iOS 屏幕实时共享功能实践(内附详细代码)

很多人对屏幕共享的印象还只停留在 PC 端做 PPT 汇报的场景中,但事实上,今天的屏幕共享早已跨界出圈了。比如一个大家很熟悉的场景 —— 游戏直播,主播就需要将自己的画面以“屏幕共享”的形式展示给观众,并且对实时性、流畅性的要求非常高。
对于很多手游主播来说,目前比较常见的做法是,通过借助 PC 端的中转将手机游戏画面进行直播分享;而实际上,通过调用融云屏幕共享 SDK,直接在手机端就可以拥有屏幕实时共享的能力。
本文就将主要围绕 iOS 屏幕共享问题展开讨论,一起了解 iOS ReplayKit 框架的发展过程,各个阶段的功能演变,以及结合融云屏幕共享 SDK 实现相应功能的代码和思路。
01 ReplayKit 发展史
iOS 端屏幕录制 ReplayKit 是从 iOS9 开始出现的。
iOS9
WWDC15 初次提供 ReplayKit 框架,它的初期出现主要用于录制视频,存于相册。
iOS9 开始录制和停止录制两个 API 有很大的局限性:
只能获取系统生成好的 MP4 文件,且不能直接获取,需要先保存到相册,再从相册获取;
不可以获取源数据,也就是 pcm 和 yuv 数据;
给开发者的权限低,不能录制其他 APP,且退出后台就不会录制了,只能录制当前 APP 画面。
可控行为在于:
停止录制可弹出一个视频预览窗口,能进行保存或取消或分享该视频文件;
录制完成后可以进行查看、编辑,或者通过指定方式分享。
开始录制视频的 API 如下所示。

/*! Deprecated. Use startRecordingWithHandler: instead. @abstract Starts app recording with a completion handler. Note that before recording actually starts, the user may be prompted with UI to confirm recording. @param microphoneEnabled Determines whether the microphone input should be included in the recorded movie audio. @discussion handler Called after user interactions are complete. Will be passed an optional NSError in the RPRecordingErrorDomain domain if there was an issue starting the recording. */ [[RPScreenRecorder sharedRecorder] startRecordingWithMicrophoneEnabled:YES handler:^(NSError * _Nullable error) { if (error) { //TODO..... } }];

调用开始录屏的时候,系统会弹出一个弹窗,需要用户进行确认后才能正常录制。
iOS 屏幕实时共享功能实践(内附详细代码)
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停止录制视频的 API 如下所示。
/*! @abstract Stops app recording with a completion handler. @discussion handler Called when the movie is ready. Will return an instance of RPPreviewViewController on success which should be presented using [UIViewController presentViewController:animated:completion:]. Will be passed an optional NSError in the RPRecordingErrorDomain domain if there was an issue stopping the recording. */ [[RPScreenRecorder sharedRecorder] stopRecordingWithHandler:^(RPPreviewViewController *previewViewController, NSError *error){ [self presentViewController:previewViewController animated:YES completion:^{ //TODO..... }]; }];

iOS10
经过 WWDC16 发布,苹果对 ReplayKit 进行了升级,开放了源数据获取途径,增加了两个 Extension 的 Target。具体情况包括:
新增 UI 和 Upload 两个 Extension 的 Target;
增加开发者权限,允许用户登录到服务并设立了直播、源数据的操作;
只能通过扩展区录制屏幕,不仅可以录制自己的 APP,还可以录制其他 APP;
只能录制 APP 屏幕,不能录制 iOS 系统屏幕。
创建 Extension 的方法如下图所示。
iOS 屏幕实时共享功能实践(内附详细代码)
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UI Extension
/* 这俩API可以理解为弹窗触发的事件回调函数; */ - (void)userDidFinishSetup { //触发Host App 的RPBroadcastActivityViewControllerDelegate }- (void)userDidCancelSetup { //触发Host App 的RPBroadcastActivityViewControllerDelegate }

Upload Extension
- (void)broadcastStartedWithSetupInfo:(NSDictionary *)setupInfo { // User has requested to start the broadcast. Setup info from the UI extension can be supplied but optional. //这里主要就是做一些初始化的行为操作 }- (void)broadcastPaused { // User has requested to pause the broadcast. Samples will stop being delivered. //接收系统暂停信号 }- (void)broadcastResumed { // User has requested to resume the broadcast. Samples delivery will resume. //接收系统恢复信号 }- (void)broadcastFinished { // User has requested to finish the broadcast. //接收系统完成信号 } //这里就是此次更新最炸的点,我们可以拿到系统源数据,而且系统还分了三类,分别为视频帧、App内声音、麦克风 - (void)processSampleBuffer:(CMSampleBufferRef)sampleBuffer withType:(RPSampleBufferType)sampleBufferType {switch (sampleBufferType) { case RPSampleBufferTypeVideo: // Handle video sample buffer break; case RPSampleBufferTypeAudioApp: // Handle audio sample buffer for app audio break; case RPSampleBufferTypeAudioMic: // Handle audio sample buffer for mic audio break; default: break; } }

