What's New with Screen Recording and Live Broadcast
Check out the new capabilities of ReplayKit 2 and see how to access its rich functionality right from Control Center. Learn about in-app capture, giving apps direct sample-level access to their audio and screen output. Get details about developing a live broadcast extension, and discover how apps can be coupled to a preferred broadcast provider.
Thank you, and welcome to What's New in Screen Recording and Live Broadcast. My name is Johnny Trenh, I'm a software engineer at Apple working on a ReplayKit team.
Today, my teammate Alexander Subbotin and I are really excited to talk to you about all the new upcoming features we have planned for ReplayKit this year.
We've got a lot to discuss, so let's go ahead and get started.
ReplayKit is a framework that allows developers to record their applications audio, video, and microphone content to a movie file that their users can then review, edit, save, or share with the rest of the world.
ReplayKit also supports Live Broadcast. For applications generating content, ReplayKit provides you with all the tools necessary to stream your application's audio, video, and microphone content to a broadcast extension.
For applications implementing a broadcast extension, ReplayKit comes equipped with easy to use Xcode templates that will help your application stream ReplayKit content. ReplayKit records both audio and video in HD quality with low-performance impact and minimal power usage. Privacy is a very big thing with us, so both recording and broadcasting comes equipped with privacy safeguards such as user consent as well as all recordings and samples that exclude system UI.
Since the release of ReplayKit, we have seen some amazing adoption from developers all around the world. Applications like Galaxy on Fire, Vainglory, Call of Champions, and Modern Combat 5, are all using ReplayKit today to record and broadcast their users' experiences with the rest of the world.
Last year we introduced Live Broadcast with ReplayKit. And we are proud to say that ReplayKit now powers some of the industry leaders in mobile streaming.
The support adoption and feedback we've received from developers has been amazing. That is why this year we're really happy to introduce ReplayKit 2.
With ReplayKit 2, our goal is to bring ReplayKit to every user and every application. We've designed our new features to take ReplayKit beyond just gaming, enabling all developers to record and broadcast their users' experiences to the whole world. And to do that, the first thing I want to talk about is In-App Screen Capture.
Look, we've already seen the amazing content your users have been creating with ReplayKit.
With ReplayKit 2, we're introducing In-App Screen Capture, which is a powerful new API that's going to give you direct access to your application's own audio, video, and microphone content straight from ReplayKit. Our goal with ReplayKit 2 was to bring ReplayKit to every application. And to do that we're making ReplayKit instantly available to every application on iOS. Previously, to use ReplayKit and to have a application using ReplayKit, you'd have to use our API. But now, users can record and broadcast their entire iOS screen experience straight from the new screen recording control found in Control Center. Also new with ReplayKit 2 is the ability to pair your application with a particular streaming service.
Developers can now seamlessly integrate their entire streaming solution right from within their own application.
Last year, we introduced front camera support for ReplayKit. This year with ReplayKit 2 we're introducing Fast Camera Switching, which is going to enable you to use both the front and rear cameras for additional video commentary.
We've got a lot of new and exciting things to talk about. So, I'm just going to go ahead and jump right in with In-App Screen Capture.
In-App Screen Capture is a powerful new API that's going to give you direct access to your application's own audio, video, and microphone content straight from ReplayKit. This new API is going to open doors to new user experiences that just weren't possible before. But, before we get into In-App Screen Capture, let's go ahead and take a look at how applications are currently using ReplayKit to handle recording.
An application that's currently using ReplayKit will call in to RPScreenRecorder to get the shared recorder instance. From there, you'll call start recording onto shared recorder instance, at which time the replay daemon will start to capture your application's audio, video, and microphone content, and create and manage a movie file just for your application.
When you call stop recording on a shared recorder instance, replay daemon will communicate with a share and preview extension and instantiate an RPPreviewViewController. We'll pass that RPPreviewViewController back to your application so that you can present it to your users, allowing them to review, edit, save, or share the recording they just made in your application.
