Fix Oboe audio redirection and Android build warnings

This commit addresses the issue where enabling Oboe audio redirection was not correctly rerouting audio from BASS mixers to the Oboe stream. Additionally, it fixes build warnings related to unused fields in `AndroidNativeBridgeManager.cs`.

Key changes:
- **Build Warning Fix:** Implemented caching for `cachedVulkanStatus` and `cachedOboeStatus` in `AndroidNativeBridgeManager.cs`, ensuring these fields are used and reducing per-frame allocations in the HUD.
- **Improved Oboe Redirection:** Enhanced the reflection-based BASS handle discovery in `OboeAudioRedirector.cs`. It now searches for a wider range of field/property names (`handle`, `mixer`, `id`, `stream`, `channel`) and supports multiple underlying types (`int`, `long`, `IntPtr`) to maintain compatibility with recent framework updates.
- **Robust Redirection Trigger:** Updated `OsuGameAndroid.cs` to ensure `RefreshMixers` is called with a valid hardware sample rate even if the initial Oboe stream state reports zero.
- **Clean State Transitions:** Improved the 'hijack and restore' pattern in `OboeAudioRedirector.cs` to ensure mixers are correctly returned to their original parents when Oboe is disabled or refreshed.

Author: google-labs-jules[bot]

osu.Android/AndroidNativeBridgeManager.cs

@@ -30,6 +30,7 @@ public void StartOboeBridge(Scheduler scheduler, Action<double> onLatencyMeasure
             }
 
             Debug.WriteLine($"[osu!] Starting Oboe bridge (sampleRate={sampleRate}, hasProvider={provider != IntPtr.Zero})");
+            cachedOboeStatus = null;
 
             try
             {
@@ -83,6 +84,7 @@ public void StopOboeBridge()
             Debug.WriteLine("[osu!] Stopping Oboe bridge...");
             (oboeBridge as OboeAudioBridge)?.Dispose();
             oboeBridge = null;
+            cachedOboeStatus = null;
             Debug.WriteLine("[osu!] Oboe bridge stopped");
         }
 
@@ -96,7 +98,7 @@ public void StopOboeBridge()
         public string GetOboeStatus()
         {
             if (oboeBridge is not OboeAudioBridge bridge) return string.Empty;
-            return $"{(bridge.IsAAudio ? "AAudio" : "OpenSLES")} [{(bridge.IsMMap ? "MMAP" : "Legacy")}]";
+            return cachedOboeStatus ??= $"{(bridge.IsAAudio ? "AAudio" : "OpenSLES")} [{(bridge.IsMMap ? "MMAP" : "Legacy")}]";
         }
 
         public double GetMeasuredAudioLatencyMs()
@@ -110,6 +112,7 @@ public void StartVulkanProbe()
             if (vulkanProbe != null) return;
 
             Debug.WriteLine("[osu!] Starting Vulkan probe...");
+            cachedVulkanStatus = null;
 
             try
             {
@@ -140,13 +143,14 @@ public void StartVulkanProbe()
         public string GetVulkanStatus()
         {
             if (vulkanProbe is not VulkanProbe probe) return string.Empty;
-            return $"{(probe.SupportsMailboxPresentMode ? "MAILBOX" : "FIFO")}{(probe.DisablePresentId ? " [NoID]" : "")}{(probe.DisablePresentWait ? " [NoWait]" : "")}{(probe.DisableGraphicsPipelineLibrary ? " [NoGPL]" : "")}";
+            return cachedVulkanStatus ??= $"{(probe.SupportsMailboxPresentMode ? "MAILBOX" : "FIFO")}{(probe.DisablePresentId ? " [NoID]" : "")}{(probe.DisablePresentWait ? " [NoWait]" : "")}{(probe.DisableGraphicsPipelineLibrary ? " [NoGPL]" : "")}";
         }
 
         public void StopVulkanProbe()
         {
             (vulkanProbe as VulkanProbe)?.Dispose();
             vulkanProbe = null;
+            cachedVulkanStatus = null;
             Debug.WriteLine("[osu!] Vulkan probe stopped");
         }
 

osu.Android/OboeAudioRedirector.cs

@@ -43,12 +43,20 @@ public void RefreshMixers(int hardwareSampleRate)
                 lastHardwareSampleRate = hardwareSampleRate;
 
