Port the Sonic 2 Clone Sound Driver to the HG version of Sonic 2

(Original guide by Caverns4)

Summary

Please note that this guide is currently in need of a few teaks, which I will be implementing once I get the chance. In the meantime, use this guide at your own risk. ~ Caverns4

The Sonic 2 Clone Driver is simply a modified version of the Sonic 1 Sound driver, designed to work with Sonic 2. The advantages to using this over the Sound Driver in Sonic 2 normally are numerous; It will be easier to modify existing songs as you won't have to worry about compressing and decompressing the music, and your music will be supported by more up to date Music editor programs.

There are a few bugs I have noticed. One is that the spindash sound will not raise pitch. The music is not a perfect adaptation of Sonic 2's music, particularly sometimes the PSG channels sound slightly different. This is most noticeable in Emerald Hill's music. Besides this, there are no problems.

If the above bugs will not bother you too badly, then you'll like using the Sonic 2 Clone Driver after working with Sonic 2's own sound driver. The Clone Driver is much easier to port music to, and in fact, Sonic 1 music can even just be bincluded into the ROM. This is because it's based on the Sonic 1 sound driver, and uses similar (if not the same) formatting. With this out of the way, now it's time to edit the Sonic 2 HG Dissasembly!

Before begining, you will need the following file:

Download Sonic 2 Clone Driver Files File: Sonic 2 Clone Driver.7z (78 kB) (info)

Step 1 - getting started

Back up your dissasembly if you haven't already.

To start, go into your sound folder, where you'll have a DAC folder, a music folder, and a PCM folder.

DELETE THEM ALL!

Also delete s2.sounddriver.asm. That's the Sonic 2 Sound Driver, so it's not necessary.

and then extract "Sonic 2 Clone Driver_fixed.7z" into the main folder of your dissasembly.

Step 2 - Deleting leftovers

Now open up s2.asm, and find the label 'SoundDriverLoad:'. Delete everything from that, up to and including:

<asm>'Mus_Continue: BINCLUDE "sound/music/Continue.bin"'</asm>

What we have done here is deleted the routines to load and decompress the Sound Driver. We don't need this anymore.

Next up, find this line:

<asm>cnop -Size_of_SEGA_sound, $8000</asm>

and delete everything from there up to (but not including) the line:

<asm> ; end of 'ROM'</asm>

Also, on the line above the 'EndOfRom:' label, you should see this:

<asm> shared word_728C_user,Obj5F_MapUnc_7240,off_3A294,MapRUnc_Sonic,movewZ80CompSize</asm>

Change it to this:

<asm> shared word_728C_user,Obj5F_MapUnc_7240,off_3A294,MapRUnc_Sonic</asm>

Finally, find the label 'sndDriverInput:'

Delete the entire function, which starts there, and ends at this line:

<asm>; End of function sndDriverInput</asm>

Now search in your assembly for "sndDriverInput", and delete any lines that point to it. There will be quite a few, but it won't hurt anything.

We've effectively deleted the old sound driver entirely from our game... Now it's time we implemented a new one.. But first, we need to prepare S2.Constants.asm

Step 3 - Overhauling Constants, fixing RAM

Open s2.constants.asm, and find the following line:

Find the line "; Music IDs". You'll see this:

<asm>; Music IDs offset := zMasterPlaylist ptrsize := 1 idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,

you may need to insert a dummy zMusIDPtr in the $80 slot</asm>

delete everything from there down to "MusID__End = id(zMusIDPtr__End)  ; A0", and paste the following where it used to be:

<asm>; Music IDs idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,

you may need to insert a dummy zMusIDPtr in the $80 slot

MusID__First = idstart MusID_2PResult = $81 MusID_EHZ = $82 MusID_MCZ_2P = $83 MusID_OOZ = $84 MusID_MTZ = $85 MusID_HTZ = $86 MusID_ARZ = $87 MusID_CNZ_2P = $88 MusID_CNZ = $89 MusID_DEZ = $8A MusID_MCZ = $8B MusID_EHZ_2P = $8C MusID_SCZ = $8D MusID_CPZ = $8E MusID_WFZ = $8F MusID_HPZ = $90 MusID_Options = $91 MusID_SpecStage = $92 MusID_Boss = $93 MusID_EndBoss = $94 MusID_Ending = $95 MusID_SuperSonic = $96 MusID_Invincible = $97 MusID_ExtraLife = $98 MusID_Title = $99 MusID_EndLevel = $9A MusID_GameOver = $9B MusID_Continue = $9C MusID_Emerald = $9D MusID_Credits = $9E MusID_Countdown = $9F MusID__End = $A0</asm>

The music is all fixed, now all that's left is the sound effects:

Find the line "; Sound IDs", and delete everything down to the line "; Special sound IDs". Leave the special IDs alone.

