How do I use AVFoundation to crop a video

Question

I\'m trying to use AVFoundation to crop videos I\'m recording. So lets say i create a AVCaptureVideoPreviewLayer and set the frame to be 300x300.

AVCaptureVi         


        

Answer 1

ios7 added a specific Layer instruction just for cropping.

videolayerInstruction setCropRectangle:atTime:

_mike

Answer 2

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){}];