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Offline downloads using the VdoCipher Flutter SDK

Overview​

The VdoCipher Flutter 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)

Generating OTP for Offline Playback​

To initialize video playback on website or app, your backend has to generate an OTP+playbackInfo using the VdoCipher API. The regular OTP does not have permission to be persisted offline. To enable offline playback you will need to send additional parameters while making the API call for the OTP.

You can specify the time period for which the offline download will be available for playback. The time period of validity is called the rental duration. Beyond the rental duration the license will expire, and the downloaded file will no longer play.

How to generate offline OTP »

You can find more details on the OTP-based playback mechanism at the API page.

Get the available options for a media​

A video in your VdoCipher dashboard may be encoded in multiple bitrates (for adaptive streaming). Hence, there are some options regarding what exactly needs to be downloaded. As adaptive playback is not possible in offline mode, you must download exactly one video track and one audio track.

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 corresponding to the video to fetch the options.

OptionsDownloader optionsDownloader = new OptionsDownloader();
              optionsDownloader.downloadOptionsWithOtp(
                  otp, playbackInfo, customPlayerId, (downloadOptions) {
                // we have received the available download options
              }, (vdoError) {
                // there was an error downloading the available options
              });

A DownloadOptions object contains a MediaInfo object (with general information about the media, such as title and description) and a list of VideoTrack and AudioTrack. These tracks contain 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 previously, we must select exactly one audio track and one video track. As soon as we have the download options, we can either make selections automatically based on user preferences (e.g. select the highest quality/bitrate) or present the options to the user to select.

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 indexes of the audio and video track we want to download from the provided AudioTrack and VideoTrack list in DownloadOptions.

// `audioTrackIndex` and `videoTrackIndex` is the track index from `downloadOptions.allAudio` and `downloadOptions.allVideo` respectively
DownloadSelections downloadSelections = new DownloadSelections(downloadOptions, videoTrackIndex, audioTrackIndex);

Enqueue request for download​

The VdoDownloadManager class handles enqueuing requests for download.

Now that we have made the selctions specifying which tracks to download. Next step is to create a DownloadRequest using DownloadSelections.

  //Create download request object from download selections
  DownloadRequest downloadRequest = new DownloadRequest(downloadSelections);
  //If you are using safetynet, set safetynet API key like this
  downloadRequest.safetyNetApiKey = API_KEY; //your api key
Safetynet is discountinued

The above section contains information on setting up SafetyNet with media download, which is no longer recommended and not supported in our latest SDK. Play integrity is now the recommended way for device attestation. Please get in touch with us through Support to use Play integrity.

Now we have a DownloadRequest that can be enqueued for download right away.

    // enqueue request to VdoDownloadManager for download
    VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance();
    vdoDownloadManager.enqueue(downloadRequest);

This will add the request to the download queue and start download when the requirements for downloads to progress are met.

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
VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance();
vdoDownloadManager.addDownloadEventListener(eventListener);

// don't forget to de-register the listener
vdoDownloadManager.removeDownloadEventListener(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.filterByMediaId([mediaId1, mediaId2]);
// set filters by status
// let's filter for downloads which are paused and downloading
query.filterByStatus([VdoDownloadManager.STATUS_PAUSED, VdoDownloadManager.STATUS_DOWNLOADING]);

Now we can use this query object to query status for the specified downloads like this.

List<DownloadStatus> downloadStatusList = await vdoDownloadManager.query(query);

A query result is provided as a future of DownloadStatus list, DownloadStatus objects provides information such as the MediaInfo, status, any errors if they occured while downloading, etc.

Offline Playback​

For playing downloaded videos, the initial step involves creating an EmbedInfo for offline playback. This EmbedInfo is then utilized in conjunction with the VdoPlayer.

import 'package:vdocipher_flutter/vdocipher_flutter.dart';

// Utilize the mediaId of the downloaded video.
EmbedInfo embedInfo = EmbedInfo.offline(mediaId: mediaId);

Widget playerWidget = VdoPlayer(
  embedInfo: embedInfo,
  onPlayerCreated: (controller) => _onPlayerCreated(controller),
  onFullscreenChange: _onFullscreenChange,
  onError: _onVdoError,
);

Note: Ensure to substitute mediaId with the actual media ID of the downloaded video.

Delete downloads​

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

VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance();
vdoDownloadManager.remove(mediaId);

Pause downloads​

To pause a media download use the stopDownload() method of VdoDownloadManager. You will also receive an onChanged() callback if you have an EventListener registered with the VdoDownloadManager.

VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance();
vdoDownloadManager.stopDownload(mediaId);

Resume downloads​

To resume a media download use the resumeDownload() method of VdoDownloadManager. You will also receive a onChanged() callback if you have an EventListener registered with the VdoDownloadManager.

VdoDownloadManager vdoDownloadManager = VdoDownloadManager.getInstance();
vdoDownloadManager.resumeDownload(mediaId);

Check if video is expired​

Not supported in iOS

To check if a video is expired, use the DownloadStatus.isExpired() method. This will return true or false based on whether the provided media id is expired or not.

// Call isExpired() method on downloadStatus object to check for expiry.
bool isExpired = await downloadStatus.isExpired();

if (isExpired) {
    // Either re-download the video or remove the video.
}
  • If the video is expired, adjust the UI accordingly. Avoid playing the expired video to prevent displaying error code 6187 along with a message; the error message will provide viewers with context about the video expiration.
  • For expired video, you can choose to either re-download the video or remove the video.