In place of the text you deleted, just paste this:

<asm>; Sound IDs idstart := $A0

SndID__First = idstart SndID_Jump = $A0  ; A0 SndID_Checkpoint = $A1  ; A1 SndID_SpikeSwitch = $A2  ; A2 SndID_Hurt = $A3  ; A3 SndID_Skidding = $A4  ; A4 SndID_BlockPush = $A5  ; A5 SndID_HurtBySpikes = $A6  ; A6 SndID_Sparkle = $A7 SndID_Beep = $A8 SndID_Bwoop = $A9 SndID_Splash = $AA SndID_Swish = $AB SndID_BossHit = $AC SndID_InhalingBubble = $AD SndID_ArrowFiring = $AE SndID_LavaBall = $AE SndID_Shield = $Af SndID_LaserBeam = $B0 SndID_Zap = $B1 SndID_Drown = $B2 SndID_FireBurn = $B3 SndID_Bumper = $B4 SndID_Ring = $B5  ; B5 SndID_RingRight = $B5 SndID_SpikesMove = $B6 SndID_Rumbling = $B7 SndID_Smash = $B9 SndID_DoorSlam = $BB SndID_SpindashRelease = $BC  ; BC SndID_Hammer = $BD SndID_Roll = $BE SndID_ContinueJingle = $BF SndID_CasinoBonus = $C0 SndID_Explosion = $C1 SndID_WaterWarning = $C2 SndID_EnterGiantRing = $C3 SndID_BossExplosion = $C4 SndID_TallyEnd = $C5 SndID_RingSpill = $C6 SndID_Flamethrower = $C8 SndID_Bonus = $C9 SndID_SpecStageEntry = $CA SndID_SlowSmash = $CB SndID_Spring = $CC SndID_Blip = $CD SndID_RingLeft = $B5 SndID_Signpost = $CF SndID_CNZBossZap = $D0 SndID_Signpost2P = $D3 SndID_OOZLidPop = $D4 SndID_SlidingSpike = $D5 SndID_CNZElevator = $D6 SndID_PlatformKnock = $D7 SndID_BonusBumper = $D8 SndID_LargeBumper = $D9 SndID_Gloop = $DA SndID_PreArrowFiring = $DB SndID_Fire = $DC SndID_ArrowStick = $DD SndID_Helicopter = $DE SndID_SuperTransform = $DF SndID_SpindashRev = $E0 SndID_Rumbling2 = $E1 SndID_CNZLaunch = $E2 SndID_Flipper = $E3 SndID_HTZLiftClick = $E4 SndID_Leaves = $E5 SndID_MegaMackDrop = $E6 SndID_DrawbridgeMove = $E7 SndID_QuickDoorSlam = $E8 SndID_DrawbridgeDown = $E9 SndID_LaserBurst = $EA SndID_Scatter = $EB SndID_LaserFloor = $EB SndID_Teleport = $EC SndID_Error = $ED SndID_MechaSonicBuzz = $EE SndID_LargeLaser = $EF SndID_OilSlide = $F0 SndID__End = $F7</asm>

The following are the lines you should NOT have deleted, just for reference:

<asm>MusID_StopSFX = $78+$80 ; F8 MusID_FadeOut = $79+$80 ; F9 SndID_SegaSound = $7A+$80 ; FA MusID_SpeedUp = $7B+$80 ; FB MusID_SlowDown = $7C+$80 ; FC MusID_Stop = $7D+$80 ; FD MusID_Pause = $7E+$80 ; FE MusID_Unpause = $7F+$80 ; FF</asm>

Now, find these lines:

<asm>Underwater_palette_2: ds.w palette_line_size ; not sure what it's used for but it's only used when there's water Underwater_palette_2_line2: ds.w palette_line_size Underwater_palette_2_line3: ds.w palette_line_size Underwater_palette_2_line4: ds.w palette_line_size

Underwater_palette: ds.w palette_line_size ; main palette for underwater parts of the screen Underwater_palette_line2: ds.w palette_line_size Underwater_palette_line3: ds.w palette_line_size Underwater_palette_line4: ds.w palette_line_size</asm>

Copy these lines to the clipboard (Or better yet, to a separate text document), we are going to be moving them in a moment.

Immediately below where those lines used to be is a line like this:

<asm> ds.b $500 ; $FFFFF100-$FFFFF5FF ; unused, leftover from the Sonic 1 sound driver (and used by it when you port it to Sonic 2)</asm>

Change it to this:

<asm> ds.b $600 ; $FFFFF000-$FFFFF5FF ; Used by the Sonic 2 Clone Driver.</asm>

The underwater palettes were overwriting some RAM that the Sonic 1/Sonic2 Clone Driver use, so we need to move them somewhere safer. Fortunately, such a place in RAM exists.