Host APP
RPBroadcastControllerDelegate //start if (![RPScreenRecorder sharedRecorder].isRecording) { [RPBroadcastActivityViewController loadBroadcastActivityViewControllerWithHandler:^(RPBroadcastActivityViewController * _Nullable broadcastActivityViewController, NSError * _Nullable error) { if (error) { NSLog(@"RPBroadcast err %@", [error localizedDescription]); } broadcastActivityViewController.delegate = self; /*RPBroadcastActivityViewControllerDelegate*/ [self presentViewController:broadcastActivityViewController animated:YES completion:nil]; }]; }#pragma mark- RPBroadcastActivityViewControllerDelegate - (void)broadcastActivityViewController:(RPBroadcastActivityViewController *)broadcastActivityViewController didFinishWithBroadcastController:(RPBroadcastController *)broadcastController error:(NSError *)error { if (error) { //TODO: NSLog(@"broadcastActivityViewController:%@",error.localizedDescription); return; }[broadcastController startBroadcastWithHandler:^(NSError * _Nullable error) { if (!error) { NSLog(@"success"); } else { NSLog(@"startBroadcast:%@",error.localizedDescription); } }]; }#pragma mark- RPBroadcastControllerDelegate - (void)broadcastController:(RPBroadcastController *)broadcastController didFinishWithError:(nullable NSError *)error{ NSLog(@"didFinishWithError: %@", error); } - (void)broadcastController:(RPBroadcastController *)broadcastController didUpdateServiceInfo:(NSDictionary *> *)serviceInf { NSLog(@"didUpdateServiceInfo: %@", serviceInf); }

【iOS 屏幕实时共享功能实践(内附详细代码)】iOS11
经过 WWDC17,苹果对 ReplayKit2 进行了再次升级,新增了 APP 外数据获取,可以直接在 Host App 中获取,具体包括:
可以直接在 Host APP 中处理录制的 APP 屏幕数据;
可以录制 iOS 系统的屏幕数据,但是需要通过控制中心手动开启。
启动 APP 屏幕录制
[[RPScreenRecorder sharedRecorder] startCaptureWithHandler:^(CMSampleBufferRef_Nonnull sampleBuffer, RPSampleBufferType bufferType, NSError * _Nullable error) { [self.videoOutputStream write:sampleBuffer error:nil]; } completionHandler:^(NSError * _Nullable error) { NSLog(@"startCaptureWithHandler:%@",error.localizedDescription); }];

停止 APP 屏幕录制
[[RPScreenRecorder sharedRecorder] stopCaptureWithHandler:^(NSError * _Nullable error) { [self.assetWriter finishWritingWithCompletionHandler:^{ //TODO }]; }];

iOS12
苹果在 WWDC18 上针对 ReplayKit 更新,新增了 RPSystemBroadcastPickerView,类用于在 APP 内可启动系统录制,极大地简化了屏幕录制的流程。
if (@available(iOS 12.0, *)) { self.systemBroadcastPickerView = [[RPSystemBroadcastPickerView alloc] initWithFrame:CGRectMake(0, 0, 50, 80)]; self.systemBroadcastPickerView.preferredExtension = ScreenShareBuildID; self.systemBroadcastPickerView.showsMicrophoneButton = NO; self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:self.systemBroadcastPickerView]; } else { // Fallback on earlier versions }

