From 2b9c14449a6ffe150aa588d52db86d69b181c701 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Sun, 11 Dec 2022 17:23:41 -0800
Subject: [PATCH] restore to 131-line audio for now

still glitching intermittently
---
 atari-asm-xex.cfg |  2 +-
 dither4.s         | 34 +++++++++++++++++-----------------
 pack-wav.js       |  3 +--
 3 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/atari-asm-xex.cfg b/atari-asm-xex.cfg
index 5fc0c97..9727725 100644
--- a/atari-asm-xex.cfg
+++ b/atari-asm-xex.cfg
@@ -21,6 +21,6 @@ SEGMENTS {
     RODATA:   load = MAIN,    type = ro   optional = yes;
     DATA:     load = MAIN,    type = rw   optional = yes;
     BSS:      load = MAIN,    type = bss, optional = yes, define = yes;
-    AUDIO:    load = MAIN,    type = ro,  optional = yes, define = yes, align = 256;
+    AUDIO:    load = MAIN,    type = ro,  optional = yes, define = yes;
     BUFFERS:  load = MAIN,    type = ro,  optional = yes, define = yes, align = 4096;
 }
diff --git a/dither4.s b/dither4.s
index bcab440..d32f2f4 100644
--- a/dither4.s
+++ b/dither4.s
@@ -27,7 +27,6 @@ sample_ptrh = $85
 sample_ptr = sample_ptrl
 scanline = $86
 audiotemp = $87
-sample_index = $80
 frame_counter = $89
 
 height = 160
@@ -95,8 +94,6 @@ audio_high_byte:
     sta sample_ptrl
     lda #.hibyte(audio_samples)
     sta sample_ptrh
-    lda #0
-    sta sample_index
 
     ; Disable display DMA
     lda #$00
@@ -171,7 +168,6 @@ wait_loop:
 
     .macro audio_play_raw
         ;ldy VCOUNT ; set on entry
-        ldy sample_index   ; 3 cycles
         lda (sample_ptr),y ; 5/6 cyc
         sta AUDC1          ; 4 cyc
     .endmacro
@@ -190,17 +186,20 @@ wait_loop:
     .endmacro
 
     .macro audio_inc
-        ; 7 cycles
-        inc sample_index   ; 5 cycles
-        bne audio_cont     ; 2
+        ; 22 cycles
+        lda sample_ptrl ; 3 cyc
+        clc             ; 2 cyc
+        adc #131        ; 2 cyc
+        sta sample_ptrl ; 3 cyc
+        lda sample_ptrh ; 3 cyc
+        adc #0          ; 2 cyc
+        sta sample_ptrh ; 3 cyc
+        cmp #.hibyte(audio_samples_end) ; 2 cyc
+        bmi audio_cont                  ; 2 cyc
 
-        ; 12 cycles, optional
-        inc sample_ptrh                 ; 5 <- here is the current hard limit
-        lda sample_ptrh                 ; 3
-        cmp #.hibyte(audio_samples_end) ; 2
-        bmi audio_cont                  ; 2
-
-        ; 5 cycles, optional
+        ; 10 cycles, optional
+        lda #.lobyte(audio_samples)     ; 2
+        sta sample_ptrl                 ; 3
         lda #.hibyte(audio_samples)     ; 2
         sta sample_ptrh                 ; 3
 
@@ -217,16 +216,17 @@ wait_loop:
         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_raw ; 8-10 cycles
+
         inner_scanline frame_offset, 128 ; 23-26 cycles before break, 12 cycles after
-        audio_inc      ; 7-24 cycles
 
         ; pair cleanup: 6 cycles
         ldy VCOUNT             ; 4 cycles
         bne each_scanline_pair ; 2 cycles
 
+        audio_inc      ; 22-32 cycles
+
         ; frame cleanup: 11 cycles
         lda frame_counter ; 3 cycles
         eor #1            ; 2 cycles
diff --git a/pack-wav.js b/pack-wav.js
index 4a74a81..f8ee37f 100644
--- a/pack-wav.js
+++ b/pack-wav.js
@@ -49,7 +49,6 @@ function audio2assembly(audio) {
     .export audio_samples
     .export audio_samples_end
 
-.align 256
 audio_samples:
     ${byte2byte(pack(audio))}
 audio_samples_end:
@@ -61,7 +60,7 @@ audio_samples_end:
 function wav2assembly(buffer) {
     let wav = new WaveFile(buffer);
     let samples = wav.getSamples();
-    let n = samples.length - (samples.length % 256);
+    let n = samples.length - (samples.length % 131);
     return audio2assembly(samples.slice(0, n));
 }