With a new In-App Screen Capture, just like with recording, you're going to call into RPScreenRecorder to get the share recorder instance. From there, you'll call start capture on the share recorder instance, at which point the replay daemon will start to capture your application's audio, video, and microphone content. But instead of creating and managing a movie file just for your application, ReplayKit will send those audio and video samples right back up to RPScreenRecorder. A capture handler block is then called, and we'll send the audio and video samples, right back to your application's process.
Your application now has direct access to its own audio, video, and microphone samples straight from ReplayKit.
Giving you direct access to your application's audio and video samples from ReplayKit will provide you with more flexibility and control over the content your users are already creating.
Just like with recording, In-App Screen Capture captures audio and video in HD quality, with low-performance impact and minimal power usage. Again, privacy is a very big thing with us, so In-App Screen Capture comes equipped with privacy safeguards such as user consent as well as all samples excluding system UI.
The API is simple and lightweight. So, let's go ahead and take a quick look at it. StartCapture takes in two blocks, a captureHandler block and a completionHandler block.
The captureHandler block is called every time ReplayKit is ready to hand your application back a sample. We provide you with a CMSampleBuffer ref an RPSampleBufferType and an NS Error. The completion handler block is called when startCapture has completed and will give you an NS Error indicating to you whether or not an error has occurred during startCapture.
The stopCapture also takes in a completionHandler which will also pass you back and NS Error indicating to you whether or not an error has occurred during stopCapture.
Let's go ahead and take a look at how we can use this in practice.
Here, in our example, what I want to do is I want to take the samples that ReplayKit has given me and I want to use it to write a simple movie file to disc using AVAssetWriter. So, here I have method called didPressCaptureButton. Inside of it, I'm simply going to grab the sharedRecorder instance from RPScreenRecorder. From there, I'll call startCapture providing it a capture handler block and a completion handler block. Remember, I'm trying to write a movie file using AVAssetWriter with the samples we get back. So it's really important for me to know how I'm going to handle these samples. So, let's take a closer look at the capture handler.
Remember, the capture handler is called every time ReplayKit is ready to hand your application back a sample. We'll provide you with a CMSampleBuffer ref, and RPSampleBufferType, and an NS Error.
Since I'm using these samples to write a simple movie using AVAssetWriter, it's really important for me to know what type of samples I'm getting back from ReplayKit. Here we have a switch on RPSampleType that's going to do just that.
If I get a sample buffer type that's video, I'm simply going to append that sample to my video input for my AVAssetWriter. If I get a sample buffer type that's audio, I'll append that sample to my audio input for my AVAssetWriter. And finally, if I get a sample buffer type that's for the microphone, I'll append that sample to my microphone input for my AVAssetWriter. And, just like that, I am now handling all the expected types of samples I'm going to get back from ReplayKit. And I'm also using them to write a simple movie to disc using AVAssetWriter.
Let's go ahead and take a closer look at the completion handler.
Just like with recording, you want to indicate to your users that a capture session has currently occurred or is in session. So, in our completion handler, we're going to simply call update the capture button with the error that we get back during our completion handler. This will allow me to update my UI and indicate to my users that a capture session has occurred. And that's it. That's all you have to do to start using this powerful new API.
I want to take a minute to revisit how In-App Screen Capture's actually working. And I'd like to remind you that your application now has direct access to its own audio, video, and microphone content straight from ReplayKit.
In our example, we use these samples to create a simple movie using AVAssetWriter, but you can do so much more with this. Now that your application has access to its own audio and video samples, you can create and manage videos right into your own application.
You can even create a custom video editor and have it seamlessly integrated in the user experience for your application.
Again, a goal of ReplayKit 2 was to bring ReplayKit to every application, not just gaming.
Here, I have the same productivity app running on two different iOS devices. Now that I have access to my application's audio and video samples, just like with broadcasts, I can encode these samples myself, and I can send them to my own personal server.
From there, I can share my application's Screen Capture with any other instance of my application running on any other device.
This just wasn't possible before, but it is now with In-App Screen Capture.
These are just some of the examples of the new user experiences you can create using In-App Screen Capture. We're really excited to see what developers are going to do with it.
