fox32rom: Add play_audio and stop_audio routines

This commit is contained in:
Ry 2022-06-20 17:11:49 -07:00
parent 8d6c90498a
commit c7464fa4bc
3 changed files with 107 additions and 0 deletions

97
audio.asm Normal file
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@ -0,0 +1,97 @@
; audio routines
; use ffmpeg to convert an audio file for playback:
; ffmpeg -i input.mp3 -f s16le -ac 1 -ar 22050 audio.raw
; fox32's audio output works by swapping between two buffers
; interrupt 0xFE (vector 0x000003F8) is fired when it's time to swap buffers
; when that interrupt fires, it calls `refill_buffer` which fills up the buffer
const CURRENT_BUFFER: 0x01FFFF00
const AUDIO_POINTER: 0x01FFFF01
const AUDIO_LENGTH: 0x01FFFF05
const OLD_BUFFER_SWAP_VECTOR: 0x01FFFF09
; play an audio clip (does not block)
; inputs:
; r0: pointer to audio clip
; r1: length of audio clip in bytes (must be a multiple of 32768 bytes)
; outputs:
; none
play_audio:
push r0
push r1
; set the interrupt vector for interrupt 0xFE and save the old one
mov [OLD_BUFFER_SWAP_VECTOR], [0x000003F8]
mov [0x000003F8], refill_buffer
; store audio pointer
mov [AUDIO_POINTER], r0
; store audio length
; floor it to the nearest multiple of 32768
and r1, 0xFFFF8000
mov [AUDIO_LENGTH], r1
; reset the current buffer to zero
; fox32 resets its current buffer to zero internally, so reset it to zero here to stay in sync
; refill_buffer will bitwise not this before checking it,
; so set it to 0xFF so that it becomes zero when checked for the first time
mov.8 [CURRENT_BUFFER], 0xFF
; enable audio playback
mov r0, 0x80000600
out r0, 1
pop r1
pop r0
ret
refill_buffer:
push r0
push r1
push r31
not.8 [CURRENT_BUFFER]
cmp.8 [CURRENT_BUFFER], 0
ifnz jmp refill_buffer_1
refill_buffer_0:
mov r31, 8192 ; 32768 bytes = 8192 words
mov r0, [AUDIO_POINTER]
mov r1, 0x0212C000 ; buffer 0 address
refill_buffer_loop:
mov [r1], [r0]
add r0, 4
add r1, 4
loop refill_buffer_loop
mov [AUDIO_POINTER], r0
sub [AUDIO_LENGTH], 32768
ifz call stop_audio
pop r31
pop r1
pop r0
reti
refill_buffer_1:
mov r31, 8192 ; 32768 bytes = 8192 words
mov r0, [AUDIO_POINTER]
mov r1, 0x02134000 ; buffer 1 address
jmp refill_buffer_loop
; stop audio playback
; inputs:
; none
; outputs:
; none
stop_audio:
push r0
; disable audio playback
mov r0, 0x80000600
out r0, 0
; restore the old buffer swap vector
mov [0x000003F8], [OLD_BUFFER_SWAP_VECTOR]
pop r0
ret

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@ -71,6 +71,10 @@ string_length: jmp [0xF0046018]
; integer jump table
string_to_int: jmp [0xF0047000]
; audio jump table
play_audio: jmp [0xF0048000]
stop_audio: jmp [0xF0048004]
; event types
const EVENT_TYPE_MOUSE_CLICK: 0x00000000
const EVENT_TYPE_MOUSE_RELEASE: 0x00000001

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@ -112,6 +112,7 @@ get_rom_version:
ret
; code
#include "audio.asm"
#include "background.asm"
#include "boot.asm"
#include "cursor.asm"
@ -218,6 +219,11 @@ get_rom_version:
org.pad 0xF0047000
data.32 string_to_int
; audio jump table
org.pad 0xF0048000
data.32 play_audio
data.32 stop_audio
org.pad 0xF004F000
standard_font_width:
data.16 8