wip

dither4.s

@@ -27,6 +27,7 @@ sample_ptrh = $85
 sample_ptr = sample_ptrl
 scanline = $86
 audiotemp = $87
+sample_index = $80
 frame_counter = $89
 
 height = 160
@@ -94,6 +95,8 @@ audio_high_byte:
     sta sample_ptrl
     lda #.hibyte(audio_samples)
     sta sample_ptrh
+    lda #0
+    sta sample_index
 
     ; Disable display DMA
     lda #$00
@@ -168,7 +171,7 @@ wait_loop:
 
     .macro audio_play_raw
         ;ldy VCOUNT ; set on entry
-        ldy #0             ; 2 cycles
+        ldy sample_index   ; 3 cycles
         lda (sample_ptr),y ; 5/6 cyc
         sta AUDC1          ; 4 cyc
     .endmacro
@@ -187,20 +190,17 @@ wait_loop:
     .endmacro
 
     .macro audio_inc
-        ; Increment sample ptr
         ; 7 cycles
-        inc sample_ptrl ; 5
+        inc sample_index   ; 5 cycles
         bne audio_cont     ; 2
 
-        ; 7 cycles, optional
+        ; 12 cycles, optional
         inc sample_ptrh                 ; 5
         lda sample_ptrh                 ; 3
         cmp #.hibyte(audio_samples_end) ; 2
         bmi audio_cont                  ; 2
 
-        ; 10 cycles, optional
-        lda #.lobyte(audio_samples)     ; 2
-        sta sample_ptrl                 ; 3
+        ; 5 cycles, optional
         lda #.hibyte(audio_samples)     ; 2
         sta sample_ptrh                 ; 3
 
@@ -210,18 +210,15 @@ wait_loop:
     .macro run_frame frame_offset
     .scope
     each_scanline_pair:
-        ;audio_prep
         sty scanline ; 3 cycles
         inner_scanline frame_offset, 0 ; 23-26 cycles before break, 12 cycles after
 
         audio_play_raw ; 11-12 cycles
+
         ldy scanline   ; 3 cycles
-        ;audio_play_lo
         inner_scanline frame_offset, 128 ; 23-26 cycles before break, 12 cycles after
 
         audio_inc         ; 7-24 cycles
-        ;audio_play_raw
-        ;audio_play_hi ; too slow
 
         ; save for later lookup
         ldy VCOUNT             ; 4 cycles