With ReplayKit 2, our goal was to bring ReplayKit to every type of application, not just gaming. And to do that, I'm really happy to introduce iOS Screen Recording and Broadcast. iOS Screen Recording and Broadcast is an amazing new user feature that's going to allow users to record and broadcast their entire iOS screen experience.
Let's go ahead and take a look at how we can use this new feature.
To use iOS Screen Recording and Broadcast, you're going to first need to enable the Screen Recording control for Control Center. To do that, we're going to jump right into settings, and Control Center. From there we'll be shown all these supported controls for Control Center. We simply add the screen recording control and we start Control Center. And just like that, you're now up and running ready to share your entire iOS screen experience. Thank you. To initiate an iOS screen recording, you simply tap the Screen Recording control.
You are now recording your entire iOS screen experience. That status bar and our screen recording control will indicate to you that a recording is ongoing by showing you recording indicator as well as the elapsed time for your current recording session.
To stop the recording you simply tap the screen recording control again.
When the recording has been stopped, you'll be presented with a notification indicating to you that the screen recording you just took has now been saved in your Photos application. Tapping on this banner will take you straight to your Photos application where you can review, edit, or share the recording you just made.
You can also 3D Touch into our screen recording control which will bring you straight to our expanded view where you'll have access to the microphone settings as well as the ability to start recording, or to stop recording.
Now, let's say I've just downloaded a broadcast application that supports ReplayKit Live Streaming. And I'd like to use that broadcast application to share my entire iOS screen experience. Well, that's actually pretty simple to do, because all you need to do is 3D Touch into our screen recording control. You'll be taken to our expanded view, where all the applications that are installed on your device that currently support ReplayKit Live Streaming will be shown. You simply need to select the service you'd like to use and tap Start Broadcast.
You are now broadcasting to the entire world your entire iOS screen experience.
Just like with recording, the status bar in the screen recording control will indicate to you that a broadcast is currently in session by showing you the recording indicator, the current selected broadcast service, and the elapsed time for your current broadcast.
To stop the broadcast, you simply tap the stop broadcast button.
Now, you can record a video to teach your grandparents how to make that FaceTime call. You can even stream a video to teach your parents how to send that important email. Or better yet, you can now record a video to teach your kids how to find their favorite TV shows and movies in iTunes. It has never been easier to share your entire iOS screen experience. iOS Screen Recording and Broadcast creates new user experiences with applications that are already using ReplayKit. So, let's take a quick minute to talk about some best practices. iOS Screen Recording and Broadcast has priority when it comes to ReplayKit. So, if your application is currently using ReplayKit to record or broadcast and the user initiates an iOS Screen Recording and Broadcast, your application will be notified via RPScreenRecorderDelegate that your session has been interrupted. In this case, the recording will be discarded and you should update your UI and notify the users accordingly. iOS Screen Recording and Broadcast is an amazing feature. It's one that we hope users and developers will use to create new exciting iOS content. And to help you do that, I'd like to bring Alexander Subbotin up to the stage to talk to you a little bit more about how we do broadcasting with ReplayKit.
Thank you, Johnny.
Good morning. My name is Alexander Subbotin and I am so excited to be here talk to you and share more details about our Live Broadcast API.
ReplayKit enables applications to stream their content to third party broadcast services directly from your iOS and tvOS device. On iOS you can also include voice and video commentary using the microphone and the camera. And all this content is absolutely secure and unaccessible with a broadcast service that you use.
This is a high level picture of how Live Broadcast really works.
All on the left, you see a player who at some point wants to broadcast his game Tower Dash to Mobcrush which is a broadcast service.
So Tower Dash communicates to the ReplayKit API to initiate the broadcast.
And once that happens, ReplayKit will present some UI that allows user to ping the broadcast service. And that would be Mobcrush for us.
And the broadcast starts. And once broadcast is running, ReplayKit will be providing audio and video samples to the mob crush app extension that directly talks to the broadcast service and the viewers around the world can watch the livestream online.
This is just a picture of how broadcast runs. And the way I want to describe it to all of you is, I want to break it into parts because if you are a client application developer, game developer the only thing you need to do is to present some ViewController initiate broadcast and couple of other fairly simple steps.
