Ffmpeg

calesthio/OpenMontage/.claude/skills/ffmpeg

作者 calesthio9327439db69021ab4b0e2776729bf3b58fdb5a87無授權條款65K 個星標收錄於 2026年10月9日更新於 2026年10月9日儲存庫5 天前更新

Video and audio processing with FFmpeg. Use for format conversion, resizing, compression, audio extraction, and preparing assets for Remotion. Triggers include converting GIF to MP4, resizing video, extracting audio, compressing files, or any media transformation task.

僅含說明Design & Creative
AI 產生的概覽

使用 FFmpeg 轉換、縮放、壓縮、剪輯與準備影音素材的參考指南。

功能
這個技能是一份 FFmpeg 與 ffprobe 指令參考，涵蓋媒體轉換工作：GIF 轉 MP4、縮放與補邊、以 CRF 和 preset 壓縮、音訊擷取與格式轉換、剪輯、變速、串接、淡入淡出，以及媒體資訊查詢。它也記錄 Remotion 相關用法，例如把示範錄影與螢幕錄製處理成素材，並提供針對 YouTube、Twitter/X、LinkedIn、網頁嵌入與 GIF 預覽的分平台匯出預設。文件包含常見錯誤的排查說明與畫質設定對照表。
適用情境
當你需要轉換、縮放、壓縮、剪輯媒體檔案或擷取音訊時使用，也適合為 Remotion 專案準備影片素材。在製作分平台匯出檔或排查 FFmpeg 錯誤（例如尺寸為奇數、輸出無法播放）時同樣有用。
執行需求
需要在本機安裝 FFmpeg 與 ffprobe，並具備相關編解碼器（例如 libx264、libmp3lame、libvpx-vp9、libopus）。這個技能沒有附帶指令碼，只有說明與指令範例。不需要網路存取，但部分範例涉及下載或上傳媒體。

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)

bash
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

bash
# 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 heightffmpeg -i input.mp4 -vf "scale=1280:-2" output.mp4

Compress Video

bash
# 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 previewffmpeg -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

bash
# Extract to MP3ffmpeg -i input.mp4 -vn -acodec libmp3lame -q:a 2 output.mp3
# Extract to AACffmpeg -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

bash
# M4A to MP3 (for ElevenLabs voice samples)ffmpeg -i input.m4a -codec:a libmp3lame -qscale:a 2 output.mp3
# WAV to MP3ffmpeg -i input.wav -codec:a libmp3lame -b:a 192k output.mp3
# Adjust volumeffmpeg -i input.mp3 -filter:a "volume=1.5" output.mp3

Trim/Cut Video

bash
# 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 timestampffmpeg -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 keyframesffmpeg -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

bash
# 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

bash
# Create file listecho "file 'clip1.mp4'" > list.txtecho "file 'clip2.mp4'" >> list.txtecho "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

bash
# 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 fadeffmpeg -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

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

ScenarioUse FFmpegUse Remotion
Constant speed (1.5x, 2x)Either works✅ Simpler
Extreme speeds (>4x or <0.25x)✅ More reliableMay have issues
Variable speed (accelerate over time)✅ Pre-processComplex workaround needed
Need perfect audio sync✅ GuaranteedUsually fine
Demo needs to fit voiceover timing✅ Pre-calculateRuntime 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.

bash
# 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):

bash
# 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

bash
# Standard 1080p, 30fps, Remotion-readyffmpeg -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

bash
# 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

bash
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 CaseCRFPresetNotes
Archive/Master18slowBest quality, large files
Production20-22mediumGood balance
Web/Preview23-25fastSmaller files
Draft/Quick28+veryfastFast 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:

bash
# 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:

bash
# 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 durationffprobe -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:

bash
# LinkedIn optimizedffmpeg -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)

bash
# 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)

bash
# 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 GIFffmpeg -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

PlatformMax ResolutionMax SizeMax DurationAudio
YouTube8K256GB12 hoursAAC 48kHz
Twitter/X1920x1200512MB140sAAC 44.1kHz
LinkedIn4096x23045GB10 minAAC 48kHz
Instagram Feed1080x13504GB60sAAC 48kHz
Instagram Reels1080x19204GB90sAAC 48kHz
TikTok1080x1920287MB10 minAAC

Batch Export for All Platforms

bash
#!/bin/bash# save as: export-all-platforms.shINPUT="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
# LinkedInffmpeg -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:

bash
# Check if FFmpeg succeededffmpeg -i input.mp4 -c:v libx264 output.mp4 && echo "Success" || echo "Failed: check input file"
# Validate output file is playableffprobe -v error -select_streams v:0 -show_entries stream=codec_name -of csv=p=0 output.mp4
# Get detailed error infoffmpeg -v error -i input.mp4 -f null - 2>&1 | head -20

Handling Common Failures

ErrorCauseFix
"No such file"Input path wrongCheck path, use quotes for spaces
"Invalid data"Corrupted inputRe-download or re-record source
"height not divisible by 2"Odd dimensionsAdd scale filter with trunc
"encoder not found"Missing codecInstall FFmpeg with full codecs
Output 0 bytesSilent failureCheck full ffmpeg output for errors

Feedback & Contributions

If this skill is missing information or could be improved:

  • Missing a command? Describe what you needed
  • Found an error? Let me know what's wrong
  • Want to contribute? I can help you:
    1. Update this skill with improvements
    2. Create a PR to github.com/digitalsamba/claude-code-video-toolkit

Just say "improve this skill" and I'll guide you through updating .claude/skills/ffmpeg/SKILL.md.

來源與署名

來源：calesthio/OpenMontage位於.claude/skills/ffmpeg提交9327439

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