shorts-generator

name	shorts-generator
description	Create vertical short videos with captions from selected clips. Handles video formatting, subtitle styling, and export.

Shorts Generator

This skill creates polished, vertical short videos with captions from your selected clips.

When to Use This Skill

• After selecting clips from highlight-finder
• Ready to create final short videos
• Need to add captions/subtitles
• Want to format for specific platforms

What This Skill Does

1. Extract Clips: Cuts selected segments from source video
2. Format Video: Converts to vertical 9:16 aspect ratio
3. Add Captions: Burns in styled subtitles
4. Enhance Audio: Normalizes and enhances speech
5. Export: Creates platform-ready files

How to Use

Create Single Short

Create a short video from 02:34 to 03:15 of VIDEO_ID

Create with Captions

Create a short with Chinese captions from clip 1

Batch Create

Create shorts from all recommended clips

Instructions

Step 1: Extract the Clip

# Extract video segment
ffmpeg -i "./output/downloads/VIDEO_ID.mp4" \
  -ss 00:02:34 -to 00:03:15 \
  -c:v libx264 -c:a aac \
  "./temp/clip_raw.mp4"

Step 2: Convert to Vertical Format

Option A: Crop Center (for horizontal video)

ffmpeg -i "./temp/clip_raw.mp4" \
  -vf "crop=ih*9/16:ih,scale=1080:1920" \
  -c:a copy \
  "./temp/clip_vertical.mp4"

Option B: Add Blur Background (preserves full frame)

ffmpeg -i "./temp/clip_raw.mp4" \
  -vf "[0:v]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,boxblur=20[bg];[0:v]scale=1080:-1[fg];[bg][fg]overlay=(W-w)/2:(H-h)/2" \
  -c:a copy \
  "./temp/clip_vertical.mp4"

Step 3: Extract Segment Subtitles

From the full SRT, extract only the relevant portion and adjust timestamps:

# Use ffmpeg to extract subtitle segment
ffmpeg -i "./output/transcripts/VIDEO_ID.srt" \
  -ss 00:02:34 -to 00:03:15 \
  "./temp/clip_subtitles.srt"

Step 4: Style and Burn Captions

ffmpeg -i "./temp/clip_vertical.mp4" \
  -vf "subtitles=./temp/clip_subtitles.srt:force_style='FontName=Arial Bold,FontSize=24,PrimaryColour=&HFFFFFF,OutlineColour=&H000000,Outline=2,Alignment=2,MarginV=50'" \
  -c:a copy \
  "./temp/clip_captioned.mp4"

Caption Style Options:

• Standard: White text, black outline, bottom center
• Trendy: Yellow highlight box, word-by-word animation
• Minimal: Small text, top or bottom
• Bold: Large text, center screen

Step 5: Enhance Audio

ffmpeg -i "./temp/clip_captioned.mp4" \
  -af "loudnorm=I=-16:TP=-1.5:LRA=11" \
  -c:v copy \
  "./output/shorts/short_001.mp4"

Step 6: Generate Thumbnail

# Extract frame at 1 second for thumbnail
ffmpeg -i "./output/shorts/short_001.mp4" \
  -ss 00:00:01 -vframes 1 \
  "./output/shorts/short_001_thumbnail.jpg"

Step 7: Report to User

## ✅ Short Video Created!

**File**: ./output/shorts/short_001.mp4
**Duration**: 41 seconds
**Format**: 1080x1920 (9:16 vertical)
**Captions**: Burned in (White + Black outline)

**Thumbnail**: ./output/shorts/short_001_thumbnail.jpg

### Preview Info
- **Resolution**: 1080x1920
- **Frame Rate**: 30 fps
- **Audio**: AAC, normalized
- **File Size**: XX MB

### Platform Compatibility
- ✅ TikTok (ready to upload)
- ✅ YouTube Shorts (ready to upload)
- ✅ Instagram Reels (ready to upload)
- ✅ 抖音 (ready to upload)

**Next steps**:
1. Review the video in ./output/shorts/
2. Create more shorts from other clips
3. Adjust caption style if needed

Output

• Short video: ./output/shorts/short_XXX.mp4
• Thumbnail: ./output/shorts/short_XXX_thumbnail.jpg

Caption Styles

Style 1: Classic (Default)

FontName=Arial Bold
FontSize=24
PrimaryColour=&HFFFFFF (White)
OutlineColour=&H000000 (Black)
Outline=2

Style 2: Modern

FontName=Montserrat Bold
FontSize=28
PrimaryColour=&H00FFFF (Yellow)
BackColour=&H80000000 (Semi-transparent black)
BorderStyle=4

Style 3: Minimal

FontName=Helvetica
FontSize=18
PrimaryColour=&HFFFFFF
Outline=1
MarginV=30

Quality Presets

• High Quality: 1080x1920, 8Mbps, best for YouTube
• Standard: 1080x1920, 4Mbps, balanced
• Fast Upload: 720x1280, 2Mbps, smaller file size