But I also know that some of you in this room broadcast service developers. And we are going to walk through the process for you and talk about how do you actually implement those extensions.
So, starting with the client side and what the client application wants to do, for that we have a fairly simple API that really wrapped up in those three classes.
There's BroadcastActivityViewController and this class is used to initiate a broadcast and it presents this built in UI where you select the broadcast service.
RPBroadcastController allows you to manage the broadcast in your code and you would usually wire to some UI where user can start, stop, pause, or resume the broadcast. And the RPBroadcastControllerDelegate is internal and this is a dedicated part about different events during the broadcast. The broadcast can stop for some reason, there could be an error, or the broadcast extension may want to pass some information to the client app, and this is where the delegate tells the user.
And now, I'm going to stop here talking about this part of the picture because last year, we covered this API in depth in our session Go Live with ReplayKit. So, in case you have not adopted the API yet, please go to the app and you can find the link to last year's session and learn more about that developer API.
Now let's talk about the second part of the equation, you have developer of the broadcast service. How do you integrate your service so that you could stream the content created by all these players, games, and other applications? And the answer is these three extensions.
The first one on the top is what we call Broadcast Setup extension, and its purpose is to present some UI where you can ask user to enter some information, you may want user to give the broadcast a particular name or maybe log in credentials or any details that you need fire up your broadcast. And the second one is called Broadcast Upload extension. And the function of this extension is to receive the media samples handed by ReplayKit and encode them, create a video stream, and upload to the online service. Each extension is a separate binary that is installed on your device along with the broadcast app. So you can install to Mobcrush, you also get setup extension and upload extension installed on your device. And each extension runs in its own process independently from Mobcrush that contains extensions and Tower Dash that initiates the broadcast. So usually these are three processes and the process of the containing app of the Mobcrush is never launched.
And to help you get started developing new broadcast extensions, we provide very easy to use Xcode templates for both types of extensions. And just add two extensions to your Xcode project and you are ready to begin. And now let's talk about how you actually code all of this. Starting from the setup extension.
As I said, the purpose of the setup extension is to present this UI for user can enter the name of the broadcast or something. But it also has another important function.
It can get some information about the client application such as a bundleID, the name of the application, or the icon of the application.
And it can upload this information to the broadcast service so that the broadcast service could build an experience for viewers when the viewer comes to the website and he knows here's this place where everyone playing Tower Dash, there's an icon of Tower Dash.
And although the extension can request from the broadcast service a URL of that particular Live Broadcast happening on the website, and share it back to the application so that the player could send it to his friends and get more followers.
The ViewController that implements this UI communicates to ReplayKit using property called extensionContext. And the class of this property is a category of NSExtensionContext that has two more functions added by ReplayKit. The first one is loadBroadcastingApplicationInfo and the second one is completeRequest with broadcastURL and setupInfo.
The first one as I said it's used to get the icon and the name of the application, and here is a small code example of how you could do that and pass this information to the broadcast session.
The broadcast service when it has this information, it can identify in the broadcast sessions, create channels, and build simple intuitive user experience of viewers experience like this. The viewer comes to the app and he has an icon and name of the application.
So, when you're done uploading this icon, and already collected all the information that you need to begin the broadcast, you should call the second one called completeRequest with broadcastURL and setupInfo. The broadcastURL will be available to the client application as a property of the broadcast controller and the setupInfo it's a dictionary that you create inside this extension and all the information you collected from the user, you put it to that dictionary, and it will be passed to the upload extension when the broadcast starts. You should also always provide an option for the user to cancel broadcast, and for that you just use your regular old cancelRequest method of the extensionContext.
Now, let's talk about the upload extension. As I said, it's function is to receive the media frames handed by ReplayKit in real time, encode them, create a video stream, and upload it to the broadcast service.
If you create a new upload extension using Xcode templates, you will find a sampleHandler class like this in your Xcode project, and this is where you override functions that take care of events like the broadcast has started, stopped, paused, or resumed. And also the function called processSampleBuffer, now this is the one that you want to override to handle incoming media samples. This is where all the magic happens. You upload, the encoding, and uploading here.
