simple implementation of midi tap tempo

Author: fps

README.md

@@ -229,6 +229,14 @@ The commands supported by mod-host are:
         * monitor audio levels for a specific jack port (on the feedback port)
         e.g.: monitor_audio_levels "system:capture_1" 1
 
+    midi_map_tempo_tap <midi_channel> <midi_cc>
+        * map the MIDI tempo tap
+        e.g.: midi_map_tempo_tap 0 0 
+
+    midi_unmap_tempo_tap
+        * unmap the MIDI tempo tap
+        e.g.: midi_unmap_tempo_tap
+
     monitor_midi_control <midi_channel> <enable>
         * listen to MIDI control change messages (on the feedback port)
         e.g.: monitor_midi_control 7 1

src/effects.c

@@ -592,6 +592,12 @@ typedef struct MIDI_CC_T {
     port_t* port;
 } midi_cc_t;
 
+typedef struct MIDI_CC_TEMPO_TAP_T {
+    int8_t channel;
+    uint8_t controller;
+    jack_nframes_t last_frame_time;
+} midi_cc_tempo_tap_t;
+
 typedef struct ASSIGNMENT_T {
     int effect_id;
     port_t *port;
@@ -755,6 +761,8 @@ typedef struct CACHED_EFFECT_FLUSH_T {
 static effect_t g_effects[MAX_INSTANCES];
 static midi_cc_t g_midi_cc_list[MAX_MIDI_CC_ASSIGN], *g_midi_learning;
 
+static midi_cc_tempo_tap_t g_midi_cc_tempo_tap;
+
 #ifdef HAVE_CONTROLCHAIN
 /* Control Chain */
 static cc_client_t *g_cc_client = NULL;
@@ -2943,6 +2951,26 @@ static int ProcessGlobalClient(jack_nframes_t nframes, void *arg)
         handled = false;
         channel = (event.buffer[0] & 0x0F);
 
+        const float max_tap_delay = 10.0f;
+        const float min_tap_delay = 0.1f;
+        if (g_midi_cc_tempo_tap.channel != -1)
+        {
+            if (channel == g_midi_cc_tempo_tap.channel && controller == g_midi_cc_tempo_tap.controller && mvalue > 63)
+            {
+                jack_nframes_t current = event.time + g_monotonic_frame_count;
+                const float delta_t = (current - g_midi_cc_tempo_tap.last_frame_time) / (float)g_sample_rate;
+                if (delta_t < max_tap_delay && delta_t > min_tap_delay)
+                {
+                    const float bpm = 60.0f / delta_t;
+                    effects_set_beats_per_minute(bpm);
+                    // printf("bpm: %f delta_t: %f current: %d last: %d\n", bpm, delta_t, current, g_midi_cc_tempo_tap.last_frame_time);
+                }
+                
+                g_midi_cc_tempo_tap.last_frame_time = current;
+                continue;
+            }
+        }
+
         for (int j = 0; j < MAX_MIDI_CC_ASSIGN; j++)
         {
             if (g_midi_cc_list[j].effect_id == ASSIGNMENT_NULL)
@@ -4313,6 +4341,8 @@ static void ExternalControllerWriteFunction(LV2UI_Controller controller,
 
 int effects_init(void* client)
 {
+    g_midi_cc_tempo_tap.channel = -1;
+
     /* This global client is for connections / disconnections and midi-learn */
     if (client != NULL)
     {
@@ -7898,6 +7928,22 @@ int effects_midi_unmap(int effect_id, const char *control_symbol)
     return ERR_LV2_INVALID_PARAM_SYMBOL;
 }
 
+int effects_midi_map_tempo_tap(int channel, int controller)
+{
+    g_midi_cc_tempo_tap.channel = channel;
+    g_midi_cc_tempo_tap.controller = controller;
+    g_midi_cc_tempo_tap.last_frame_time = g_monotonic_frame_count;
+    return SUCCESS;
+}
+
+int effects_midi_unmap_tempo_tap()
+{
+    g_midi_cc_tempo_tap.channel = -1;
+    g_midi_cc_tempo_tap.controller = 0;
+    return SUCCESS;
+}
+
+
 int effects_licensee(int effect_id, char **licensee_ptr)
 {
     if (!InstanceExist(effect_id))

src/effects.h

@@ -172,6 +172,8 @@ int effects_get_parameter_info(int effect_id, const char *control_symbol, float
 int effects_midi_learn(int effect_id, const char *control_symbol, float minimum, float maximum);
 int effects_midi_map(int effect_id, const char *control_symbol, int channel, int controller, float minimum, float maximum);
 int effects_midi_unmap(int effect_id, const char *control_symbol);
+int effects_midi_map_tempo_tap(int channel, int controller);
+int effects_midi_unmap_tempo_tap();
 int effects_licensee(int effect_id, char **licensee);
 int effects_set_beats_per_minute(double bpm);
 int effects_set_beats_per_bar(float bpb);

src/mod-host.c

@@ -430,6 +430,20 @@ static void midi_unmap_cb(proto_t *proto)
     protocol_response_int(resp, proto);
 }
 
+static void midi_map_tempo_tap_cb(proto_t *proto)
+{
+    int resp;
+    resp = !effects_midi_map_tempo_tap(atoi(proto->list[1]), atoi(proto->list[2]));
+    protocol_response_int(resp, proto);
+}
+
+static void midi_unmap_tempo_tap_cb(proto_t *proto)
+{
+    int resp;
+    resp = !effects_midi_unmap_tempo_tap();
+    protocol_response_int(resp, proto);
+}
+
 static void cc_map_cb(proto_t *proto)
 {
     int resp;
@@ -1063,6 +1077,8 @@ static int mod_host_init(jack_client_t* client, int socket_port, int feedback_po
     protocol_add_command(MIDI_LEARN, midi_learn_cb);
     protocol_add_command(MIDI_MAP, midi_map_cb);
     protocol_add_command(MIDI_UNMAP, midi_unmap_cb);
+    protocol_add_command(MIDI_MAP_TEMPO_TAP, midi_map_tempo_tap_cb);
+    protocol_add_command(MIDI_UNMAP_TEMPO_TAP, midi_unmap_tempo_tap_cb);
     protocol_add_command(CC_MAP, cc_map_cb);
     protocol_add_command(CC_VALUE_SET, cc_value_set_cb);
     protocol_add_command(CC_UNMAP, cc_unmap_cb);

src/mod-host.h

@@ -83,6 +83,8 @@
 #define MIDI_LEARN              "midi_learn %i %s %f %f"
 #define MIDI_MAP                "midi_map %i %s %i %i %f %f"
 #define MIDI_UNMAP              "midi_unmap %i %s"
+#define MIDI_MAP_TEMPO_TAP      "midi_map_tempo_tap %i %i"
+#define MIDI_UNMAP_TEMPO_TAP    "midi_map_tempo_tap"
 #define CC_MAP                  "cc_map %i %s %i %i %s %f %f %f %i %i %s %i ..."
 #define CC_VALUE_SET            "cc_value_set %i %s %f"
 #define CC_UNMAP                "cc_unmap %i %s"