mirror of
https://github.com/irmen/prog8.git
synced 2024-12-22 03:29:41 +00:00
107 lines
3.2 KiB
Lua
107 lines
3.2 KiB
Lua
; This program can stream a simple uncompressed PCM file from the sdcard.
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;
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; It is hardwired to play a 16 bit stereo PCM file,
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; but you can type in the sample rate you want to play it in.
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;
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; It uses simple polling on the AFLOW flag rather than actually using a IRQ hander,
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; to see when to refill the FIFO buffer.
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;
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; The sample data is simply read using diskio.f_read() routine, but that uses MACPTR internally for fast loads.
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%import diskio
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%import textio
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%option no_sysinit
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main {
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sub start() {
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str MUSIC_FILENAME = "?"*32
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txt.print("what sample rate (hz) do you want to play at: ")
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void txt.input_chars(MUSIC_FILENAME)
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music.vera_rate_hz = conv.str2uword(MUSIC_FILENAME)
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if music.vera_rate_hz==0
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music.vera_rate_hz=44100
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music.calculate_vera_rate(music.vera_rate_hz)
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txt.print("\nname of raw .pcm file to play on drive 8: ")
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while 0==txt.input_chars(MUSIC_FILENAME) {
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; until user types a name...
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}
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if diskio.f_open(MUSIC_FILENAME) {
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cx16.rombank(0)
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void diskio.fastmode(1)
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music.start()
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while music.stream() {
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txt.chrout('.')
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}
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} else {
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txt.print("\nio error")
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}
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}
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}
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music {
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uword audio_buffer = memory("audiobuffer", 1024, 0)
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uword vera_rate_hz
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ubyte vera_rate
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sub start() {
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cx16.VERA_AUDIO_RATE = 0 ; halt playback
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cx16.VERA_AUDIO_CTRL = %10111011 ; stereo 16 bit, volume 11
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sys.memset(audio_buffer, 1024, 0)
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cx16.VERA_AUDIO_RATE = vera_rate ; start playback
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}
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sub calculate_vera_rate(uword sample_rate) {
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const uword vera_freq_factor = 25_000_000 / 65536
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vera_rate = (sample_rate / vera_freq_factor) as ubyte + 1
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vera_rate_hz = vera_rate * vera_freq_factor
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}
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sub stream() -> bool {
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while cx16.VERA_ISR & %00001000 == 0 {
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; poll until AFLOW is raised ("fifo is less than 25% full, feed me more data soon!")
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}
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; Reading directly from disk into the audio fifo is possible, but can result in hick ups.:
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; diskio.reset_read_channel()
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; void, cx16.r14 = cx16.MACPTR(0, &cx16.VERA_AUDIO_DATA, true)
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; void, cx16.r15 = cx16.MACPTR(0, &cx16.VERA_AUDIO_DATA, true)
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; return cx16.r14+cx16.r15 == 1024
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; so instead: copy current buffer to Vera audio FIFO and immediately read the next 1 KB block from disk into the buffer.
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fill_fifo()
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return diskio.f_read(audio_buffer, 1024) == 1024
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}
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asmsub fill_fifo() {
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; copy 1024 bytes of audio data from the buffer into vera's fifo, quickly!
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%asm {{
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lda p8v_audio_buffer
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sta _loop+1
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sta _lp2+1
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lda p8v_audio_buffer+1
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sta _loop+2
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sta _lp2+2
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ldx #4
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ldy #0
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_loop lda $ffff,y
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sta cx16.VERA_AUDIO_DATA
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iny
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_lp2 lda $ffff,y
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sta cx16.VERA_AUDIO_DATA
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iny
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bne _loop
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inc _loop+2
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inc _lp2+2
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dex
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bne _loop
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rts
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}}
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}
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}
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