So, when the broadcast starts, ReplayKit notifies extension that it will begin providing it with media samples and ReplayKit is using the function called broadcastStarted with setupInfo of this. And here's a code example that shows you that you do receive a setupInfo as an argument of that function, and you could extract say, name of the broadcast from the dictionary and pass it to the broadcast session, or in case a broadcast has started from the Control Center you can just let know the session about this one. And now, let me zoom in on the processSampleBuffer function. ReplayKit provides extension with three types of the media samples.
Video samples captured from the screen. Audio samples captured from the application, this is the audio your application's playing back right now. And the audio samples captured from the microphone. And you can use any technology to encode this media, but as a practical matter we provide you a lower level API called VideoToolbox. This is a framework that provides access to the hardware accelerated encoding and decoding.
All samples go to the upload extension and handled by the function processSampleBuffer.
And the function should encode and upload the media samples. Here in this code example, we show you how you could use a VideoToolbox to encode the video sample.
In your real code, you would also have to implement the call back to receive the encoded data, et cetera. But here I would like to speak about the VideoToolbox, because it's especially important when you do your video processing in an app extension. Because app extensions have much lower memory limits compared to the programmed applications. And having access to this hardware accelerated video encoding is vital for the ReplayKit upload extensions. And this year, we have great news, VideoToolbox is also available on tvOS now. So, you can build highly optimized, very efficient extensions for both platforms.
This is a high level picture of how Live Broadcast works, and who implements each part.
Again if you are a game developer, client application developer, all you need to worry about is just present the ViewController initiate and stop the broadcast, and you could implement this API and be done by the end of this session.
And if you are a broadcast service developer there's a little more work on your side. You need to receive the samples, encode them, and upload to the broadcast service.
There's one more thing I need to go over before we finish with this part of the talk. Is that so far we've been assuming that all the data flows upwards from the application to the online service, but indeed it is also possible for the data to be flowing back from the online service to the application. And that could be some viewers feedback, like the comments of the viewers or likes, or any kind of data number viewers.
And for that we provide an API that helps you to deliver this information from the extension to the client application.
And you have to just put this data in a dictionary and use the function called updateServiceInfo from within your extension. And that dictionary would be available to the application as a property of the broadcast controller. The name of the property is serviceInfo and it's KVO observable, so you can monitor this and update the UI appropriately.
This is it for the Live Broadcast API overview. And having all this information you can build absolutely new products, given that you also construct the broadcast from the Control Center you can build third parties screen mirroring or video share, sharing of the screen during the video conference.
Thank you, and please come, please welcome Johnny back on stage.
Thank you, Alexander. So, as Alexander has just stated, current broadcaster application, you would need to present to the user a RPBroadcastActivity ViewController that allows them to choose a public service to broadcast your application to. Well, sometimes you don't want to broadcast your application to a public service. Sometimes, you want your application to use your broadcasting service. Well, with ReplayKit 2 and Broadcast Pairing, you can do just that. Broadcast Pairing enables you to fully and seamlessly integrate your entire streaming solution, all from within your own application.
Here we have our budget application and we have our conference application that supports ReplayKit Live Streaming and has implemented a broadcast extension. I want our budget application to stream exclusively to our conference application's broadcast extension. So to do that, I'm going to initiate a broadcast pair. Our budget application is going to call load with preferred extension on the class RPActivityViewController. We'll get back an instance of RPBroadcastActivity ViewController much like we do with general broadcast initiation, but here is the main difference between Broadcast Pairing and general broadcast initiation. Because when you go and present that ViewController, instead of the user being presented with a picker that allows them to choose a public service, they'll be presented with an alert that indicates to them your application's intent to use a particular broadcast service. Here, our budget application wants to stream to our conference application's broadcast service. When a user taps accept, ReplayKit will immediately launch the paired broadcast extension allowing the user to input any information that might be important to the broadcasting session.
