The Predictive Content Delivery (PCD) SDK allows users to download videos intelligently to mobile devices. Users initiate downloads by browsing your video catalog and selecting the content to watch.

A sophisticated Download Manager checks the battery, device storage, network, and other variables to make sure that the video transfer will succeed. Errors are thrown if the video transfer fails.

Downloads continue whether the app is active in the foreground, running in the background, or entirely closed. In addition, the SDK acts as a data cache, providing access to content along with its current download state.


This document is for developers implementing the PCD SDK; deep knowledge of Android and/or iOS is assumed.

There are separate instructions for Android and iOS. Configuring your project to support these platforms is covered in the following chapters.

Getting Started with iOS

The fastest way to get started with the SDK is to try the sample app. Once you've downloaded the Zip file and changed the necessary requirements and dependencies, you're ready to go.

After you're done playing witht the sample app, the next steps are SDK initialization and registration. These steps are covered in detail in Integrating With Your iOS Application.

Requirements and Dependencies

SDK Contents

When you download the PCD SDK zip, the contents include: 

Trying the Sample App

The easiest way to get started is to try one of the sample apps.

  1. Open one of the examples in the examples/ folder.
  2. Substitute your SDK license key for the existing key.
  3. Run the app. # Integrating With Your iOS Application

To start using the PCD SDK with your own app, you'll need to include the SDK in your app. If you've already set up Android to work with PCD, you'll note that iOS has a couple extra steps to enable background execution, remote notifications, and app transport security. Once these are complete you can continue with initialization and registration.

Installing the iOS SDK

  1. Download the PCD SDK and unzip it in a folder under your project, e.g. ~/myproject/pcd_sdk.
  2. Locate VocSdk.framework under ~/myproject/pcdsdk/iphoneos/ and copy it into your project folder, e.g. ~/myproject/VocSdk.framework. This makes the framework available before the first build so you can add it to your project. On each build afterward it will be copied here by the copyvocsdk build phase script.
  3. Add the framework to your Xcode project by opening your project in Xcode and choose File > Add Files to... and choose ~/myproject/VocSdk.framework.
  4. Click the project name in the Project navigator to open the project settings.
  5. Click the General tab, and under Embedded Binaries, click + and choose VocSdk.framework. Click Add.

Adding a Build Phase

The right framework for your platform - simulator or device - must be copied into place before building your app. This requires a build phase to be added to your project settings.

  1. In Project Settings, choose your build target then click on Build Phases.
  2. Click the + to add a new build phase, and choose New Run Script Phase.
  3. Drag this build phase to position it after Target Dependencies.
  4. Single-click its name and rename it to copy_vocsdk.
  5. Click the arrow to expand the copy_vocsdk row.
  6. Leave the default shell setting of /bin/sh.
  7. Add the following text to the script area, noting that the path is relative to your .xcodeproj file and may need modification depending on where you unzipped it (pcdsdk in this example).
./pcd_sdk/  "${PROJECT_DIR}/pcd_sdk"

The second parameter, ${PROJECTDIR}/pcdsdk, is the location of the /iphoneos and /iphonesimulator folders from the distribution archive.

In this example, the folder structure is as follows:


The script will copy the correct VocSdk.framework to the /myproject/, folder at the start of every build.

Including the SDK

Import the VocSdk header in any class files where the SDK is required. Also define a single VocService object for your app. Create your VocService object in the app delegate to make the SDK available early in the app lifecycle and to simplify access to the VocService from other classes.

#import <VocSdk/VocSdk.h>
@property (strong , nonatomic) id <VocService>  vocService;

Enabling Background Execution

The PCD SDK downloads content while the application is running. Various factors determine when to start downloading, how much to download, and when to pause downloads. Influencing factors include the state of the mobile network and the quality state of the provider network.

When your app is in the foreground, downloads are happening without any need for changes in your code. However, in order to get best results, the PCD SDK should be able to download when your app is not in the foreground. In order to do that, you need to enable your app for background execution.

There are two types of background execution that the SDK uses to download content. Enable these two modes within the Xcode project settings, Capabilities tab, and Background Modes section:

To enable background fetch in the PCD SDK, you need to implement the system method UIApplicationDelegate application:performFetchWithCompletionHandler: and, from there, pass the message to the VocService by calling VocService application:performFetchWithCompletionHandler:

Here is what that looks like:

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler
    if (![ self.vocService application:application performFetchWithCompletionHandler:completionHandler ]) {

Enabling Remote Notifications

To make remote notifications work in the PCD SDK you need to enable the SDK backend to send push notifications to your app, and make the supporting code changes.

