insertTimeRanges

/*

 concat videos and save to saveURL

 must save the AVURLAsset in a array

 */

- (void)concatVideos:(NSArray *)videos saveTo:(NSURL *)saveURL completion:(void(^)(NSError *))completion {

    // overwrite file

    NSError *error;

    [self removeFileAt:saveURL error:&error];

    // arrays

    NSMutableArray *assets = [[NSMutableArray alloc] init];

    NSMutableArray *timeRanges = [[NSMutableArray alloc] init];

    NSMutableArray *tracks = [[NSMutableArray alloc] init];

    for (NSURL *url in videos) {

            AVURLAsset *tmpAsset = [AVURLAsset assetWithURL:filePath1];

            CMTimeRange range = CMTimeRangeMake(kCMTimeZero, tmpAsset.duration);

            [assetsaddObject:tmpAsset];//坑 必须要保存下AVURLAsset

            [timeRangesaddObject:[NSValue valueWithCMTimeRange:range]];

            [tracksaddObject:[[tmpAsset tracksWithMediaType:AVMediaTypeAudio] firstObject]];

    }

    // output

    AVMutableComposition *composition = [AVMutableComposition composition];

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

    [compositionTrack insertTimeRanges:timeRanges ofTracks:tracks atTime:kCMTimeZero error:&error];

    // export

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

    if (self.saveFileType) {

        exporter.outputFileType =self.saveFileType;

    }else {

        exporter.outputFileType = AVFileTypeMPEG4;

    }

    exporter.outputURL = saveURL;

    [exporter exportAsynchronouslyWithCompletionHandler:^{

        completion(exporter.error);

    }];

}