02 融云 RongRTCReplayKitExt
为减轻开发者的集成负担,融云专门打造了 RongRTCReplayKitExt 库,以服务于屏幕共享业务。
设计思路
Upload Extension
SampleHandler 进行数据的接收、RCRTCReplayKitEngine 初始化配置 ;
RCRTCReplayKitEngine 初始化 socket 通讯、处理YUV数据转i420、控制内存峰值。
App
原有发布流程:
IM 连接--加入房间--发布资源(RCRTCScreenShareOutputStream);
内部做 socket 初始化、实现协议接收处理过的数据、推流。
iOS 屏幕实时共享功能实践(内附详细代码)
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代码示例
Upload extension
#import "SampleHandler.h" #import static NSString *const ScreenShareGroupID = @"group.cn.rongcloud.rtcquickdemo.screenshare"; @interface SampleHandler () @end@implementation SampleHandler- (void)broadcastStartedWithSetupInfo:(NSDictionary *)setupInfo { // User has requested to start the broadcast. Setup info from the UI extension can be supplied but optional. [[RCRTCReplayKitEngine sharedInstance] setupWithAppGroup:ScreenShareGroupID delegate:self]; }- (void)broadcastPaused { // User has requested to pause the broadcast. Samples will stop being delivered. }- (void)broadcastResumed { // User has requested to resume the broadcast. Samples delivery will resume. }- (void)broadcastFinished { [[RCRTCReplayKitEngine sharedInstance] broadcastFinished]; }- (void)processSampleBuffer:(CMSampleBufferRef)sampleBuffer withType:(RPSampleBufferType)sampleBufferTypeAPI_AVAILABLE(ios(10.0)) { switch (sampleBufferType) { case RPSampleBufferTypeVideo: [[RCRTCReplayKitEngine sharedInstance] sendSampleBuffer:sampleBuffer withType:RPSampleBufferTypeVideo]; break; case RPSampleBufferTypeAudioApp: // Handle audio sample buffer for app audio break; case RPSampleBufferTypeAudioMic: // Handle audio sample buffer for mic audio break; default: break; } }#pragma mark - RongRTCReplayKitExtDelegate -(void)broadcastFinished:(RCRTCReplayKitEngine *)broadcast reason:(RongRTCReplayKitExtReason)reason { NSString *tip = @""; switch (reason) { case RongRTCReplayKitExtReasonRequestedByMain: tip = @"屏幕共享已结束......"; break; case RongRTCReplayKitExtReasonDisconnected: tip = @"应用断开....."; break; case RongRTCReplayKitExtReasonVersionMismatch: tip = @"集成错误(SDK 版本号不相符合)........"; break; }NSError *error = [NSError errorWithDomain:NSStringFromClass(self.class) code:0 userInfo:@{ NSLocalizedFailureReasonErrorKey:tip }]; [self finishBroadcastWithError:error]; }

Host App
- (void)joinRoom { RCRTCVideoStreamConfig *videoConfig = [[RCRTCVideoStreamConfig alloc] init]; videoConfig.videoSizePreset = RCRTCVideoSizePreset720x480; videoConfig.videoFps = RCRTCVideoFPS30; [[RCRTCEngine sharedInstance].defaultVideoStream setVideoConfig:videoConfig]; RCRTCRoomConfig *config = [[RCRTCRoomConfig alloc] init]; config.roomType = RCRTCRoomTypeNormal; [self.engine enableSpeaker:YES]; __weak typeof(self) weakSelf = self; [self.engine joinRoom:self.roomId config:config completion:^(RCRTCRoom *_Nullable room, RCRTCCode code) { __strong typeof(weakSelf) strongSelf = weakSelf; if (code == RCRTCCodeSuccess) { self.room = room; room.delegate = self; [self publishScreenStream]; } else { [UIAlertController alertWithString:@"加入房间失败" inCurrentViewController:strongSelf]; } }]; }- (void)publishScreenStream { self.videoOutputStream = [[RCRTCScreenShareOutputStream alloc] initWithAppGroup:ScreenShareGroupID]; RCRTCVideoStreamConfig *videoConfig = self.videoOutputStream.videoConfig; videoConfig.videoSizePreset = RCRTCVideoSizePreset1280x720; videoConfig.videoFps = RCRTCVideoFPS24; [self.videoOutputStream setVideoConfig:videoConfig]; [self.room.localUser publishStream:self.videoOutputStream completion:^(BOOL isSuccess, RCRTCCode desc) { if (isSuccess) { NSLog(@"发布自定义流成功"); } else { NSLog(@"发布自定义流失败%@", [NSString stringWithFormat:@"订阅远端流失败:%ld", (long) desc]); } }]; }

03 一些注意事项
第一,ReplayKit2 内存不能超过 50MB,一旦超过峰值系统会进行强制回收,所以在 Extension 里面处理数据需要格外注意内存释放。
第二,进程之前通讯,如果是以 CFDefaultcenter 不能携带参数,只能发送消息;如果需要携带参数,必须做本地文件缓存。这里需要注意的一个问题是,在 debug 模式下运行可以打印出数据,在 release 下获取不到本地文件数据,具体实现可参见 Github 中的攻略。
最后想小小吐槽一下:非正常结束录屏时,系统往往会出现弹窗,且这个弹窗无法删除,只能重启设备 —— 这应该算是 iOS 系统一个比较恼人的 BUG 了。

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