Mixer engine: output routing, full state restore, MIDI learn API, PipeWire multi-channel support

src/AlsaDriver.cpp

@@ -411,6 +411,16 @@ namespace pipedal
             return this->sampleRate;
         }
 
+        virtual uint32_t GetDeviceCaptureChannels() const override
+        {
+            return (uint32_t)this->captureChannels;
+        }
+
+        virtual uint32_t GetDevicePlaybackChannels() const override
+        {
+            return (uint32_t)this->playbackChannels;
+        }
+
         JackServerSettings jackServerSettings;
 
         std::string alsa_device_name;

src/AudioDriver.hpp

@@ -57,6 +57,12 @@ namespace pipedal {
 
         virtual uint32_t GetSampleRate() = 0;
 
+        /// Get the number of capture (input) channels the device actually provides.
+        virtual uint32_t GetDeviceCaptureChannels() const = 0;
+
+        /// Get the number of playback (output) channels the device actually provides.
+        virtual uint32_t GetDevicePlaybackChannels() const = 0;
+
         virtual size_t GetMidiInputEventCount() = 0;
         virtual MidiEvent*GetMidiEvents() = 0;
 

src/AudioHost.cpp

@@ -1501,6 +1501,25 @@ public:
     {
         return this->sampleRate;
     }
+
+    virtual uint32_t GetDeviceCaptureChannels() override
+    {
+        if (this->audioDriver)
+        {
+            return this->audioDriver->GetDeviceCaptureChannels();
+        }
+        return 2;
+    }
+
+    virtual uint32_t GetDevicePlaybackChannels() override
+    {
+        if (this->audioDriver)
+        {
+            return this->audioDriver->GetDevicePlaybackChannels();
+        }
+        return 2;
+    }
+
     void HandleAlsaSequencerDevicesChanged(
         AlsaSequencerDeviceMonitor::MonitorAction action, int client, const std::string &clientName)
     {

src/AudioHost.hpp

@@ -237,6 +237,12 @@ namespace pipedal
         virtual void SetAlsaSequencerConfiguration(const AlsaSequencerConfiguration &alsaSequencerConfiguration) = 0;
         virtual uint32_t GetSampleRate() = 0;
 
+        /// Get the number of capture (input) channels the audio device provides.
+        virtual uint32_t GetDeviceCaptureChannels() = 0;
+
+        /// Get the number of playback (output) channels the audio device provides.
+        virtual uint32_t GetDevicePlaybackChannels() = 0;
+
         virtual JackConfiguration GetServerConfiguration() = 0;
 
         virtual void SetPedalboard(const std::shared_ptr<Lv2Pedalboard> &pedalboard) = 0;

src/DummyAudioDriver.cpp

@@ -136,6 +136,16 @@ namespace pipedal
             return this->sampleRate;
         }
 
+        virtual uint32_t GetDeviceCaptureChannels() const override
+        {
+            return (uint32_t)deviceCaptureBuffers.size();
+        }
+
+        virtual uint32_t GetDevicePlaybackChannels() const override
+        {
+            return (uint32_t)devicePlaybackBuffers.size();
+        }
+
         JackServerSettings jackServerSettings;
         AlsaSequencer::ptr alsaSequencer;
 

src/MixerApi.cpp

@@ -330,6 +330,22 @@ std::string MixerApi::getStateJson() const
     }
     writer.write_raw("]");
 
