src/channel.c

@@ -6,13 +6,6 @@
 
 void channel_add(jack_client_t *client, int idx)
 {
-    channels[idx].active = 1;
-    atomic_store(&channels[idx].state, STATE_IDLE);
-    channels[idx].prev_state = -1;
-    channels[idx].loop_count = 0;
-    channels[idx].record_pos = 0;
-    channels[idx].playback_pos = 0;
-
     char in_name[64], out_name[64];
     snprintf(in_name, sizeof(in_name), "channel%d_input", next_channel_id);
     snprintf(out_name, sizeof(out_name), "channel%d_output", next_channel_id);
@@ -23,8 +16,20 @@ void channel_add(jack_client_t *client, int idx)
     channels[idx].audio_out = jack_port_register(client, out_name,
                                                  JACK_DEFAULT_AUDIO_TYPE,
                                                  JackPortIsOutput, 0);
-    if (!channels[idx].audio_in || !channels[idx].audio_out)
+    if (!channels[idx].audio_in || !channels[idx].audio_out) {
         fprintf(stderr, "Failed to register ports for channel %d\n", next_channel_id);
+        /* Do NOT mark channel active – process loop will skip it */
+        channels[idx].active = 0;
+        return;
+    }
+
+    channels[idx].active = 1;
+    atomic_store(&channels[idx].state, STATE_IDLE);
+    channels[idx].prev_state = -1;
+    channels[idx].loop_count = 0;
+    channels[idx].record_pos = 0;
+    channels[idx].playback_pos = 0;
+
     next_channel_id++;
     channel_count++;
 }

src/looper.c

@@ -35,6 +35,12 @@ int process_callback(jack_nframes_t nframes, void *arg)
     for (int c = 0; c < MAX_CHANNELS; c++) {
         if (!channels[c].active) continue;
 
+        /* Guard against NULL ports (e.g. if port registration failed) */
+        if (!channels[c].audio_in || !channels[c].audio_out) {
+            fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n", c);
+            continue;
+        }
+
         jack_default_audio_sample_t *in  = (jack_default_audio_sample_t *)
             jack_port_get_buffer(channels[c].audio_in, nframes);
         jack_default_audio_sample_t *out = (jack_default_audio_sample_t *)