iOS 屏幕实时共享功能实践(内附详细代码)

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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.....        }}];
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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。

微信图片_20210906123342.jpg 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.....            }];}];
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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。

微信图片_20210906123404.jpg 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}
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Upload Extension

- (void)broadcastStartedWithSetupInfo:(NSDictionary<NSString *,NSObject *> *)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;    }}
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Host APP

RPBroadcastControllerDelegate//startif (![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 <NSString *, NSObject <NSCoding> *> *)serviceInf {    NSLog(@"didUpdateServiceInfo: %@", serviceInf);}
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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);}];
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停止 APP 屏幕录制

[[RPScreenRecorder sharedRecorder] stopCaptureWithHandler:^(NSError * _Nullable error) {        [self.assetWriter finishWritingWithCompletionHandler:^{            //TODO        }];}];
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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}
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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。

微信图片_20210906123418.jpg

代码示例

Upload extension

#import "SampleHandler.h"#import <RongRTCReplayKitExt/RongRTCReplayKitExt.h>
static NSString *const ScreenShareGroupID = @"group.cn.rongcloud.rtcquickdemo.screenshare";
@interface SampleHandler ()<RongRTCReplayKitExtDelegate>@end
@implementation SampleHandler
- (void)broadcastStartedWithSetupInfo:(NSDictionary<NSString *, NSObject *> *)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)sampleBufferType  API_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];}
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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]);                                }                            }];}
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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。

分类:
iOS
分类:
iOS