To enable the PCD backend to send push notifications to your app, you need to upload your app push certificate (APNS) to the PCD license management portal. The PCD backend must have a valid APNS certificate for your app at all times otherwise push notifications will not work. If you revoke or renew your certificate, make sure you upload it to the PCD license management portal. Instructions on how to generate an APNS push certificate are available on Apple’s web site:

The first step for your app is to register for remote notification and hand the push token to the SDK in the AppDelegate call application:didRegisterForRemoteNotificationsWithDeviceToken:.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary
    // the client must register for remote notifications
    [[UIApplication sharedApplication] registerForRemoteNotifications];
    // the client must call this method during launch cycle
    // to request permission from user to use notification
    UIUserNotificationType notificationType = UIUserNotificationTypeAlert;
    [[UIApplication sharedApplication] registerUserNotificationSettings:
     [UIUserNotificationSettings settingsForTypes:notificationType categories:nil]];

- (void)application:(UIApplication *)application
    didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken
    // pass push token to SDK
    [self.vocService setDevicePushToken:deviceToken];

Also in your application delegate, implement the system method: UIApplicationDelegate application:didReceiveRemoteNotification:fetchCompletionHandler: and pass this notification to the VocService:

VocService application:didReceiveRemoteNotification:fetchCompletionHandler:

For example:

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler
    if ([ self.vocService application:application didReceiveRemoteNotification:userInfo fetchCompletionHandler:completionHandler ]) {
        // remote notification was for VoC SDK
    // remote notification is not for VoC SDK, handle remote notification

If the client is testing against the development APNS instead of production APNS, the SDK needs to be configured to use development APNS before the SDK registration.

vocService.config.useProductionApns = NO;

Remote notification and fetch are enabled in background by adding the following key-subkey to the app’s info.plist file:


Enabling App Transport Security

Starting in iOS 9.0, a new app security feature called App Transport Security (ATS) was introduced and is enabled by default. With ATS enabled, connections must use secure HTTPS instead of HTTP. Additionally, if the app contents that PCD SDK needs to download contain non-SSL items, those downloads will fail. Application developers must ensure that either

The optional ATS key to allow insecure (HTTP) content follows:



The SDK is initialized by the VocServiceFactory call createServiceWithDelegate:delegateQueue:options:error:. Initialization and registration should take place early in the app lifecycle to begin prepositioning files as early as possible.

The recommended place for this is in AppDelegate’s application:didFinishLaunchingWithOptions:. The create call inputs a reference to the SDK delegate (see SDK Delegate) as well as a configuration options dictionary. The SDK delegate is the class you designate to respond to SDK activity.

The example below is inserted into AppDelegate.m. It initializes the SDK and tells it that AppDelegate will be the delegate to handle SDK messages.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
    NSError *error = nil;
    self.vocService = [VocServiceFactory  createServiceWithDelegate:self
                       delegateQueue:[ NSOperationQueue  mainQueue ] options:nil
                       error:&error ];
    if (! self.vocService) {
        // error handling - could not start service
        return NO;
    // app initialized
    return YES;


Registration is a one-time event that activates the VocService with a particular license key. This key is linked to a content catalog, generation of usage statistics, and other SDK capabilities. It is required for most SDK features so registration should occur early within the application.

The VocService returned from initialization has a state property that indicates whether registration already succeeded on this device. If VocService.state is equal to VocServiceStateNotRegistered then registration must be called as follows. Otherwise the SDK is already running.

NSString *sdkLicense = @"Your Akamai Provided License Key";
[self.vocService registerWithLicense:sdkLicense
 segments:nil completion:^(NSError *__nullable error) {
    if (error) {                                                           
    // handle failed registration

Registration requires a valid SDK license. This license is associated with a particular content set defined on the server portal. The segments field is nil.

Once registration is successful, the SDK calls the didRegister: method on VocServiceDelegate. This can be used to report or log any problems starting the SDK. This callback is made every time the app starts. The first time the app registers, it is called in response to registerWithLicense. After that, the app is already registered so it is called in response to createServiceWithDelegate.

The service delegate also receives didInitialize: to indicate that all services are actively running.

SDK Events

The SDK notifies your app of various events throughout its life cycle. Messages are sent asynchronously to an SDK delegate in your code that implements the VocServiceDelegate protocol. All of the delegate methods are optional.

