Objective c AVCaptureSession启动内存警告

每次启动AVCaptureSession时，我都会收到一条内存警告，导致超时崩溃。
我以异步方式启动会话，Instruments工具说应用程序消耗了大约2MB的内存。 你知道如何克服这个问题吗？2MB的分配内存是否太多

谢谢！ [iOS 4.3，ARC]

@autoreleasepool {
    //Init capture session
    session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetPhoto;


    //Resize container view
    CGRect cameraContainerFrame = cameraContainerView.frame;
    cameraContainerFrame.size = CGSizeMake(320, 426);
    cameraContainerView.frame = cameraContainerFrame;

    CALayer *viewLayer = [cameraContainerView layer];
    [viewLayer setMasksToBounds:YES];

    //Create preview layer
    captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

    CGRect bounds = [cameraContainerView bounds];
    [captureVideoPreviewLayer setFrame:bounds];


    if ([captureVideoPreviewLayer isOrientationSupported]) {
        [captureVideoPreviewLayer setOrientation:AVCaptureVideoOrientationPortrait];
    }    
    [captureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    [viewLayer addSublayer:captureVideoPreviewLayer];

    //Get input device
    captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    if ([captureDevice lockForConfiguration:nil]){
        captureDevice.focusMode = AVCaptureFocusModeContinuousAutoFocus;
        captureDevice.whiteBalanceMode = AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance;
        [captureDevice unlockForConfiguration];
    }

    NSError *error = nil;
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];
    if (!input) {
        // Handle the error appropriately.
        DLog(@"ERROR: trying to open camera: %@", error);
    }
    //Add input to session
    [session addInput:input];

    //Output
    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [NSDictionary dictionaryWithObject:AVVideoCodecJPEG forKey:AVVideoCodecKey];
    [stillImageOutput setOutputSettings:outputSettings];
    [session addOutput:stillImageOutput];

    //Save state
    cameraSessionInitialized = YES;
    [session startRunning];
}

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如果您不关心质量，这确实可以消除内存警告。我正在试图找出如何使它与AVCaptureSessionPresetPhoto一起工作。

我没有感觉到

AVCaptureSessionPresetPhoto

和

AVCaptureSessionPresetMedium

之间的质量变化，所以您的回答帮助了我，谢谢

session.sessionPreset = AVCaptureSessionPresetMedium;