diff --git a/src/TeamsISO.Engine.NdiInterop/NdiNative.cs b/src/TeamsISO.Engine.NdiInterop/NdiNative.cs
new file mode 100644
index 0000000..24f61d2
--- /dev/null
+++ b/src/TeamsISO.Engine.NdiInterop/NdiNative.cs
@@ -0,0 +1,154 @@
+using System.Runtime.InteropServices;
+
+namespace TeamsISO.Engine.NdiInterop;
+
+/// <summary>
+/// P/Invoke declarations for the NewTek/Vizrt NDI SDK 6 native library.
+/// On Windows the import target is <c>Processing.NDI.Lib.x64.dll</c>; the loader resolves it
+/// from the NDI Runtime installation path or from the application directory.
+/// </summary>
+internal static class NdiNative
+{
+    private const string LibName = "Processing.NDI.Lib.x64";
+
+    // ---- Lifecycle ----
+    [DllImport(LibName, EntryPoint = "NDIlib_initialize", CallingConvention = CallingConvention.Cdecl)]
+    [return: MarshalAs(UnmanagedType.U1)]
+    public static extern bool Initialize();
+
+    [DllImport(LibName, EntryPoint = "NDIlib_destroy", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void Destroy();
+
+    [DllImport(LibName, EntryPoint = "NDIlib_version", CallingConvention = CallingConvention.Cdecl)]
+    public static extern IntPtr Version();
+
+    // ---- Find ----
+    [DllImport(LibName, EntryPoint = "NDIlib_find_create_v2", CallingConvention = CallingConvention.Cdecl)]
+    public static extern IntPtr FindCreateV2(IntPtr p_create_settings);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_find_destroy", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void FindDestroy(IntPtr p_instance);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_find_get_current_sources", CallingConvention = CallingConvention.Cdecl)]
+    public static extern IntPtr FindGetCurrentSources(IntPtr p_instance, out uint p_no_sources);
+
+    // ---- Receive ----
+    [DllImport(LibName, EntryPoint = "NDIlib_recv_create_v3", CallingConvention = CallingConvention.Cdecl)]
+    public static extern IntPtr RecvCreateV3(ref RecvCreateV3 p_create_settings);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_recv_destroy", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void RecvDestroy(IntPtr p_instance);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_recv_capture_v3", CallingConvention = CallingConvention.Cdecl)]
+    public static extern FrameType RecvCaptureV3(
+        IntPtr p_instance,
+        out VideoFrameV2 p_video_data,
+        IntPtr p_audio_data,
+        IntPtr p_metadata,
+        uint timeout_in_ms);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_recv_free_video_v2", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void RecvFreeVideoV2(IntPtr p_instance, ref VideoFrameV2 p_video_data);
+
+    // ---- Send ----
+    [DllImport(LibName, EntryPoint = "NDIlib_send_create", CallingConvention = CallingConvention.Cdecl)]
+    public static extern IntPtr SendCreate(ref SendCreate p_create_settings);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_send_destroy", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void SendDestroy(IntPtr p_instance);
+
+    [DllImport(LibName, EntryPoint = "NDIlib_send_send_video_v2", CallingConvention = CallingConvention.Cdecl)]
+    public static extern void SendSendVideoV2(IntPtr p_instance, ref VideoFrameV2 p_video_data);
+
+    // ---- Enums ----
+
+    public enum FrameType
+    {
+        None = 0,
+        Video = 1,
+        Audio = 2,
+        Metadata = 3,
+        Error = 4,
+        StatusChange = 100
+    }
+
+    public enum RecvBandwidth
+    {
+        MetadataOnly = -10,
+        AudioOnly = 10,
+        Lowest = 0,
+        Highest = 100
+    }
+
+    public enum RecvColorFormat
+    {
+        BgrxBgra = 0,
+        UyvyBgra = 1,
+        Rgbx_Rgba = 2,
+        UyvyRgba = 3,
+        Fastest = 100,
+        Best = 101
+    }
+
+    public enum FrameFormatType
+    {
+        Progressive = 1,
+        Interleaved = 0,
+        FieldZero = 2,
+        FieldOne = 3,
+        Max = 0x7FFFFFFF
+    }
+
+    public static class FourCC
+    {
+        public const uint UYVY = 0x59565955; // 'U','Y','V','Y'
+        public const uint BGRA = 0x41524742; // 'B','G','R','A'
+        public const uint BGRX = 0x58524742; // 'B','G','R','X'
+        public const uint RGBA = 0x41424752; // 'R','G','B','A'