- (void) vocService :(nonnull VocService *) vocService didBecomeNotRegistered :(nonnull NSDictionary *) info;
- (void) vocService :(nonnull VocService *) vocService didFailToRegister :(nonnull NSError *) error;
- (void) vocService :(nonnull VocService *) vocService didRegister :(nonnull NSDictionary *) info;
- (void) vocService :(nonnull VocService *) vocService didInitialize :(nonnull NSDictionary *) info;
- (void) vocService :(nonnull VocService *) vocService itemsDiscovered :(nonnull NSArray *) items;
- (void) vocService :(nonnull VocService *) vocService itemsStartDownloading :(nonnull NSArray *) items;
- (void) vocService :(nonnull VocService *) vocService itemsDownloaded :(nonnull NSArray *) items;
- (void) vocService :(nonnull VocService *) vocService itemsEvicted :(nonnull NSArray *) items; 
- (void) vocService :(nonnull VocService *) vocService hlsServerStarted:(nonnull NSURL*)url; 
- (void) vocService :(nonnull VocService *) vocService hlsServerStopped:(nonnull NSURL*)url;

The SDK delegate is passed to the SDK in the initialization call. Typically, this is the app delegate since its lifetime will span that of the SDK, from registration until shutdown. Define your app delegate as follows to implement the SDK delegate protocol.

@interface AppDelegate : UIResponder < UIApplicationDelegate, VocServiceDelegate>

Download to Go

The PCD SDK has a number of ways users can get content, but it's suggested that you start by using Download to Go (D2G). D2G allows users to browse your video catalog and download one or more selections to their mobile device.

Setting up D2G

Before you can use D2G, you need to ingest your video catalog to the PCD Server. Ingesting content isn't a self-service operation at this time, so talk to your Akamai representative about ingesting content. Each content( example a video) ingested is represented by a unique Content Id.

Initiating a Download

To initiate a download, you need the content ID.

  1. The client can access the item using the API - VocService::getItemsWithContentIds: sourceName:completion:.
  2. If the items that match the contentIds and sourceName exists locally, the completion block receives a VocItemSet instance with those items. VocItemSet has an array property -”items” which includes those items.
  3. If the items that match the contentId and sourceName don't exist locally, a server lookup is performed to get the metadata. When the lookup is successful, the items are available locally and VocItemSet::items holds those new items.
  4. The client needs to listen to the changes made to VocItemSet to get notified when remote lookup adds new items. This can be achieved by adopting the listener protocol VocObjSetChangeListener and implementing the method VocObjSetChangeListener::vocService:objSetDidChange:added:updated:removed:objectsBefore:. Add this listener instance as the listener for VocItemSet instance received in the completion block.
  5. The client can use VocItemSet::items to download the content.

iOS Sample

To initiate a download using ContentId, see the following example:

@interface ViewController () <VocObjSetChangeListener> 
@property (strong, nonatomic) id<VocItemSet>  itemSet;
- (void)downloadContent
    NSSet *contentIds = [[NSSet alloc] initWithObjects:@"<ingested content id>", nil];

    [appDelegate().vocService getItemsWithContentIds:contentIds
     sourceName:@"ProviderName" completion:^(NSError *error, id<VocItemSet>  itemSet)
        if (error) {
            // If the item is not found locally, it will report a not found error
            if ([error.domain isEqualToString:VOCSDKErrorDomain] && error.code == VocErrItemNotFound) {
                NSSet<NSString *> *missing = error.userInfo[@"notfound"];
        // Add the listener
        self.itemSet = itemSet;
        [itemSet addListener:self];

Accessing Content

Content begins loading onto the device once the client has initiated a download. Downloading also happens automatically in background.

Playing HLS Video Content

HTTP Live Streaming (HLS) video can be played from fully- or partially-downloaded content. Playback requires starting the SDK’s on-device HLS server. From that server, a playback link is then requested for the content.

The client starts the HLS server by calling VocService::startHLSServerWithCompletion:completion before playing the HLS content. The completion block is executed only after the HLS server is started. In the passed completion block, the client can access the HLS server URL and append to it the content item’s relative URL. Feed this URL to the media player to play the HLS content. Once playback is finished, stop the media server by calling VocService::stopHLSServer. The client controls the starting and stopping of the HLS server.

id<VocItemHLSVideo> hlsVideo = ...;

[appDelegate.vocService startHLSServerWithCompletion:^(BOOL success) {
    if (success) {
        NSURL *url = [appDelegate.vocService.hlsServerUrl URLByAppendingPathComponent:hlsVideo.hlsServerRelativePath];

        [self playVideo:url];

Playing Cached Non-HLS Video

Clients can play content from a URL if the item is not yet cached, or from the local path if the item is cached.

