fix(control-surface): reserve loopback URL ACL at install time

The control surface uses HttpListener (http.sys), which denies prefix
registration to standard users -- on every non-Administrator install the
REST/WebSocket surface died at startup with Access is denied (5), taking
the /ui phone panel and Companion integration with it. The MSI runs
elevated, so it now reserves http://127.0.0.1:9755/ on install and deletes
the reservation on uninstall.

Deliberately NOT the strong wildcard: verified empirically that an idle
http://+:9755/ RESERVATION makes http.sys answer 503 for every request to
the loopback-bound listener without the request ever reaching the app.
The in-app failure guidance suggested exactly that reservation; corrected
to recommend the bound prefix and warn about the stale-wildcard trap.

Verified on a clean install: urlacl present, GET / and /ui and
/participants all 200 as a standard user; reservation removed on
uninstall.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -4,6 +4,44 @@ All notable changes to Dragon-ISO are documented here. The format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and this project
 adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.2.0-beta.1] — 2026-07-06
+
+Beta pre-release for the framerate and reliability work since 1.1.0.
+
+### Engine
+
+- **Exact rational framerate end-to-end** — the configured target framerate
+  now flows from settings to every NDI sender as an exact rational
+  (e.g. 59.94 = 60000/1001), and each outgoing video frame is stamped with
+  it. Previously every output advertised 59.94 regardless of configuration;
+  advertising the wrong rational causes drift and A/V desync downstream.
+- **Audio FourCC fix** — corrected the PCMs16 FourCC constant; audio FourCCs
+  are now pinned by tests to their ASCII packing.
+- **Finder rebuild hardening** — a failed NDI finder rebuild no longer leaves
+  a disposed finder behind (the self-heal path can retry cleanly).
+- **Scaler zero-dimension guard** — a source frame with a zero dimension is
+  dropped instead of crashing the pipeline.
+
+### Installer
+
+- **MSI ProductVersion now tracks the build version** — it was hardcoded to
+  1.0.0.0, so in-place upgrades (MajorUpgrade) never saw a newer version.
+  Upgrading from an earlier install may require a manual uninstall once.
+- **Control surface works out of the box for standard users** — the installer
+  now reserves the http.sys URL namespace for `http://127.0.0.1:9755/`
+  (removed again on uninstall). Previously the REST/WebSocket control surface
+  failed with "Access is denied" on every non-Administrator launch. Note for
+  LAN-reachable mode: it still needs its own `http://+:9755/` reservation
+  (the app logs the exact command), and that reservation must be deleted when
+  reverting to loopback-only — while idle it makes http.sys 503 every request.
+- **CAB embedded in the MSI** — the installer is a single self-contained
+  file again; distributing only the MSI no longer fails with error 1302.
+
+## [1.1.0] — 2026-05-31
+
+Rebrand release: TeamsISO becomes **Dragon-ISO** across source paths,
+installer metadata, and documentation. No functional engine changes.
+
 ## [1.0.0] — 2026-05-17
 
 First general release. Windows-only, .NET 8 WPF, NDI 6.
@@ -83,4 +121,6 @@ First general release. Windows-only, .NET 8 WPF, NDI 6.
 - WiX MSI installer with proper Add/Remove Programs metadata, Start Menu
   + Desktop shortcuts, and in-place upgrade.
 
-[1.0.0]: https://forge.wilddragon.net/zgaetano/Dragon-ISO/releases/tag/v1.0.0
+[1.2.0-beta.1]: https://forge.wilddragon.net/WildDragonLLC/dragon-iso/releases/tag/v1.2.0-beta.1
+[1.1.0]: https://forge.wilddragon.net/WildDragonLLC/dragon-iso/releases/tag/v1.1.0
+[1.0.0]: https://forge.wilddragon.net/WildDragonLLC/dragon-iso/releases/tag/v1.0.0

Directory.Build.props

@@ -6,10 +6,10 @@
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
     <AnalysisLevel>latest</AnalysisLevel>
-    <Version>1.0.0</Version>
+    <Version>1.2.0-beta.1</Version>
     <Authors>Wild Dragon LLC</Authors>
     <Company>Wild Dragon LLC</Company>
-    <Product>TeamsISO</Product>
+    <Product>Dragon-ISO</Product>
     <Copyright>Copyright © Wild Dragon LLC 2026</Copyright>
   </PropertyGroup>
 </Project>

installer/Dragon-ISO.Installer.wixproj

@@ -17,8 +17,17 @@
     -->
     <PublishDir>$(MSBuildThisFileDirectory)..\publish\Dragon-ISO\</PublishDir>
 
