TLUG.NomiKai++; synthSound(&hardware);

TLUGに行ってきた．
BarCamp-Tokyo2009の中の人がHypertextについて話してたのと，XMLとSQLの香りがするsemantic webの話だった．
皆さんはレイヤが高いですな，あいかわらず． :)
飲み会/二次会ではshojiさんのSunオフレコ話とかJARIさん（北欧のイケメン）のアレとか色々．

帰ってからmatsuuさんのBarCamp-Tokyo2009用の下ごしらえっぽいモノとして，それっぽいgraphvizな絵をでっち上げた．
多分，もうちっと弄る．


上の絵をでっち上げていたら，#vhdlでhardware sound synthesize野郎が現れていた． :DDD

05/10 03:54:30 mad
    I'm planning on making sound generation stuff
05/10 03:56:23 mad
    most of that stuff is based around a phase register being incremented
    by the frequency on each sound cycle (which is pretty low rate -
    typically around 44khz)
05/10 04:02:43 bpadalino
    sounds like a cordic should help you out
05/10 04:04:46 hiyuh
    cordic is not for making sound, imho.
05/10 04:09:48 hiyuh
    that sounds like singletone, variable freq in narrow range, and
    presicion is not so important.
05/10 04:10:38 hiyuh
    maybe, making rom-based nco is enough to do.
05/10 04:14:39 bpadalino
    i don't know if a saw wave would sound very good, but as a phase
    accumulator - a cordic sounds like it would work well
05/10 04:30:24 hiyuh
    I meant cordic is expensive for that use.
05/10 04:30:29 hiyuh
    and saw wave + filter for singletone is not a possibility, anyway.
05/10 04:32:34 hiyuh
    phase accum -> sin or cos rom in appropriate precision -> singletone,
    it's simple rom-based nco.
05/10 04:40:47 bpadalino
    you really think a cordic is that expensive ?
05/10 04:51:49 hiyuh
    bpadalino: yes
05/10 04:51:58 bpadalino
    interesting
05/10 04:55:54 bpadalino
    hiyuh, so if you wanted to create 20 tones, how would you go about
    doing that ?
05/10 04:57:07 hiyuh
    20 tones in same time?
05/10 04:57:31 bpadalino
    yeah
05/10 04:59:05 hiyuh
    these tones are elaborate-time fixed or run-time fixed?
05/10 05:00:05 hiyuh
    I meant these tones are fixed before logic synthesize, or not.
05/10 05:00:29 bpadalino
    runtime fixed tones .. frequency fixed before synthesis, but phase
    programmable ..
05/10 05:00:44 bpadalino
    and i want the sum of the 20 tones on the output
05/10 05:07:54 hiyuh
    you mean "amplitude * (sin(2*pi*f1*t + theta1(t)) + ... sin(2*pi*f20*t
    + theta20(t)))"?
05/10 05:09:10 bpadalino
    yeah
05/10 05:10:53 hiyuh
    if I were you, I'd like to make semi-fixed digital filter or just
    do IFFT.
05/10 05:12:42 bpadalino
    that's what i had figured before, but i was just curious what someone
    else might have thought
05/10 05:13:00 hiyuh
    heh
05/10 05:14:18 bpadalino
    i would like to do my own generic systolic FFT sometime ... i think
    that might be fun
05/10 05:16:23 mad
    the tones parameters are written to at performance time
05/10 05:18:05 mad
    It's for music generation, so the applicable freqs are about 20hz to
    20khz (although tones over something like 4khz aren't particularly
    musical)
05/10 05:19:17 anonissimus
    mad: but as harmonics they are
05/10 05:19:33 mad
    Precision has to be at least 1%, esp. in the "most common range"
    (around 50hz ~ 1000hz)
05/10 05:19:50 mad
    anonissimus: yeah, but those are generated from another process
05/10 05:21:16 anonissimus
    ah
05/10 05:21:38 anonissimus
    know more on music than on generting it with hardware :)
05/10 05:21:57 mad
    My plan is: start with pure phase accumulator, then twist the phase
    around in a couple of functions (incl. one that uses multiplication),
    then use sine wave/funky waveform LUT, apply volume and panning,
    sum the channels together, DAC
05/10 05:24:12 mad
    Uses about 140 bits of registers per channel
05/10 05:27:44 mad
    A real practical design would actually be sample based instead
    (with samples in RAM)
05/10 05:29:23 hiyuh
    you know, your plan violates my assumption that described in the
    above expr.
05/10 05:29:25 hiyuh
    so what I was saying is not good way for you.
05/10 05:29:59 mad
    mm, right
05/10 05:31:35 mad
    sound synthesis isn't so hard because the sampling rate is low
    anyways... and you can do it well in software if you have enough CPU
05/10 05:32:14 hiyuh
    yeah, that's why soft synth is popular atm.
05/10 05:32:40 mad
    no kidding, since it pretty much solves it

つまり，敢えてsoftware sound synthesizeしないっつーことですか？
そいつは物好きだなぁ． :)