+    // Output routing
+    writer.write_member("outputRoutes", "");
+    writer.write_raw("[");
+    first = true;
+    for (const auto& route : mixerEngine_->outputRoutes()) {
+        if (!first) writer.write_raw(",");
+        first = false;
+        writer.start_object();
+        writer.write_member("sourceBusId", route.sourceBusId);
+        writer.write_member("sourceStartChannel", (int64_t)route.sourceStartChannel);
+        writer.write_member("targetStartChannel", (int64_t)route.targetStartChannel);
+        writer.write_member("channels", (int64_t)route.channels);
+        writer.end_object();
+    }
+    writer.write_raw("]");
+
     writer.end_object();
     return ss.str();
 }
@@ -665,3 +681,64 @@ void MixerApi::loadMidiMappingsFromFile()
     if (!mixerEngine_) return;
     mixerEngine_->midiMapper().loadFromFile();
 }
+
+// ---------------------------------------------------------------------------
+// Output Routing
+// ---------------------------------------------------------------------------
+
+std::string MixerApi::getOutputRoutesJson() const
+{
+    if (!mixerEngine_) return "[]";
+
+    const auto& routes = mixerEngine_->outputRoutes();
+
+    std::stringstream ss;
+    json_writer writer(ss, false);
+    writer.write_raw("[");
+    bool first = true;
+    for (const auto& route : routes) {
+        if (!first) writer.write_raw(",");
+        first = false;
+        writer.start_object();
+        writer.write_member("sourceBusId", route.sourceBusId);
+        writer.write_member("sourceStartChannel", (int64_t)route.sourceStartChannel);
+        writer.write_member("targetStartChannel", (int64_t)route.targetStartChannel);
+        writer.write_member("channels", (int64_t)route.channels);
+        writer.end_object();
+    }
+    writer.write_raw("]");
+    return ss.str();
+}
+
+void MixerApi::setOutputRoutesFromJson(const std::string& json)
+{
+    if (!mixerEngine_) return;
+
+    std::vector<MixerEngine::MixerOutputRoute> routes;
+
+    std::istringstream ss(json);
+    json_reader reader(ss);
+    reader.consume('[');
+    while (reader.peek() != ']')
+    {
+        MixerEngine::MixerOutputRoute route{};
+        reader.start_object();
+        while (reader.peek() != '}')
+        {
+            std::string key = reader.read_string();
+            reader.consume(':');
+            if (key == "sourceBusId") reader.read(&route.sourceBusId);
+            else if (key == "sourceStartChannel") { int64_t v; reader.read(&v); route.sourceStartChannel = (int)v; }
+            else if (key == "targetStartChannel") { int64_t v; reader.read(&v); route.targetStartChannel = (int)v; }
+            else if (key == "channels") { int64_t v; reader.read(&v); route.channels = (int)v; }
+            else reader.skip_property();
+            if (reader.peek() == ',') reader.consume(',');
+        }
+        reader.end_object();
+        routes.push_back(route);
+        if (reader.peek() == ',') reader.consume(',');
+    }
+    reader.consume(']');
+
+    mixerEngine_->setOutputRoutes(routes);
+}

src/MixerApi.hpp

@@ -87,6 +87,17 @@ public:
     /// Get the full mixer state as a JSON string
     std::string getStateJson() const;
 
+    /// --- Output Routing ---
+
+    /// Get output routes as a JSON array string
+    std::string getOutputRoutesJson() const;
+
+    /// Set output routes from a JSON array string
+    void setOutputRoutesFromJson(const std::string& json);
+
+    /// Apply a full mixer state from a JSON string
+    void setFullState(const std::string& stateJson);
+
     /// --- Scenes ---
 
     /// Save current mixer state as a scene
@@ -101,6 +112,52 @@ public:
     /// Delete a scene
     bool deleteScene(const std::string& sceneId);
 
