[ scummvm-Bugs-805691 ] FMTOWNS: Missing opcodes

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Bugs item #805691, was opened at 2003-09-13 19:29
Message generated for change (Tracker Item Submitted) made by Item Submitter
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Thomas Combeleran (hibernatus)
Assigned to: Nobody/Anonymous (nobody)
Summary: FMTOWNS: Missing opcodes

Initial Comment:
Hi, here are what the missing FM Towns opcodes are 

supposed to do:



in resourceRoutines:

- case 0x20: Does nothing. Never used.



- case 0x21: Does nothing. Never used.



- case 0x23: Sets the CD loudness (just a guess, not 

confirmed by UNZ).

Used in Loom (CD loudness divided by 2 while a pattern 

is played).

Not implemented in Indy3 (it reads getVarOrDirectByte

(0x20) and breaks).

Takes 2 bytes (resid and foo in the current code). Must 

be for stereo, but then left == right everywhere.



- case 0x24: Sets the loudness of a sound resource.

Used in Indy3 and Zak.

My guess is that foo is left loudness and bar is right 

loudness, but UNZ doesn't play stereo :)

If foo + bar == 0 (which includes FF + 01 for example), 

the default loudness will be used.

The default loudness is at 0x0E and 0x0F in the sound 

resource.



- case 0x25: Sets the pitch of a sound resource.

Used in Indy3 and Loom.

If foo == 0, the sound is played normally.

pitch = foo - center semitones.

"center" is at 0x32 in the sfx resource (always 0x3C in 

zak256, but sometimes different in Indy3).





in startMusic:

- case 0xFF: Gets the CD loudness.

Used in Loom (when the CD loudness is divided by 2 with 

resourceRoutines)

It returns (left + right + 1) / 2.





About the loudness and pitch:

In the original engine there's an array which contains the 

loudness and the pitch of each sound.

After a sound is played (startSound), the pitch and 

loudness are reset.

So if you set a pitch +1 and then play the sound twice 

you'll hear +1 then +0.

At least that's how it worked with Indy3.



(for ender: i had already added a struct in the 

disassembly, now you can replace field0 by count, field1 

by left, field2 by right and field3 by pitch)



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