prog8/examples/cx16/pcmaudio/adpcm.p8
2023-02-24 01:38:03 +01:00

266 lines
8.7 KiB
Lua

%import textio
%import floats
%option no_sysinit
%zeropage basicsafe
;
; IMA ADPCM decoding and playback example.
; https://wiki.multimedia.cx/index.php/IMA_ADPCM
; https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM
;
; IMA ADPCM encodes two 16-bit PCM audio samples in 1 byte (1 word per nibble)
; thus compressing the audio data by a factor of 4.
; The encoding precision is about 13 bits per sample so it's a lossy compression scheme.
;
; NOTE: this program requires 16 bits MONO audio, and 256 byte encoded block size!
; HOW TO CREATE SUCH IMA-ADPCM ENCODED AUDIO? Use sox or ffmpeg:
; $ sox --guard source.mp3 -r 8000 -c 1 -e ima-adpcm out.wav trim 01:27.50 00:09
; $ ffmpeg -i source.mp3 -ss 00:01:27.50 -to 00:01:36.50 -ar 8000 -ac 1 -c:a adpcm_ima_wav -block_size 256 -map_metadata -1 -bitexact out.wav
; Or use a tool such as https://github.com/dbry/adpcm-xq .
;
main {
ubyte adpcm_blocks_left
uword @requirezp nibblesptr
sub start() {
wavfile.parse()
txt.print_ub(wavfile.num_adpcm_blocks)
txt.print(" blocks = ")
txt.print_uw(wavfile.adpcm_size)
txt.print(" adpcm bytes\nsamplerate = ")
txt.print_uw(wavfile.sample_rate)
txt.print(" vera rate = ")
txt.print_uw(wavfile.vera_rate_hz)
txt.print("\n(b)enchmark or (p)layback? ")
when c64.CHRIN() {
'b' -> benchmark()
'p' -> playback()
}
}
sub benchmark() {
nibblesptr = wavfile.adpcm_data_ptr
txt.print("\ndecoding all blocks...\n")
c64.SETTIM(0,0,0)
repeat wavfile.num_adpcm_blocks {
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
nibblesptr += 4
repeat 252 {
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
adpcm.decode_nibble(nibble>>4) ; second word
nibblesptr++
}
}
float duration_secs = (c64.RDTIM16() as float) / 60.0
floats.print_f(duration_secs)
txt.print(" seconds (approx)\n")
const float PCM_WORDS_PER_BLOCK = 1 + 252*2
float words_per_second = PCM_WORDS_PER_BLOCK * (wavfile.num_adpcm_blocks as float) / duration_secs
txt.print_uw(words_per_second as uword)
txt.print(" decoded pcm words/sec\n")
float src_per_second = wavfile.adpcm_size as float / duration_secs
txt.print_uw(src_per_second as uword)
txt.print(" adpcm data bytes/sec\n")
}
sub playback() {
nibblesptr = wavfile.adpcm_data_ptr
adpcm_blocks_left = wavfile.num_adpcm_blocks
cx16.VERA_AUDIO_CTRL = %10101111 ; mono 16 bit
cx16.VERA_AUDIO_RATE = 0 ; halt playback
repeat 1024 {
cx16.VERA_AUDIO_DATA = 0
}
sys.set_irqd()
cx16.CINV = &irq_handler
cx16.VERA_IEN = %00001000 ; enable AFLOW
sys.clear_irqd()
cx16.VERA_AUDIO_RATE = wavfile.vera_rate ; start playback
txt.print("\naudio via irq\n")
repeat {
; audio will play via the IRQ.
}
; not reached:
; cx16.VERA_AUDIO_CTRL = %00100000
; cx16.VERA_AUDIO_RATE = 0
; txt.print("audio off.\n")
}
sub irq_handler() {
if cx16.VERA_ISR & %00001000 {
; AFLOW irq.
;; cx16.vpoke(1,$fa0c, $a0) ; paint a screen color
; refill the fifo buffer with one decoded adpcm block (1010 bytes of pcm data)
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr += 4
repeat 252 {
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
adpcm.decode_nibble(nibble>>4) ; second word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr++
}
adpcm_blocks_left--
if adpcm_blocks_left==0 {
; restart adpcm data from the beginning
nibblesptr = wavfile.adpcm_data_ptr
adpcm_blocks_left = wavfile.num_adpcm_blocks
txt.print("end of data, restarting.\n")
}
} else {
; TODO not AFLOW, handle other IRQ
}
;; cx16.vpoke(1,$fa0c, 0) ; back to other screen color
%asm {{
ply
plx
pla
rti
}}
}
}
adpcm {
; IMA ADPCM decoder.
