这个真的很浪费时间，网上能查到视频合成，也能查到多个视频合成视频，可都是针对合成后的视频旋转，我遇到的是需要合成的视频，只有某一段需要旋转，一直找不到原因，最终还是参考很多大神写的文章最总捣鼓出来了

//多个视频合成一个视频

+ (void)multipleVideosMakeAVideoWitharr:(NSArray*)array completion:(outputStrBlock)completion{

    //包含多个轨道的媒体信息，可以添加、删除轨道

    AVMutableComposition *composition = [[AVMutableComposition alloc] init];

    //程文件中的轨道，有音频轨、视频轨等，里面可以插入各种对应的素材；

    AVMutableCompositionTrack *videoCompositionTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

    AVMutableCompositionTrack *audioCompositionTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

    CMTime totalDuration = CMTimeAdd(kCMTimeZero, kCMTimeZero);

    NSMutableArray *mutArr = [NSMutableArray array];

    for(inti =0; i

        AVAsset*videoAsset = [AVAssetassetWithURL:[NSURLURLWithString:array[i]]];

        AVAssetTrack*videoTrack = [[videoAssettracksWithMediaType:AVMediaTypeVideo]firstObject];

        AVAssetTrack*audioTrack = [[videoAssettracksWithMediaType:AVMediaTypeAudio]firstObject];

        [videoCompositionTrackinsertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)ofTrack:videoTrackatTime:totalDurationerror:nil];

       [audioCompositionTrackinsertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)ofTrack:audioTrackatTime:totalDurationerror:nil];

    //视频操作指令

        AVMutableVideoCompositionInstruction *instrucation = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

         instrucation.timeRange=CMTimeRangeMake(totalDuration, videoAsset.duration);

        //视频轨道操作指令，需要添加

        AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoCompositionTrack];

        if(videoAsset.naturalSize.width> videoAsset.naturalSize.height) {

            CGAffineTransform t1 =CGAffineTransformMakeTranslation( videoAsset.naturalSize.width/2+ videoAsset.naturalSize.height/2,-videoAsset.naturalSize.height/2);

            CGAffineTransformt2 =CGAffineTransformRotate(t1,degreesToRadians(90));

            [layerInstructionsetTransform:t2atTime:kCMTimeZero];

        }else{

            CGAffineTransformt1 =CGAffineTransformMakeTranslation( videoAsset.naturalSize.width,0);

            CGAffineTransformt2 =CGAffineTransformRotate(t1,degreesToRadians(0));

            [layerInstructionsetTransform:t2atTime:kCMTimeZero];

        }

        instrucation.layerInstructions=@[layerInstruction];

        [mutArraddObject:instrucation];

        totalDuration =CMTimeAdd(totalDuration,videoAsset.duration);

    }

    AVMutableVideoComposition *mainComposition = [AVMutableVideoComposition videoComposition];

    mainComposition.instructions= mutArr;

    mainComposition.frameDuration=CMTimeMake(1,30);

    //    mainComposition.renderSize = CGSizeMake(renderW, renderW); // 裁剪出对应大小

    CGSizerenderSize=CGSizeMake(videoCompositionTrack.naturalSize.width, videoCompositionTrack.naturalSize.height);;

    mainComposition.renderSize= renderSize;// 裁剪出对应大小

    mainComposition.renderScale  =1;

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];

    [formattersetDateFormat:@"yyyyMMddHHmmss"];

    NSString*current = [formatterstringFromDate:[NSDatedate]];

    NSURL*videoPath = [selffilePathWithFileName:[NSStringstringWithFormat:@"%@.mp4",current]];

    AVAssetExportSession *export = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];

    export.outputURL= videoPath;

    export.videoComposition= mainComposition;

    export.outputFileType = AVFileTypeQuickTimeMovie;

    export.shouldOptimizeForNetworkUse = YES;

    [exportexportAsynchronouslyWithCompletionHandler:^{

        if ([export status] == AVAssetExportSessionStatusCompleted) {

            NSLog(@"%@",[NSThreadcurrentThread]);

            NSLog(@"%@",export.outputURL);

            NSLog(@"导出成功");

            if(completion) {

                completion(export.outputURL.absoluteString);

            }

        }else{

            dispatch_async(dispatch_get_main_queue(), ^{

                NSLog(@"导出失败");

                if(completion) {

                    completion(@"");

                }

            });

        }

    }];

}