Technical Q&A QA1744

Setting the orientation of video with AV Foundation

Q:  How do I set the orientation of video with AV Foundation?

A: AV Foundation Capture

You can set an orientation on a AVCaptureConnection to specify how you want the images oriented in the AVCaptureOutput output destination (AVCaptureMovieFileOutput, AVCaptureStillImageOutput or AVCaptureVideoDataOutput) or AVCaptureVideoPreviewLayer for the connection.

Use the AVCaptureConnection supportsVideoOrientation property (getter= isVideoOrientationSupported) to determine whether the object supports changing the orientation of the video, and the videoOrientation property to specify how you want the images oriented in the the output destination or preview layer. For example, here's a code snippet showing how to set the videoOrientation for a AVCaptureStillImageOutput's AVCaptureConnection to AVCaptureVideoOrientationLandscapeLeft:

Listing 1  Setting the videoOrientation for a AVCaptureStillImageOutput's AVCaptureConnection.

#import <AVFoundation/AVFoundation.h>
AVCaptureStillImageOutput *stillImageOutput = <#A still image output#>;
AVCaptureConnection *connection =
    [stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
if ([connection isVideoOrientationSupported])
    [connection setVideoOrientation: AVCaptureVideoOrientationLandscapeLeft];

Applications that do not take into consideration the video track transform and still image exif metadata may not display these media items in the proper orientation.

AVCaptureVideoDataOutput clients may receive physically rotated CVPixelBuffers in their -captureOutput:didOutputSampleBuffer:fromConnection: delegate callback. All 4 AVCaptureVideoOrientation modes are supported, and rotation is hardware accelerated. To request buffer rotation, a client calls -setVideoOrientation: on the AVCaptureVideoDataOutput's video AVCaptureConnection.


If you are using an AVAssetWriter object to write a movie file, you can use the transform property of the associated AVAssetWriterInput to specify the output file orientation. This will write a display transform property into the output file as the preferred transformation of the visual media data for display purposes. See the AVAssetWriterInput.h interface file for the details.

AVMutableComposition, AVMutableVideoComposition and AVAssetExportSession


If you are using an AVMutableComposition to edit your visual assets, you can set the preferredTransform property on any of the video tracks (AVMutableCompositionTrack).


If you are using an AVMutableVideoComposition to edit the video tracks in a video composition, use an AVMutableVideoCompositionLayerInstruction object to modify the transform to apply to a given track in the video composition. Use the setTransform:atTime: method to set a value of the transform at a time within the time range of the instruction, or use the setTransformRampFromStartTransform:toEndTransform:timeRange: method to set a transform ramp to apply during a given time range.

Otherwise, if you specify the AVAssetExportPresetPassthrough export option to let all tracks pass through but you still want to set a transform on the composition, set the preferredTransform property on the composition tracks as described above.

Document Revision History


Updated to include information about using an AVCaptureVideoPreviewLayer's AVCaptureConnection videoOrientation property to set the orientation instead of the deprecated AVCaptureVideoPreviewLayer orientation property. Modified code snippet to show how to get the AVCaptureConnection for the AVCaptureOutput. Other miscellaneous changes.


Updated to include information about AVMutableComposition, AVMutableVideoComposition and AVAssetExportSession.


Added information about physically rotating CVPixelBuffers in the AVCaptureVideoDataOutput -captureOutput:didOutputSampleBuffer:fromConnection: delegate callback.


New document that describes how to set the orientation of video with AV Foundation.