expo-trim-video

A native Expo module for trimming videos on Android and iOS devices.

Features

• ✅ Trim videos by specifying start and end times
• ✅ Support for various video formats (MP4, MOV, etc.)
• ✅ Handle file:// and content:// URIs
• ✅ Error handling for invalid inputs and file issues
• ✅ Fast video processing using native platform APIs
• ✅ Cross-platform support for Android and iOS

Installation

npm install expo-trim-video

Usage

import { trimVideo } from 'expo-trim-video';

// Trim a video from 5 seconds to 15 seconds
try {
  const result = await trimVideo({
    uri: 'file:///path/to/your/video.mp4', // or content:// URI
    start: 5,  // Start time in seconds
    end: 15    // End time in seconds
  });
  
  console.log('Trimmed video saved to:', result.uri);
} catch (error) {
  console.error('Error trimming video:', error.message);
}

API

trimVideo(options: TrimVideoOptions): Promise<TrimVideoResult>

Trims a video file according to the specified options.

Parameters

• options.uri (string): The URI of the video file to trim. Supports:

  • File URIs: file:///path/to/video.mp4
  • Content URIs (Android): content://...
  • Photos URIs (iOS): ph://...
  • Absolute paths: /storage/emulated/0/Movies/video.mp4

• options.start (number): Start time in seconds (must be >= 0)

• options.end (number): End time in seconds (must be > start and <= video duration)

Returns

Promise that resolves to:

{
  uri: string; // File URI of the trimmed video
}

Error Codes

• INVALID_ARGUMENTS: Missing or invalid URI
• INVALID_START: Start time is negative
• INVALID_END: End time exceeds video duration
• INVALID_RANGE: Start time is greater than or equal to end time
• INVALID_URI: Invalid URI format (iOS)
• FILE_NOT_FOUND: Video file not found or invalid
• TRIM_ERROR: General error during video processing

Platform Support

• ✅ Android: Full support using MediaExtractor/MediaMuxer
• ✅ iOS: Full support using AVFoundation
• ❌ Web: Not supported (returns error)

Example App

The example app demonstrates how to use the module:

1. Enter a video URI (file path or content URI)
2. Set start and end times
3. Tap "Trim Video" to process

To run the example:

cd example
npm install

# For Android
npx expo run:android

# For iOS
npx expo run:ios

Technical Details

Android Implementation

The Android implementation uses:

• MediaExtractor to read video data
• MediaMuxer to write the trimmed output
• MediaMetadataRetriever to validate video duration and get metadata

The module preserves:

• Video quality (no re-encoding when possible)
• Audio tracks
• Video rotation metadata
• Original codecs and formats

iOS Implementation

The iOS implementation uses:

• AVAsset to load and analyze video files
• AVAssetExportSession for efficient video trimming
• CMTime for precise time handling

The module preserves:

• Video quality using AVAssetExportPresetHighestQuality
• Audio tracks
• Video orientation and metadata
• Optimal file compression

Performance

Video trimming is performed efficiently by:

Android:

• Seeking to the start position using SEEK_TO_CLOSEST_SYNC
• Copying video/audio samples without re-encoding
• Processing only the required time range

iOS:

• Using AVAssetExportSession for hardware-accelerated processing
• Setting precise time ranges with CMTimeRange
• Preserving original video quality and metadata

Troubleshooting

Common Issues

1. "File not found" error:

   • Ensure the video file exists and is accessible
   • Check file permissions
   • Try using a content:// URI (Android) or ph:// URI (iOS) for media files

2. "End time exceeds video duration":

   • Check the actual video duration
   • Ensure end time is less than video length

3. "Invalid range" error:

   • Ensure start < end
   • Both times must be positive

4. "Invalid URI format" (iOS):

   • Ensure the URI is properly formatted
   • Use file:// prefix for local files
   • Use ph:// for Photos library assets

Getting Video URIs

You can get video URIs using:

• expo-document-picker for user-selected files
• expo-media-library for accessing device media
• expo-file-system for app-specific files
• expo-image-picker for camera/gallery videos

License

MIT

Contributing

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