To play a mp4 prepositioned video:

id<VocItemVideo> video =  ...;
NSURL   *url = video.file.url;
if (video.state == VOCItemCached || video.state == VOCItemPartiallyCached)  {
    url = [NSURL fileURLWithPath: video.localPath];

//Set the media player's content URL to this URL
[self playVideo:url];

Record Video Consumption by the User

When a user watches a video partially or fully, the client reports the consumption to the PCD SDK.

id<VocItemVideo> video =  ...;

// When user navigates back from the video player
// The total watched duration of the video
NSTimeInterval end = CMTimeGetSeconds(player.currentItem.currentTime);

// If playback did not start at the beginning put the position in start.
NSTimeInterval start = 0;
[video recordConsumption:[NSDate date] startingAt:start endingAt:end];

Content Item States

Each item progresses through different states before getting cached. VocItem has a state property which can take the following values.

VOCItemState Description
VOCItemDiscovered Item has been identified. Various device policies dictate whether the item gets queued for download.
VOCItemQueued Item has been added to downloading queue; it is currently not downloading. It will start downloading.
VOCItemDownloading Item is being downloaded.
VOCItemIdle Item is currently not downloading. Item has been previously queued for downloading but did not finish. Download will resume automatically at some point. Reason for stopping download can be found in VocItem downloadError.
VOCItemPaused Item is currently not downloading. It has been explicitly paused with VocService pauseItems
VOCItemCached Item was downloaded successfully. Cached content is ready for use.
VOCItemPartiallyCached Item is configured for partial download. Requested part was downloaded successfully. Cached content is ready for use.
VOCItemFailed If PCD SDK is unsuccessful to download any main content file after a number of attempts, the item will be marked as failed and the downloaded content will be removed. No more download attempts will be made on the item, unless an explicit download for this item is triggered again. VocItem downloadError, can be used to verify the reason for download failure, error codes are provided in the table below.
VOCItemDeleted Item has been deleted and cannot be used any more. There are no cached files.

Download Failure and Idle Error Codes

Error code Description
VocErrDownloadFailed After a number of attempts the file cannot be downloaded due to problems that are not related to network connection like permissions, missing file, wrong url, server not responding, etc.
VocErrDownloadNetworkError Network connection error, download will resume automatically.
VocErrCancelled File download had to be interrupted because of PCD policy, or no more background time or download order optimizations.
VOCErrDownloadCacheLimit Error code indicating no space left in cache to download file.

Content Filters

Each of the set-building methods accepts a filter that defines the set. In each example above we used the “all” filter to get a complete set of items. Specific subsets can also be created by using alternative filters. These sets will behave as before, but will notify their listeners only when the filter is matched.

Object Type Filter Protocol Available Filters
Source VocSourceFilter allWithSort:
Category VocItemCategoryFilter allWithSort: categoriesSelected: categoriesSelectedWithContent: subCategories: SearchField: suggestions:
Item VocItemFilter allWithSort: itemsDownloadingWithSort: itemsWithCategory:sortDescriptors: itemsDownloadedWithCategory:sortDescriptors: itemsSavedWithSort: itemsDownloadedNotViewedWithSort
Video (subset of Item) VocItemVideoFilter allWithSort: videosDownloadingWithSort: videosWithCategory:sortDescriptors: videosDownloadedWithCategory:sortDescriptors: videosDownloadedOrDownloadingWithCategory:sortDescriptors: videosSavedWithSort: videosDownloadedNotViewedWithSort:

Most filters also accept an array of sort descriptors. The .sources, .categories, and .items properties within their respective sets are each an ordered array. The sort descriptor defines the order of those arrays. Pass a nil descriptor if order is unimportant.

NSArray *sortDesc =   @[[[ NSSortDescriptor  alloc ] initWithKey:@"name"  ascending:YES selector:@selector(caseInsensitiveCompare:)]];

[ vocService getSourcesWithFilter:[ VocItemSourceFilter allWithSort:sortDesc ] completion:^(NSError *__nullable error,  id < VocSourceSet >  __nullable set) {
    // set.sources is ordered by each source's "name" property

Managing Downloads

Pause and Resume Downloading a Specific Item

The client can pause a specific content item download by making the VocService call pauseItemDownload: . VocItem has a readonly property, paused which the client can use to identify items that are paused. Alternatively, the same pause operation can be performed on one or more VocItems by making the VocService call pauseDownloadForItems:completion:. A paused download will not resume until a specific download request has been made.