+    /// --- MIDI Control Surface Mapping ---
+
+    /// Get all MIDI mappings as JSON
+    std::string getMidiMappingsJson() const;
+
+    /// Set all MIDI mappings from JSON
+    void setMidiMappingsFromJson(const std::string& json);
+
+    /// Add a single MIDI mapping
+    void addMidiMapping(int midiChannel, int ccNumber,
+                         const std::string& targetType, int64_t targetId,
+                         float minValue, float maxValue);
+
+    /// Remove MIDI mapping by CC and channel
+    void removeMidiMapping(int midiChannel, int ccNumber);
+
+    /// Remove MIDI mapping by index
+    void removeMidiMappingByIndex(size_t index);
+
+    /// Clear all MIDI mappings
+    void clearMidiMappings();
+
+    /// Toggle MIDI learn mode
+    void setMidiLearnMode(bool enabled);
+    bool getMidiLearnMode() const;
+
+    /// Set the pending learn target (which UI control was touched)
+    void setMidiLearnTarget(const std::string& targetType, int64_t targetId);
+
+    /// Commit a learned mapping (captured CC + pending target)
+    bool commitMidiLearnMapping();
+
+    /// Get last learned CC event info (for UI feedback)
+    struct LearnedEventInfo {
+        bool hasEvent = false;
+        int midiChannel = -1;
+        int ccNumber = -1;
+    };
+    LearnedEventInfo getLastLearnedMidiEvent() const;
+
+    /// Save MIDI mappings to config file
+    void saveMidiMappingsToFile() const;
+
+    /// Load MIDI mappings from config file
+    void loadMidiMappingsFromFile();
+
 private:
     MixerEngine* mixerEngine_ = nullptr;
 };

src/MixerEngine.cpp

@@ -7,6 +7,7 @@
 #include "MixerBus.hpp"
 #include "Lv2Pedalboard.hpp"
 #include "IHost.hpp"
+#include "MidiEvent.hpp"
 #include <algorithm>
 #include <cmath>
 
@@ -374,17 +375,31 @@ void MixerEngine::process(
 
     // Step 2: Process each channel
     size_t numChannels = channels_.size();
+
+    // Determine channel pairing mode:
+    // For 1-2 total input channels: stereo pairing per strip (backward compatible)
+    // For 3+ input channels: each strip is mono (one input channel → stereo output with pan)
+    bool stereoPairing = (inputChannels <= 2);
+
     for (size_t ch = 0; ch < numChannels; ++ch) {
         auto* channel = channels_[ch].get();
 
         // Build input buffer pointers for this channel
-        // Channel ch reads from device input ch (if available)
         float* channelInputs[2] = { nullptr, nullptr };
+        if (stereoPairing) {
+            // Stereo pairing: channel 0 ← inputs[0,1], channel 1 ← inputs[2,3], etc.
+            uint32_t baseInput = (uint32_t)(ch * 2);
+            if (baseInput < inputChannels) {
+                channelInputs[0] = deviceInputs[baseInput];
+                if (baseInput + 1 < inputChannels) {
+                    channelInputs[1] = deviceInputs[baseInput + 1];
+                }
+            }
+        } else {
+            // Mono per strip: each channel gets exactly one input
             if (ch < inputChannels) {
-            channelInputs[0] = deviceInputs[ch]; // mono input
+                channelInputs[0] = deviceInputs[ch];
-            // For stereo, pair consecutive channels: (0,1), (2,3), etc.
+                // Second input stays nullptr → mono processing
-            if (ch + 1 < inputChannels) {
-                channelInputs[1] = deviceInputs[ch + 1];
             }
         }
 
@@ -395,10 +410,15 @@ void MixerEngine::process(
             channelOutputs[1] = channelOutputBuffers_[ch].data() + maxBufferSize_;
         }
 
+        // Determine the actual number of input channels for this strip
+        size_t stripInputChannels = 0;
+        if (channelInputs[0] != nullptr) stripInputChannels = 1;
+        if (channelInputs[1] != nullptr) stripInputChannels = 2;
+
         // Process the channel strip
         channel->process(
             (const float* const*)channelInputs,
-            std::min((size_t)2, (size_t)inputChannels),
+            stripInputChannels,
             channelOutputs,
             2,
             frames
@@ -416,7 +436,9 @@ void MixerEngine::process(
         bus->process(frames);
     }
 
