Unity与Hololens下Web Camera录屏失败：VideoCapture.CreateAsync未生成实例

Hey there! Let's break down why your VideoCapture instance isn't creating even though the HoloLens camera light turns on—super frustrating, I know. Let's go through the most likely fixes step by step:

1. Double-Check Camera Permissions (Beyond Unity Settings) #

You said you enabled Webcam and Microphone in Player Settings, but sometimes Unity doesn't sync these correctly to the UWP package manifest. Here's how to verify:

• Export your Unity project to a UWP solution.
• Open the Package.appxmanifest file in Visual Studio.
• Navigate to the Capabilities tab and make sure both Webcam and Microphone are checked.
• Also, head to your HoloLens device settings: Go to Settings > Privacy > Camera, find your app, and confirm it has permission to access the camera (sometimes the initial permission prompt gets missed or denied).

2. Verify VideoCapture.CreateAsync Parameters #

The HoloLens has specific camera hardware, and incorrect parameters here can silently fail:

• For HoloLens 1: There's only one front-facing透视 camera. Make sure you're passing true for the useFrontCamera parameter:

  VideoCapture.CreateAsync(true, OnVideoCaptureCreated);
  

• For HoloLens 2: There are two cameras—front透视 and rear photo. If you're trying to use the rear camera but don't specify a supported resolution, it might fail. Try explicitly picking a supported resolution first:

  // Grab the highest supported resolution
  Resolution supportedRes = VideoCapture.SupportedResolutions
      .OrderByDescending(res => res.width * res.height)
      .First();
  // Create capture with explicit resolution and audio settings
  VideoCapture.CreateAsync(supportedRes, VideoCapture.AudioState.ApplicationAndMicAudio, OnVideoCaptureCreated);
  

3. Ensure You're Calling the API in the Right Context #

Async operations like CreateAsync need to run on Unity's main thread, and timing matters:

• Don't call it in Awake()—wait until Start() or use a coroutine to wait for permission first:

  IEnumerator Start()
  {
      // Request permission explicitly before trying to create capture
      yield return Application.RequestUserAuthorization(UserAuthorization.WebCam);
      
      if (Application.HasUserAuthorization(UserAuthorization.WebCam))
      {
          VideoCapture.CreateAsync(true, OnVideoCaptureCreated);
      }
      else
      {
          Debug.LogError("Camera permission was denied!");
      }
  }
  

4. Check Unity and HoloLens Version Compatibility #

Older Unity versions have known bugs with HoloLens VideoCapture:

• Stick to Unity 2019.4 LTS or newer—these versions have better UWP/HoloLens support and fix many async capture issues.
• Ensure your HoloLens is running the latest OS update (Settings > Update & Security > Windows Update) to avoid driver or API mismatches.

5. Debug with Visual Studio for Exact Error Details #

The best way to get to the root cause is to debug directly on the HoloLens:

• Connect your HoloLens to your PC via USB or Wi-Fi.
• Open your exported UWP solution in Visual Studio.
• Set the debugger to Device (or Remote Machine for Wi-Fi) and start debugging.
• Check the Output window in Visual Studio—Unity will log specific errors like "Unsupported resolution" or "No camera device found" that will point you exactly to the problem.

Bonus: Try Fallback to UWP MediaCapture #

If Unity's VideoCapture API still fails, you can directly use the UWP MediaCapture API via a C# wrapper in your Unity project. This gives you more low-level control and might bypass Unity's abstraction layer issues.

内容的提问来源于stack exchange，提问作者Mediarea