How to Use Avfoundation to Crop a Video

How do I use AVFoundation to crop a video

Soemthing like this. 99% of this code just sets it up to do a custom CGAffineTransform, and then save out the result.

I'm assuming that you want the cropped video to take up full size/width of the output - so that e.g a Scale Affine is the correct solution (you zoom in on the video, giving the effect of having cropped + resized).

AVAsset* asset = // your input

AVAssetTrack *clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

AVMutableVideoComposition* videoComposition = [[AVMutableVideoComposition videoComposition]retain];
videoComposition.renderSize = CGSizeMake(320, 240);
videoComposition.frameDuration = CMTimeMake(1, 30);

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30) );

AVMutableVideoCompositionLayerInstruction* transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];
CGAffineTransform finalTransform = // setup a transform that grows the video, effectively causing a crop
    [transformer setTransform:finalTransform atTime:kCMTimeZero];
    instruction.layerInstructions = [NSArray arrayWithObject:transformer];
videoComposition.instructions = [NSArray arrayWithObject: instruction];

exporter = [[AVAssetExportSession alloc] initWithAsset:saveComposition presetName:AVAssetExportPresetHighestQuality] ;
exporter.videoComposition = videoComposition;
exporter.outputURL=url3;
exporter.outputFileType=AVFileTypeQuickTimeMovie;

[exporter exportAsynchronouslyWithCompletionHandler:^(void){}];

Possible to use AV Foundation to crop a video?

1) Use AVAssetReader to open your video and extract CMSampleBuffers

Link

2) Modify CMSampleBuffer:

Link

3) Create AVAssetWriter and add modified CMSampleBuffers to it's input

Link

In this article CVPixelBuffer is used as an input to AVAssetWriter

using adapter. You actually don't need an adapter because
you have CMSampleBuffers
ready you can add them straight
to the input using appendSampleBuffer: method.

Crop video with AVFoundation

Notice in the // rotate to portrait portion of the code they're making affine transformations. Modify those transformations to align the video how you want.

Crop Video to Square in iOS [Swift 3]

You're not actually setting the video composition on the exporter

So try

exportSession.videoComposition = videoComposition

before starting the export.

Cropping AVAsset video with AVFoundation

Here is my interpretation of your question: You are capturing video on a device with a screen ratio of 4:3, thus your AVCaptureVideoPreviewLayer is 4:3, but the video input device captures video in 16:9 so the resulting video is 'larger' than seen in the preview.

If you are simply looking to crop the extra pixels not caught by the preview then check out this http://www.netwalk.be/article/record-square-video-ios. This article shows how to crop the video into a square. However you'll only need a few modifications to crop to 4:3. I've gone and tested this, here are the changes I made:

Once you have the AVAssetTrack for the video you will need to calculate a new height.

// we convert the captured height i.e. 1080 to a 4:3 screen ratio and get the new height
CGFloat newHeight = clipVideoTrack.naturalSize.height/3*4;

Then modify these two lines, using newHeight.

videoComposition.renderSize = CGSizeMake(clipVideoTrack.naturalSize.height, newHeight);

CGAffineTransform t1 = CGAffineTransformMakeTranslation(clipVideoTrack.naturalSize.height, -(clipVideoTrack.naturalSize.width - newHeight)/2 );

So what we've done here is set the renderSize to a 4:3 ratio - the exact dimension are based on the input device. We then use a CGAffineTransform to translate the video position so that what we saw in the AVCaptureVideoPreviewLayer is what is rendered to our file.

Edit: If you want to put it all together and crop a video based on the device's screen ratio (3:2, 4:3, 16:9) and take the video orientation into mind we need to add a few things.

First here is the modified sample code with a few critical alterations:

// output file
NSString* docFolder = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString* outputPath = [docFolder stringByAppendingPathComponent:@"output2.mov"];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputPath])
    [[NSFileManager defaultManager] removeItemAtPath:outputPath error:nil];

// input file
AVAsset* asset = [AVAsset assetWithURL:outputFileURL];

AVMutableComposition *composition = [AVMutableComposition composition];
[composition  addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

// input clip
AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

// crop clip to screen ratio
UIInterfaceOrientation orientation = [self orientationForTrack:asset];
BOOL isPortrait = (orientation == UIInterfaceOrientationPortrait || orientation == UIInterfaceOrientationPortraitUpsideDown) ? YES: NO;
CGFloat complimentSize = [self getComplimentSize:videoTrack.naturalSize.height];
CGSize videoSize;

if(isPortrait) {
    videoSize = CGSizeMake(videoTrack.naturalSize.height, complimentSize);
} else {
    videoSize = CGSizeMake(complimentSize, videoTrack.naturalSize.height);
}

AVMutableVideoComposition* videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.renderSize = videoSize;
videoComposition.frameDuration = CMTimeMake(1, 30);

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30) );

// rotate and position video
AVMutableVideoCompositionLayerInstruction* transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];

CGFloat tx = (videoTrack.naturalSize.width-complimentSize)/2;
if (orientation == UIInterfaceOrientationPortrait || orientation == UIInterfaceOrientationLandscapeRight) {
    // invert translation
    tx *= -1;
}

