47-[AVCaptureVideoDataOutput _updateRemoteQueue:] 偶尔会出现崩溃

Question

(void)captureOutput:(AVCaptureOutput )captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection )connection

调用这个代理方法 偶尔会崩溃 bugly显示如下

8 AVFoundation -[AVCaptureVideoDataOutput _handleRemoteQueueOperation:] + 344
9 AVFoundation ___47-[AVCaptureVideoDataOutput _updateRemoteQueue:]_block_invoke + 100
10 CoreMedia ___FigRemoteOperationReceiverCreateMessageReceiver_block_invoke + 272
11 CoreMedia ___FigRemoteQueueReceiverSetHandler_block_invoke.2 + 224
12 libdispatch.dylib __dispatch_client_callout + 16### 问题描述

相关代码

// 请把代码文本粘贴到下方（请勿用图片代替代码）

pragma mark 相机相关

• (AVCaptureSession *)captureSession {
  if (!_captureSession) {

  //创建会话层
  _captureSession = [[AVCaptureSession alloc] init];
  [_captureSession setSessionPreset:AVCaptureSessionPreset1920x1080];

  }
  return _captureSession;

}

• (AVCaptureDeviceInput *)captureInput {
  if (!_captureInput) {

  _captureInput = [AVCaptureDeviceInput deviceInputWithDevice:self.captureDevice error:nil];

  }
  return _captureInput;

}

• (AVCaptureStillImageOutput *)captureOutput {
  if (!_captureOutput) {

  //创建、配置输出
  _captureOutput = [[AVCaptureStillImageOutput alloc] init];
  NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey,nil];
  [_captureOutput setOutputSettings:outputSettings];

  }
  return _captureOutput;

}

• (AVCaptureVideoDataOutput *)captureDataOutput {
  if (!_captureDataOutput) {

  _captureDataOutput = [[AVCaptureVideoDataOutput alloc] init];
  _captureDataOutput.alwaysDiscardsLateVideoFrames = YES;
  dispatch_queue_t queue = dispatch_queue_create("cameraQueue", NULL);
  [_captureDataOutput setSampleBufferDelegate:self queue:queue];
  NSString* formatKey = (NSString*)kCVPixelBufferPixelFormatTypeKey;
  NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
  NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:formatKey];
  [_captureDataOutput setVideoSettings:videoSettings];

  }
  return _captureDataOutput;

}

• (AVCaptureVideoPreviewLayer *)capturePreviewLayer {
  if (!_capturePreviewLayer) {

  _capturePreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession: self.captureSession];
  _capturePreviewLayer.frame = CGRectMake(0,0, ScreenW, ScreenH);
  _capturePreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

  }
  return _capturePreviewLayer;

}

• (AVCaptureDevice *)captureDevice {
  if (!_captureDevice) {

  NSArray *deviceArr = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
  for (AVCaptureDevice *device in deviceArr)
  {
      if (device.position == AVCaptureDevicePositionBack){
          _captureDevice = device;
          _captureInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
      }
  }

  }
  return _captureDevice;

}
//输入设备

if ([self.captureSession canAddInput:self.captureInput]) {
    [self.captureSession addInput:self.captureInput];
}
//输出设备
if ([self.captureSession canAddOutput:self.captureDataOutput]) {
    [self.captureSession addOutput:self.captureDataOutput];
}
//输出设备
if ([self.captureSession canAddOutput:self.captureOutput]) {
    [self.captureSession addOutput:self.captureOutput];
}
//添加预览层
[self.view.layer addSublayer:self.capturePreviewLayer];

 [self.view.layer addSublayer:self.detectLayer];
 self.view.layer.masksToBounds = YES;
 [self.view addSubview:self.squareView];

Answer 1

这个 queue 放在作为函数的局部变量，不合适。

dispatch_queue_t queue = dispatch_queue_create("cameraQueue", NULL);
[_captureDataOutput setSampleBufferDelegate:self queue:queue];

系统的代理回调在一个创建的局部的队列变量中执行，
然后如果碰巧这个 queue 没被系统回收，代理就调用有效。
如果这个 queue 被系统回收了，代理调用有崩

---

---

这个肯定不能放在函数内创建，dispatch_queue_t queue

看到就怪怪的

你可以用系统提供的队列。

如果要用你自定制的，

苹果是这么做的

@property (nonatomic) dispatch_queue_t sessionQueue;

使用 AVFoundation, 苹果的实例代码, 你应该看一下。

AFN 用的是单例。

static dispatch_queue_t url_session_manager_processing_queue() {
    static dispatch_queue_t af_url_session_manager_processing_queue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        af_url_session_manager_processing_queue = dispatch_queue_create("com.alamofire.networking.session.manager.processing", DISPATCH_QUEUE_CONCURRENT);
    });

    return af_url_session_manager_processing_queue;
}