trim-convert.sh

A fast and efficient tool for trimming MP4 videos with minimal processing and optional audio extraction.

Features

• ✂️ Trim videos between specified start and end times
• 🔄 Minimal processing with smart stream copying when possible
• 🔊 Extract audio in AAC format automatically
• ⚡ Cross-platform compatibility (macOS and Linux)
• 🛠️ Flexible options with sensible defaults

Installation

1. Clone this repository or download the script:

   curl -O https://raw.githubusercontent.com/nipunbatra/trim-convert/main/trim-convert.sh

2. Make the script executable:

   chmod +x trim-convert.sh

3. Ensure you have ffmpeg installed:

   • macOS: brew install ffmpeg
   • Ubuntu/Debian: sudo apt install ffmpeg
   • Fedora/CentOS: sudo dnf install ffmpeg

Usage

./trim-convert.sh [options] input.mp4

Options

Option	Description
-s, --start TIME	Start time (format: HH:MM:SS or seconds)
-e, --end TIME	End time (format: HH:MM:SS or seconds)
-o, --output PREFIX	Output file prefix (default: "trimmed")
-h, --help	Show help message

Examples

# Trim from 1m30s to 5m45s
./trim-convert.sh -s 00:01:30 -e 00:05:45 video.mp4

# Trim from start to 10 minutes
./trim-convert.sh -e 00:10:00 video.mp4

# Trim from 2 minutes to the end
./trim-convert.sh -s 00:02:00 video.mp4

# Custom output name
./trim-convert.sh -o my_clip -s 00:01:30 -e 00:05:45 video.mp4

# Process entire file (just extract audio)
./trim-convert.sh video.mp4

How It Works

1. The script analyzes the input video to determine if it can use stream copying (no re-encoding) based on keyframe positioning
2. It attempts to use the fastest method possible while maintaining quality
3. If stream copying would result in imprecise cuts, it falls back to re-encoding
4. The audio track is extracted as a separate AAC file

Output

• PREFIX.mp4: The trimmed video file
• PREFIX.aac: The extracted audio file

Technical Details

• Uses ffmpeg's stream copying (-c copy) when possible to avoid quality loss
• Falls back to high-quality, fast encoding when necessary (-c:v libx264 -preset ultrafast -crf 17)
• Handles keyframe detection for optimal cutting points
• Works with both relative (seconds) and absolute (HH:MM:SS) time formats

Requirements

• ffmpeg (version 4.0+)
• Bash shell

License

MIT License - See LICENSE file for details

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.