Lower the resolution of Videos - iPhone

Lowering Video Resolution on iPhone: A Comprehensive Guide

Learn how to effectively reduce the resolution of videos captured on your iPhone, saving storage space and facilitating easier sharing, using both built-in features and programmatic approaches.

Modern iPhones capture stunning high-resolution videos, often in 4K at 60 frames per second. While this delivers incredible visual quality, it also consumes significant storage space and can make sharing videos over the internet cumbersome. This article will guide you through various methods to lower the resolution of your iPhone videos, from adjusting camera settings to programmatic solutions for developers.

Adjusting Camera Settings for Future Recordings

The simplest way to manage video resolution is to configure your iPhone's camera settings before you even start recording. This ensures that all subsequent videos are captured at your desired resolution, preventing the need for post-capture conversion. While this doesn't affect existing videos, it's a crucial first step for long-term storage and sharing efficiency.

1. Open Settings

Navigate to the 'Settings' app on your iPhone's home screen.

2. Access Camera Settings

Scroll down and tap on 'Camera'.

3. Select Record Video

Tap on 'Record Video' to view available resolution and frame rate options.

4. Choose Desired Resolution

Select a lower resolution and frame rate combination, such as '1080p HD at 30 fps' or '720p HD at 30 fps', depending on your needs. A lower resolution will result in smaller file sizes.

Programmatic Video Resolution Reduction (iOS Development)

For developers, programmatically lowering video resolution offers greater control and can be integrated into custom applications. The AVFoundation framework provides powerful tools for video processing, including exporting videos at different presets. This approach is ideal for apps that need to capture, process, and upload videos efficiently.

flowchart TD
    A[Start] --> B{Select Video from Library}
    B --> C[Load AVAsset]
    C --> D[Create AVAssetExportSession]
    D --> E{Set Export Preset (e.g., AVAssetExportPresetMediumQuality)}
    E --> F[Set Output File Type (e.g., AVFileTypeMPEG4)]
    F --> G[Set Output URL]
    G --> H[Perform Export]
    H --> I{Export Complete?}
    I -- Yes --> J[Save to Photo Library/Upload]
    I -- No --> K[Handle Error]
    J --> L[End]
    K --> L[End]

Workflow for Programmatic Video Resolution Reduction using AVAssetExportSession

The core of programmatic video resolution reduction involves using AVAssetExportSession. This class allows you to transcode the contents of an AVAsset (your video) to a new file, specifying an export preset that dictates the output quality and resolution. Common presets include AVAssetExportPresetLowQuality, AVAssetExportPresetMediumQuality, and AVAssetExportPresetHighestQuality.

import AVFoundation
import Photos

func lowerVideoResolution(videoURL: URL, completion: @escaping (Result<URL, Error>) -> Void) {
    let asset = AVAsset(url: videoURL)
    
    // Choose an export preset. AVAssetExportPresetMediumQuality is a good balance.
    guard let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality) else {
        completion(.failure(NSError(domain: "VideoExport", code: 0, userInfo: [NSLocalizedDescriptionKey: "Could not create export session."])))
        return
    }
    
    let outputFileName = UUID().uuidString + ".mp4"
    let outputURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(outputFileName)
    
    exportSession.outputURL = outputURL
    exportSession.outputFileType = .mp4
    exportSession.shouldOptimizeForNetworkUse = true
    
    exportSession.exportAsynchronously { 
        DispatchQueue.main.async {
            switch exportSession.status {
            case .completed:
                completion(.success(outputURL))
            case .failed:
                completion(.failure(exportSession.error ?? NSError(domain: "VideoExport", code: 1, userInfo: [NSLocalizedDescriptionKey: "Export failed."])))
            case .cancelled:
                completion(.failure(NSError(domain: "VideoExport", code: 2, userInfo: [NSLocalizedDescriptionKey: "Export cancelled."])))
            default:
                break
            }
        }
    }
}

// Example usage:
// Assuming 'originalVideoURL' is the URL of the video you want to process
// lowerVideoResolution(videoURL: originalVideoURL) { result in
//     switch result {
//     case .success(let reducedResolutionVideoURL):
//         print("Video resolution reduced. New URL: \(reducedResolutionVideoURL)")
//         // You can now save this URL to Photos library or upload it
//     case .failure(let error):
//         print("Error reducing video resolution: \(error.localizedDescription)")
//     }
// }

Swift code to lower video resolution using AVAssetExportSession.

Considerations for ALAssetsLibrary (Deprecated)

Historically, ALAssetsLibrary was used for accessing the photo library. However, it has been deprecated since iOS 9 and replaced by the Photos framework (PHPhotoLibrary). While you might encounter older code examples using ALAssetsLibrary, it is strongly recommended to use Photos for any new development to ensure compatibility and leverage modern APIs.

If you are working with legacy code that still uses ALAssetsLibrary, be aware that it might not function correctly on newer iOS versions. The Photos framework offers a more robust and feature-rich way to interact with the user's media.