ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<ValleyBell>
superctr: Maybe it also uses delta-PCM?
<superctr>
no, it says in the thread
<ValleyBell>
ah, okay
<superctr>
it's somewhat similar to BRR
<ValleyBell>
I just quickly skimmed over most of the posts
<superctr>
basically 0x400-0x7fff contain 4-bit exponents (each 4-bit value contains the exponent for 16 samples), 0x8000-0xfffff contain 8-bit mantissas
<ValleyBell>
hmm.. it doesn't look like any of the dumps or research from that thread has make it into MAME yte
<ValleyBell>
*yet
<superctr>
nope
<superctr>
also, the Sound Canvas VA plugin contains the raw unencrypted samples from the SC88
<superctr>
in the 12-bit compressed format though
<m4t>
is it encrypted in the traditional sense, or are the address lines just mixed up?
<m4t>
address/data
<ValleyBell>
It's just mixed address/data lines.
<ValleyBell>
Still, awesome research there.
<m4t>
:)
<ValleyBell>
IIRC the samples on the CM-32P sounded very tinny as well and in the end the solution was that all the samples were delta-values.
<ValleyBell>
so I thought this might be the case here as well
<ValleyBell>
Anyway, I don't have an account on vogons (and don't feel like making one right now). I wouldn't mind talking about the CM-32P descrambling though.
<ValleyBell>
In any case, it would be nice to see the SC-88 sound ROMs (posted in the thread as SC88327328.zip/SC88IC325326.zip) being referenced in MAME.
<superctr>
<ValleyBell> IIRC the samples on the CM-32P sounded very tinny as well and in the end the solution was that all the samples were delta-values. <- hm, that could be true
<superctr>
anyway, if you add delta-PCM then this basically becomes ADPCM lol
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<cr1901_modern>
cbmuser: On the m68k.info page, one idea is for something called a "Gemini" server. Is this Gemini? https://gemini.circumlunar.space
<cbmuser>
no idea
<cbmuser>
best is to ask during the next m68k meeting
<cbmuser>
I'm not in charge of the website, Carsten Strotmann is
<cr1901_modern>
Ahhh whoops :P
<cr1901_modern>
Right, that's this Friday at 6PM UTC
<cr1901_modern>
I'll try to be there
<cr1901_modern>
I should probably put "68k" on topic specifically b/c it was used as a companion to all the FM synth chips on arcade boards lol
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<superctr>
Nah
<superctr>
Most arcade boards with FM chips typically had an 8-bit CPU dedicated to controlling the sound chips, usually a Z80
<ValleyBell>
Sega used the Z80 as sound CPU until they switched to 68000+SCSP on Model 2.
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<superctr>
Model 1 used a 68000
<Sarayan>
Thrill drive uses a 68000 too for sound with horribly-compiled C code
<Sarayan>
think -O0 without even peephole optimization
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