Square cropping and fixing the video orientation in iOS

Question

I am capturing the video using UIImagePickerController, i can crop the video using the following code,

AVAsset *asset = [AVAsset assetWithURL:url];

//create         


        

Answer 1

This is my code to create a vine-like video from a video on disk. This is written in swift:

static let MaxDuration: CMTimeValue = 12

class func compressVideoAsset(_ asset: AVAsset, output: URL, completion: @escaping (_ data: Data?) -> Void)
{
    let session = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)!
    session.videoComposition = self.squareVideoCompositionForAsset(asset)
    session.outputURL = output
    session.outputFileType = AVFileTypeMPEG4
    session.shouldOptimizeForNetworkUse = true
    session.canPerformMultiplePassesOverSourceMediaData = true

    let duration = CMTimeValue(CGFloat(asset.duration.value) / CGFloat(asset.duration.timescale) * 30)
    session.timeRange = CMTimeRange(start: kCMTimeZero, duration: CMTime(value: min(duration, VideoCompressor.MaxDuration * 30), timescale: 30))

    session.exportAsynchronously(completionHandler: { () -> Void in
        let data = try? Data(contentsOf: output)

        DispatchQueue.main.async(execute: { () -> Void in
            completion(data)
        })
    })
}

private class func squareVideoCompositionForAsset(_ asset: AVAsset) -> AVVideoComposition
{
    let track = asset.tracks(withMediaType: AVMediaTypeVideo)[0]
    let length = min(track.naturalSize.width, track.naturalSize.height)

    var transform = track.preferredTransform

    let size = track.naturalSize
    let scale: CGFloat = (transform.a == -1 && transform.b == 0 && transform.c == 0 && transform.d == -1) ? -1 : 1 // check for inversion

    transform = transform.translatedBy(x: scale * -(size.width - length) / 2, y: scale * -(size.height - length) / 2)

    let transformer = AVMutableVideoCompositionLayerInstruction(assetTrack: track)
    transformer.setTransform(transform, at: kCMTimeZero)

    let instruction = AVMutableVideoCompositionInstruction()
    instruction.timeRange = CMTimeRange(start: kCMTimeZero, duration: kCMTimePositiveInfinity)
    instruction.layerInstructions = [transformer]

    let composition = AVMutableVideoComposition()
    composition.frameDuration = CMTime(value: 1, timescale: 30)
    composition.renderSize = CGSize(width: length, height: length)
    composition.instructions = [instruction]

    return composition
}