+    <!--
+      MSI ProductVersion must be numeric x.y.z (no -beta/-rc suffix), and it is
+      what MajorUpgrade compares — so it must track the real build version, not
+      a hardcoded literal. Strip any prerelease suffix from $(Version). Note:
+      two prereleases of the same x.y.z share a ProductVersion and won't
+      upgrade over each other; bump the patch digit between betas.
+    -->
+    <MsiProductVersion>$([System.Text.RegularExpressions.Regex]::Match('$(Version)', '^\d+\.\d+(\.\d+)?').Value)</MsiProductVersion>
+
     <!-- Pass MSBuild values into WiX preprocessor. -->
-    <DefineConstants>PublishDir=$(PublishDir);AssetsDir=$(MSBuildThisFileDirectory)..\src\Dragon-ISO.App\Assets\</DefineConstants>
+    <DefineConstants>PublishDir=$(PublishDir);AssetsDir=$(MSBuildThisFileDirectory)..\src\Dragon-ISO.App\Assets\;ProductVersion=$(MsiProductVersion)</DefineConstants>
 
     <!-- Code-signing hook (set externally for release builds; left empty for dev). -->
     <SignOutput Condition=" '$(SignOutput)' == '' ">false</SignOutput>
@@ -30,6 +39,8 @@
   -->
   <ItemGroup>
     <PackageReference Include="WixToolset.UI.wixext" Version="5.0.2" />
+    <!-- WixQuietExec for the URL ACL custom actions (control surface, port 9755). -->
+    <PackageReference Include="WixToolset.Util.wixext" Version="5.0.2" />
   </ItemGroup>
 
 </Project>

installer/Package.wxs

@@ -23,7 +23,7 @@
 
   <Package Name="Dragon-ISO"
            Manufacturer="Wild Dragon LLC"
-           Version="1.0.0.0"
+           Version="$(var.ProductVersion)"
            UpgradeCode="9F4A8B2C-1D3E-4A5B-9C6D-8E7F0A1B2C3D"
            Scope="perMachine"
            Compressed="yes"
@@ -224,5 +224,62 @@
       </Component>
     </ComponentGroup>
 
+    <!--
+        URL ACL reservation for the control surface (REST/WebSocket, default
+        port 9755). The server uses HttpListener (http.sys), and http.sys
+        denies prefix registration to non-elevated processes unless the URL
+        namespace is reserved — without this, the control surface fails with
+        "Access is denied (5)" on every standard-user launch and the operator
+        has to run the app elevated or run netsh by hand. The MSI already runs
+        elevated, so reserve the namespace here.
+
+        IMPORTANT — reserve ONLY the explicit loopback prefix, never
+        http://+:9755/. Verified empirically 2026-07-06: an idle strong-
+        wildcard RESERVATION poisons http.sys routing for the app's IP-bound
+        registration — every request 503s inside http.sys without ever
+        reaching the listener. The LAN-reachable mode (which binds
+        http://+:9755/) remains an opt-in that needs its own reservation;
+        the app logs the exact netsh command when that bind fails, and the
+        operator must delete that + reservation again if they revert to
+        loopback-only.
+
+        SDDL D:(A;;GX;;;WD) = allow GENERIC_EXECUTE (listen) to Everyone by
+        SID, which survives non-English locales where "Everyone" isn't a
+        valid account name. Operators who change the port in settings still
+        need the app's documented netsh one-liner for the new port.
+        Return="ignore": an already-existing reservation (repair/reinstall)
+        exits non-zero and must not fail the install.
+    -->
+    <SetProperty Id="AddControlSurfaceUrlAcl"
+                 Value="&quot;[System64Folder]netsh.exe&quot; http add urlacl url=http://127.0.0.1:9755/ sddl=D:(A;;GX;;;WD)"
+                 Sequence="execute"
+                 Before="AddControlSurfaceUrlAcl" />
+    <CustomAction Id="AddControlSurfaceUrlAcl"
+                  BinaryRef="Wix4UtilCA_X64"
+                  DllEntry="WixQuietExec64"
+                  Execute="deferred"
+                  Impersonate="no"
+                  Return="ignore" />
+
+    <SetProperty Id="RemoveControlSurfaceUrlAcl"
+                 Value="&quot;[System64Folder]netsh.exe&quot; http delete urlacl url=http://127.0.0.1:9755/"
+                 Sequence="execute"
+                 Before="RemoveControlSurfaceUrlAcl" />
+    <CustomAction Id="RemoveControlSurfaceUrlAcl"
+                  BinaryRef="Wix4UtilCA_X64"
+                  DllEntry="WixQuietExec64"
+                  Execute="deferred"
+                  Impersonate="no"
+                  Return="ignore" />
+
+    <InstallExecuteSequence>
+      <Custom Action="AddControlSurfaceUrlAcl"
+              After="InstallFiles"
+              Condition="NOT Installed OR REINSTALL" />
+      <Custom Action="RemoveControlSurfaceUrlAcl"
+              After="InstallInitialize"
+              Condition="REMOVE=&quot;ALL&quot;" />
+    </InstallExecuteSequence>
+
   </Package>
 </Wix>