What we need, are $100 free bytes. So, first off, find the line:

<asm>Normal_palette: ds.w palette_line_size</asm>

Paste the underwater_palette lines right above it.

Right above the lines you just pasted, you should see the following:

<asm>Sprite_Table: ds.b $280 ; Sprite attribute table buffer ds.b $80 ; unused, but SAT buffer can spill over into this area when there are too many sprites on-screen</asm>

Replace them both with just this:

<asm>Sprite_Table: ds.b $200 ; Sprite attribute table buffer</asm>

Step 4 - Introducing the new Sound Driver!

Go back to s2.asm, and right above this line:

<asm> ; end of 'ROM'</asm>

Paste this:

<asm> include "Sonic 2 Clone Driver.asm"</asm>

Now, before anything else, open up Sonic 2 Clone Driver.asm, and find and replace (CRTL+H usually) all instances of "INCBIN" with "BINCLUDE" (Without the quotes).

Repeat the process, replacing all intances of "@loc" with "Lloc". The HG dissasembly does not like local routines, so this converts them into normal routines to avoid errors.

At this point, you can build your ROM if you want. You wont get any sound, but the game will run.

Step 5 - Let the music play!

Go back to S2.asm, and find the label "VintRet:"

In that function, right after the label, paste this line:

<asm> jsr Init_Sonic1_Sound_Driver</asm>

If you were to build your ROM again now, you still wouldn't have sound. We're going to fix that now. Go back to s2.constants.asm, and find these lines:

<asm>Music_to_play: ds.b 1 SFX_to_play: ds.b 1 ; normal SFX_to_play_2: ds.b 1 ; alternating stereo unk_FFE3: ds.b 1 Music_to_play_2: ds.b 1 ; alternate (higher priority?) slot</asm>

Replce theme with this:

<asm> ds.b 1

                   ds.b	1
                   ds.b	1

unk_FFE3: ds.b 1

                   ds.b	1</asm>

If you want to, you can also move the line with 'unk_FFE3' down one line and replace the four resulting "ds.b 1"s with a single "ds.l".

Now, we need to remake the music_to_play and SFX_to_play constants, but a bit differently. Anywhere in s2.constants.asm you deem appropriate (for example, right before the block of RAM equates we just modified, paste this code:

<asm>Music_Pause = $FFFFF003 Music_to_play = $FFFFF00A SFX_to_play = $FFFFF00B</asm>

Go back to S2.asm; we've got more changes to make.

First off, search for and replace all instances of "SFX_to_play_2" with just "SFX_to_play", and "Music_to_play_2" with "Music_to_play".

This fixes most things, but if were to play the game, both the Sega Sound and pausing the game are... REALLY messed up. Lets fix this, too.

Find this line, again, in s2.asm

<asm> move.b #MusID_Pause,(Music_to_play).w ; pause music</asm>

Replace it with this:

<asm> move.b #1,(Music_Pause).w ; pause music</asm>

And replace all instances of this line:

<asm> move.b #MusID_Unpause,(Music_to_play).w</asm>

With this:

<asm> move.b #$80,(Music_Pause).w ; resume music</asm>

Step 6 - Identity Crisis

Open s2.constants.asm. 393 is a lot of errors, but all it takes to fix them is a copy+paste job for you.

Find the line "; Music IDs". You'll see this:

<asm>; Music IDs offset := zMasterPlaylist ptrsize := 1 idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,

you may need to insert a dummy zMusIDPtr in the $80 slot</asm>

delete everything from there down to "MusID__End = id(zMusIDPtr__End)  ; A0", and paste the following where it used to be:

<asm>; Music IDs offset := MusicIndex ptrsize := 1 idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,

you may need to insert a dummy zMusIDPtr in the $80 slot

MusID__First = idstart MusID_2PResult = $81 MusID_EHZ = $82 MusID_MCZ_2P = $83 MusID_OOZ = $84 MusID_MTZ = $85 MusID_HTZ = $86 MusID_ARZ = $87 MusID_CNZ_2P = $88 MusID_CNZ = $89 MusID_DEZ = $8A MusID_MCZ = $8B MusID_EHZ_2P = $8C MusID_SCZ = $8D MusID_CPZ = $8E MusID_WFZ = $8F MusID_HPZ = $90 MusID_Options = $91 MusID_SpecStage = $92 MusID_Boss = $93 MusID_EndBoss = $94 MusID_Ending = $95 MusID_SuperSonic = $96 MusID_Invincible = $97 MusID_ExtraLife = $98 MusID_Title = $99 MusID_EndLevel = $9A MusID_GameOver = $9B MusID_Continue = $9C MusID_Emerald = $9D MusID_Credits = $9E MusID_Countdown = $9F MusID__End = $A0</asm>

The music is all fixed, now all that's left is the sound effects:

Find the line "; Sound IDs", and delete everything down to the line "; Special sound IDs". Leve the special IDs alone.

