TASK 3 milestone 1: webcam capture (MediaCapture CPU-first, CameraManager refcount, picker, clip/mirror, schema v2, tests)

2026-08-06 14:35:34 -07:00
parent d97b5d375c
commit 98cdc4b3f4
23 changed files with 1099 additions and 40 deletions
@@ -0,0 +1,128 @@
+using System;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
+using System.Threading.Tasks;
+using Windows.Graphics.Imaging;
+using Windows.Media.Capture;
+using Windows.Media.Capture.Frames;
+using Windows.Media.MediaProperties;
+using ytLive.Helpers;
+
+namespace ytLive.Services;
+
+/// <summary>
+/// CPU-first MediaCapture source. Requests BGRA8 frames from the camera's video
+/// preview source; the capture pipeline does any format conversion, so every
+/// frame arrives as a normalized <see cref="VideoFrame"/>. Frames arrive on a
+/// worker thread — marshal before touching WPF.
+/// </summary>
+public sealed class MediaCaptureFrameSource : ICameraFrameSource
+{
+    private readonly string _deviceId;
+    private MediaCapture? _capture;
+    private MediaFrameReader? _frameReader;
+
+    public string DeviceId => _deviceId;
+
+    public event Action<VideoFrame>? FrameAvailable;
+
+    public MediaCaptureFrameSource(string deviceId)
+    {
+        _deviceId = deviceId;
+    }
+
+    public async Task StartAsync()
+    {
+        var capture = new MediaCapture();
+        MediaFrameReader? reader = null;
+        try
+        {
+            var settings = new MediaCaptureInitializationSettings
+            {
+                VideoDeviceId = _deviceId,
+                StreamingCaptureMode = StreamingCaptureMode.Video,
+                MemoryPreference = MediaCaptureMemoryPreference.Cpu,
+            };
+            await capture.InitializeAsync(settings);
+
+            var colorSource = capture.FrameSources
+                .FirstOrDefault(pair => pair.Value.Info.MediaStreamType == MediaStreamType.VideoPreview)
+                .Value;
+            if (colorSource == null)
+                throw new InvalidOperationException($"No video preview source on camera '{_deviceId}'.");
+
+            reader = await capture.CreateFrameReaderAsync(colorSource, MediaEncodingSubtypes.Bgra8);
+            reader.FrameArrived += OnFrameArrived;
+            await reader.StartAsync();
+
+            _capture = capture;
+            _frameReader = reader;
+        }
+        catch
+        {
+            if (reader != null)
+            {
+                reader.FrameArrived -= OnFrameArrived;
+                reader.Dispose();
+            }
+            capture.Dispose();
+            throw;
+        }
+    }
+
+    public async Task StopAsync()
+    {
+        var reader = _frameReader;
+        _frameReader = null;
+        if (reader != null)
+        {
+            reader.FrameArrived -= OnFrameArrived;
+            try
+            {
+                await reader.StopAsync();
+            }
+            catch (Exception ex)
+            {
+                AppLog.Write($"MediaCaptureFrameSource: stop frame reader failed: {ex.Message}");
+            }
+            reader.Dispose();
+        }
+
+        var capture = _capture;
+        _capture = null;
+        capture?.Dispose();
+    }
+
+    private void OnFrameArrived(MediaFrameReader sender, MediaFrameArrivedEventArgs args)
+    {
+        using var frame = sender.TryAcquireLatestFrame();
+        var videoFrame = frame?.VideoMediaFrame?.SoftwareBitmap;
+        if (videoFrame == null) return;
+
+        var bitmap = videoFrame.BitmapPixelFormat == BitmapPixelFormat.Bgra8
+            ? videoFrame
+            : SoftwareBitmap.Convert(videoFrame, BitmapPixelFormat.Bgra8);
+
+        try
+        {
+            using var buffer = bitmap.LockBuffer(BitmapBufferAccessMode.Read);
+            using var reference = buffer.CreateReference();
+            if (WindowsRuntimeMarshal.TryGetDataUnsafe(reference, out var pixelsPtr, out var capacity))
+            {
+                var pixels = new byte[capacity];
+                Marshal.Copy(pixelsPtr, pixels, 0, (int)capacity);
+                FrameAvailable?.Invoke(new VideoFrame(bitmap.PixelWidth, bitmap.PixelHeight, pixels));
+            }
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"MediaCaptureFrameSource: frame copy failed: {ex.Message}");
+        }
+        finally
+        {
+            if (!ReferenceEquals(bitmap, videoFrame))
+                bitmap.Dispose();
+        }
+    }
+}