src/Dragon-ISO.App/Services/ControlSurfaceServer.cs

@@ -97,11 +97,17 @@ public sealed partial class ControlSurfaceServer : IAsyncDisposable
     /// "headless show machine + thin client controller" setups. When false
     /// (default), binds to <c>127.0.0.1</c> only.
     ///
-    /// LAN binding requires either running Dragon-ISO as Administrator OR a
+    /// Binding requires either running Dragon-ISO as Administrator OR a
-    /// one-time URL ACL reservation at the OS level:
+    /// one-time URL ACL reservation at the OS level for the prefix actually
-    /// <code>netsh http add urlacl url=http://+:9755/ user=Everyone</code>
+    /// being bound (the installer reserves the loopback default,
-    /// If neither is in place the listener throws AccessDeniedException
+    /// <c>http://127.0.0.1:9755/</c>):
-    /// which we catch and surface as a logger warning.
+    /// <code>netsh http add urlacl url=http://127.0.0.1:9755/ sddl=D:(A;;GX;;;WD)</code>
+    /// or <c>url=http://+:9755/</c> for LAN mode. CAUTION: an idle
+    /// <c>http://+:port/</c> reservation makes http.sys 503 every request to
+    /// the loopback-bound listener — only add it while LAN mode is in use,
+    /// and delete it when reverting to loopback-only. If no reservation is
+    /// in place the listener throws AccessDeniedException which we catch and
+    /// surface as a logger warning.
     /// </summary>
     public void Start(int port, bool bindToLan = false)
     {
@@ -123,9 +129,11 @@ public sealed partial class ControlSurfaceServer : IAsyncDisposable
         {
             _logger?.LogWarning(ex,
                 "Could not start control surface on {Prefix}. " +
-                "If binding to LAN, run as Administrator once OR run: " +
+                "Run as Administrator once OR reserve the URL namespace: " +
-                "netsh http add urlacl url=http://+:{Port}/ user=Everyone",
+                "netsh http add urlacl url={UrlAclUrl} sddl=D:(A;;GX;;;WD) " +
-                prefix, port);
+                "(if switching back from LAN mode, also delete the stale " +
+                "http://+:{Port}/ reservation — while idle it 503s the loopback listener)",
+                prefix, prefix, port);
             _listener = null;
             return;
         }

src/Dragon-ISO.Engine.NdiInterop/NdiInteropPInvoke.cs

@@ -275,7 +275,7 @@ public sealed class NdiInteropPInvoke : INdiInterop, IDisposable
 
     // ---- Send ----
 
-    public NdiSenderHandle CreateSender(string outputName, string? groups = null)
+    public NdiSenderHandle CreateSender(string outputName, string? groups = null, int frameRateN = 60000, int frameRateD = 1001)
     {
         var trimmedGroups = NormalizeGroups(groups);
         var nameUtf8 = Marshal.StringToHGlobalAnsi(outputName);
@@ -297,7 +297,7 @@ public sealed class NdiInteropPInvoke : INdiInterop, IDisposable
                     $"NDIlib_send_create returned null for output '{outputName}' on groups '{trimmedGroups ?? "<default>"}'.");
             if (trimmedGroups is not null)
                 _logger.LogInformation("NDI sender '{Output}' created on groups: {Groups}", outputName, trimmedGroups);
-            return new NdiPInvokeSenderHandle(native, outputName);
+            return new NdiPInvokeSenderHandle(native, outputName, frameRateN, frameRateD);
         }
         finally
         {
@@ -310,6 +310,29 @@ public sealed class NdiInteropPInvoke : INdiInterop, IDisposable
     {
         var pInvokeSender = (NdiPInvokeSenderHandle)sender;
 