// t1: rotate and position video since it may have been cropped to screen ratio
CGAffineTransform t1 = CGAffineTransformTranslate(videoTrack.preferredTransform, tx, 0);
// t2/t3: mirror video horizontally
CGAffineTransform t2 = CGAffineTransformTranslate(t1, isPortrait?0:videoTrack.naturalSize.width, isPortrait?videoTrack.naturalSize.height:0);
CGAffineTransform t3 = CGAffineTransformScale(t2, isPortrait?1:-1, isPortrait?-1:1);

[transformer setTransform:t3 atTime:kCMTimeZero];
instruction.layerInstructions = [NSArray arrayWithObject: transformer];
videoComposition.instructions = [NSArray arrayWithObject: instruction];

// export
exporter = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality] ;
exporter.videoComposition = videoComposition;
exporter.outputURL=[NSURL fileURLWithPath:outputPath];
exporter.outputFileType=AVFileTypeQuickTimeMovie;

[exporter exportAsynchronouslyWithCompletionHandler:^(void){
    NSLog(@"Exporting done!");

    // added export to library for testing
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:[NSURL fileURLWithPath:outputPath]]) {
        [library writeVideoAtPathToSavedPhotosAlbum:[NSURL fileURLWithPath:outputPath]
                                    completionBlock:^(NSURL *assetURL, NSError *error) {
             NSLog(@"Saved to album");
             if (error) {

             }
         }];
    }
}];

What we added here is a call to get the new render size of the video based on cropping its dimensions to the screen ratio. Once we crop the size down, we need to translate the position to recenter the video. So we grab its orientation to move it in the proper direction. This will fix the off-center issue we saw with UIInterfaceOrientationLandscapeLeft. Finally CGAffineTransform t2, t3 mirror the video horizontally.

And here are the two new methods that make this happen:

- (CGFloat)getComplimentSize:(CGFloat)size {
    CGRect screenRect = [[UIScreen mainScreen] bounds];
    CGFloat ratio = screenRect.size.height / screenRect.size.width;

    // we have to adjust the ratio for 16:9 screens
    if (ratio == 1.775) ratio = 1.77777777777778;

    return size * ratio;
}

- (UIInterfaceOrientation)orientationForTrack:(AVAsset *)asset {
    UIInterfaceOrientation orientation = UIInterfaceOrientationPortrait;
    NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];

    if([tracks count] > 0) {
        AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
        CGAffineTransform t = videoTrack.preferredTransform;

        // Portrait
        if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0) {
            orientation = UIInterfaceOrientationPortrait;
        }
        // PortraitUpsideDown
        if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0) {
            orientation = UIInterfaceOrientationPortraitUpsideDown;
        }
        // LandscapeRight
        if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0) {
            orientation = UIInterfaceOrientationLandscapeRight;
        }
        // LandscapeLeft
        if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0) {
            orientation = UIInterfaceOrientationLandscapeLeft;
        }
    }
    return orientation;
}

These are pretty straight forward. The only thing to note is that in the getComplimentSize: method we have to manually adjust the ratio for 16:9 since the iPhone5+ resolution is mathematically shy of true 16:9.

How to crop a video in iOS

In AVVideoSetttings.h there is the AVVideoScalingModeKey. This key combined with the defined values control how the video is scaled/cropped when encoding the images to the video container. For example if you specified a value of AVVideoScalingModeFit then cropping is used. Check out the header for how other values effect the video images.

Crop Recorded Video Frame

Below is my code which is used to crop video.we need to set AVVideoCompressionPropertiesKey which contains AVVideoCleanApertureKey key for video settings.

I Reffered : How to crop video into square iOS with AVAssetWriter

NSDictionary *videoCleanApertureSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                            [NSNumber numberWithInt:cx], AVVideoCleanApertureWidthKey,
                                            [NSNumber numberWithInt:cx], AVVideoCleanApertureHeightKey,
                                            [NSNumber numberWithInt:10], AVVideoCleanApertureHorizontalOffsetKey,
                                            [NSNumber numberWithInt:10], AVVideoCleanApertureVerticalOffsetKey,
                                            nil];
NSDictionary *videoAspectRatioSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                          [NSNumber numberWithInt:3], AVVideoPixelAspectRatioHorizontalSpacingKey,
                                          [NSNumber numberWithInt:3],AVVideoPixelAspectRatioVerticalSpacingKey,
                                          nil];
NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithInt:960000], AVVideoAverageBitRateKey,
                               [NSNumber numberWithInt:1],AVVideoMaxKeyFrameIntervalKey,
                               videoCleanApertureSettings, AVVideoCleanApertureKey,
                               //videoAspectRatioSettings, AVVideoPixelAspectRatioKey,
                               //AVVideoProfileLevelH264Main30, AVVideoProfileLevelKey,
                               nil];
NSString *targetDevice = [[UIDevice currentDevice] model];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoScalingModeResizeAspectFill,AVVideoScalingModeKey,
                               AVVideoCodecH264, AVVideoCodecKey,
                               codecSettings,AVVideoCompressionPropertiesKey,
                               [NSNumber numberWithInt:cx], AVVideoWidthKey,
                               [NSNumber numberWithInt:cx], AVVideoHeightKey,
                               nil];
_videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];