Windows Phone 8.1 相机初始化 - 访问被拒绝异常

问题描述

使用适用于 Windows Phone 的 8.1 MediaCapture 类.

Using the 8.1 MediaCapture classes for Windows Phone.

已声明音频"和网络摄像头"的功能，其中 90% 是导致异常的原因.

Have declared the capabilities for "Audio" and "Webcam", which 90% is what would be the cause of the exception.

Kicker 是，它在 WP 模拟器中完美运行，但在实际设备上中断.

Kicker is, it works perfectly in the WP emulator, but breaks on an actual device.

确切的例外是这里:

我添加了大量检查，以确保我们没有重新初始化已经初始化的相机或尝试在初始化之前读取..等等(因为我认为问题是由以下原因引起的)所以这不太可能就是这样.

I have added a mountain of checks to make sure we aren't re-initializing the already initialized camera or trying to read before the initializations.. etc (as I assumed the issue was being caused by) So it is very unlikely to be that.

    private async Task InitializeCameraAsync()
    {
        if (_isInitialized)
        {
            Debug.WriteLine("Skipping unnecessary initialization");
            return;
        }

        Debug.WriteLine("Initializing camera media capture...");
        _deviceCapture = new MediaCapture();
        await _deviceCapture.InitializeAsync(new MediaCaptureInitializationSettings
        {
            VideoDeviceId = _cameraInfoCollection[_currentVideoDevice].Id,
            PhotoCaptureSource = PhotoCaptureSource.VideoPreview,
            AudioDeviceId = _microphoneInfoCollection[_currentAudioDevice].Id
            StreamingCaptureMode = StreamingCaptureMode.Video
        });
        Debug.WriteLine("Initialized camera media capture!");

        // For code completion only, unlikely to be relevant

        // Set up low-lag photo capture
        if (IsNotUsingInstantCapture)
        {
            Debug.WriteLine("Preparing low-lag photo capture");
            var imageEncoding = ImageEncodingProperties.CreateJpeg();
            imageEncoding.Width = PhotoCaptureWidth;
            imageEncoding.Height = PhotoCaptureHeight;
            _lowLagPhotoCapture = await _deviceCapture.PrepareLowLagPhotoCaptureAsync(imageEncoding);
        }

        _isInitialized = true;
        Debug.WriteLine("Initialized camera!");
    }

_mediacapture 随后被绑定到 xaml CaptureElement 的 .source 以显示预览.

_mediacapture is then being bound to the .source of a xaml CaptureElement to show a preview.

推荐答案

这是 Windows api 的临时错误.它已在 2014 年 9 月 24 日发布的 Windows Phone 8.1 更新中得到修复.

It was a temporary bug with the Windows api. It was fixed with the Windows Phone 8.1 update that was released the 24th of september 2014.

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