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

I know this question is old but some people may still be wondering why some of the videos from the camera roll zoom in after they're cropped. I faced this problem and realized that the cropRect I was using as a frame was not scaled for the different aspect ratios of the video. To fix this problem I simply added the code below to crop the very top of the video into a square. If you want to change the position just change the y value but make sure to scale it according to the video. Luca Iaco provided some great code to get started with. I appreciate it!

CGSize videoSize = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize];
float scaleFactor;

if (videoSize.width > videoSize.height) {

    scaleFactor = videoSize.height/320;
}
else if (videoSize.width == videoSize.height){

    scaleFactor = videoSize.height/320;
}
else{
    scaleFactor = videoSize.width/320;
}

CGFloat cropOffX = 0;
CGFloat cropOffY = 0;
CGFloat cropWidth = 320 *scaleFactor;
CGFloat cropHeight = 320 *scaleFactor;

Answer 2

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
}

Answer 3

I suppose the source code come from this link ( project code included )

http://www.one-dreamer.com/cropping-video-square-like-vine-instagram-xcode/

You need first to know the REAL video orientation:

- (UIImageOrientation)getVideoOrientationFromAsset:(AVAsset *)asset
{
    AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    CGSize size = [videoTrack naturalSize];
    CGAffineTransform txf = [videoTrack preferredTransform];

    if (size.width == txf.tx && size.height == txf.ty)
        return UIImageOrientationLeft; //return UIInterfaceOrientationLandscapeLeft;
    else if (txf.tx == 0 && txf.ty == 0)
        return UIImageOrientationRight; //return UIInterfaceOrientationLandscapeRight;
    else if (txf.tx == 0 && txf.ty == size.width)
        return UIImageOrientationDown; //return UIInterfaceOrientationPortraitUpsideDown;
    else
        return UIImageOrientationUp;  //return UIInterfaceOrientationPortrait;
}

I made that function in a way that it return the right orientation as if it was an image

Then, i modified the function to fix the right orientation, supporting any crop region not just a square, like this:

// apply the crop to passed video asset (set outputUrl to avoid the saving on disk ). Return the exporter session object
- (AVAssetExportSession*)applyCropToVideoWithAsset:(AVAsset*)asset AtRect:(CGRect)cropRect OnTimeRange:(CMTimeRange)cropTimeRange ExportToUrl:(NSURL*)outputUrl ExistingExportSession:(AVAssetExportSession*)exporter WithCompletion:(void(^)(BOOL success, NSError* error, NSURL* videoUrl))completion
{

    //create an avassetrack with our asset
    AVAssetTrack *clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    //create a video composition and preset some settings
    AVMutableVideoComposition* videoComposition = [AVMutableVideoComposition videoComposition];
    videoComposition.frameDuration = CMTimeMake(1, 30);

    CGFloat cropOffX = cropRect.origin.x;
    CGFloat cropOffY = cropRect.origin.y;
    CGFloat cropWidth = cropRect.size.width;
    CGFloat cropHeight = cropRect.size.height;

    videoComposition.renderSize = CGSizeMake(cropWidth, cropHeight);

    //create a video instruction
    AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    instruction.timeRange = cropTimeRange;

    AVMutableVideoCompositionLayerInstruction* transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];

    UIImageOrientation videoOrientation = [self getVideoOrientationFromAsset:asset];

    CGAffineTransform t1 = CGAffineTransformIdentity;
    CGAffineTransform t2 = CGAffineTransformIdentity;

    switch (videoOrientation) {
        case UIImageOrientationUp:
            t1 = CGAffineTransformMakeTranslation(clipVideoTrack.naturalSize.height - cropOffX, 0 - cropOffY );
            t2 = CGAffineTransformRotate(t1, M_PI_2 );
            break;
        case UIImageOrientationDown:
            t1 = CGAffineTransformMakeTranslation(0 - cropOffX, clipVideoTrack.naturalSize.width - cropOffY ); // not fixed width is the real height in upside down
            t2 = CGAffineTransformRotate(t1, - M_PI_2 );
            break;
        case UIImageOrientationRight:
            t1 = CGAffineTransformMakeTranslation(0 - cropOffX, 0 - cropOffY );
            t2 = CGAffineTransformRotate(t1, 0 );
            break;
        case UIImageOrientationLeft:
            t1 = CGAffineTransformMakeTranslation(clipVideoTrack.naturalSize.width - cropOffX, clipVideoTrack.naturalSize.height - cropOffY );
            t2 = CGAffineTransformRotate(t1, M_PI  );
            break;
        default:
            NSLog(@"no supported orientation has been found in this video");
            break;
    }

    CGAffineTransform finalTransform = t2;
    [transformer setTransform:finalTransform atTime:kCMTimeZero];

    //add the transformer layer instructions, then add to video composition
    instruction.layerInstructions = [NSArray arrayWithObject:transformer];
    videoComposition.instructions = [NSArray arrayWithObject: instruction];

    //Remove any prevouis videos at that path
    [[NSFileManager defaultManager]  removeItemAtURL:outputUrl error:nil];

    if (!exporter){
        exporter = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality] ;
    }

    // assign all instruction for the video processing (in this case the transformation for cropping the video
    exporter.videoComposition = videoComposition;
    //exporter.outputFileType = AVFileTypeQuickTimeMovie;

    if (outputUrl){

        exporter.outputURL = outputUrl;
        [exporter exportAsynchronouslyWithCompletionHandler:^{

             switch ([exporter status]) {
                 case AVAssetExportSessionStatusFailed:
                     NSLog(@"crop Export failed: %@", [[exporter error] localizedDescription]);
                     if (completion){
                         dispatch_async(dispatch_get_main_queue(), ^{
                             completion(NO,[exporter error],nil);
                         });
                         return;
                     }
                     break;
                 case AVAssetExportSessionStatusCancelled:
                     NSLog(@"crop Export canceled");
                     if (completion){
                         dispatch_async(dispatch_get_main_queue(), ^{
                             completion(NO,nil,nil);
                         });
                         return;
                     }
                     break;
                 default:
                     break;
            }

            if (completion){
                dispatch_async(dispatch_get_main_queue(), ^{
                    completion(YES,nil,outputUrl);
                });
            }

        }];
    }

    return exporter;
}

Tested in all recorded video orientation (Up,Down,Lanscape R, Landscape L) in both normal and front camera cases. I tested it on iPhone 5S (iOS 8.1), iPhone 6 Plus (iOS 8.1)

Hope it helps