AVVideoComposition не работает в iOS 8

Я работаю над приложением, в котором я создаю видео и экспортирую его в каталог. Он отлично работает в iOS 7, но не работает в iOS 8.

Ниже мой код:

AVAsset *pVideoTrack = [AVAsset assetWithURL:[NSURL fileURLWithPath:assetPath]];
AVVideoComposition *origionalComposition = [AVVideoComposition videoCompositionWithPropertiesOfAsset:pVideoTrack];

AVAssetTrack *clipVideoTrack = [[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

AVMutableComposition* mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo  preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, pVideoTrack.duration)
                               ofTrack:clipVideoTrack
                                atTime:kCMTimeZero error:nil];
[compositionVideoTrack setPreferredTransform:[[[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];

BOOL bIsPotrait = [self checkVideoOrientationProperty:[[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]];

CGSize videoSize = CGSizeMake(0, 0);
if(bIsPotrait)
   videoSize = CGSizeMake([[[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height, [[[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width);

else
   videoSize = [[[pVideoTrack tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize];

AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition];
videoComp.renderSize = videoSize;

AVAssetTrack *videoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];

[layerInstruction setTransform:clipVideoTrack.preferredTransform atTime:kCMTimeZero];

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mixComposition duration]);

videoComp.instructions = [NSArray arrayWithObject: instruction];

videoComp.frameDuration = origionalComposition.frameDuration;
videoComp.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:animatedWaterMarkLayer];

 _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
  _assetExport.videoComposition = videoComp;

NSString *CasheDirectory = [UICommonMethods GetLibraryCacheDirectoryPath];
NSString *outputPath = [CasheDirectory stringByAppendingPathComponent:kWatermarkVideoName];
NSURL *exportUrl = [NSURL fileURLWithPath:outputPath];

if ([[NSFileManager defaultManager] fileExistsAtPath:outputPath])
    [[NSFileManager defaultManager] removeItemAtPath:outputPath error:nil];

_assetExport.outputFileType = AVFileTypeQuickTimeMovie;
_assetExport.outputURL = exportUrl;
_assetExport.shouldOptimizeForNetworkUse = NO;

[_assetExport exportAsynchronouslyWithCompletionHandler:^
 {
     dispatch_async(dispatch_get_main_queue(), ^{

         switch ([_assetExport status]) {
             case AVAssetExportSessionStatusExporting:
                 NSLog(@"Export in progress ");
             case AVAssetExportSessionStatusFailed:
                 NSLog(@"Export failed (%d): %@", [[_assetExport error] code], [[_assetExport error] localizedFailureReason]);
                 [_assetExport cancelExport];
                 break;
             case AVAssetExportSessionStatusCancelled:
                 NSLog(@"Export canceled");
                 break;
             case AVAssetExportSessionStatusCompleted:
                 NSLog(@"Export done");
                 NSLog (@"finished writing %f", [dtStartDate timeIntervalSinceNow]);
                 break;
             case AVAssetExportSessionStatusWaiting:
                 NSLog (@"AVAssetExportSessionStatusWaiting");
                 break;
             case AVAssetExportSessionStatusUnknown:
                 NSLog (@"AVAssetExportSessionStatusUnknown");
                 break;
         }

     });


 }];

Это дает «Медиа-данные не могут быть декодированы. Они могут быть повреждены». ошибка при работе на iOS 8.