+    }
+
+    // ---- Structs ----
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct Source
+    {
+        public IntPtr p_ndi_name;     // const char*
+        public IntPtr p_url_address;  // const char* (union, treat as URL)
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct RecvCreateV3
+    {
+        public Source source_to_connect_to;
+        public RecvColorFormat color_format;
+        public RecvBandwidth bandwidth;
+        [MarshalAs(UnmanagedType.U1)] public bool allow_video_fields;
+        public IntPtr p_ndi_recv_name; // const char*
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct SendCreate
+    {
+        public IntPtr p_ndi_name;     // const char*
+        public IntPtr p_groups;       // const char*
+        [MarshalAs(UnmanagedType.U1)] public bool clock_video;
+        [MarshalAs(UnmanagedType.U1)] public bool clock_audio;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct VideoFrameV2
+    {
+        public int xres;
+        public int yres;
+        public uint FourCC;
+        public int frame_rate_N;
+        public int frame_rate_D;
+        public float picture_aspect_ratio;
+        public FrameFormatType frame_format_type;
+        public long timecode;
+        public IntPtr p_data;
+        public int line_stride_in_bytes; // (union with data_size_in_bytes)
+        public IntPtr p_metadata;
+        public long timestamp;
+    }
+}
diff --git a/src/TeamsISO.Engine.NdiInterop/NdiPInvokeHandles.cs b/src/TeamsISO.Engine.NdiInterop/NdiPInvokeHandles.cs
new file mode 100644
index 0000000..ae67830
--- /dev/null
+++ b/src/TeamsISO.Engine.NdiInterop/NdiPInvokeHandles.cs
@@ -0,0 +1,61 @@
+using TeamsISO.Engine.Interop;
+
+namespace TeamsISO.Engine.NdiInterop;
+
+internal sealed class NdiPInvokeFindHandle : NdiFindHandle
+{
+    public IntPtr Native { get; private set; }
+
+    public NdiPInvokeFindHandle(IntPtr native) => Native = native;
+
+    public override void Dispose()
+    {
+        if (Native != IntPtr.Zero)
+        {
+            NdiNative.FindDestroy(Native);
+            Native = IntPtr.Zero;
+        }
+    }
+}
+
+internal sealed class NdiPInvokeReceiverHandle : NdiReceiverHandle
+{
+    public IntPtr Native { get; private set; }
+    public string SourceName { get; }
+
+    public NdiPInvokeReceiverHandle(IntPtr native, string sourceName)
+    {
+        Native = native;
+        SourceName = sourceName;
+    }
+
+    public override void Dispose()
+    {
+        if (Native != IntPtr.Zero)
+        {
+            NdiNative.RecvDestroy(Native);
+            Native = IntPtr.Zero;
+        }
+    }
+}
+
+internal sealed class NdiPInvokeSenderHandle : NdiSenderHandle
+{
+    public IntPtr Native { get; private set; }
+    public string OutputName { get; }
+
+    public NdiPInvokeSenderHandle(IntPtr native, string outputName)
+    {
+        Native = native;
+        OutputName = outputName;
+    }
+
+    public override void Dispose()
+    {
+        if (Native != IntPtr.Zero)
+        {
+            NdiNative.SendDestroy(Native);
+            Native = IntPtr.Zero;
+        }
+    }
+}
diff --git a/src/TeamsISO.Engine.NdiInterop/NdiVersion.cs b/src/TeamsISO.Engine.NdiInterop/NdiVersion.cs
new file mode 100644
index 0000000..4d7c896
--- /dev/null
+++ b/src/TeamsISO.Engine.NdiInterop/NdiVersion.cs
@@ -0,0 +1,20 @@
+namespace TeamsISO.Engine.NdiInterop;
+
+/// <summary>
+/// Constants describing the NDI SDK version this build was compiled against.
+/// The runtime version reported by <see cref="NdiNative.Version"/> is compared against
+/// <see cref="ExpectedRuntimeVersionPrefix"/> by the engine's runtime probe to detect
+/// installations that pre-date or post-date the SDK headers (per spec §6).
+/// </summary>
+public static class NdiVersion
+{
+    /// <summary>The SDK family this build targets (NDI 6).</summary>
+    public const string SdkFamily = "NDI 6";
+
+    /// <summary>
+    /// Prefix of the runtime version string we expect (NDI runtime reports e.g.
+    /// "NDI SDK for Windows v6.0.1.0"). Any major change of the leading "v6" is treated
+    /// as a mismatch.
+    /// </summary>
+    public const string ExpectedRuntimeVersionPrefix = "NDI SDK for Windows v6";
+}