From 03cb18e0655acc70fcd8c8c7e3637c84ae36d01e Mon Sep 17 00:00:00 2001
From: "Robin E. R. Davies" <rerdavies@gmail.com>
Date: Sun, 29 Jun 2025 08:30:26 -0400
Subject: [PATCH] Midi handling in the Dummy Audio driver.

---
 PiPedalCommon/src/AlsaSequencer.cpp |  7 +++
 src/AlsaDriver.cpp                  | 12 ++----
 src/DummyAudioDriver.cpp            | 66 ++++++++++++++++++++++++++---
 todo.txt                            |  2 +-
 4 files changed, 72 insertions(+), 15 deletions(-)

diff --git a/PiPedalCommon/src/AlsaSequencer.cpp b/PiPedalCommon/src/AlsaSequencer.cpp
index d3d5afd..71a636d 100644
--- a/PiPedalCommon/src/AlsaSequencer.cpp
+++ b/PiPedalCommon/src/AlsaSequencer.cpp
@@ -244,6 +244,13 @@ namespace pipedal
             // convert rc to message
             throw std::runtime_error(SS("Failed to open ALSA sequencer:" << snd_strerror(rc)));
         }
+        size_t inputBufferSize = snd_seq_get_input_buffer_size(seqHandle);
+        (void)inputBufferSize;
+
+        rc = snd_seq_set_input_buffer_size(seqHandle, 128*1024);
+        if (rc < 0) {
+            Lv2Log::warning("Failed resize the ALSA sequencer input buffer: %s",snd_strerror(rc));
+        }
         snd_seq_set_client_name(seqHandle, "PiPedal");
 
         inPort = snd_seq_create_simple_port(seqHandle, "PiPedal:in",
diff --git a/src/AlsaDriver.cpp b/src/AlsaDriver.cpp
index feb108e..5df7144 100644
--- a/src/AlsaDriver.cpp
+++ b/src/AlsaDriver.cpp
@@ -303,12 +303,8 @@ namespace pipedal
             : driverHost(driverHost)
         {
             midiEventMemoryIndex = 0;
-            midiEventMemory.resize(MAX_MIDI_EVENT * MAX_MIDI_EVENT_SIZE);
+            midiEventMemory.resize(MIDI_MEMORY_BUFFER_SIZE);
             midiEvents.resize(MAX_MIDI_EVENT);
-            for (size_t i = 0; i < midiEvents.size(); ++i)
-            {
-                midiEvents[i].buffer = midiEventMemory.data() + i * MAX_MIDI_EVENT_SIZE;
-            }
         }
         virtual ~AlsaDriverImpl()
         {
@@ -1522,7 +1518,7 @@ namespace pipedal
             } while (frames > 0);
             return framesRead;
         }
-
+    protected:
         void ReadMidiData(uint32_t audioFrame)
         {
             AlsaMidiMessage message;
@@ -1558,6 +1554,7 @@ namespace pipedal
                 
             }
         }
+    private:
 
         long WriteBuffer(snd_pcm_t *handle, uint8_t *buf, size_t frames)
         {
@@ -1782,8 +1779,7 @@ namespace pipedal
             Lv2Log::debug("Audio thread joined.");
         }
 
-        static constexpr size_t MAX_MIDI_EVENT_SIZE = 3;
-        static constexpr size_t MIDI_BUFFER_SIZE = 16 * 1024;
+        static constexpr size_t MIDI_MEMORY_BUFFER_SIZE = 32 * 1024;
         static constexpr size_t MAX_MIDI_EVENT = 4 * 1024;
 
         size_t midiEventCount = 0;
diff --git a/src/DummyAudioDriver.cpp b/src/DummyAudioDriver.cpp
index 88848a5..37b25bb 100644
--- a/src/DummyAudioDriver.cpp
+++ b/src/DummyAudioDriver.cpp
@@ -104,6 +104,11 @@ namespace pipedal
             captureChannels = channels;
             playbackChannels = channels;
 
+            midiEventMemoryIndex = 0;
+            midiEventMemory.resize(MIDI_MEMORY_BUFFER_SIZE);
+            midiEvents.resize(MAX_MIDI_EVENT);
+
+
         }
         virtual ~DummyDriverImpl()
         {
@@ -124,6 +129,15 @@ namespace pipedal
         JackServerSettings jackServerSettings;
         AlsaSequencer::ptr alsaSequencer;
 
+        static constexpr size_t MIDI_MEMORY_BUFFER_SIZE = 32 * 1024;
+        static constexpr size_t MAX_MIDI_EVENT = 4 * 1024;
+
+        size_t midiEventCount = 0;
+        std::vector<MidiEvent> midiEvents;
+        size_t midiEventMemoryIndex = 0;
+        std::vector<uint8_t> midiEventMemory;
+
+
         unsigned int periods = 0;
 
 
@@ -159,11 +173,13 @@ namespace pipedal
             }
         }
 
-        virtual size_t GetMidiInputEventCount() override {
-            return 0;
+        virtual size_t GetMidiInputEventCount() override
+        {
+            return midiEventCount;
         }
-        virtual MidiEvent*GetMidiEvents() {
-            return nullptr;
+        virtual MidiEvent *GetMidiEvents() override
+        {
+            return this->midiEvents.data();
         }
 
 
@@ -224,6 +240,43 @@ namespace pipedal
 
         bool block = false;
 
+        void ReadMidiData(uint32_t audioFrame)
+        {
+            AlsaMidiMessage message;
+
+            midiEventCount = 0;
+            while(alsaSequencer->ReadMessage(message,0))
+            {
+                size_t messageSize = message.size;
+                if (messageSize == 0) 
+                {
+                    continue;
+                }
+                if (midiEventMemoryIndex + messageSize  >= this->midiEventMemory.size()) {
+                    continue;
+                }
+                if (midiEventCount >= this->midiEvents.size()) {
+                    midiEvents.resize(midiEventCount*2);
+                }
+                // for now, prevent META event messages from propagating. 
+                if (message.data[0] == 0xFF && message.size > 1) {
+                    continue;
+                }
+                MidiEvent *pEvent = midiEvents.data() + midiEventCount++;
+                pEvent->time = audioFrame;
+                pEvent->size = messageSize; 
+                pEvent->buffer = midiEventMemory.data() + midiEventMemoryIndex;
+
+                memcpy(
+                    midiEventMemory.data() + midiEventMemoryIndex,
+                    message.data,
+                    message.size);
+                midiEventMemoryIndex += messageSize;
+                
+            }
+        }
+
+
         void AudioThread()
         {
             SetThreadName("dummyAudioDriver");
@@ -236,11 +289,14 @@ namespace pipedal
 
                 while (true)
                 {
+
                     if (terminateAudio())
                     {
                         break;
                     }
 
+                    ReadMidiData((uint32_t)0);
+
                     ssize_t framesRead = this->bufferSize;
                     this->driverHost->OnProcess(framesRead);
 
@@ -340,8 +396,6 @@ namespace pipedal
             Lv2Log::debug("Audio thread joined.");
         }
 
-        static constexpr size_t MIDI_BUFFER_SIZE = 16 * 1024;
-        static constexpr size_t MAX_MIDI_EVENT = 4 * 1024;
 
     public:
 
diff --git a/todo.txt b/todo.txt
index f3ed0a6..354eb88 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,4 +1,4 @@
-Route the midi connections. 
+VU decay on a timer.
 
 Midi handling in the dummy audio connector.