-    // Step 5: Write master bus to device outputs
+    // Step 5: Write buses to physical outputs according to output routing
+    if (outputRoutes_.empty()) {
+        // Legacy fallback: write master bus to device outputs 1:1
         if (masterBus_) {
             for (uint32_t outCh = 0; outCh < outputChannels; ++outCh) {
                 if (deviceOutputs[outCh] == nullptr) continue;
@@ -425,7 +447,6 @@ void MixerEngine::process(
                 if (src) {
                     std::copy(src, src + frames, deviceOutputs[outCh]);
                 } else if (outCh == 1) {
-                // Mono to stereo: copy L to R if R bus channel doesn't exist
                     const float* srcL = masterBus_->buffer(0);
                     if (srcL) {
                         std::copy(srcL, srcL + frames, deviceOutputs[outCh]);
@@ -433,6 +454,32 @@ void MixerEngine::process(
                 }
             }
         }
+    } else {
+        // Use configured output routes
+        for (const auto& route : outputRoutes_) {
+            MixerBus* sourceBus = getBus(route.sourceBusId);
+            if (!sourceBus) continue;
+
+            for (int ch = 0; ch < route.channels; ++ch) {
+                uint32_t targetCh = (uint32_t)(route.targetStartChannel + ch);
+                if (targetCh >= outputChannels) break;
+                if (deviceOutputs[targetCh] == nullptr) continue;
+
+                const float* src = sourceBus->buffer(route.sourceStartChannel + ch);
+                if (src) {
+                    std::copy(src, src + frames, deviceOutputs[targetCh]);
+                }
+            }
+        }
+    }
+}
+
+// --- MIDI Control Surface Mapping ---
+
+bool MixerEngine::processMidiEvent(const MidiEvent& event)
+{
+    midiMapper_.setMixerEngine(this);
+    return midiMapper_.processEvent(event);
 }
 
 // --- State Serialization ---
@@ -474,6 +521,94 @@ MixerEngine::MixerSnapshot MixerEngine::captureSnapshot() const
     return snap;
 }
 
+// --- Output Routing ---
+
+void MixerEngine::setOutputRoutes(const std::vector<MixerOutputRoute>& routes)
+{
+    outputRoutes_ = routes;
+}
+
+void MixerEngine::addOutputRoute(int64_t busId, int sourceStartChannel, int targetStartChannel, int channels)
+{
+    // Remove any existing route that conflicts with the target
+    outputRoutes_.erase(
+        std::remove_if(outputRoutes_.begin(), outputRoutes_.end(),
+            [busId, targetStartChannel](const MixerOutputRoute& r) {
+                return r.sourceBusId == busId &&
+                       r.targetStartChannel == targetStartChannel;
+            }),
+        outputRoutes_.end()
+    );
+
+    MixerOutputRoute route;
+    route.sourceBusId = busId;
+    route.sourceStartChannel = sourceStartChannel;
+    route.targetStartChannel = targetStartChannel;
+    route.channels = channels;
+    outputRoutes_.push_back(route);
+}
+
+void MixerEngine::removeOutputRoutes(int64_t busId)
+{
+    outputRoutes_.erase(
+        std::remove_if(outputRoutes_.begin(), outputRoutes_.end(),
+            [busId](const MixerOutputRoute& r) { return r.sourceBusId == busId; }),
+        outputRoutes_.end()
+    );
+}
+
+std::vector<MixerEngine::MixerOutputRoute> MixerEngine::findOutputRoutesForBus(int64_t busId) const
+{
+    std::vector<MixerOutputRoute> result;
+    for (const auto& route : outputRoutes_) {
+        if (route.sourceBusId == busId) {
+            result.push_back(route);
+        }
+    }
+    return result;
+}
+
+// --- Auto channel creation ---
+
+void MixerEngine::autoCreateChannels(uint32_t inputChannelCount)
+{
+    // Remove existing channels if any
+    for (int i = (int)channels_.size() - 1; i >= 0; --i) {
+        removeChannel(i);
+    }
+
+    // Create one channel strip per input
+    for (uint32_t i = 0; i < inputChannelCount; ++i) {
+        addChannel((int)i);
+        auto* ch = getChannel((int)i);
+        if (ch) {
+            char label[32];
+            snprintf(label, sizeof(label), "Input %u", i + 1);
+            ch->setLabel(label);
+        }
+    }
+
+    // Set default output routes:
+    // For 1-2 channels: master bus → physical 1-2 (backward compatible)
+    // For 3+ channels: master bus → physical 1-2, then pair remaining channels
+    //   in groups of 2 to physical 3-4, 5-6, etc.
+    outputRoutes_.clear();
+
+    if (!masterBus_) return;
+
+    // Always route master bus to physical 1-2
+    MixerOutputRoute masterRoute;
+    masterRoute.sourceBusId = masterBus_->id();
+    masterRoute.sourceStartChannel = 0;
+    masterRoute.targetStartChannel = 0;
+    masterRoute.channels = 2;
+    outputRoutes_.push_back(masterRoute);
+
+    // If more than 2 channels, don't auto-create additional output routes.
+    // The user should configure them via the output routing UI.
+    // (Aux buses, subgroups, etc. are not auto-routed)
+}
+
 void MixerEngine::applySnapshot(const MixerSnapshot& snapshot)
 {
     // Apply channel states

