Add new view that renders local video using AVCaptureLayerPreview.

talk/app/webrtc/objc/avfoundationvideocapturer.mm

 /*
  * libjingle
  * Copyright 2015 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 15 matching lines @@
  */
 
 #include "talk/app/webrtc/objc/avfoundationvideocapturer.h"
 
 #include "webrtc/base/bind.h"
 
 #import <AVFoundation/AVFoundation.h>
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
+#import "webrtc/base/objc/RTCDispatcher.h"
+
 // TODO(tkchin): support other formats.
 static NSString* const kDefaultPreset = AVCaptureSessionPreset640x480;
 static cricket::VideoFormat const kDefaultFormat =
     cricket::VideoFormat(640,
                          480,
                          cricket::VideoFormat::FpsToInterval(30),
                          cricket::FOURCC_NV12);
 
-// This queue is used to start and stop the capturer without blocking the
-// calling thread. -[AVCaptureSession startRunning] blocks until the camera is
-// running.
-static dispatch_queue_t kBackgroundQueue = nil;
-
 // This class used to capture frames using AVFoundation APIs on iOS. It is meant
 // to be owned by an instance of AVFoundationVideoCapturer. The reason for this
 // because other webrtc objects own cricket::VideoCapturer, which is not
 // ref counted. To prevent bad behavior we do not expose this class directly.
 @interface RTCAVFoundationVideoCapturerInternal : NSObject
     <AVCaptureVideoDataOutputSampleBufferDelegate>
 
 @property(nonatomic, readonly) AVCaptureSession* captureSession;
 @property(nonatomic, readonly) BOOL isRunning;
 @property(nonatomic, assign) BOOL useBackCamera;  // Defaults to NO.
@@ skipping 14 matching lines @@
   AVCaptureVideoDataOutput* _videoOutput;
   // The cricket::VideoCapturer that owns this class. Should never be NULL.
   webrtc::AVFoundationVideoCapturer* _capturer;
   BOOL _orientationHasChanged;
 }
 
 @synthesize captureSession = _captureSession;
 @synthesize useBackCamera = _useBackCamera;
 @synthesize isRunning = _isRunning;
 
-+ (void)initialize {
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    kBackgroundQueue = dispatch_queue_create(
-        "com.google.webrtc.RTCAVFoundationCapturerBackground",
-        DISPATCH_QUEUE_SERIAL);
-  });
-}
-
 - (instancetype)initWithCapturer:(webrtc::AVFoundationVideoCapturer*)capturer {
   NSParameterAssert(capturer);
   if (self = [super init]) {
     _capturer = capturer;
     if (![self setupCaptureSession]) {
       return nil;
     }
     NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
     [center addObserver:self
                selector:@selector(deviceOrientationDidChange:)
@@ skipping 23 matching lines @@
   [self updateSessionInput];
 }
 
 - (void)startCaptureAsync {
   if (_isRunning) {
     return;
   }
   _orientationHasChanged = NO;
   [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
   AVCaptureSession* session = _captureSession;
-  dispatch_async(kBackgroundQueue, ^{
+  [RTCDispatcher dispatchAsyncOnType:RTCDispatcherTypeCaptureSession
+                               block:^{
     [session startRunning];
-  });
+  }];
   _isRunning = YES;
 }
 
 - (void)stopCaptureAsync {
   if (!_isRunning) {
     return;
   }
   [_videoOutput setSampleBufferDelegate:nil queue:nullptr];
   AVCaptureSession* session = _captureSession;
-  dispatch_async(kBackgroundQueue, ^{
+  [RTCDispatcher dispatchAsyncOnType:RTCDispatcherTypeCaptureSession
+                               block:^{
     [session stopRunning];
-  });
+  }];
   [[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];
   _isRunning = NO;
 }
 
 #pragma mark AVCaptureVideoDataOutputSampleBufferDelegate
 
 - (void)captureOutput:(AVCaptureOutput*)captureOutput
     didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
            fromConnection:(AVCaptureConnection*)connection {
   NSParameterAssert(captureOutput == _videoOutput);
@@ skipping 278 matching lines @@
 
 void AVFoundationVideoCapturer::SignalFrameCapturedOnStartThread(
     const cricket::CapturedFrame* frame) {
   RTC_DCHECK(_startThread->IsCurrent());
   // This will call a superclass method that will perform the frame conversion
   // to I420.
   SignalFrameCaptured(this, frame);
 }
 
 }  // namespace webrtc