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PostPosted: May 11th, 2014, 4:31 am 
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Joined: May 8th, 2014, 7:31 am
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This is a long shot - I've no idea if anyone in this forum is interested in MML or the nitty-gritty technical aspects of PC98 audio - but I'm not sure where else to turn.

I've been familiarizing myself with KAJA's PMD48 sound driver on the np21nt (from np2fmgen) emulator, using the external fmgen.dll, with hopes of composing some cool FM music. Things are going okay, except I've run into a frustrating and seemingly insurmountable problem trying to replace the awful default drum sounds it provides for the YM2608's rhythm channels.

The file PPS.DOC instructs you to use a third-party application called PCMCONV to convert YM2608 ADPCM (.spb) sound files to "4-bit unsigned PCM" (.spc) sound files, which can be test played using the PUT command or bundled into a .PPS file with the MAKEPPS command for use in music. The problem is that every time I attempt to do this, the resulting .spc file sounds like corrupted noise and nothing like the original sound.

PCMCONV claims to support the following formats:
Code:
      .spb   YM2608(OPNA) のADPCM
      .pcm   MSM6258(X68k)のADPCM
      .snd   RF5C68(TOWNS)のPCM
      .spk   Macintosh    のPCM
      .spc   符号なし4bit のPCM (4-bit unsigned PCM)
      .pc8   符号つき8bit のPCM (8-bit signed PCM)
      .p16   符号つき16bitのPCM(リトルエンディアン) (16-bit signed PCM, little-endian)
      .phl   符号つき16bitのPCM(ビッグエンディアン) (16-bit signed PCM, big-endian)
      .wav   MS-WindowsのWaveファイル

I've tried just about every type of WAV file and raw ADPCM and PCM I can find a way to convert to, with various bit depths and sample rates, and nothing has produced a usable .spc file. I've gone so far as to do conversions using another X68000 converter application I tracked down, PCM3PCM, which appears to support several of these exact formats:

Code:
   .n16   16000Hz   YM2608 4bit ADPCM      モノラル
   .p16   15625Hz   符号あり 16bit PCM(big)      モノラル
   .phl   15625Hz   符号あり 16bit PCM(big)      モノラル
   .pc8   15625Hz   符号あり  8bit PCM      モノラル
   .pcm   15625Hz   MSM6258V  4bit ADPCM      モノラル

None work any better as inputs to PCMCONV, of course. The only difference is some formats convert to a few short glitchy pops instead of a half-second bleep.

Meanwhile, I can find utterly no information on the .spc format that I need, no programs capable of importing and exporting 4-bit PCM, and indeed little evidence that 4-bit PCM is actually used outside of highly technical documents dealing with electrical engineering. I'm wondering if it's a typo for ADPCM (which is typically 4-bit.)

Evidence that SSGPCM playback isn't just screwed up entirely:
PMD48 comes with an example PPS file (PPS01.PPS in PMD_SAM.LZH). The sounds from it (extracted with PPSDIV) play back perfectly using the PUT command and in MML songs. Even when converted with PCMCONV to other formats and back, they still play properly.

The most bizarre thing about this:
When I convert my "corrupted" .spcs back to WAV format, they're still clearly the original sound, just degraded in quality. The sample rate of all WAV files written by PCMCONV is 65535hz though. (I've tried supplying PCMCONV with WAV files in the exact same format as far as I can tell, 8-bit unsigned integer with a sample rate of 65535. No dice with those either.)

Here's a link to a ZIP including one of the working example sounds in every format PCMCONV can convert to, as well as one of my own sound files that won't play back properly upon conversion to .spc (SNARE2.WAV is the .spc reconverted to WAV by PCMCONV.)

I'd greatly appreciate advice from anyone who's used this software, any information on any of these sound formats (especially .spc!), pointers to another forum where people might know more about this, or anything at all, really. I think I'm going to have to give up on this if no one else can point the way. (Which isn't such a big problem, since the fmgen DLL does support loading drum sounds externally. But there's only six slots for those, and I might want to record my songs on a G.I.M.I.C. or real PC98 someday too...)


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PostPosted: May 13th, 2014, 3:41 pm 
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Joined: June 23rd, 2007, 10:34 pm
Posts: 408
Location: You know
I hope some people here will be able to help you, but you might also ask around at VGM Rips and on the DefleMask forum.

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PostPosted: December 27th, 2015, 9:57 pm 
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Joined: December 3rd, 2015, 8:01 am
Posts: 6
I know this is very, very old but I threw myself against this problem headfirst for 4 hours today. Had all the same issues you had—wav exports converted through PCMCONV would turn out horrid noise no matter what. What a pain!

Here's what I did:
-Using Audacity, I exported my samples as 16k, 8-bit Apple/SGI PCM files (using the "Other Uncompressed Formats" dialog) as [sample].AIF
-From there, I used KAJA's AINF utility to extract the .AIF to .PC8 to use with PCMCONV
-After compiling the PPS, the samples sound a lot more like what they're supposed to. Beware that if you use sample rates higher than 16k, you may get aliasing distortion!


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