Offline downloads using the VdoCipher Android SDK

Overview

The VdoCipher Android SDK offers capability to download videos to local storage for offline playback on Android devices running Lollipop and above (API level 20+).

It includes APIs to :

  • Fetch available download options for a video in your dashboard
  • Download media assets to local storage
  • Track download progress
  • Manage downloads (query or delete downloads)

We'll explore a typical download workflow in this document. The Sample App on Github provides code examples for a typical use case.

Get the available options for a media

A video in your VdoCipher dashboard may be encoded in multiple bitrates (for adaptive streaming) or has multiple audio tracks for different languages. Hence, there are some options regarding what exactly needs to be downloaded. For offline playback, adaptive doesn't make sense, and also the user typically has a preferred language. So, you must specify exactly one video track and exactly one audio track for download.

The first step is to get the available options for the media. We'll use the OptionsDownloader class for this. We'll need a playbackInfo and otp or signature corresponding to the video to fetch the options.

  OptionsDownloader optionsDownloader = new OptionsDownloader();
    // assuming we have otp and playbackInfo
    optionsDownloader().downloadOptionsWithOtp(otp, playbackInfo, new OptionsDownloader.Callback() {
    @Override
    public void onOptionsReceived(DownloadOptions options) {
      // we have received the available download options
      Log.i("ok", "onOptionsReceived");
      // ...
    }

    @Override
    public void onOptionsNotReceived(ErrorDescription errDesc) {
      // there was an error downloading the available options
      String errMsg = "onOptionsNotReceived : " + errDesc.toString();
      Log.e("error", errMsg);
    }
    });
    

The available options are received in the OptionsDownloader.Callback#onOptionsReceived() callback in the form of a DownloadOptions instance. A DownloadOptions object contains a MediaInfo object (with general details of the media, such as title, description as set in your VdoCipher dashboard, etc.) and an array of Track objects corresponding to the available audio and video track options. Each Track object in the array corresponds to a audio or video track (specified by Track#type) and contains relevant information such as bitrate, resolution, language, etc.

Once we've obtained the available options, the next step is to make a selection of which tracks to download.

Select the tracks to download

As mentioned earlier in this document, we need to select exactly one audio track and one video track.

Once we have the download options, we may make selections automatically based on user preferences etc. (e.g. select the highest quality/bitrate) or present the options to the user to choose.

Once a selection has been made (automatically or by the user), make a DownloadSelections object using the options we received in the previous step and the indices of the tracks we want to download in the Track array in the DownloadOptions.

  // selections must include exactly one audio track (Track#TYPE_AUDIO) and one video track (Track#TYPE_VIDEO)
  // track indices are the index of the track in the Track array in received DownloadOptions
  int[] selectionIndices = new int[]{audioTrackIndex, videoTrackIndex};
  DownloadSelections downloadSelections = new DownloadSelections(downloadOptions, selectionIndices);
    

Now we have made the selctions specifying which tracks to download. Next step is to specify some more options such as download location on local storage and create a DownloadRequest.

Specify more options

We need to specify a storage location for the media files to be downloaded. This location must be folder on external storage. External storage does not necessarily mean a removable media such as a SD card. Specifically, the location should be inside the directory tree returned by Context#getExternalFilesDir(). This will also ensure the media files are deleted when the app in uninstalled. If this behavior is not required for some reason, you may choose a folder in the directory tree returned by Environment#getExternalStorageDirectory() which is the public shared storage, although this location is not recommended.

We'll store all downloads to a dedicated folder on the external storage.

  // ensure external storage is in read-write mode
  if (!isExternalStorageWritable()) {
    // External storage is not available; can't proceed
    Log.e("error", "external storage not available");
    Toast.makeText(this, "external storage not available", Toast.LENGTH_LONG).show();
    return;
  }

  // we'll download all videos to directory "offlineVideos" on the primary external storage
  String downloadLocation;
  try {
    downloadLocation = getExternalFilesDir(null).getPath() + File.separator + "offlineVideos";
  } catch (NullPointerException npe) {
    Log.e("error", "external storage not available: " + Log.getStackTraceString(npe));
    Toast.makeText(this, "external storage not available", Toast.LENGTH_LONG).show();
    return;
  }

  // ensure download directory is created
  File dlLocation = new File(downloadLocation);
  if (!(dlLocation.exists() && dlLocation.isDirectory())) {
    // directory not created yet; let's create it
    if (!dlLocation.mkdir()) {
      Log.e("error", "failed to create storage directory");
      Toast.makeText(this, "failed to create storage directory", Toast.LENGTH_LONG).show();
      return;
    }
  }

Now we'll create a new DownloadRequest.

  // build a DownloadRequest
  DownloadRequest request = new DownloadRequest.Builder(downloadSelections, downloadLocation).build();
    

Now we have a DownloadRequest that can be enqueued for download right away. We'll do this in the next step.

Enqueue request for download

The VdoDownloadManager class handles enqueuing requests for download. This class a familiar API somewhat similar to the DownloadManager in Android sdk.

  VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance(activityContext);

  // enqueue request to VdoDownloadManager for download
  try {
    vdoDownloadManager.enqueue(request);
  } catch (IllegalArgumentException | IllegalStateException e) {
    Log.e("error", "error enqueuing download request");
    Toast.makeText(this, "error enqueuing download request", Toast.LENGTH_LONG).show();
  }
    

This will add the request to the download queue and start download when all requests enqueued before have completed.

Monitoring download progress

We can monitor the progress of the download queue by registering a EventListener with the VdoDownloadManager.

  // register a listener for download events; recommended to do this in Activity's onStart()
  VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance(activityContext);
  vdoDownloadManager.addEventListener(eventListener);

  // don't forget to de-register the listener in Activity's onStop() to avoid memory leaks
  vdoDownloadManager.removeEventListener(eventListener);
    

Query for downloads

VdoDownloadManager allows querying for all downloads managed by it or only specific downloads specified by filters.

Queries provide status of all downloads that are queued or downloding or completed. Make a Query object and specify any filters you want.

  Query query = new Query();

  // set mediaId filters if these are the only videos for which you want the status
  query.setFilterByMediaId(mediaId1, mediaId2);

  // set filters by status
  // here we filter for downloads which are queued and downloading
  query.setFilterByStatus(VdoDownloadManager.STATUS_PENDING, VdoDownloadManager.STATUS_DOWNLOADING);
    

Now we can use this query object to query status for the specified downloads. A query result is provided as a list of DownloadStatus objects which provides information such as the MediaInfo, status, any errors if they occured while downloading, etc.

The query results are provided asynchronously to a QueryResultListener provided as an argument to the query method.

  vdoDownloadManager.query(query, new VdoDownloadManager.QueryResultListener() {
    @Override
    public void onQueryResult(List statusList) {
      int size = statusList.size();
      Log.i(TAG, size + " results found");
    }
  });
    

Delete a download

To delete a media download use the VdoDownloadManager#remove() method. This will cancel the download if it is still downloading or pending and remove any downloaded media files. You will also receive a EventListener#onDeleted() callback if you have an EventListener register with the VdoDownloadManager.

  VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance(activityContext);
  vdoDownloadManager.remove(mediaIdtoDelete);