nullsound: implement legato FX (0xEA)

Author: dciabrin

nullsound/doc/nss.md

@@ -62,7 +62,7 @@ This document details the current level of support for Furnace features in NSS.
 | F2 | Single tick pitch slide down | 💜     |      |
 | 03 | Portamento                   | 💚     |      |
 | E1 | Note slide up                | 💚     |      |
-| EA | Toggle legato                | 💜     |      |
+| EA | Toggle legato                | 💚     |      |
 | E2 | Note slide down              | 💚     |      |
 | E6 | Quick legato (compatibility) | 🚫     |      |
 | E8 | Quick legato up              | 💚     |      |

nullsound/fx-legato.s

@@ -61,6 +61,7 @@ _legato_post_sign:
         ld      LEGATO_DELAY(ix), a
 
         set     BIT_FX_LEGATO, NOTE_FX(ix)
+        set     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
 
         pop     bc
         inc     hl
@@ -88,9 +89,14 @@ _legato_update_pos:
         ;; to recompute the note and tune values without shift, so force it here
         set     BIT_LOAD_NOTE, PIPELINE(ix)
 
-        ;; stop FX
+        ;; stop FX if that was a quick legato
+        ;; (otherwise a dedicated opcode must be used to disable legato)
         ld      LEGATO_TRANSPOSE(ix), #0
+        bit     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
+        jr      nz, _legato_update_end
         res     BIT_FX_LEGATO, NOTE_FX(ix)
+_legato_update_end:
+        res     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
 
         ret
 
@@ -117,3 +123,23 @@ quick_legato_down::
         ;; a: direction
         xor     a
         jp      legato_init
+
+
+;;; LEGATO
+;;; Enable the legato mode for current channel
+;;; ------
+;;;   ix  : state for channel
+;;; hl modified
+legato::
+        set     BIT_FX_LEGATO, NOTE_FX(ix)
+        ret
+
+
+;;; LEGATO_OFF
+;;; Disable the legato mode for current channel
+;;; ------
+;;;   ix  : state for channel
+;;; hl modified
+legato_off::
+        res     BIT_FX_LEGATO, NOTE_FX(ix)
+        ret

nullsound/nss-adpcm-b.s

@@ -203,7 +203,7 @@ _b_post_fx_vibrato:
         call    eval_arpeggio_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
 _b_post_fx_arpeggio:
-        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        bit     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
         jr      z, _b_post_fx_legato
         call    eval_legato_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
@@ -451,10 +451,16 @@ adpcm_b_configure_note_on:
         jr      _b_cfg_note_prepare_ym2610
 _b_cfg_note_update:
         ;; update the current note and prepare the ym2610
-        res     BIT_NOTE_STARTED, PIPELINE(ix)
         ld      NOTE(ix), a
         ld      NOTE16+1(ix), a
         ld      NOTE16(ix), #0
+        ;; do not stop the current note if a legato is in progress
+        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        jr      z, _b_post_cfg_note_update
+        set     BIT_LOAD_NOTE, PIPELINE(ix)
+        jr      _b_cfg_note_end
+_b_post_cfg_note_update:
+        res     BIT_NOTE_STARTED, PIPELINE(ix)
 _b_cfg_note_prepare_ym2610:
         ;; stop playback on the channel, and let the pipeline restart it
         ld      b, #REG_ADPCM_B_START_STOP

nullsound/nss-fm.s

@@ -677,7 +677,7 @@ _fm_post_fx_vibrato:
         call    eval_arpeggio_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
 _fm_post_fx_arpeggio:
-        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        bit     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
         jr      z, _fm_post_fx_legato
         call    eval_legato_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
@@ -991,10 +991,16 @@ fm_configure_note_on:
         jr      _fm_cfg_note_prepare_ym2610
 _fm_cfg_note_update:
         ;; update the current note and prepare the ym2610
-        res     BIT_NOTE_STARTED, PIPELINE(ix)
         ld      NOTE(ix), a
         ld      NOTE16+1(ix), a
         ld      NOTE16(ix), #0
+        ;; do not stop the current note if a legato is in progress
+        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        jr      z, _fm_post_cfg_note_update
+        set     BIT_LOAD_NOTE, PIPELINE(ix)
+        jr      _fm_cfg_note_end
+_fm_post_cfg_note_update:
+        res     BIT_NOTE_STARTED, PIPELINE(ix)
 _fm_cfg_note_prepare_ym2610:
         ;; stop playback on the channel, and let the pipeline restart it
         ld      a, (state_fm_ym2610_channel)

nullsound/nss-ssg.s

@@ -333,7 +333,7 @@ _ssg_post_fx_vibrato:
         call    eval_arpeggio_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
 _ssg_post_fx_arpeggio:
-        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        bit     BIT_FX_QUICK_LEGATO, NOTE_FX(ix)
         jr      z, _ssg_post_fx_legato
         call    eval_legato_step
         set     BIT_LOAD_NOTE, PIPELINE(ix)
@@ -845,10 +845,16 @@ ssg_configure_note_on:
         jr      _ssg_cfg_note_prepare_ym2610
 _ssg_cfg_note_update:
         ;; update the current note and prepare the ym2610
-        res     BIT_NOTE_STARTED, PIPELINE(ix)
         ld      NOTE(ix), a
         ld      NOTE16+1(ix), a
         ld      NOTE16(ix), #0
+        ;; do not stop the current note if a legato is in progress
+        bit     BIT_FX_LEGATO, NOTE_FX(ix)
+        jr      z, _ssg_post_cfg_note_update
+        set     BIT_LOAD_NOTE, PIPELINE(ix)
+        jr      _ssg_cfg_note_end
+_ssg_post_cfg_note_update:
+        res     BIT_NOTE_STARTED, PIPELINE(ix)
 _ssg_cfg_note_prepare_ym2610:
         ;; init macro position
         ld      a, MACRO_DATA(ix)

nullsound/stream.s

@@ -601,6 +601,8 @@ nss_opcodes:
         .nss_op note_portamento
         .nss_op vibrato
         .nss_op vibrato_off
+        .nss_op legato
+        .nss_op legato_off
 
 
 

nullsound/struct-fx.inc

@@ -173,6 +173,7 @@ _trigger_size:
         .lclequ BIT_FX_VIBRATO,         2
         .lclequ BIT_FX_ARPEGGIO,        3
         .lclequ BIT_FX_LEGATO,          4
+        .lclequ BIT_FX_QUICK_LEGATO,    5
 
         ;; Trigger FX function interface
         .lclequ TRIGGER_LOAD_NOTE_FUNC,         0

tools/nsstool.py

@@ -337,6 +337,8 @@ def register_nss_ops():
         ("note_porta",  ["speed"]),
         ("vibrato",     ["speed_depth"]),
         ("vibrato_off", ),
+        ("legato",      ),
+        ("legato_off",  ),
 
 
         # reserved opcodes
@@ -646,6 +648,14 @@ def convert_row(row, channel):
         # quick legato down
         elif fx == 0xe9:
             out.fx.append(quick_legato_d(fxval))
+        # legato
+        elif fx == 0xea:
+            if fxval in [-1, 0]:
+                # opcode must be executed before a note opcode
+                out.pre_fx.append(legato_off())
+            else:
+                # opcode must be executed before a note opcode
+                out.post_fx.append(legato())
         # note cut
         elif fx == 0xec:
             out.fx.append(factory.cut(fxval))