如何在物镜c中校正视频方向 [英] how to correct orientation of video in objective c

问题描述

我正在使用UIImagePickerController在iPhone中捕获视频，但是视频显示的是向右旋转90度.

I am using UIImagePickerController to capture video in iPhone but video is showing rotated 90 digree to right.

如何解决此问题

有什么方法可以纠正方向.

Is there any way by which we can correct the orientation.

推荐答案

您需要使用AVExportSession重新编码视频，以将视频旋转到正确的方向，例如

you need make the re-encode video using AVExportSession to rotate video to correct orientation like said Oleksiy Ivanov. So you need something like this:

NSError *error = nil;
AVURLAsset *videoAssetURL = [[AVURLAsset alloc] initWithURL:self.videoUrl options:nil]; 

AVMutableComposition *composition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

AVAssetTrack *videoTrack = [[videoAssetURL tracksWithMediaType:AVMediaTypeVideo] firstObject];
AVAssetTrack *audioTrack = [[videoAssetURL tracksWithMediaType:AVMediaTypeAudio] firstObject];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAssetURL.duration) ofTrack:videoTrack atTime:kCMTimeZero error:&error];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAssetURL.duration) ofTrack:audioTrack atTime:kCMTimeZero error:&error];

CGAffineTransform transformToApply = videoTrack.preferredTransform;
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];
[layerInstruction setTransform:transformToApply atTime:kCMTimeZero];
[layerInstruction setOpacity:0.0 atTime:videoAssetURL.duration];

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake( kCMTimeZero, videoAssetURL.duration);
instruction.layerInstructions = @[layerInstruction];

AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.instructions = @[instruction];
videoComposition.frameDuration = CMTimeMake(1, 30); //select the frames per second
videoComposition.renderScale = 1.0;
videoComposition.renderSize = CGSizeMake(640, 640); //select you video size

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality];

exportSession.outputURL = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:@"videoname.MOV"]];
exportSession.outputFileType = AVFileTypeMPEG4; //very important select you video format (AVFileTypeQuickTimeMovie, AVFileTypeMPEG4, etc...)
exportSession.videoComposition = videoComposition;
exportSession.shouldOptimizeForNetworkUse = NO;
exportSession.timeRange = CMTimeRangeMake(kCMTimeZero, videoAssetURL.duration);

[exportSession exportAsynchronouslyWithCompletionHandler:^{

            switch ([exportSession status]) {

                case AVAssetExportSessionStatusCompleted: {

                    NSLog(@"Triming Completed");

                    //generate video thumbnail
                    self.videoUrl = exportSession.outputURL;
                    AVURLAsset *videoAssetURL = [[AVURLAsset alloc] initWithURL:self.videoUrl options:nil];
                    AVAssetImageGenerator *genrateAsset = [[AVAssetImageGenerator alloc] initWithAsset:videoAssetURL];
                    genrateAsset.appliesPreferredTrackTransform = YES;
                    CMTime time = CMTimeMakeWithSeconds(0.0,600);
                    NSError *error = nil;
                    CMTime actualTime;

                    CGImageRef cgImage = [genrateAsset copyCGImageAtTime:time actualTime:&actualTime error:&error];
                    self.videoImage = [[UIImage alloc] initWithCGImage:cgImage];
                    CGImageRelease(cgImage);

                    break;
                }
                default: {
                    break;
                }
            }
        }];

只需要为您的视频网址更改self.videoUrl，它就可以正常工作:)

just need change self.videoUrl for you video url and it should work fine :)

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