src/MixerEngine.hpp

@@ -11,6 +11,7 @@
 #include <functional>
 #include "MixerChannelStrip.hpp"
 #include "MixerBus.hpp"
+#include "MidiMapper.hpp"
 
 namespace pipedal {
 
@@ -70,6 +71,11 @@ public:
     /// Returns a pointer to the new channel (valid until removed).
     MixerChannelStrip* addChannel(int physicalInputIndex);
 
+    /// Auto-create channels based on the number of detected input channels.
+    /// Removes existing channels and creates one strip per input.
+    /// Also sets up default output routes.
+    void autoCreateChannels(uint32_t inputChannelCount);
+
     /// Remove a channel by its channel index.
     void removeChannel(int channelIndex);
 
@@ -113,6 +119,32 @@ public:
     /// Clear all routes.
     void clearRoutes();
 
+    /// --- Output Routing ---
+
+    /// Describes a mapping from a mixer bus to physical output channels.
+    /// Multiple routes can be active simultaneously (e.g. Master→1-2, Aux1→3-4).
+    struct MixerOutputRoute {
+        int64_t sourceBusId;      // Bus to route from
+        int sourceStartChannel;   // Starting channel on the bus (0=L, 1=R)
+        int targetStartChannel;   // Starting physical output channel
+        int channels;             // Number of consecutive channels to route (1 or 2 typically)
+    };
+
+    /// Get the current output routing table (bus → physical output channel mapping).
+    const std::vector<MixerOutputRoute>& outputRoutes() const { return outputRoutes_; }
+
+    /// Set the entire output routing table.
+    void setOutputRoutes(const std::vector<MixerOutputRoute>& routes);
+
+    /// Add a single output route.
+    void addOutputRoute(int64_t busId, int sourceStartChannel, int targetStartChannel, int channels);
+
+    /// Remove all output routes for a given bus.
+    void removeOutputRoutes(int64_t busId);
+
+    /// Get all routes for a given bus.
+    std::vector<MixerOutputRoute> findOutputRoutesForBus(int64_t busId) const;
+
     /// Get all current routes.
     const std::vector<MixerRouteEntry>& routes() const { return routes_; }
 
@@ -143,6 +175,16 @@ public:
     /// True if any channel has solo engaged.
     bool anySoloActive() const;
 
