mirror of
https://github.com/Pecusx/scorch_src.git
synced 2026-05-21 21:34:20 +02:00
Pecusx
153 lines
2.9 KiB
NASM
153 lines
2.9 KiB
NASM
; --- dmsc LZSS player routine
|
|
|
|
song_data
|
|
ins 'mmm_16.lzs'
|
|
song_end
|
|
|
|
buffers
|
|
.ds 256 * 9
|
|
|
|
POKEY2 = POKEY+$10 ; stereo
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
; Song Initialization - this runs in the first tick:
|
|
;
|
|
.proc init_song
|
|
|
|
; pokeys init
|
|
lda #3 ; stereo
|
|
sta POKEY+$0f ; stereo
|
|
sta POKEY2+$0f ; stereo
|
|
|
|
mva #1 bit_data
|
|
|
|
; Example: here initializes song pointer:
|
|
|
|
;mwa #song_data song_ptr
|
|
|
|
; Init all channels:
|
|
ldx #8
|
|
ldy #0
|
|
clear
|
|
; Read just init value and store into buffer and POKEY
|
|
jsr get_byte
|
|
sta POKEY, x
|
|
sta POKEY2,x ; stereo
|
|
sta stereo_buff,x ; stereo
|
|
sty chn_copy, x
|
|
cbuf
|
|
sta buffers + 255
|
|
inc cbuf + 2
|
|
dex
|
|
bpl clear
|
|
|
|
; Initialize buffer pointer:
|
|
sty bptr
|
|
sty cur_pos
|
|
rts
|
|
.endp
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
; Wait for next frame
|
|
;
|
|
.proc wait_frame
|
|
|
|
lda 20
|
|
delay
|
|
cmp 20
|
|
beq delay
|
|
.endp
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
; Play one frame of the song
|
|
;
|
|
.proc play_frame
|
|
ldx #8 ; stereo
|
|
@ lda stereo_buff,x ; stereo
|
|
sta POKEY2,x ; stereo
|
|
dex ;stereo
|
|
bpl @- ; stereo
|
|
|
|
lda #>buffers
|
|
sta bptr+1
|
|
|
|
lda song_data
|
|
sta chn_bits
|
|
ldx #8
|
|
|
|
; Loop through all "channels", one for each POKEY register
|
|
chn_loop:
|
|
lsr chn_bits
|
|
bcs skip_chn ; C=1 : skip this channel
|
|
|
|
lda chn_copy, x ; Get status of this stream
|
|
bne do_copy_byte ; If > 0 we are copying bytes
|
|
|
|
; We are decoding a new match/literal
|
|
lsr bit_data ; Get next bit
|
|
bne got_bit
|
|
jsr get_byte ; Not enough bits, refill!
|
|
ror ; Extract a new bit and add a 1 at the high bit (from C set above)
|
|
sta bit_data ;
|
|
got_bit:
|
|
jsr get_byte ; Always read a byte, it could mean "match size/offset" or "literal byte"
|
|
bcs store ; Bit = 1 is "literal", bit = 0 is "match"
|
|
|
|
sta chn_pos, x ; Store in "copy pos"
|
|
|
|
jsr get_byte
|
|
sta chn_copy, x ; Store in "copy length"
|
|
|
|
; And start copying first byte
|
|
do_copy_byte:
|
|
dec chn_copy, x ; Decrease match length, increase match position
|
|
inc chn_pos, x
|
|
ldy chn_pos, x
|
|
|
|
; Now, read old data, jump to data store
|
|
lda (bptr), y
|
|
|
|
store:
|
|
ldy cur_pos
|
|
sta POKEY,x ; Store to output and buffer
|
|
sta stereo_buff,x ; stereo
|
|
sta (bptr), y
|
|
|
|
skip_chn:
|
|
; Increment channel buffer pointer
|
|
inc bptr+1
|
|
|
|
dex
|
|
bpl chn_loop ; Next channel
|
|
|
|
inc cur_pos
|
|
.endp
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
; Check for ending of song and jump to the next frame
|
|
;
|
|
|
|
; not checking really so the tune gets funky :)))
|
|
;lda song_ptr + 1
|
|
;cmp #>song_end
|
|
;bne wait_frame
|
|
;lda song_ptr
|
|
;cmp #<song_end
|
|
;bne wait_frame
|
|
|
|
end_loop
|
|
rts
|
|
|
|
song_ptr = get_byte + 1
|
|
.proc get_byte
|
|
lda song_data+1
|
|
inc song_ptr
|
|
bne skip
|
|
inc song_ptr+1
|
|
skip
|
|
rts
|
|
.endp
|
|
|
|
stereo_buff ; stereo
|
|
.ds 9 ; stereo
|
|
|