ Pre-calculate	Runtime adjustment

Remotion limitation: playbackRate must be constant. Dynamic interpolation like playbackRate={interpolate(frame, [0, 100], [1, 5])} won't work correctly because Remotion evaluates frames independently.

# Speed up demo to fit a scene (e.g., 60s demo into 20s = 3x speed)
ffmpeg -i demo-raw.mp4 \
  -filter_complex "[0:v]setpts=0.333*PTS[v];[0:a]atempo=3.0[a]" \
  -map "[v]" -map "[a]" \
  public/demos/demo-fast.mp4

# Slow motion for emphasis (0.5x speed)
ffmpeg -i action.mp4 \
  -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" \
  -map "[v]" -map "[a]" \
  public/demos/action-slow.mp4

# Speed up without audio (common for screen recordings)
ffmpeg -i demo.mp4 -filter:v "setpts=0.5*PTS" -an public/demos/demo-2x.mp4

# Timelapse effect (10x speed, drop audio)
ffmpeg -i long-demo.mp4 -filter:v "setpts=0.1*PTS" -an public/demos/timelapse.mp4

Calculate speed factor:

• To fit X seconds of video into Y seconds of scene: speed = X / Y
• setpts multiplier = 1 / speed (e.g., 3x speed = setpts=0.333*PTS)
• atempo value = speed (e.g., 3x speed = atempo=3.0)

Extreme speed (>2x audio): Chain atempo filters (each limited to 0.5-2.0 range):

# 4x speed audio
-filter_complex "[0:a]atempo=2.0,atempo=2.0[a]"

# 8x speed audio
-filter_complex "[0:a]atempo=2.0,atempo=2.0,atempo=2.0[a]"

Prepare Demo Recording for Remotion

# Standard 1080p, 30fps, Remotion-ready
ffmpeg -i raw-recording.mp4 \
  -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,fps=30" \
  -c:v libx264 -crf 18 -preset slow \
  -c:a aac -b:a 192k \
  -movflags faststart \
  public/demos/demo.mp4

Screen Recording to Remotion Asset

# From iPhone/iPad recording (usually 60fps, variable resolution)
ffmpeg -i iphone-recording.mov \
  -vf "scale=1920:-2,fps=30" \
  -c:v libx264 -crf 20 \
  -an \
  public/demos/mobile-demo.mp4

Batch Convert GIFs

for f in assets/*.gif; do
  ffmpeg -i "$f" -movflags faststart -pix_fmt yuv420p \
    -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" \
    "public/demos/$(basename "$f" .gif).mp4"
done

Common Issues

"Height not divisible by 2"

Add scale filter: -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2"

Video won't play in browser

Use: -movflags faststart -pix_fmt yuv420p -c:v libx264

Audio out of sync after speed change

Use filter_complex with atempo: -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]"

File too large

Increase CRF (23→28) or reduce resolution

Quality Guidelines

Use Case	CRF	Preset	Notes
Archive/Master	18	slow	Best quality, large files
Production	20-22	medium	Good balance
Web/Preview	23-25	fast	Smaller files
Draft/Quick	28+	veryfast	Fast encoding

Platform-Specific Output Optimization

After Remotion renders your video (typically to out/video.mp4), use FFmpeg to optimize for each distribution platform.

Workflow Integration

Remotion render (master)     FFmpeg optimization      Platform upload
       ↓                            ↓                       ↓
   out/video.mp4  ────────→  out/video-youtube.mp4  ───→  YouTube
                  ────────→  out/video-twitter.mp4  ───→  Twitter/X
                  ────────→  out/video-linkedin.mp4 ───→  LinkedIn
                  ────────→  out/video-web.mp4      ───→  Website embed

YouTube (Recommended Settings)

YouTube re-encodes everything, so upload high quality:

# YouTube optimized (1080p)
ffmpeg -i out/video.mp4 \
  -c:v libx264 -preset slow -crf 18 \
  -profile:v high -level 4.0 \
  -bf 2 -g 30 \
  -c:a aac -b:a 192k -ar 48000 \
  -movflags +faststart \
  out/video-youtube.mp4

# YouTube Shorts (vertical 1080x1920)
ffmpeg -i out/video.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2" \
  -c:v libx264 -crf 18 -c:a aac -b:a 192k \
  out/video-shorts.mp4

Twitter/X

Twitter has strict limits: max 140s, 512MB, 1920x1200:

