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pt3: optimize amplitude code

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This commit is contained in:
Peter Ferrie 2019-06-02 23:24:25 -04:00 committed by Vince Weaver
parent 089d963d23
commit 90b8a76a4b
1 changed files with 16 additions and 16 deletions
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32
pt3_player/pt3_lib.s
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@ -796,7 +796,6 @@ calc_amplitude:
lda sample_b1 ; a->amplitude= (b1 & 0xf);
and #$f
sta note_a+NOTE_AMPLITUDE,X
;========================================
; if b0 top bit is set, it means sliding
@ -805,32 +804,31 @@ calc_amplitude:
bit sample_b0 ; if ((b0 & 0x80)!=0) {
bpl done_amp_sliding ; so if top bit not set, skip
tay
;================================
; if top bits 0b11 then slide up
; if top buts 0b10 then slide down
; if top bits 0b10 then slide down
; if ((b0 & 0x40)!=0) {
lda note_a+NOTE_AMPLITUDE_SLIDING,X
sec
bvc amp_slide_down
amp_slide_up:
; if (a->amplitude_sliding < 15) {
; a pain to do signed compares
lda note_a+NOTE_AMPLITUDE_SLIDING,X
sec
sbc #15
bvc asu_signed
eor #$80
asu_signed:
bpl done_amp_sliding ; skip if A>=15
inc note_a+NOTE_AMPLITUDE_SLIDING,X ; a->amplitude_sliding++;
bne done_amp_sliding
bne done_amp_sliding_y
amp_slide_down:
; if (a->amplitude_sliding > -15) {
; a pain to do signed compares
lda note_a+NOTE_AMPLITUDE_SLIDING,X
sec
sbc #$f1 ; -15
bvc asd_signed
eor #$80
@ -839,28 +837,29 @@ asd_signed:
dec note_a+NOTE_AMPLITUDE_SLIDING,X ; a->amplitude_sliding--;
done_amp_sliding_y:
tya
done_amp_sliding:
; a->amplitude+=a->amplitude_sliding;
clc
lda note_a+NOTE_AMPLITUDE,X
adc note_a+NOTE_AMPLITUDE_SLIDING,X
sta note_a+NOTE_AMPLITUDE,X
; clamp amplitude to 0 - 15
lda note_a+NOTE_AMPLITUDE,X
check_amp_lo:
bpl check_amp_hi
lda #0
beq write_clamp_amplitude
bmi write_clamp_amplitude
check_amp_hi:
cmp #16
bcc done_clamp_amplitude ; blt
bcc write_amplitude ; blt
lda #15
.byte $2C
write_clamp_amplitude:
sta note_a+NOTE_AMPLITUDE,X
lda #0
write_amplitude:
sta note_amp_smc+1
done_clamp_amplitude:
@ -874,7 +873,8 @@ done_clamp_amplitude:
asl ; 2
asl ; 2
asl ; 2
ora note_a+NOTE_AMPLITUDE,X ; 4+
note_amp_smc:
ora #0 ; 4+
tay ; 2
lda VolumeTable,Y ; 4+