+    /// --- MIDI Control Surface Mapping ---
+
+    /// Access the MIDI mapper for CC control surface mapping.
+    MidiMapper& midiMapper() { return midiMapper_; }
+    const MidiMapper& midiMapper() const { return midiMapper_; }
+
+    /// Process a MIDI event (typically from the real-time audio thread).
+    /// Routes CC messages to the midi mapper. Returns true if consumed.
+    bool processMidiEvent(const struct MidiEvent& event);
+
     /// --- State Serialization ---
 
     struct MixerSnapshot {
@@ -181,6 +223,9 @@ private:
     // Routing entries
     std::vector<MixerRouteEntry> routes_;
 
+    // Output routing entries (bus → physical output channel mapping)
+    std::vector<MixerOutputRoute> outputRoutes_;
+
     // Audio configuration
     uint32_t sampleRate_ = 48000;
     size_t maxBufferSize_ = 512;
@@ -188,6 +233,9 @@ private:
     // IHost reference for FX preparation
     IHost* pHost_ = nullptr;
 
+    // MIDI CC control surface mapper
+    MidiMapper midiMapper_;
+
     // Next bus ID counter
     static std::atomic<int64_t> nextBusId_;
 

src/PiPedalModel.cpp

@@ -33,6 +33,7 @@
 #include "CpuGovernor.hpp"
 #include "RegDb.hpp"
 #include "RingBufferReader.hpp"
+#include "MixerEngine.hpp"
 #include "PiPedalUI.hpp"
 #include "atom_object.hpp"
 #include "Lv2PluginChangeMonitor.hpp"
@@ -3088,6 +3089,24 @@ void PiPedalModel::SetMixerEngine(const std::shared_ptr<MixerEngine>& engine)
     {
         this->audioHost->SetMixerEngine(engine);
     }
+
+    if (engine && this->audioHost && this->audioHost->IsOpen())
+    {
+        // Auto-create channels based on detected input channel count
+        uint32_t inputChannels = this->audioHost->GetDeviceCaptureChannels();
+        if (inputChannels == 0) inputChannels = 2; // default to stereo
+
+        engine->autoCreateChannels(inputChannels);
+
+        Lv2Log::info(SS("Mixer engine initialized with "
+                        << inputChannels << " channels, "
+                        << engine->channelCount() << " strips created."));
+    }
+
+    // Load saved MIDI control surface mappings
+    if (engine) {
+        engine->midiMapper().loadFromFile();
+    }
 }
 
 void PiPedalModel::SetSelectedPedalboardPlugin(uint64_t clientId, uint64_t pedalboardId)

src/PiPedalSocket.cpp

@@ -1395,6 +1395,25 @@ public:
     }
     REGISTER_MESSAGE_HANDLER(mixerGetScenes)
 
+    /************************************************************************/
+    /*  Mixer Output Routing Messages                                      */
+    /************************************************************************/
+
+    void handle_mixerGetOutputRoutes(int replyTo, json_reader *pReader)
+    {
+        std::string json = this->mixerApi.getOutputRoutesJson();
+        this->JsonReply(replyTo, "mixerOutputRoutes", json.c_str());
+    }
+    REGISTER_MESSAGE_HANDLER(mixerGetOutputRoutes)
+
+    void handle_mixerSetOutputRoutes(int replyTo, json_reader *pReader)
+    {
+        std::string json;
+        pReader->read(&json);
+        this->mixerApi.setOutputRoutesFromJson(json);
+    }
+    REGISTER_MESSAGE_HANDLER(mixerSetOutputRoutes)
+
     /************************************************************************/
     /*  MIDI Control Surface Mapping Messages                              */
     /************************************************************************/

src/PipeWireDriver.cpp

@@ -157,6 +157,16 @@ namespace pipedal
             return this->sampleRate;
         }
 
+        virtual uint32_t GetDeviceCaptureChannels() const override
+        {
+            return this->captureChannels;
+        }
+
+        virtual uint32_t GetDevicePlaybackChannels() const override
+        {
+            return this->playbackChannels;
+        }
+
         virtual size_t GetMidiInputEventCount() override
         {
             return midiEventCount;