Objective c 视频文件裁剪中的方向问题

嗨，我只是简单地裁剪视频文件，然后通过AVAssetExportSession将其导出到目录中。 但问题是纵向视频将方向更改为横向，并在我保存的目录中显示为旋转90度。我不知道如何修复它。我的代码有问题吗？希望你能理解

firstAsset = [AVAsset assetWithURL:firstUrl];

if(firstAsset !=nil)
{

 AVVideoComposition *origionalComposition = [AVVideoComposition videoCompositionWithPropertiesOfAsset:firstAsset];
    AVMutableComposition* mixComposition = [[AVMutableComposition alloc] init];

    //VIDEO TRACK

    AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    [firstTrack insertTimeRange:timeRange ofTrack:[[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];

AVMutableVideoCompositionInstruction*Main指令=[AVMutableVideoCompositionInstruction videoCompositionInstruction]； MainInstruction.timeRange=时间范围

    AVMutableVideoCompositionLayerInstruction *FirstlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:firstTrack];
    AVAssetTrack *FirstAssetTrack = [[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];


    [FirstlayerInstruction setTransform:FirstAssetTrack.preferredTransform atTime:kCMTimeZero];

    MainInstruction.layerInstructions = [NSArray arrayWithObjects:FirstlayerInstruction,nil];

    AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition];
    MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction];
    MainCompositionInst.frameDuration = origionalComposition.frameDuration;
     MainCompositionInst.renderScale = 1.0;
    MainCompositionInst.renderSize = CGSizeMake(FirstAssetTrack.naturalSize.height, FirstAssetTrack.naturalSize.width);

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Crop Videos"];

    NSString *videoName =[NSString stringWithFormat:@"Video_%d.mov",videoNumber];
    NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:videoName];


    NSURL *url = [NSURL fileURLWithPath:myPathDocs];

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
    exporter.outputURL=url;
    exporter.outputFileType = AVFileTypeQuickTimeMovie;
    exporter.shouldOptimizeForNetworkUse = YES;
    [exporter exportAsynchronouslyWithCompletionHandler:^
     {
         dispatch_async(dispatch_get_main_queue(), ^{
             [self exportDidFinish:exporter];
         });
     }];
}

---

如果有人知道，请回答。。提前感谢

您尚未添加AVMutableVideoCompositionLayerInstruction，请确保相应地更改它

// 1.0 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the  orientation.

AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
AVAssetTrack *videoAssetTrack = [[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

BOOL isVideoAssetPortrait_  = NO;
CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
    isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {

    isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {
    isVideoAssetPortrait_  = NO;
}
if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {
    isVideoAssetPortrait_  = NO;
}
[videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
[videolayerInstruction setOpacity:0.0 atTime:self.videoAsset.duration];

// 1.2 - Add instructions
mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

CGSize naturalSize;
if(isVideoAssetPortrait_){
    naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
} else {
    naturalSize = videoAssetTrack.naturalSize;
}

mainCompositionInst.renderSize = naturalSize;
mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake(1, 30);

这是正在运行的代码：

AVURLAsset* videoAsset = [AVURLAsset assetWithURL:"PATH OF VIDEO"]; 
//create mutable composition
AVMutableComposition *mixComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                               preferredTrackID:kCMPersistentTrackID_Invalid];

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                                        ofTrack:[[videoAsset  tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
                                                         atTime:kCMTimeZero
                                                          error:&videoInsertError];



AVMutableVideoCompositionInstruction * MainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);

//FIXING ORIENTATION//
AVMutableVideoCompositionLayerInstruction *FirstlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTrack];

AVAssetTrack *FirstAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

UIImageOrientation FirstAssetOrientation_  = UIImageOrientationUp;

BOOL  isFirstAssetPortrait_  = NO;

CGAffineTransform firstTransform = FirstAssetTrack.preferredTransform;

if(firstTransform.a == 0 && firstTransform.b == 1.0 && firstTransform.c == -1.0 && firstTransform.d == 0)
{
    FirstAssetOrientation_= UIImageOrientationRight;
    isFirstAssetPortrait_ = YES;
}
if(firstTransform.a == 0 && firstTransform.b == -1.0 && firstTransform.c == 1.0 && firstTransform.d == 0)
{
    FirstAssetOrientation_ =  UIImageOrientationLeft;
    isFirstAssetPortrait_ = YES;
}
if(firstTransform.a == 1.0 && firstTransform.b == 0 && firstTransform.c == 0 && firstTransform.d == 1.0)
{
    FirstAssetOrientation_ =  UIImageOrientationUp;
}
if(firstTransform.a == -1.0 && firstTransform.b == 0 && firstTransform.c == 0 && firstTransform.d == -1.0)
{
    FirstAssetOrientation_ = UIImageOrientationDown;
}

CGFloat FirstAssetScaleToFitRatio = 1.0;

if(isFirstAssetPortrait_)
{
    FirstAssetScaleToFitRatio = FirstAssetTrack.naturalSize.width/FirstAssetTrack.naturalSize.height;
    CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
    [FirstlayerInstruction setTransform:CGAffineTransformConcat(FirstAssetTrack.preferredTransform, FirstAssetScaleFactor) atTime:kCMTimeZero];
}
else
{
    CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
    [FirstlayerInstruction setTransform:CGAffineTransformConcat(CGAffineTransformConcat(FirstAssetTrack.preferredTransform, FirstAssetScaleFactor),CGAffineTransformMakeTranslation(0, 0)) atTime:kCMTimeZero];
}
[FirstlayerInstruction setOpacity:0.0 atTime:videoAsset.duration];

MainInstruction.layerInstructions = [NSArray arrayWithObjects:FirstlayerInstruction,nil];

AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition];
MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction];
MainCompositionInst.frameDuration = CMTimeMake(1, 30);
//MainCompositionInst.renderSize = CGSizeMake(FirstAssetTrack.naturalSize.width, FirstAssetTrack.naturalSize.height);
MainCompositionInst.renderSize = [[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize];

最后，

save

或使用

AVAssetExportSession

类进行“导出”

export.outputURL=FinalPath;

---

谢谢你，但我很抱歉它不起作用，我已经试过很多次了。还有其他方法吗？？？？？你所做的，你的代码没有反映出你已经使用了它。更新你的代码，你已经完成了。