ios 10中的AVAssetExportSession不适用于iPhone 7
当我在AVSsetExportSession中将两个video混合在ios 9中时，它的工作完美无缺。 但是当我在iOS 10的AVAssetExportSession混合，它不工作。 如果有任何知道的原因，请帮助我，谢谢。
真实的代码适用于iphone 6s和更早版本，但不适用于iPhone 7
例如
-(void) blendVideoOverVideo:(NSURL*)mainVideoUrl andBlendVideoUrl:(NSURL*)liveEffectUrl { AVURLAsset *mainVideoUrlAsset =[AVURLAsset URLAssetWithURL:mainVideoUrl options:nil]; // AVPlayerItem* mainVideoPlayerItem =[[AVPlayerItem alloc]initWithAsset:mainVideoUrlAsset]; AVAssetTrack* mainVideoTrack =[[mainVideoUrlAsset tracksWithMediaType:AVMediaTypeVideo]firstObject]; CGSize mainVideoSize = [mainVideoTrack naturalSize]; AVMutableComposition* mixComposition = [[AVMutableComposition alloc] init]; AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:mainVideoUrl options:nil]; if(mainVideoUrl!=nil) { if([[audioAsset tracksWithMediaType:AVMediaTypeAudio] count]) { AVMutableCompositionTrack *compositionCommentaryTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; [compositionCommentaryTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, mainVideoUrlAsset.duration ) ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil]; } } AVMutableCompositionTrack *mainVideoConpositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; [mainVideoConpositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, mainVideoUrlAsset.duration) ofTrack:mainVideoTrack atTime:kCMTimeZero error:nil]; AVMutableVideoCompositionLayerInstruction *mainVideoLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:mainVideoConpositionTrack]; //SEcond Track AVURLAsset *blendVideoUrlAsset =[AVURLAsset URLAssetWithURL:liveEffectUrl options:nil]; // AVPlayerItem* blendVideoPlayerItem =[[AVPlayerItem alloc]initWithAsset:blendVideoUrlAsset]; AVAssetTrack* blendVideoTrack =[[blendVideoUrlAsset tracksWithMediaType:AVMediaTypeVideo]firstObject]; CGSize blendVideoSize = [blendVideoTrack naturalSize]; AVMutableCompositionTrack *blendVideoConpositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; CMTime oldTime=CMTimeMakeWithSeconds(CMTimeGetSeconds(blendVideoUrlAsset.duration), blendVideoUrlAsset.duration.timescale); // CMTime timeNew=CMTimeMakeWithSeconds(CMTimeGetSeconds(blendVideoUrlAsset.duration)/2, blendVideoUrlAsset.duration.timescale); [blendVideoConpositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, oldTime) ofTrack:blendVideoTrack atTime:kCMTimeZero error:nil]; AVMutableVideoCompositionLayerInstruction *blendVideoLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:blendVideoConpositionTrack]; AVMutableVideoCompositionInstruction * MainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction]; MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, mainVideoUrlAsset.duration); CGAffineTransform Scale = CGAffineTransformMakeScale(1.0f,1.0f); CGAffineTransform Move = CGAffineTransformMakeTranslation(0,0); [mainVideoLayerInstruction setTransform:CGAffineTransformConcat(Scale,Move) atTime:kCMTimeZero]; [blendVideoLayerInstruction setOpacity:0.5 atTime:kCMTimeZero]; // [blendVideoLayerInstruction setOpacity:0.0 atTime:timeNew]; CGFloat cropOffX = 1.0; CGFloat cropOffY = 1.0; if(blendVideoSize.height>mainVideoSize.height) { cropOffY = mainVideoSize.height/blendVideoSize.height; }else{ cropOffY = mainVideoSize.height/blendVideoSize.height; } if(blendVideoSize.width>mainVideoSize.width) { cropOffX = mainVideoSize.width/blendVideoSize.width; } Scale = CGAffineTransformMakeScale(cropOffX,cropOffY); Move = CGAffineTransformMakeTranslation(0.1, 0.1); [blendVideoLayerInstruction setTransform:CGAffineTransformConcat(Scale,Move) atTime:kCMTimeZero]; MainInstruction.layerInstructions = [NSArray arrayWithObjects:blendVideoLayerInstruction,mainVideoLayerInstruction,nil]; AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition]; MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction]; MainCompositionInst.frameDuration = CMTimeMake(1, 30); MainCompositionInst.renderSize = mainVideoSize; NSString *fullName= [NSString stringWithFormat:@"video%d.mov",arc4random() % 1000]; NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *myPathDocs = [documentsDirectory stringByAppendingPathComponent:fullName]; if([[NSFileManager defaultManager] fileExistsAtPath:myPathDocs]) { [[NSFileManager defaultManager] removeItemAtPath:myPathDocs error:nil]; } NSURL *url = [NSURL fileURLWithPath:myPathDocs]; AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality]; exporter.outputURL=url; CMTime start; CMTime duration; NSLog(@"Main Video dura %f blend dura - %f, ",CMTimeGetSeconds(mainVideoUrlAsset.duration),CMTimeGetSeconds(blendVideoUrlAsset.duration)); if(CMTimeGetSeconds(blendVideoUrlAsset.duration)>CMTimeGetSeconds(mainVideoUrlAsset.duration)) { start = CMTimeMakeWithSeconds(0.0, blendVideoUrlAsset.duration.timescale); duration = CMTimeMakeWithSeconds(CMTimeGetSeconds(mainVideoUrlAsset.duration), blendVideoUrlAsset.duration.timescale); } else if(CMTimeGetSeconds(mainVideoUrlAsset.duration)>CMTimeGetSeconds(blendVideoUrlAsset.duration)) { start = CMTimeMakeWithSeconds(0.0, mainVideoUrlAsset.duration.timescale); duration = CMTimeMakeWithSeconds(CMTimeGetSeconds(mainVideoUrlAsset.duration), mainVideoUrlAsset.duration.timescale); } CMTimeRange range = CMTimeRangeMake(start, duration); exporter.timeRange = range; [exporter setVideoComposition:MainCompositionInst]; exporter.outputFileType = AVFileTypeQuickTimeMovie; __weak typeof(self) weakSelf = self; [weakSelf createMBCircularProgress:exporter]; [exporter exportAsynchronouslyWithCompletionHandler:^{ dispatch_async(dispatch_get_main_queue(), ^{ [weakSelf exportDidFinish:exporter]; }); }]; } 这段代码将运行在iPhone 6s，6,5等ios 9甚至iOS 10，但此代码将不会运行在iPhone 7模拟器。
解决scheme是我们需要使用最新的XCode 8.1 beta来运行这个
It's a bug. It's fixed in Xcode 8.1 beta.
Xcode 8.1 beta [AVAssetExportSession allExportPresets] iPhone 7模拟器现在返回
AVAssetExportPreset1920x1080, AVAssetExportPresetLowQuality, AVAssetExportPresetAppleM4A, AVAssetExportPreset640x480, AVAssetExportPreset3840x2160, AVAssetExportPresetHighestQuality, AVAssetExportPreset1280x720, AVAssetExportPresetMediumQuality, AVAssetExportPreset960x540
Xcode 8.0 [AVAssetExportSession allExportPresets] iPhone 7模拟器返回一个空的数组
AVAssetExportSession可以是NULL，所以在工作之前需要检查NULL https://developer.apple.com/library/content/qa/qa1730/_index.html