src/entities/song.h

@@ -30,6 +30,7 @@ struct Header {
     std::string name;
     int ppq;
     float bpm;
+    double tempo;
 };
 
 struct Song {
@@ -37,6 +38,13 @@ struct Song {
     std::vector<Track> tracks;
 };
 
+int ticksToMilliseconds(int ticks, double tempo, int ppq) {
+    double microseconds = (ticks * tempo) / ppq;
+    
+    // Convert to milliseconds with rounding
+    return static_cast<int>(microseconds / 1000.0 + 0.5);
+}
+
 Song parseSong(const rapidjson::Document& doc) {
     assert(doc.IsObject());
 
@@ -51,6 +59,7 @@ Song parseSong(const rapidjson::Document& doc) {
         if (h.HasMember("tempos") && h["tempos"].IsArray()) {
             const auto& tempos = h["tempos"].GetArray();
             header.bpm = tempos[0]["bpm"].GetFloat();
+            header.tempo = 60000000.0 / header.bpm;
         }
         song.header = header;
     }
@@ -76,9 +85,9 @@ Song parseSong(const rapidjson::Document& doc) {
                     note.name = n["name"].GetString();
                     note.midi = n["midi"].GetInt();
                     note.duration_ticks = n["durationTicks"].GetInt();
-                    note.duration_ms = n["duration"].GetFloat() * 1000;
+                    note.duration_ms = ticksToMilliseconds(note.duration_ticks, song.header.tempo, song.header.ppq);
                     note.ticks = n["ticks"].GetInt();
-                    note.position_ms = n["time"].GetFloat() * 1000;
+                    note.position_ms = ticksToMilliseconds(note.ticks, song.header.tempo, song.header.ppq);
                     track.notes.push_back(note);
                 }
             }

src/main.cpp

@@ -35,6 +35,7 @@ int main(int argc, char** argv)
     Song& song = song_manager->load_song("mary_had_a_lil_lamb", "assets/songs/json/mary.json");
     printf("Song name: %s\n", song.header.name.c_str());
     printf("Song bpm: %f\n", song.header.bpm);
+    printf("Song tempo: %f\n", song.header.tempo);
     printf("First note duration: %d\n", song.tracks[0].notes[0].duration_ms);