When the user has finished inputting all their information, ReplayKit will start broadcasting to the paired broadcast extension. And just like that, our budget application is now streaming exclusively to its paired broadcast extension. Let's go ahead and take a look at the API for Broadcast Pairing. The API for Broadcast Pairing is very simple. It's a new class method on RPBroadcastActivity ViewController called load(withPreferredExtension. We'll hand you back an instance of broadcastActivityViewController that you can then present to your users. Let's jump in and take a look at how our budget application is going to imitate a broadcast pair in a little bit more detail. Here, I have a method called didPressBroadcastPairButton. Inside of it, I'm simply going to call load(withPreferredExtension: on the class RPBroadcastActivity ViewController. We'll go ahead and get back an instance of RPBroadcastActivity ViewController that. When we go ahead and present the user be presented with an alert that indicates to them my application's intent to use a particular broadcasting service. Once the user accepts, ReplayKit will handle the rest and we'll the broadcasting extension that's been paired.
Broadcast Pairing has been designed so that the broadcasting app and the broadcasting service are tightly coupled. So, initiating a Broadcast Pairing session, developers are going to have to supply a bundleID for the broadcast extension. Users will also need to accept the broadcasting pair through the alert, which will be shown every time you wish to initiate a Broadcasting Pair session.
Broadcast Pairing allows you to seamlessly integrate your entire streaming solution all within your own application.
Now, we know that creating replays and Live Streams with user commentary is a fantastic way to get new user engagement in your application as well as generating a community around your application. That's why last year we introduced front camera support for ReplayKit. And which is why this year we're also introducing Fast Camera Switching for ReplayKit 2. Fast Camera Switching allows you to change the camera feed in the camera preview view found in RPScreenRecorder to use either the front camera or the rear camera. The camera preview view found in RPScreenRecorder is a subclass of UIView, so it can be added to just about any application.
Developers are responsible for UI elements that allow the user to present and dismiss the camera preview view, as well as UI elements to allow the user to switch the camera preview view. Let's go ahead and take a quick look at the API for Fast Camera Switching.
The API for Fast Camera Switching is really simple. It consists of a new property on RPScreenRecorder called cameraPosition, which is used to note the current cameraPosition for the sharedRecorder instance. CameraPosition is an enumeration RPCameraPosition which includes RPCameraPosition front and RPCameraPosition back which is used for the front and back cameras respectively. Let's go ahead and jump into an example of how we can start using Fast Camera Switching. Wow, that photo looked a lot better on a smaller screen. Here, we have a function called showPreviewView. Inside we're simply going to grab this sharedRecorder instance on RPScreenRecorder. From there, I'll grab the cameraPreviewView for the RP, for the sharedRecorder instance. Since the sharedRecorder instance and its cameraView is a subclass of UI view, I'm simply going to add it as a subview to my view in my application. And just like that, we're now using the cameraPreviewView and the front facing camera for our video commentary. Let's go ahead and take a quick look at how we can use Fast Camera Switching.
Here, I have a method called didPressCameraSwitch. Again, I'm simply going to grab a sharedRecorder instance from our RPScreenRecorder. I'm really interested in knowing what the current cameraPosition is. So, in our method here, we're going to check to see what the current cameraPosition is. And whatever it is, I'm going to switch it to its opposite. So here, We notice that our cameraPosition for our sharedRecorder is using RPCameraPosition.front. I'm simply going to set the shareRecorder's cameraPosition to be RPCameraPosition.back. And just like that, our preview view is now using the rear camera for its video commentary. It really is just that easy and it really is just that fast.
Fast Camera Switching will give you additional tools to provide your users with to create more engaging video commentary in the content their creating in your application.
We have covered a lot today. So let's go ahead and take a minute to recap. In ReplayKit 2, we introduced In-App Screen Capture, which is a powerful new API that's going to give you direct access to your application's own audio, video, and microphone content straight from ReplayKit.
With iOS Screen Recording and Broadcast, users can now record and broadcast their entire iOS screen experience straight from Control Center.
We introduced Broadcast Pairing which enable you to seamlessly integrate your entire streaming solution all within your own application.
And finally, with Fast Camera Switching you now have more tools to provide your users with to create more engaging video commentary.
For more information about our session today, visit us at developer.apple.com. We are session 606. We hope you have a wonderful WWDC. Thank you. [ Applause ]
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