Combine video clips in iOS using AVFoundation

combine-video-clips.m

-(void) composeVideoClips:(NSMutableArray<AVURLAsset *> *)videoClips
           forComposition:(AVMutableComposition *)composition
                mediaType:(NSString *)mediaType
{
    AVMutableCompositionTrack * composedTrack =
    [composition addMutableTrackWithMediaType:mediaType
                             preferredTrackID:kCMPersistentTrackID_Invalid];
    
    CMTime time = kCMTimeZero;
    for (AVURLAsset *videoClip in videoClips) {
        [composedTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoClip.duration)
                               ofTrack:[videoClip tracksWithMediaType:mediaType].firstObject
                                atTime:time
                                 error:nil];
        
        time = CMTimeAdd(time, videoClip.duration);
    }
}

-(void) combineVideoClipsWithPaths:(NSArray<NSString *> *)paths
                        resultPath:(NSString *)resultPath
                        completion:(void (^)())completion
{
    NSMutableArray<AVURLAsset *> *videoClips = [NSMutableArray array];
    for (NSString *path in paths) {
        NSURL *url = [NSURL fileURLWithPath:path];
        AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:nil];
        [videoClips addObject:asset];
    }
    
    AVMutableComposition* composition = [AVMutableComposition composition];
    [self composeVideoClips:videoClips forComposition:composition mediaType:AVMediaTypeVideo];
    [self composeVideoClips:videoClips forComposition:composition mediaType:AVMediaTypeAudio];
    
    NSURL *url = [[NSURL alloc] initFileURLWithPath:resultPath];
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    
    exporter.outputURL = url;
    exporter.outputFileType = AVFileTypeMPEG4;
    exporter.shouldOptimizeForNetworkUse = YES;
    
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        if (exporter.status == AVAssetExportSessionStatusCompleted && completion) {
            completion();
        }
    }];
}