+        // Pin the managed buffer so the native call can read it directly.
+        var pixels = frame.Pixels.ToArray();
+        var handle = GCHandle.Alloc(pixels, GCHandleType.Pinned);
+        try
+        {
+            var nativeFrame = BuildVideoFrame(
+                frame, handle.AddrOfPinnedObject(),
+                pInvokeSender.FrameRateN, pInvokeSender.FrameRateD);
+            NdiNative.SendSendVideoV2(pInvokeSender.Native, ref nativeFrame);
+        }
+        finally
+        {
+            handle.Free();
+        }
+    }
+
+    /// <summary>
+    /// Pure assembly of the native frame descriptor — extracted so the stamping
+    /// (frame rate, stride, dimensions) is unit-testable without an NDI runtime.
+    /// </summary>
+    internal static NdiNative.VideoFrameV2 BuildVideoFrame(
+        ProcessedFrame frame, IntPtr data, int frameRateN, int frameRateD)
+    {
         var fourcc = frame.Format switch
         {
             PixelFormat.Bgra => NdiNative.FourCC.BGRA,
@@ -318,32 +341,21 @@ public sealed class NdiInteropPInvoke : INdiInterop, IDisposable
             _ => NdiNative.FourCC.BGRA
         };
 
-        // Pin the managed buffer so the native call can read it directly.
+        return new NdiNative.VideoFrameV2
-        var pixels = frame.Pixels.ToArray();
-        var handle = GCHandle.Alloc(pixels, GCHandleType.Pinned);
-        try
         {
-            var nativeFrame = new NdiNative.VideoFrameV2
+            xres = frame.Width,
-            {
+            yres = frame.Height,
-                xres = frame.Width,
+            FourCC = fourcc,
-                yres = frame.Height,
+            frame_rate_N = frameRateN,
-                FourCC = fourcc,
+            frame_rate_D = frameRateD,
-                frame_rate_N = 60000,
+            picture_aspect_ratio = 0.0f, // 0 = derive from xres/yres
-                frame_rate_D = 1001, // 59.94 default; controller-supplied later
+            frame_format_type = NdiNative.FrameFormatType.Progressive,
-                picture_aspect_ratio = 0.0f, // 0 = derive from xres/yres
+            timecode = NdiTimecodeSynthesize, // synthesize
-                frame_format_type = NdiNative.FrameFormatType.Progressive,
+            p_data = data,
-                timecode = NdiTimecodeSynthesize, // synthesize
+            line_stride_in_bytes = frame.Width * BytesPerPixel(frame.Format),
-                p_data = handle.AddrOfPinnedObject(),
+            p_metadata = IntPtr.Zero,
-                line_stride_in_bytes = frame.Width * BytesPerPixel(frame.Format),
+            timestamp = frame.TimestampTicks
-                p_metadata = IntPtr.Zero,
+        };
-                timestamp = frame.TimestampTicks
-            };
-            NdiNative.SendSendVideoV2(pInvokeSender.Native, ref nativeFrame);
-        }
-        finally
-        {
-            handle.Free();
-        }
     }
 
     private const long NdiTimecodeSynthesize = unchecked((long)0x8000000000000000UL); // NDIlib_send_timecode_synthesize

src/Dragon-ISO.Engine.NdiInterop/NdiPInvokeHandles.cs

@@ -44,10 +44,18 @@ internal sealed class NdiPInvokeSenderHandle : NdiSenderHandle
     public IntPtr Native { get; private set; }
     public string OutputName { get; }
 
