Inherits from NSObject
Declared in OTSubscriberKit.h

Overview

An OTSubscriberKit (subscriber) object renders media data bound to an OTStream. The OTSubscriberKit class lets you set a custom video renderer for the video stream. Use this class if you are interested in providing your own video processing and rendering implementation. Otherwise, use the OTSubscriber class, which includes a pre-built video processor and renderer.

The stream property references the stream that you have subscribed to. The OTSubscriberKit class includes methods that let you disable and enable local audio and video playback for the subscribed stream.

Getting basic information about a Subscriber

  session

The OTSession object that owns this subscriber. An instance will have one and only one OTSession associated with it, and this property is immutable.

@property (readonly) OTSession *session

Declared In

OTSubscriberKit.h

  stream

The stream this subscriber is bound to. Any media channels on the stream should be available for display/playback with this instance.

@property (readonly) OTStream *stream

Declared In

OTSubscriberKit.h

  delegate

The OTSubscriberKitDelegate object that serves as a delegate, handling basic events for this OTSubscriber object.

@property (nonatomic, assign) id<OTSubscriberKitDelegate> _Nullable delegate

Declared In

OTSubscriberKit.h

Working with audio and video

  audioLevelDelegate

Periodically receives reports of audio levels for this subscriber.

@property (nonatomic, assign) id<OTSubscriberKitAudioLevelDelegate> _Nullable audioLevelDelegate

Discussion

This is a separate delegate object from that set as the [OTSubscriberKit delegate] property (the OTSubscriberKitDelegate object).

If you do not set this property, the audio sampling subsystem is disabled.

Declared In

OTSubscriberKit.h

  subscribeToAudio

Whether to subscribe to the stream’s audio.

@property (nonatomic) BOOL subscribeToAudio

Discussion

The default value is YES.

Setting this property has no effect if the [OTStream hasAudio] property is set to NO.

Declared In

OTSubscriberKit.h

  subscribeToVideo

Whether to subscribe to the stream’s video.

@property (nonatomic) BOOL subscribeToVideo

Discussion

The default value is YES.

Setting this property has no effect if the [OTStream hasVideo] property is set to NO.

Declared In

OTSubscriberKit.h

  videoRender

The video renderer for this instance.

@property (nonatomic, retain) id<OTVideoRender> _Nullable videoRender

Declared In

OTSubscriberKit.h

  preferredResolution

The preferred resolution for the subscriber’s stream. This method is part of the subscriber quality preference beta feature. For more information, see the OpenTok Beta Programs page.

@property (nonatomic) CGSize preferredResolution

Discussion

Limiting the video resolution and frame rate (see [OTSubscriberKit preferredFrameRate]) reduces the network and CPU usage on the subscribing client. You may want to use lower resolution based on the dimensions of subscriber’s video in the app. You may want to use a lower frame rate or resolution for subscribers to a stream that is less important (and smaller) than other streams.

Not every resolution is available to a subscriber. When you set the preferred resolution, the OpenTok iOS SDK picks the best resolution available that matches your constraints. The resolutions available depend on the maximum resolution the Publisher sets for the stream, which is set as the [OTStream videoDimensions] property for the stream. Each of the resolutions available for a stream will use the same aspect ratio.

Declared In

OTSubscriberKit.h

  preferredFrameRate

The preferred frame rate for the subscriber’s stream. This method is part of the subscriber quality preference beta feature. For more information, see the OpenTok Beta Programs page.

@property (nonatomic) float preferredFrameRate

Discussion

Limiting the frame rate and video resolution (see [OTSubscriberKit preferredResolution]) reduces the network and CPU usage on the subscribing client. You may want to use lower resolution based on the dimensions of subscriber’s video in the app. You may want to use a lower frame rate or resolution for subscribers to a stream that is less important (and smaller) than other streams.

The frame rates available are based on the value of the maximum frame rate available for the stream. When you set the preferred frame rate for the subscriber, the OpenTok iOS SDK picks the best frame rate available that is closest to the preferredFrameRate setting, based on the client’s bandwidth and CPU constraints.

The actual frame rates available depend, dynamically, on network and CPU resources available to the publisher.

Declared In

OTSubscriberKit.h

Getting audio and video statistics

  networkStatsDelegate

The OTSubscriberKitNetworkStatsDelegate object that periodically receives subscriber quality statistics.

@property (nonatomic, assign) id<OTSubscriberKitNetworkStatsDelegate> _Nullable networkStatsDelegate

Discussion

This delegate object is sent messages reporting the following:

  • Total audio and video packets lost
  • Total audio and video packets received
  • Total audio and video bytes received

This is a separate delegate object from that set as the [OTSubscriberKit delegate] property (the OTSubscriberKitDelegate object).

Declared In

OTSubscriberKit.h

Initializing a Subscriber

– initWithStream:delegate:

Initializes a subscriber and binds it to an OTStream instance. Once initialized, the instance is permanently bound to the stream.

- (_Nullable id)initWithStream:(nonnull OTStream *)stream delegate:(nullable id<OTSubscriberKitDelegate>)delegate

Parameters

stream

The OTStream object to bind this instance to.

delegate

The delegate (OTSubscriberKitDelegate) that will handle events generated by this instance.

Discussion

The OpenTok iOS SDK supports a limited number of simultaneous audio-video streams in an app:

  • In a relayed session, the limit is two streams. An app can have up to two subscribers, or one publisher and one subscriber.

  • In a routed session, an app can support one audio-video publisher, one audio-video subscriber, and up to three additional subscribed audio-only streams simultaneously.

(For information on relayed and routed sessions see the documentation on the media mode of a session.)

Initializing a subscriber causes it to start streaming data from the OpenTok server, regardless of whether the view of the subscriber object is added to a superview.

You can stream audio only (without subscribing to the video stream) by setting the [OTSubscriberKit subscribeToVideo] property to NO immediately after initializing the OTSubscriber object. You can stream video only (without subscribing to the audio stream) by setting the [OTSubscriberKit subscribeToAudio] property to NO immediately after initializing the OTSubscriber object.

When the subscriber connects to the stream, the [OTSubscriberKitDelegate subscriberDidConnectToStream:] message is sent.

For an OTSubscriber object, when the first frame of video has been decoded, the [OTSubscriberDelegate subscriberVideoDataReceived:] message is sent.

If the subscriber fails to connect to the stream, the [OTSubscriberKitDelegate subscriber:didFailWithError:] message is sent.

Declared In

OTSubscriberKit.h