Added converter for delta time to real time

Author: lemcoder

core/src/commonMain/kotlin/pl/lemanski/mikroSoundFont/io/midi/MidiFile.kt

@@ -1,6 +1,9 @@
 package pl.lemanski.mikroSoundFont.io.midi
 
+import pl.lemanski.mikroSoundFont.midi.MidiMessage
+import pl.lemanski.mikroSoundFont.midi.MidiMetaMessage
 import pl.lemanski.mikroSoundFont.midi.MidiTrack
+import pl.lemanski.mikroSoundFont.midi.UnsupportedMidiMessage
 
 data class MidiFile(
     val header: Header,
@@ -10,4 +13,36 @@ data class MidiFile(
         val trackCount: Int,
         val division: Int,
     )
+
+    fun getMessagesOverTime(): List<MidiMessage> {
+        val division = header.division
+        var ticks2time = 500000 / (1000.0 * division)
+        var tempoTicks = 0     // Tick count at the last tempo change
+        var tempoMsec = 0      // Milliseconds at the last tempo change
+
+        val allMessages = mutableListOf<MidiMessage>()
+
+        for (track in tracks) {
+            var trackTicks = 0
+
+            for (msg in track.messages) {
+                if (msg is UnsupportedMidiMessage) continue
+                trackTicks += msg.time
+
+                val millis = tempoMsec + ((trackTicks - tempoTicks) * ticks2time).toInt()
+                msg.time = millis
+
+                if (msg is MidiMetaMessage.SetTempo) {
+                    val tempo = msg.tempo
+                    ticks2time = tempo / (1000.0 * division)
+                    tempoTicks = trackTicks
+                    tempoMsec = millis
+                }
+
+                allMessages.add(msg)
+            }
+        }
+
+        return allMessages.sortedBy { it.time }
+    }
 }

core/src/commonMain/kotlin/pl/lemanski/mikroSoundFont/io/midi/message/read/MidiMetaMessageParser.kt

@@ -42,25 +42,21 @@ internal class MidiMetaMessageParser(
         )
     }
 
-    private fun parseSetTempo(deltaTime: Int, dataSize: Int): MidiMessage = skipMessage(dataSize)
-//    {
-//        if (dataSize != 3) {
-//            throw InvalidMidiDataException("Malformed MIDI. Set Tempo message must be 3 bytes long.")
-//        }
-//
-//        var tempoValue = 0
-//        repeat(dataSize) {
-//            buffer.readByte()
-//            tempoValue = tempoValue shl 8 or buffer.readByte().toInt()
-//        }
-//
-//        val bpm = 60_000_000 / tempoValue // 1 minute in microseconds / tempoValue
-//
-//        return MidiMetaMessage.SetTempo(
-//            time = deltaTime,
-//            bpm = bpm
-//        )
-//    }
+    private fun parseSetTempo(deltaTime: Int, dataSize: Int): MidiMetaMessage.SetTempo {
+        if (dataSize != 3) {
+            throw InvalidMidiDataException("Malformed MIDI. Set Tempo message must be 3 bytes long.")
+        }
+
+        var tempoValue = 0
+        repeat(dataSize) {
+            tempoValue = tempoValue shl 8 or buffer.readByte().toInt()
+        }
+
+        return MidiMetaMessage.SetTempo(
+            time = deltaTime,
+            tempo = tempoValue
+        )
+    }
 
     private fun skipMessage(dataSize: Int): MidiMessage {
         buffer.skip(dataSize.toLong())

core/src/commonMain/kotlin/pl/lemanski/mikroSoundFont/midi/MidiMessage.kt

@@ -41,18 +41,18 @@ package pl.lemanski.mikroSoundFont.midi
  */
 sealed interface MidiMessage {
     val type: MidiMessageType
-    val time: Int
+    var time: Int
 }
 
 sealed class MidiSystemMessage : MidiMessage {
     data object Sysex : MidiSystemMessage() {
         override val type: MidiMessageType = MidiMessageType.SYS_EX
-        override val time: Int = 0
+        override var time: Int = 0
     }
 
     data object Eox : MidiSystemMessage() {
         override val type: MidiMessageType = MidiMessageType.EOX
-        override val time: Int = 0
+        override var time: Int = 0
     }
 
     // other messages
@@ -82,22 +82,22 @@ sealed class MidiSystemMessage : MidiMessage {
 
 sealed class MidiMetaMessage : MidiMessage {
     data class SetTempo(
-        override val time: Int,
-        val bpm: Int,
+        override var time: Int,
+        val tempo: Int,
     ) : MidiMetaMessage() {
         override val type: MidiMessageType = MidiMessageType.SET_TEMPO
     }
 
     data class EndOfTrack(
-        override val time: Int
+        override var time: Int
     ) : MidiMetaMessage() {
         override val type: MidiMessageType = MidiMessageType.END_OF_TRACK
     }
 }
 
 sealed class MidiVoiceMessage : MidiMessage {
     data class NoteOn(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val key: Int,
         val velocity: Int,
@@ -106,7 +106,7 @@ sealed class MidiVoiceMessage : MidiMessage {
     }
 