-    public NdiPInvokeSenderHandle(IntPtr native, string outputName)
+    // The NDI SDK carries frame rate per-frame (VideoFrameV2.frame_rate_N/D),
+    // not on send_create, so the handle remembers the configured rational and
+    // SendFrame stamps it onto every outgoing frame.
+    public int FrameRateN { get; }
+    public int FrameRateD { get; }
+
+    public NdiPInvokeSenderHandle(IntPtr native, string outputName, int frameRateN = 60000, int frameRateD = 1001)
     {
         Native = native;
         OutputName = outputName;
+        FrameRateN = frameRateN;
+        FrameRateD = frameRateD;
     }
 
     public override void Dispose()

src/Dragon-ISO.Engine/Pipeline/IsoPipeline.cs

@@ -378,9 +378,10 @@ public sealed class IsoPipeline : IAsyncDisposable
 
         using var receiver = new NdiReceiver(
             interop, config.SourceName, rawWriter, loggerFactory.CreateLogger<NdiReceiver>());
+        var (frameRateN, frameRateD) = config.Settings.FrameRate;
         using var sender = new NdiSender(
             interop, config.OutputName, processedChannel.Reader, loggerFactory.CreateLogger<NdiSender>(),
-            config.OutputGroups);
+            config.OutputGroups, frameRateN, frameRateD);
 
         var processor = new FrameProcessor(
             config.Settings, scaler, new SolidFrameRenderer(),

src/tests/Dragon-ISO.Engine.Tests/Fakes/FakeNdiInterop.cs

@@ -23,6 +23,8 @@ public sealed class FakeNdiInterop : INdiInterop
     public string? LastFinderGroups { get; private set; }
     /// <summary>Per-output <c>groups</c> string seen by <see cref="CreateSender"/>; null = default Public.</summary>
     public Dictionary<string, string?> SenderGroups { get; } = new();
+    /// <summary>Per-output rational frame rate (N, D) seen by <see cref="CreateSender"/>.</summary>
+    public Dictionary<string, (int N, int D)> SenderFrameRates { get; } = new();
 
     /// <summary>
     /// Number of finders created so far (initial construction + every rebuild).
@@ -77,10 +79,11 @@ public sealed class FakeNdiInterop : INdiInterop
         return null; // no audio queued — simulate timeout
     }
 
-    public NdiSenderHandle CreateSender(string outputName, string? groups = null)
+    public NdiSenderHandle CreateSender(string outputName, string? groups = null, int frameRateN = 60000, int frameRateD = 1001)
     {
         SenderCreatedCount[outputName] = SenderCreatedCount.GetValueOrDefault(outputName) + 1;
         SenderGroups[outputName] = groups;
+        SenderFrameRates[outputName] = (frameRateN, frameRateD);
         SentFrames.GetOrAdd(outputName, _ => new List<ProcessedFrame>());
         return new FakeSenderHandle(outputName);
     }

src/tests/Dragon-ISO.Engine.Tests/Interop/NdiInteropSendFrameTests.cs

@@ -0,0 +1,63 @@
+using System.Runtime.Versioning;
+using DragonISO.Engine.NdiInterop;
+using DragonISO.Engine.Pipeline;
+
+namespace DragonISO.Engine.Tests.Interop;
+
+// NdiInteropPInvoke is [SupportedOSPlatform("windows")]; these tests exercise
+// pure helpers that never touch native code, but inherit the platform tag.
+// Same pattern as NdiInteropNormalizeGroupsTests.
+[SupportedOSPlatform("windows")]
+
+// NdiPInvokeSenderHandle and NdiInteropPInvoke.BuildVideoFrame are internal;
+// the engine tests project has access via InternalsVisibleTo.
+public class NdiInteropSendFrameTests
+{
+    private static ProcessedFrame MakeFrame(int width, int height, PixelFormat format) =>
+        new(width, height, 42, new byte[width * height * 4], format);
+
+    [Fact]
+    public void SenderHandle_CarriesFrameRate()
+    {
+        // CreateSender stashes the configured rational on the handle so SendFrame
+        // can stamp every outgoing video frame without re-plumbing the settings.
+        var handle = new NdiPInvokeSenderHandle(IntPtr.Zero, "Dragon-ISO_01", 30000, 1001);
+
+        handle.FrameRateN.Should().Be(30000);
+        handle.FrameRateD.Should().Be(1001);
+    }
+
+    [Fact]
+    public void BuildVideoFrame_StampsConfiguredFrameRate()
+    {
+        var frame = MakeFrame(1280, 720, PixelFormat.Bgra);
+
+        var native = NdiInteropPInvoke.BuildVideoFrame(frame, IntPtr.Zero, 24000, 1001);
+
+        native.frame_rate_N.Should().Be(24000,
+            because: "advertising the wrong rational causes drift and A/V desync downstream");
+        native.frame_rate_D.Should().Be(1001);
+    }
+
+    [Fact]
+    public void BuildVideoFrame_PreservesDimensionsAndStride()
+    {
+        var frame = MakeFrame(1920, 1080, PixelFormat.Bgra);
+
+        var native = NdiInteropPInvoke.BuildVideoFrame(frame, IntPtr.Zero, 60000, 1001);
+
+        native.xres.Should().Be(1920);
+        native.yres.Should().Be(1080);
+        native.line_stride_in_bytes.Should().Be(1920 * 4, because: "BGRA is 4 bytes per pixel");
+    }
+
+    [Fact]
+    public void BuildVideoFrame_MapsUyvyStride()
+    {
+        var frame = MakeFrame(1280, 720, PixelFormat.Uyvy);
+
+        var native = NdiInteropPInvoke.BuildVideoFrame(frame, IntPtr.Zero, 60000, 1001);
+
+        native.line_stride_in_bytes.Should().Be(1280 * 2, because: "UYVY is 2 bytes per pixel");
+    }
+}