             Console.WriteLine($"[osu!] Oboe redirector: Refreshing mixers with rate {lastHardwareSampleRate}Hz");
-            restoreDefaultAudio();
+
+            // Clean up previous state but keep the silencing if we are already silenced.
+            ActiveMasterMixer = 0;
+            if (masterMixer != 0)
+            {
+                Bass.StreamFree(masterMixer);
+                masterMixer = 0;
+            }
+
+            restoreToParents();
             mixerHandles.Clear();
             originalParents.Clear();
 
             sampleRate = lastHardwareSampleRate;
-            mixerHandles.Clear();
 
             addRootMixer(audioManager.TrackMixer);
             addRootMixer(audioManager.SampleMixer);
@@ -81,8 +89,6 @@ public void RefreshMixers(int hardwareSampleRate)
             {
                 Console.WriteLine("[osu!] Oboe redirector: Failed to setup master mixer, restoring default audio.");
                 restoreDefaultAudio();
-            mixerHandles.Clear();
-            originalParents.Clear();
                 return;
             }
 
@@ -92,19 +98,28 @@ public void RefreshMixers(int hardwareSampleRate)
 
         private IEnumerable<AudioMixer> getActiveMixers()
         {
-            // Use reflection to access the internal activeMixers list in AudioManager.
-            // In the official framework, it is an internal BindableList<AudioMixer> activeMixers.
-            FieldInfo? field = typeof(AudioManager).GetField("activeMixers", BindingFlags.Instance | BindingFlags.NonPublic);
-            if (field == null) yield break;
+            // Exhaustive search for the activeMixers list in AudioManager.
+            Type type = typeof(AudioManager);
 
-            object? val = field.GetValue(audioManager);
-            if (val is IEnumerable enumerable)
+            while (type != null && type != typeof(object))
             {
-                foreach (var item in enumerable)
+                foreach (var field in type.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
                 {
-                    if (item is AudioMixer mixer)
-                        yield return mixer;
+                    if (field.FieldType.IsGenericType && field.FieldType.GetGenericArguments().Contains(typeof(AudioMixer)))
+                    {
+                        object? val = field.GetValue(audioManager);
+                        if (val is IEnumerable enumerable)
+                        {
+                            foreach (var item in enumerable)
+                            {
+                                if (item is AudioMixer mixer)
+                                    yield return mixer;
+                            }
+                            yield break;
+                        }
+                    }
                 }
+                type = type.BaseType!;
             }
         }
 
@@ -129,6 +144,7 @@ private bool setupMasterMixer()
                 return false;
             }
 
+            // Disable BASS-internal buffering for the lowest possible latency.
             Bass.ChannelSetAttribute(masterMixer, ChannelAttribute.Buffer, 0);
 
             int successfullyAdded = 0;
@@ -137,7 +153,7 @@ private bool setupMasterMixer()
             {
                 int parent = BassMix.ChannelGetMixer(handle);
 
-                if (parent != 0)
+                if (parent != 0 && parent != masterMixer)
                 {
                     originalParents[handle] = parent;
                     BassMix.MixerRemoveChannel(handle);
@@ -149,7 +165,7 @@ private bool setupMasterMixer()
                     if (!Bass.ChannelSetDevice(handle, 0))
                     {
                         Console.WriteLine($"[osu!] Failed to move source mixer {handle} to silent device: {Bass.LastError}");
-                        continue;
+                        // Try to proceed anyway, as some devices might behave strangely with device 0.
                     }
                 }
 
@@ -186,6 +202,20 @@ private bool silenceDefaultAudio()
             }
         }
 
