From ce569211b842c20c10e55e15032e1aed06c401c0 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Wed, 7 Dec 2022 16:35:07 -0800
Subject: [PATCH] sorta runs but not in time

---
 dither4.s | 58 +++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 10 deletions(-)

diff --git a/dither4.s b/dither4.s
index 3f1e314..e3cc121 100644
--- a/dither4.s
+++ b/dither4.s
@@ -26,6 +26,7 @@ sample_ptrl = $84
 sample_ptrh = $85
 sample_ptr = sample_ptrl
 scanline = $86
+audiotemp = $87
 
 height = 160
 bytes_per_line = 40
@@ -66,6 +67,29 @@ displaylist:
     .byte $41 ; jump and blank
     .addr displaylist
 
+audio_high_byte:
+    .scope
+        .macro byteseq val
+            .repeat 16
+                .byte val | $10
+            .endrep
+        .endmacro
+        byteseq $0
+        byteseq $1
+        byteseq $2
+        byteseq $3
+        byteseq $4
+        byteseq $5
+        byteseq $7
+        byteseq $8
+        byteseq $9
+        byteseq $a
+        byteseq $b
+        byteseq $c
+        byteseq $d
+        byteseq $e
+        byteseq $f
+    .endscope
 
 .code
 
@@ -125,21 +149,28 @@ wait_start:
     ; Resynchronize the scanline counter
 wait_loop:
     lda VCOUNT
+    tay ; save for audio lookup
     bne wait_loop
     lda #(256 - scanline_offset)
     sta scanline
 
 each_scanline:
+    .macro audio_prep
+        ldy VCOUNT ; 4 cycles
+        lda (sample_ptr),y ; 5/6 cyc
+        sta audiotemp ; 3 cyc
+    .endmacro
+
     .macro inner_scanline
         ; it'll fire on unused lines, but harmlessly
         ldy scanline ; 3 cyc
         inc scanline ; 5 cyc
 
         ; Leisurely memory fetches
-        lda palette1,y
-        pha
-        ldx palette2,y
-        lda palette3,y
+        lda palette1,y ; 5
+        pha            ; ...3?
+        ldx palette2,y ; 5
+        lda palette3,y ; 5
         tay
         pla
 
@@ -152,14 +183,18 @@ each_scanline:
         sty COLPF2
     .endmacro
 
-    .macro audio_play
-        ldy VCOUNT ; 4 cycles
-        lda (sample_ptr),y ; 5/6 cyc
+    .macro audio_play_lo ; 11 cycles
+        lda audiotemp ; 3 cyc
+        and #$0f ; 2 cyc
+        ora #$10 ; 2 cyc
         sta AUDC1 ; 4 cyc
     .endmacro
 
-    inner_scanline
-    audio_play
+    .macro audio_play_hi ; 12 cycles
+        ldy audiotemp ; 3 cyc
+        lda audio_high_byte,y ; 5 cyc
+        sta AUDC1 ; 4 cyc
+    .endmacro
 
     .macro audio_inc
         ; Increment sample ptr
@@ -186,8 +221,11 @@ each_scanline:
         audio_cont:
     .endmacro
 
-
+    audio_prep
     inner_scanline
+    audio_play_lo
+    inner_scanline
+    audio_play_hi
 
     lda VCOUNT
     cmp #130 ;#130