src/tests/Dragon-ISO.Engine.Tests/Pipeline/IsoPipelineTests.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.Logging.Abstractions;
 using DragonISO.Engine.Domain;
 using DragonISO.Engine.Pipeline;
+using DragonISO.Engine.Tests.Fakes;
 
 namespace DragonISO.Engine.Tests.Pipeline;
 
@@ -76,6 +77,32 @@ public class IsoPipelineTests
         await pipeline.StopAsync();
     }
 
+    [Fact]
+    public async Task ProductionCtor_PassesConfiguredFrameRate_ToSender()
+    {
+        // The operator configures 29.97 in settings; the NDI sender for every ISO
+        // output must be created with that exact rational (30000/1001), not the
+        // hardwired 59.94 default.
+        var interop = new FakeNdiInterop();
+        var config = new IsoPipelineConfig(
+            Guid.NewGuid(),
+            "Teams - Alice",
+            "Alice-ISO",
+            FrameProcessingSettings.Default with { Framerate = TargetFramerate.Fps29_97 });
+        var pipeline = new IsoPipeline(
+            config, interop, new ManagedNearestNeighborFrameScaler(), new FakeFrameClock(),
+            FastBackoff(), NoDelay(), NullLoggerFactory.Instance);
+
+        await pipeline.StartAsync();
+        var deadline = DateTime.UtcNow.AddSeconds(2);
+        while (!interop.SenderFrameRates.ContainsKey("Alice-ISO") && DateTime.UtcNow < deadline)
+            await Task.Delay(10);
+        await pipeline.StopAsync();
+
+        interop.SenderFrameRates.Should().ContainKey("Alice-ISO");
+        interop.SenderFrameRates["Alice-ISO"].Should().Be((30000, 1001));
+    }
+
     [Fact]
     public async Task Supervisor_FailsRepeatedly_TransitionsToError()
     {

src/tests/Dragon-ISO.Engine.Tests/Pipeline/NdiSenderTests.cs

@@ -12,6 +12,21 @@ public class NdiSenderTests
     private static ProcessedFrame MakeFrame(long ts) =>
         new(1920, 1080, ts, new byte[1920 * 1080 * 4], PixelFormat.Bgra);
 
+    [Fact]
+    public void Ctor_ForwardsFrameRate_ToCreateSender()
+    {
+        var interop = new FakeNdiInterop();
+        var input = Channel.CreateUnbounded<ProcessedFrame>();
+
+        using var sender = new NdiSender(
+            interop, Output, input.Reader, NullLogger<NdiSender>.Instance,
+            outputGroups: null, frameRateN: 30000, frameRateD: 1001);
+
+        interop.SenderFrameRates[Output].Should().Be((30000, 1001),
+            because: "the sender must hand the configured rational frame rate to the interop " +
+                     "so the NDI stream advertises 29.97 rather than the 59.94 default");
+    }
+
     [Fact]
     public async Task SendNextAsync_FrameAvailable_ForwardsToInterop()
     {