视频合并

//本地视频

-(void)mergeAsset:(AVAsset *)firstAsset WithAsset:(AVAsset *)secondAsset{

    if (firstAsset !=nil && secondAsset!=nil) {
        //1.创建一个AVMutableComposition实例,它将持有AVMutableCompositionTrack实例
        AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];
       //2. 创建一个轨道,类型是AVMediaTypeAudio
        AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                             preferredTrackID:kCMPersistentTrackID_Invalid];
        AVMutableCompositionTrack *secondTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                            preferredTrackID:kCMPersistentTrackID_Invalid];
         //获取firstAsset中的音频,插入轨道
        [firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, firstAsset.duration)
                            ofTrack:[[firstAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
        [secondTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, firstAsset.duration)
                            ofTrack:[[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];
        //获取secondAsset中的音频,插入轨道
        [firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, secondAsset.duration)
    ofTrack:[[secondAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:firstAsset.duration error:nil];
        [secondTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, secondAsset.duration)
                            ofTrack:[[secondAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:firstAsset.duration error:nil];
        //添加背景音乐

//        AVAsset*  audioAsset = [AVAsset assetWithURL: [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Eson1" ofType:@"mp3"]]];

        // 3 - Audio track
//        if (audioAsset!=nil){
//            AVMutableCompositionTrack *AudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio
//                                                                                preferredTrackID:kCMPersistentTrackID_Invalid];
//            [AudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeAdd(firstAsset.duration, secondAsset.duration))
//                                ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//        }
        // 4 - Get path
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:
                                 [NSString stringWithFormat:@"mergeVideo-%d.mov",arc4random() % 1000]];
        NSURL *url = [NSURL fileURLWithPath:myPathDocs];
        // 5 - Create exporter
        AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                          presetName:AVAssetExportPresetHighestQuality];
        exporter.outputURL=url;
        exporter.outputFileType = AVFileTypeQuickTimeMovie;
        exporter.shouldOptimizeForNetworkUse = YES;
        [exporter exportAsynchronouslyWithCompletionHandler:^{
            dispatch_async(dispatch_get_main_queue(), ^{
                [self exportDidFinish:exporter];
            });
        }];
    }
}