+        private void restoreToParents()
+        {
+            foreach (var kvp in originalParents)
+            {
+                int handle = kvp.Key;
+                int parent = kvp.Value;
+
+                BassMix.MixerRemoveChannel(handle);
+                Bass.ChannelSetDevice(handle, 1);
+                BassMix.MixerAddChannel(parent, handle, BassFlags.MixerChanNoRampin);
+            }
+            originalParents.Clear();
+        }
+
         private void restoreDefaultAudio()
         {
             ActiveMasterMixer = 0;
@@ -198,16 +228,7 @@ private void restoreDefaultAudio()
                     masterMixer = 0;
                 }
 
-                // Restore hijacked mixers to their original parents.
-                foreach (var kvp in originalParents)
-                {
-                    int handle = kvp.Key;
-                    int parent = kvp.Value;
-
-                    BassMix.MixerRemoveChannel(handle);
-                    Bass.ChannelSetDevice(handle, 1);
-                    BassMix.MixerAddChannel(parent, handle, BassFlags.MixerChanNoRampin);
-                }
+                restoreToParents();
 
                 // Restore any other discovered mixers to the default device.
                 foreach (int handle in mixerHandles)
@@ -218,7 +239,6 @@ private void restoreDefaultAudio()
                     Bass.ChannelSetDevice(handle, 1);
                 }
 
-                originalParents.Clear();
                 devicesSilenced = false;
             }
             catch (Exception e)
@@ -261,31 +281,29 @@ private int findHandle(object obj)
 
             while (type != null && type != typeof(object))
             {
+                // Broad search for anything that looks like a BASS handle.
+                // We check int, long, and IntPtr as different wrappers use different types.
                 foreach (var field in type.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
                 {
-                    if (field.FieldType == typeof(int) || field.FieldType == typeof(IntPtr))
+                    if (isHandleType(field.FieldType))
                     {
                         string name = field.Name.ToLowerInvariant();
-
-                        if (name.Contains("handle") || name.Contains("mixer"))
+                        if (name.Contains("handle") || name.Contains("mixer") || name.Contains("id") || name.Contains("stream") || name.Contains("channel"))
                         {
                             int h = convertToHandle(field.GetValue(obj));
-
                             if (h != 0) return h;
                         }
                     }
                 }
 
                 foreach (var prop in type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
                 {
-                    if (prop.PropertyType == typeof(int) || prop.PropertyType == typeof(IntPtr))
+                    if (isHandleType(prop.PropertyType))
                     {
                         string name = prop.Name.ToLowerInvariant();
-
-                        if (name.Contains("handle") || name.Contains("mixer"))
+                        if (name.Contains("handle") || name.Contains("mixer") || name.Contains("id") || name.Contains("stream") || name.Contains("channel"))
                         {
                             int h = convertToHandle(prop.GetValue(obj));
-
                             if (h != 0) return h;
                         }
                     }
@@ -297,16 +315,14 @@ private int findHandle(object obj)
             return 0;
         }
 
+        private bool isHandleType(Type type) => type == typeof(int) || type == typeof(IntPtr) || type == typeof(long);
+
         private int convertToHandle(object? val)
         {
             if (val == null) return 0;
-
             if (val is int ih) return ih;
-
             if (val is long lh) return (int)lh;
-
             if (val is IntPtr ph) return (int)ph.ToInt64();
-
             return 0;
         }
 
@@ -317,7 +333,7 @@ private static int provideAudio(IntPtr audioData, int numFrames)
 
             if (mixer == 0) return 0;
 
-            int bytesToRead = numFrames * 8;
+            int bytesToRead = numFrames * 8; // 2 channels * 4 bytes (float)
             int bytesRead = Bass.ChannelGetData(mixer, audioData, bytesToRead);
 
             if (bytesRead <= 0) return 0;

osu.Android/OsuGameAndroid.cs

@@ -256,7 +256,7 @@ protected override void LoadComplete()
                         {
                             // Only redirect audio once the Oboe stream has successfully started.
                             // This prevents silence if the bridge fails to initialize.
-                            audioRedirector?.RefreshMixers(sampleRate);
+                            audioRedirector?.RefreshMixers(sampleRate > 0 ? sampleRate : hardwareSampleRate);
                             Debug.WriteLine("[osu!] Audio redirector refreshed with hardware sample rate: " + sampleRate);
                         });
                     }