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.
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
captureVideoPreviewLayer.delegate = self;
captureVideoPreviewLayer.frame = CGRectMake(0,0, 300, 300);
[previewView.layer addSublayer:captureVideoPreviewLayer];
The user sees the video cropped. I'd like to save the video exactly the way the user is viewing it. Using AVCaptureMovieFileOutput, the video obviously gets saved without cropping. I was considering using a AVCaptureVideoDataOutput to intercept the frames and crop them myself, but I was wondering if there is a more efficient way to do this, perhaps with AVExportSession and using an AVVideoComposition.
Any guidance would be appreciated.
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){}];
ios7 added a specific Layer instruction just for cropping.
videolayerInstruction setCropRectangle:atTime:
_mike
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