     data class NoteOff(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val key: Int,
         val velocity: Int,
@@ -115,7 +115,7 @@ sealed class MidiVoiceMessage : MidiMessage {
     }
 
     data class KeyPressure(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val key: Int,
         val keyPressure: Int,
@@ -124,7 +124,7 @@ sealed class MidiVoiceMessage : MidiMessage {
     }
 
     data class ControlChange(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val control: Int,
         val controlValue: Int,
@@ -133,23 +133,23 @@ sealed class MidiVoiceMessage : MidiMessage {
     }
 
     data class ProgramChange(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val program: Int,
     ) : MidiVoiceMessage() {
         override val type: MidiMessageType = MidiMessageType.PROGRAM_CHANGE
     }
 
     data class ChannelPressure(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val channelPressure: Int,
     ) : MidiVoiceMessage() {
         override val type: MidiMessageType = MidiMessageType.CHANNEL_PRESSURE
     }
 
     data class PitchBend(
-        override val time: Int,
+        override var time: Int,
         val channel: Int,
         val pitchBend: Int,
     ) : MidiVoiceMessage() {
@@ -159,5 +159,5 @@ sealed class MidiVoiceMessage : MidiMessage {
 
 data object UnsupportedMidiMessage : MidiMessage {
     override val type: MidiMessageType = MidiMessageType.UNSUPPORTED
-    override val time: Int = 0
+    override var time: Int = 0
 }

core/src/commonMain/kotlin/pl/lemanski/mikroSoundFont/midi/MidiSequencer.kt

@@ -6,7 +6,6 @@ import pl.lemanski.mikroSoundFont.getLogger
 class MidiSequencer(
     private val soundFont: SoundFont,
     private val sampleRate: Int,
-    private val channelCount: Int,
     private val sampleBlockSize: Int
 ) {
     private val logger = getLogger()
@@ -39,19 +38,9 @@ class MidiSequencer(
         return audioBuffer
     }
 
-    private fun MidiMessage.process() {
-        type.let {
-            when (it) {
-                MidiMessageType.NOTE_OFF -> {
-                    (this as MidiVoiceMessage.NoteOff)
-                    soundFont.noteOff(channel, key)
-                }
-                MidiMessageType.NOTE_ON  -> {
-                    (this as MidiVoiceMessage.NoteOff)
-                    soundFont.noteOn(channel, key, velocity / 127.0f)
-                }
-                else                     -> logger.log("Unknown message type")
-            }
-        }
+    private fun MidiMessage.process() = when (this) {
+        is MidiVoiceMessage.NoteOff -> soundFont.noteOff(channel, key)
+        is MidiVoiceMessage.NoteOn  -> soundFont.noteOn(channel, key, velocity / 127.0f)
+        else                        -> logger.log("Unknown message type")
     }
 }

core/src/commonTest/kotlin/pl/lemanski/mikroSoundFont/midi/MidiTest.kt

@@ -1,7 +1,12 @@
 package pl.lemanski.mikroSoundFont.midi
 
+import pl.lemanski.mikroSoundFont.MikroSoundFont
 import pl.lemanski.mikroSoundFont.io.loadFile
 import pl.lemanski.mikroSoundFont.io.midi.MidiFileParser
+import pl.lemanski.mikroSoundFont.io.saveFile
+import pl.lemanski.mikroSoundFont.io.toByteArrayLittleEndian
+import pl.lemanski.mikroSoundFont.io.wav.WavFileHeader
+import pl.lemanski.mikroSoundFont.io.wav.toByteArray
 import kotlin.test.Test
 
 class MidiTest {
@@ -11,10 +16,17 @@ class MidiTest {
     fun testMidi() {
         val midiFileBuffer = loadFile("$dir\\venture.mid")
         val midiFile = MidiFileParser(midiFileBuffer).parse()
-        midiFile.tracks.forEach {
-            it.messages.forEach {
-                println(it.type.name)
-            }
-        }
+        val messages = midiFile.getMessagesOverTime()
+
+        val soundFont = MikroSoundFont.load("$dir\\font.sf2")
+
+        val sequencer = MidiSequencer(soundFont, 44100, 512)
+        sequencer.loadMidiEvents(messages)
+        val wavBytes = sequencer.generate()
+
+        val wavHeader =  WavFileHeader.write(44_100u, wavBytes.size.toUInt(), 2u)
+        val file = wavHeader.toByteArray() + wavBytes.toByteArrayLittleEndian()
+
+        saveFile(file, "$dir\\output.wav")
     }
 }

lib/src/androidMain/kotlin/pl/lemanski/mikroSoundFont/MikroSoundFont.android.kt

@@ -1,11 +1,9 @@
 package pl.lemanski.mikroSoundFont
 
+import pl.lemanski.mikroSoundFont.internal.getSoundFontDelegate
+
 actual object MikroSoundFont {
-    actual fun load(path: String): SoundFont {
-        TODO("Not yet implemented")
-    }
+    actual fun load(path: String): SoundFont = getSoundFontDelegate(path)
 
-    actual fun load(memory: ByteArray): SoundFont {
-        TODO("Not yet implemented")
-    }
+    actual fun load(memory: ByteArray): SoundFont = getSoundFontDelegate(memory)
 }