compressing a video in iOS

Question

I've looked at this question and this question, neither have been able to help.

I have tried the following:

- (void)compress:(NSURL *)videoPath completionBlock:(void(^)(id data, BOOL result))block{
    self.outputFilePath = [[NSString alloc] initWithFormat:@"%@%@", NSTemporaryDirectory(), @"output.mov"];
    NSURL *outputURL = [NSURL fileURLWithPath:self.outputFilePath];
    [self compressVideoWithURL:self.movieURL outputURL:outputURL handler:^(AVAssetExportSession *exportSession) {

    }];
}

- (void)compressVideoWithURL:(NSURL*)inputURL
                   outputURL:(NSURL*)outputURL
                     handler:(void (^)(AVAssetExportSession*))handler {

    AVURLAsset *asset = [AVURLAsset assetWithURL:self.movieURL];
    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
    exportSession.fileLengthLimit = 3000000;
    exportSession.outputURL = outputURL;
    exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    exportSession.shouldOptimizeForNetworkUse = YES;
    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        NSData *newOutputData = [NSData dataWithContentsOfURL:outputURL];
        NSLog(@"Size of New Video(bytes):%d",[newOutputData length]);
    }];
}

I know that self.movieUrl is not nil. But when I printed the size (in bytes) of the NSData associated with the video, they were the same before and after, both 30,000,000 bytes.

But according to this question, the above code should work.

What am I doing wrong exactly?

Answer 1

I have figured it out, thanks to this question (Swift version): IOS Video Compression Swift iOS 8 corrupt video file

I have the objective C version. Here is the method:

 - (void)compressVideo:(NSURL*)inputURL
        outputURL:(NSURL*)outputURL
          handler:(void (^)(AVAssetExportSession*))completion  {
AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:urlAsset presetName:AVAssetExportPresetMediumQuality];
exportSession.outputURL = outputURL;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
exportSession.shouldOptimizeForNetworkUse = YES;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
    completion(exportSession);
  }];
}

And calling the method:

NSURL* uploadURL = [NSURL fileURLWithPath:
                     [NSTemporaryDirectory() stringByAppendingPathComponent:@"temporaryPreview.mov"]];

[self compressVideo:self.movieURL outputURL:uploadURL handler:^(AVAssetExportSession *completion) {
    if (completion.status == AVAssetExportSessionStatusCompleted) {
        NSData *newDataForUpload = [NSData dataWithContentsOfURL:uploadURL];
        NSLog(@"Size of new Video after compression is (bytes):%d",[newDataForUpload length]);
    }
}];

This reduced the file size of my videos from 32 MB to 1.5 MB.

Answer 2

In Swift 3.0

Select video from Camera roll

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
     if info[UIImagePickerControllerMediaType] as? String == (kUTTypeMovie as? String) {
        // here your video capture code
        let videoURL = info[UIImagePickerControllerMediaURL] as! NSURL!
        let data = NSData(contentsOf: videoURL! as URL)!
        print("File size before compression: \(Double(data.length / 1048576)) mb")
        let compressedURL = NSURL.fileURL(withPath: NSTemporaryDirectory() + NSUUID().uuidString + ".m4v")
        compressVideo(inputURL: videoURL as! URL, outputURL: compressedURL) { (exportSession) in
                guard let session = exportSession else {
                    return
                }

                switch session.status {
                case .unknown:
                    break
                case .waiting:
                    break
                case .exporting:
                    break
                case .completed:
                    guard let compressedData = NSData(contentsOf: compressedURL) else {
                        return
                    }
                   print("File size after compression: \(Double(compressedData.length / 1048576)) mb")
                case .failed:
                    break
                case .cancelled:
                    break
                }
            }
       }
       self.dismiss(animated: true, completion: nil)
 }

Compression type :

AVAssetExportPresetLowQuality
AVAssetExportPresetMediumQuality
AVAssetExportPresetHighestQuality
AVAssetExportPreset640x480 
AVAssetExportPreset960x540

Compress video method

 func compressVideo(inputURL: URL, outputURL: URL, handler:@escaping (_ exportSession: AVAssetExportSession?)-> Void) {
        let urlAsset = AVURLAsset(url: inputURL, options: nil)
        guard let exportSession = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetLowQuality) else {
            handler(nil)

            return
        }

        exportSession.outputURL = outputURL
        exportSession.outputFileType = AVFileTypeQuickTimeMovie
        exportSession.shouldOptimizeForNetworkUse = true
        exportSession.exportAsynchronously { () -> Void in
            handler(exportSession)
        }
    }

Output :

File size before compression: 25.0 mb
File size after compression: 7.0 mb