fix: E6x skipped on xm2taud.py

TAUD_NOTE_EFFECTS.md

@@ -1014,8 +1014,8 @@ There is no separate "use fadeout" flag — both extremes share the same field,
   - L_gain = if (pan < 0x80) 1.0 else 1.0 - (pan - 128.0) / 128.0
   - R_gain = if (pan < 0x80) pan / 128.0 else 1.0
 - Panning-equal-power:
-  - L_gain = cos(pi*x / 512.0)
-  - R_gain = sin(pi*x / 512.0)
+  - L_gain = cos(πx / 512.0)
+  - R_gain = sin(πx / 512.0)
 - Amiga tone (both coarse and fine E/F pitch slides). The `slideArg` is a **raw tracker period-unit count** (no scaling), with sign matching linear mode (negative for E, positive for F). Coarse slides apply on every non-first tick; fine slides apply once on tick 0 — the per-step arithmetic is identical:
   - AMIGA_BASE_PERIOD = 428.0  (period at the Taud reference pitch C4 for a standard 8363 Hz instrument, NTSC clock — identical to PT "C-2" period 428)
   - period = AMIGA_BASE_PERIOD × 2^(−(noteVal − C4) / 4096)

terranmon.txt

@@ -2327,8 +2327,8 @@ TODO:
         2026-05-06 .taud files predate the P bit and need re-conversion
         for pan/pf envelopes to play. See byte 15/17/19 spec for the LOOP
         word bit layout.
-    [ ] implement extended tone mode (MONOTONE compat)
-    [ ] pattern loops stops working after processed once (test with slumberjack.xm)
+    [x] slumberjack.xm: E6x commands are not processed
+    [ ] implement linear-freq tone mode (MONOTONE compat)
     [ ] milkytracker-style volume ramping (on sample-end only)
 
 

xm2taud.py

@@ -611,10 +611,11 @@ def encode_effect_xm(cmd: int, arg: int, ch: int = 0, row: int = 0,
             # Set finetune — convert to S5x sub-effect (4-bit signed nibble).
             return (TOP_S, 0x5000 | (val << 8), None, None)
         if sub == 0x6:
-            # Set loop point / loop. Taud S6x = fine pattern delay; the
-            # closest analogue here is dropping with a warn if val>0.
-            vprint(f"    dropped E6{val:X} (set loop) at ch{ch} row{row}")
-            return (TOP_NONE, 0, None, None)
+            # XM E6x = pattern loop (E60 sets loop start, E6x with x>0 loops
+            # x times). Maps directly onto Taud SBx, which has identical
+            # semantics — the engine handles per-voice loopStartRow /
+            # loopCount in applySEffect (sub 0xB).
+            return (TOP_S, 0xB000 | (val << 8), None, None)
         if sub == 0x8:
             # Pan position 0..15 → set pan column (XM nybble × 17 → 8-bit).
             pan8 = (val << 4) | val