技能库智客分类：媒体内容 ffmpeg

Ffmpeg

用FFmpeg进行视频和音频处理. 用于格式转换,再大小调整,压缩,音频提取,并准备资产进行再动. 触发器包括将GIF转换为MP4,调整视频大小,取出音频,压缩文件,或任何媒体转换任务.

10476 安装量

官方网址：skills.sh

技能介绍

先看中文介绍；官方 description 原文单独保留，不改写 SKILL.md。

做什么

何时用

源有频繁的密钥框

代理如何加载

按 Agent Skills 渐进披露：启动时只加载 name 与 description（约 100 token）；任务匹配后才读入整份 SKILL.md 正文；scripts/、references/、assets/ 仅在需要时再读。本文件正文结构：FFmpeg for Video Production、Quick Reference、GIF to MP4 (Remotion-compatible)、Resize Video、To 1920x1080 (maintain aspect ratio, add black bars)、To 1920x1080 (crop to fill)。

文件分析

文件分析：除 SKILL.md 外，正文还引用了 assets/，属于带资源的技能包，代理会按需再读这些文件。

官方 description（原文）

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.

FFmpeg for Video ProductionQuick ReferenceGIF to MP4 (Remotion-compatible)Resize VideoTo 1920x1080 (maintain aspect ratio, add black bars)To 1920x1080 (crop to fill)Scale to width, auto heightCompress VideoGood quality, smaller file (CRF 23 is default, lower = better quality)Aggressive compression for web previewTarget file size (e.g., ~10MB for 60s video = ~1.3Mbps)Extract Audio

来源分类：skills.sh agent-skill

来源与网址

市场来源：skills.sh

GitHub 完整包

开源榜 Skill 分类

SKILL.md 与 Agent 调用

官方规范 ↗

name: ffmpeg
description: 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.

发现技能客户端向 Agent 提供名称与描述目录。
匹配与调用用户指定或任务匹配后，载入 SKILL.md 指令。
按需加载按步骤读取参考文档、使用脚本与素材。

具体调用语法与可用工具以目标 Agent 客户端为准。查看调用机制说明 ↗

安装这个技能

Skills CLI ↗

先选择目标 Agent 和安装范围，保留技能包的附属文件，安装后检查客户端能否发现该技能。

该技能引用了附属文件，请从来源获取完整目录；仅复制 SKILL.md 可能缺少依赖。

交给 Agent 安装

复制安装指令给支持 Agent Skills 的代理，确认其中的目标目录与客户端匹配。

把 Agent Skill「ffmpeg」安装到我的项目：SKILL.md 原文与官方 description 见 https://zicq.com/zh/skills/skl-dbcd38a62777691f-Ffmpeg.html
请存为 .cursor/skills/ffmpeg/SKILL.md 或 .claude/skills/ffmpeg/SKILL.md，frontmatter 的 name 与 description 保持原样，不要改写。
该技能还带 scripts/、references/、assets/ 等文件，请从 https://github.com/digitalsamba/claude-code-video-toolkit 取完整目录，不要只建一个 SKILL.md。

GitHub 完整包 ↗

终端安装 · Skills CLI

需要 Node.js 与 npx。先查看仓库技能列表，确认实际名称。

npx skills add 'https://github.com/digitalsamba/claude-code-video-toolkit' --list

目标客户端安装范围

npx skills add 'https://github.com/digitalsamba/claude-code-video-toolkit' --skill 'ffmpeg'

CLI 会交互选择目标 Agent，默认安装到项目；用户级安装使用 -g。先通过查看命令核对仓库内容，再用 npx skills list 检查已安装技能。

SKILL.md 原文可复制，不会改动源文件

---
name: ffmpeg
description: 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.
---

# 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 height
ffmpeg -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 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

```bash
# 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

```bash
# 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

```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 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

```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 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

```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 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

```bash
# 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.

```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-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

```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 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:

```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 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:

```bash
# 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)

```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 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

```bash
#!/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:

```bash
# 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 |

---

## 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`.

阅读排版

name: ffmpeg description: 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.

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 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 |

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

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Ffmpeg

技能介绍

做什么

何时用

代理如何加载

文件分析

SKILL.md 与 Agent 调用

安装这个技能

name: ffmpeg description: 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.

FFmpeg for Video Production

Quick Reference

GIF to MP4 (Remotion-compatible)

Resize Video

Compress Video

Extract Audio

Convert Audio Formats

Trim/Cut Video

Speed Up / Slow Down

Concatenate Videos

Add Fade In/Out

Get Video Info

Remotion-Specific Patterns

Video Speed Adjustment for Remotion

Prepare Demo Recording for Remotion

Screen Recording to Remotion Asset

Batch Convert GIFs

Common Issues

"Height not divisible by 2"

Video won't play in browser

Audio out of sync after speed change

File too large

Quality Guidelines

Platform-Specific Output Optimization

Workflow Integration

YouTube (Recommended Settings)

Twitter/X

LinkedIn

Website/Embed (Optimized for Fast Loading)

GIF (for Previews/Thumbnails)

Platform Requirements Quick Reference

Batch Export for All Platforms

Error Handling

Handling Common Failures

Feedback & Contributions

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