video_compress_kit_ios #

The iOS implementation of video_compress_kit.

Usage #

You should not depend on this package directly. Add the app-facing package instead:

dependencies:
  video_compress_kit: ^0.0.1

The iOS implementation is automatically endorsed and registered.

How It Works #

Video Compression Pipeline #

Uses Apple's AVAssetReader / AVAssetWriter pipeline backed by the VideoToolbox hardware encoder on all modern iOS devices. No third-party native libraries — uses only system frameworks, adding ~0 KB to your app binary.

Input MP4
  → AVAssetReader (demux + decode via VideoToolbox)
  → AVAssetWriter (re-encode at target resolution + bitrate)
      ├─ H.264 Profile: Baseline / Main / High
      │     (AVVideoProfileLevelKey)
      ├─ Bitrate: AVVideoAverageBitRateKey (VBR/CBR)
      │     or AVVideoQualityKey (CQ mode)
      ├─ Color: BT.709 full-range pixel format
      │     (kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
      └─ Faststart: shouldOptimizeForNetworkUse = true
  → Audio passthrough via AVAssetReaderTrackOutput
  → Output MP4

Image Compression Pipeline #

Uses Apple's UIImage for decode/scale and ImageIO (CGImageDestination) for format-specific encoding. WebP support via UTType.webP (iOS 14+).

Input image (JPEG / PNG / HEIC / etc.)
  → UIImage(contentsOfFile:)
  → Scale to maxWidth / maxHeight
      (UIGraphicsBeginImageContextWithOptions, proportional)
  → Encode to output format:
      ├─ JPEG: UIImage.jpegData(compressionQuality:)
      ├─ PNG:  UIImage.pngData()
      └─ WebP: CGImageDestination + UTType.webP (iOS 14+)
  → Copy EXIF metadata (if keepExif = true)
      (CGImageSource → CGImageDestinationAddImageFromSource)
  → Output file

Per-Session Architecture #

Each compressVideo() call creates a VideoCompressor instance stored in a [String: VideoCompressor] dictionary protected by NSLock. This enables:

• Concurrent compressions — multiple videos processed in parallel
• Per-session progress — each compressor reports progress tagged with its session ID
• Per-session cancellation — cancel a specific session without affecting others
• Cancel all — iterate the dictionary and cancel every active session

┌────────────────────────────────┐
│  VideoCompressKitIosPlugin     │
│                                │
│  compressors: [String: VC]     │
│  compressorsLock: NSLock       │
│  ┌───────────┬───────────┐     │
│  │ "job-1"   │ "job-2"   │     │
│  │ Compressor│ Compressor│     │
│  └───────────┴───────────┘     │
│                                │
│  cancelCompression("job-1")    │
│   → compressors["job-1"].cancel│
│                                │
│  cancelCompression(nil)        │
│   → cancel ALL                 │
└────────────────────────────────┘

Video Feature Support Matrix #

Image Feature Support Matrix #

WebP on iOS: WebP encoding requires iOS 14.0 or later. On iOS 13.x, requesting ImageFormat.webp will return an error. The decoder supports WebP on iOS 14+ via UTType.webP.

Requirements #

Native APIs Used #

License #

MIT — see LICENSE.