[appDelegate.vocService pauseItemDownload :vocItemVideo completion :^(NSError* _Nullable error) {}];

The client can resume the download of an item or items by making the VocService call downloadItems:.

[appDelegate.vocService downloadItems:@[vocItemVideo] completion:^(NSError *_Nullable error) {}];

Delete, Lock, or Save an Item

The SDK provides two delete options for each item:

Note: Some content consumers exhibit unexpected behavior if the item gets deleted while it is consumed. The SDK doesn’t know whether the item is currently consumed unless it is notified explicitly. It is recommended to call VocItem::lock before the item gets consumed and VocItem::unlock after the consumption is completed.

The SDK initiates a purge mechanism based on certain device parameters. To avoid an item getting deleted using the purge mechanism, the user can mark the item as saved by calling VocItem::save.

Track Progress of a Downloading Video

There are two properties in VocItem that will allow the client app to calculate download progress.

The client app can listen for bytesDownloaded changes by subscribing to the VocObjSetChangeListener protocol (refer to Listening for Data Set Changes) or using key-value observing (KVO). Alternatively, the client app can use a timer to periodically poll bytesDownloaded and update the progress.

Listening for Data Set Changes

Data sets send notifications when items are added, changed, or removed. This is the best way to detect when individual items have finished downloading. To listen for object set changes a class must subscribe to the VocObjSetChangeListener protocol.

@interface MyClass() <VocObjSetChangeListener>

Setting the data set listener is done via addListener: and is demonstrated in the sections below for sources, categories, and items. Listeners receive callbacks before and after any changes.

(void)vocService:(nonnull id < VocService >)vocService objSetWillChange:(nonnull id < VocObjSet >)objSet
                  added:(nonnull NSSet *)added updated:(nonnull NSSet *)updated removed:(nonnull NSSet *)removed
    objectsAfterChanges:(nonnull NSArray *)objectsAfterChanges
    if ([ objSet isEqual:self.itemSet ]) {
        NSLog(@"%ld items will change",   (unsigned long)updated.count);

(void)vocService:(nonnull id < VocService >)vocService objSetDidChange:(nonnull id < VocObjSet >)objSet
             added:(nonnull NSSet *)added updated:(nonnull NSSet *)updated removed:(nonnull NSSet *)removed
     objectsBefore:(nonnull NSArray *)objectsBefore
    if ([ objSet isEqual:self.itemSet ]) {
        NSLog(@"%ld items have changed",   (unsigned long)updated.count);

SDK Settings

VocService has a property, ‘config,’ which provides a rich set of API to configure the SDK behavior. Default values for some of the configurations in VocConfig.h are set at the global level (to server values) and you could override those at the client level. You should discuss with the PCD SDK team about your default value preferences for permitted network types for download (wifi, cellular, or both), content items per category, daily download size limit, maximum size allowed per file download, permitted time of day for downloading, etc. Some of the important configurations are the following.

Network Preference

The API provides control over whether downloads are permitted on wifi, cellular, or both. Setting the VocConfig networkSelection property affects downloads that have not already started.

self.vocService.config.networkSelection = VOCNetworkSelectionWifiAndCellular;

Item Download Behavior

The default behavior of the SDK is to preposition all the content from the content catalog. VocConfig has a property, itemDownloadBehavior, which provides the client an option to define the download behavior of the PCD SDK. This configuration can be configured to restrict the auto download of the content and the user will be responsible for downloading the content. The content catalog will still be downloaded after registering the PCD SDK. The client has to make an explicit call to trigger a content download from the catalog. The SDK download behaviors are auto download, download of thumbnail files only and no download. self.vocService.config.itemDownloadBehavior = VOCItemDownloadThumbnailOnly ;

Auto Purge

The default behavior of the SDK is to perform content purge based on certain device specific parameters. VocConfig has a property, enableAutoPurge, which provides the client an option to disable auto purge and the user will be responsible for the deletion of the content. self.vocService.config.enableAutoPurge = NO ;

Maximum Number of Concurrent Downloads

The default behavior of the SDK is to perform any number of concurrent file downloads. VocConfig has a property, maxConcurrentDownloads, which provides the client an option to restrict the number of simultaneous downloads. self.vocService.config.maxConcurrentDownloads = 10 ;