; https://wiki.multimedia.cx/index.php/IMA_ADPCM
; https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM
ubyte[] t_index = [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8]
uword[] t_step = [
7, 8, 9, 10, 11, 12, 13, 14,
16, 17, 19, 21, 23, 25, 28, 31,
34, 37, 41, 45, 50, 55, 60, 66,
73, 80, 88, 97, 107, 118, 130, 143,
157, 173, 190, 209, 230, 253, 279, 307,
337, 371, 408, 449, 494, 544, 598, 658,
724, 796, 876, 963, 1060, 1166, 1282, 1411,
1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
32767]
uword @zp predict
ubyte @zp index
uword @zp pstep
sub init(uword startPredict, ubyte startIndex) {
predict = startPredict
index = startIndex
pstep = t_step[index]
}
sub decode_nibble(ubyte nibble) {
; this is the hotspot of the decoder algorithm!
cx16.r0s = 0 ; difference
if nibble & %0100
cx16.r0s += pstep
pstep >>= 1
if nibble & %0010
cx16.r0s += pstep
pstep >>= 1
if nibble & %0001
cx16.r0s += pstep
pstep >>= 1
cx16.r0s += pstep
if nibble & %1000
cx16.r0s = -cx16.r0s
predict += cx16.r0s as uword
index += t_index[nibble]
if_neg ; was: if index & 128
index = 0
else if index > len(t_step)-1
index = len(t_step)-1
pstep = t_step[index]
}
}
wavfile {
const ubyte WAVE_FORMAT_PCM = $1
const ubyte WAVE_FORMAT_ADPCM = $2
const ubyte WAVE_FORMAT_IEEE_FLOAT = $3
const ubyte WAVE_FORMAT_ALAW = $6
const ubyte WAVE_FORMAT_MULAW = $7
const ubyte WAVE_FORMAT_DVI_ADPCM = $11
uword sample_rate
uword vera_rate_hz
ubyte vera_rate
uword adpcm_size
uword adpcm_data_ptr
ubyte num_adpcm_blocks
sub parse() {
; "RIFF" , filesize (int32) , "WAVE", "fmt ", fmtsize (int32)
; we assume file sizes are <= 64Kb so don't have to worry about the upper 16 bits
uword @zp header = &wavdata.wav_data
if header[0]!=iso:'R' or header[1]!=iso:'I' or header[2]!=iso:'F' or header[3]!=iso:'F'
or header[8]!=iso:'W' or header[9]!=iso:'A' or header[10]!=iso:'V' or header[11]!=iso:'E'
or header[12]!=iso:'f' or header[13]!=iso:'m' or header[14]!=iso:'t' or header[15]!=iso:' ' {
txt.print("not a valid wav file\n")
sys.exit(1)
}
; uword filesize = peekw(header+4)
uword chunksize = peekw(header+16)
uword wavefmt = peekw(header+20)
uword nchannels = peekw(header+22)
sample_rate = peekw(header+24) ; we assume sample rate <= 65535 so we can ignore the upper word
uword block_align = peekw(header+32)
if block_align!=256 or nchannels!=1 or wavefmt!=WAVE_FORMAT_DVI_ADPCM {
txt.print("invalid wav specs\n")
sys.exit(1)
}
; skip chunks until we reach the 'data' chunk
header += chunksize + 20
repeat {
chunksize = peekw(header+4) ; assume chunk size never exceeds 64kb so ignore upper word
if header[0]==iso:'d' and header[1]==iso:'a' and header[2]==iso:'t' and header[3]==iso:'a'
break
header += 8 + chunksize
}
adpcm_data_ptr = header + 8
adpcm_size = chunksize
num_adpcm_blocks = (chunksize / 256) as ubyte ; NOTE: THE ADPCM DATA NEEDS TO BE ENCODED IN 256-byte BLOCKS !
const float vera_freq_factor = 25e6 / 65536.0
vera_rate = (sample_rate as float / vera_freq_factor) + 1.0 as ubyte
vera_rate_hz = (vera_rate as float) * vera_freq_factor as uword
}
}
wavdata {
%option align_page
wav_data:
%asmbinary "adpcm-mono.wav"
wav_data_end:
}