# Twitter optimized (under 15MB target for fast upload)
ffmpeg -i out/video.mp4 \
  -c:v libx264 -preset medium -crf 24 \
  -profile:v main -level 3.1 \
  -vf "scale='min(1280,iw)':'min(720,ih)':force_original_aspect_ratio=decrease" \
  -c:a aac -b:a 128k -ar 44100 \
  -movflags +faststart \
  -fs 15M \
  out/video-twitter.mp4

# Check file size and duration
ffprobe -v error -show_entries format=duration,size -of csv=p=0 out/video-twitter.mp4

LinkedIn

LinkedIn prefers MP4 with AAC audio, max 10 minutes:

# LinkedIn optimized
ffmpeg -i out/video.mp4 \
  -c:v libx264 -preset medium -crf 22 \
  -profile:v main \
  -vf "scale='min(1920,iw)':'min(1080,ih)':force_original_aspect_ratio=decrease" \
  -c:a aac -b:a 192k -ar 48000 \
  -movflags +faststart \
  out/video-linkedin.mp4

Website/Embed (Optimized for Fast Loading)

# Web-optimized MP4 (small file, progressive loading)
ffmpeg -i out/video.mp4 \
  -c:v libx264 -preset medium -crf 26 \
  -profile:v baseline -level 3.0 \
  -vf "scale=1280:720" \
  -c:a aac -b:a 128k \
  -movflags +faststart \
  out/video-web.mp4

# WebM alternative (better compression, wider browser support)
ffmpeg -i out/video.mp4 \
  -c:v libvpx-vp9 -crf 30 -b:v 0 \
  -vf "scale=1280:720" \
  -c:a libopus -b:a 128k \
  -deadline good \
  out/video-web.webm

GIF (for Previews/Thumbnails)

# High-quality GIF (first 5 seconds)
ffmpeg -i out/video.mp4 -t 5 \
  -vf "fps=15,scale=480:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" \
  out/preview.gif

# Smaller file GIF
ffmpeg -i out/video.mp4 -t 3 \
  -vf "fps=10,scale=320:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" \
  out/preview-small.gif

Platform Requirements Quick Reference

Platform	Max Resolution	Max Size	Max Duration	Audio
YouTube	8K	256GB	12 hours	AAC 48kHz
Twitter/X	1920x1200	512MB	140s	AAC 44.1kHz
LinkedIn	4096x2304	5GB	10 min	AAC 48kHz
Instagram Feed	1080x1350	4GB	60s	AAC 48kHz
Instagram Reels	1080x1920	4GB	90s	AAC 48kHz
TikTok	1080x1920	287MB	10 min	AAC

Batch Export for All Platforms

#!/bin/bash
# save as: export-all-platforms.sh
INPUT="out/video.mp4"

# YouTube (high quality)
ffmpeg -i "$INPUT" -c:v libx264 -preset slow -crf 18 \
  -c:a aac -b:a 192k -movflags +faststart \
  out/video-youtube.mp4

# Twitter (compressed)
ffmpeg -i "$INPUT" -c:v libx264 -crf 24 \
  -vf "scale='min(1280,iw)':'-2'" \
  -c:a aac -b:a 128k -movflags +faststart \
  out/video-twitter.mp4

# LinkedIn
ffmpeg -i "$INPUT" -c:v libx264 -crf 22 \
  -c:a aac -b:a 192k -movflags +faststart \
  out/video-linkedin.mp4

# Web embed (small)
ffmpeg -i "$INPUT" -c:v libx264 -crf 26 \
  -vf "scale=1280:720" \
  -c:a aac -b:a 128k -movflags +faststart \
  out/video-web.mp4

echo "Exported:"
ls -lh out/video-*.mp4

Error Handling

Common errors and fixes when processing video:

# Check if FFmpeg succeeded
ffmpeg -i input.mp4 -c:v libx264 output.mp4 && echo "Success" || echo "Failed: check input file"

# Validate output file is playable
ffprobe -v error -select_streams v:0 -show_entries stream=codec_name -of csv=p=0 output.mp4

# Get detailed error info
ffmpeg -v error -i input.mp4 -f null - 2>&1 | head -20

Handling Common Failures

Error	Cause	Fix
"No such file"	Input path wrong	Check path, use quotes for spaces
"Invalid data"	Corrupted input	Re-download or re-record source
"height not divisible by 2"	Odd dimensions	Add scale filter with trunc
"encoder not found"	Missing codec	Install FFmpeg with full codecs
Output 0 bytes	Silent failure	Check full ffmpeg output for errors

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