In place of the text you deleted, just paste this:

<asm>; Sound IDs offset := SoundIndex ptrsize := 2 idstart := $A0

SndID__First = idstart SndID_Jump = $A0  ; A0 SndID_Checkpoint = $A1  ; A1 SndID_SpikeSwitch = $A2  ; A2 SndID_Hurt = $A3  ; A3 SndID_Skidding = $A4  ; A4 SndID_BlockPush = $A5  ; A5 SndID_HurtBySpikes = $A6  ; A6 SndID_Sparkle = $A7 SndID_Beep = $A8 SndID_Bwoop = $A9 SndID_Splash = $AA SndID_Swish = $AB SndID_BossHit = $AC SndID_InhalingBubble = $AD SndID_ArrowFiring = $AE SndID_LavaBall = $AE SndID_Shield = $Af SndID_LaserBeam = $B0 SndID_Zap = $B1 SndID_Drown = $B2 SndID_FireBurn = $B3 SndID_Bumper = $B4 SndID_Ring = $B5  ; B5 SndID_RingRight = $B5 SndID_SpikesMove = $B6 SndID_Rumbling = $B7 SndID_Smash = $B9 SndID_DoorSlam = $BB SndID_SpindashRelease = $BC  ; BC SndID_Hammer = $BD SndID_Roll = $BE SndID_ContinueJingle = $BF SndID_CasinoBonus = $C0 SndID_Explosion = $C1 SndID_WaterWarning = $C2 SndID_EnterGiantRing = $C3 SndID_BossExplosion = $C4 SndID_TallyEnd = $C5 SndID_RingSpill = $C6 SndID_Flamethrower = $C8 SndID_Bonus = $C9 SndID_SpecStageEntry = $CA SndID_SlowSmash = $CB SndID_Spring = $CC SndID_Blip = $CD SndID_RingLeft = $B5 SndID_Signpost = $CF SndID_CNZBossZap = $D0 SndID_Signpost2P = $D3 SndID_OOZLidPop = $D4 SndID_SlidingSpike = $D5 SndID_CNZElevator = $D6 SndID_PlatformKnock = $D7 SndID_BonusBumper = $D8 SndID_LargeBumper = $D9 SndID_Gloop = $DA SndID_PreArrowFiring = $DB SndID_Fire = $DC SndID_ArrowStick = $DD SndID_Helicopter = $DE SndID_SuperTransform = $DF SndID_SpindashRev = $E0 SndID_Rumbling2 = $E1 SndID_CNZLaunch = $E2 SndID_Flipper = $E3 SndID_HTZLiftClick = $E4 SndID_Leaves = $E5 SndID_MegaMackDrop = $E6 SndID_DrawbridgeMove = $E7 SndID_QuickDoorSlam = $E8 SndID_DrawbridgeDown = $E9 SndID_LaserBurst = $EA SndID_Scatter = $EB SndID_LaserFloor = $EB SndID_Teleport = $EC SndID_Error = $ED SndID_MechaSonicBuzz = $EE SndID_LargeLaser = $EF SndID_OilSlide = $F0 SndID__End = $F7</asm>

Step 7 - I am Error

Now we are going back to s2.sounddriver.asm. There are 4 more errors here. As before, we're going to solve this by simply emptying out the relavent routines. We can't just delete stuff because a few things in it

are still going to be referenced. So the first Routine to clean out is zDACAfterDur. change that and remove zloc_22A inside it so it looks like this:

<asm>zDACAfterDur:

   ret</asm>
 

There is one more routine to empty. That routine is zloc_78E, or zBGMLoad. Starting at this line:

<asm>zBGMLoad:</asm>

delete everything down to here:

<asm>  ; End of DAC/FM init, begin PSG init</asm>

And there you have it! Close s2.sounddriver.asm, Build you ROM and test it!

Additional Step

Uh-oh! if you've played up to Chemical Plant Zone Act 2, you'll notice the driver crashes on that level!

This is because of water. In Sonic 2, the underwater palettes are stored in a section of RAM that is now used by the sound driver,

because it's based on Sonic 1's sound driver. What we need to do now is relocate the water palette table in RAM, so the Sound Driver can do what it likes. I am going to assume

you haven't modified the RAM allocation in your hack here, and go step by step. If you have modifying the RAM in your game, you

are probably on your own.

Let's go back to s2.constants.asm, and find these lines:

<asm>Underwater_palette_2: ds.w palette_line_size  ; not sure what it's used for but it's only used when there's water Underwater_palette_2_line2: ds.w palette_line_size Underwater_palette_2_line3: ds.w palette_line_size Underwater_palette_2_line4: ds.w palette_line_size

Underwater_palette: ds.w palette_line_size  ; main palette for underwater parts of the screen Underwater_palette_line2: ds.w palette_line_size Underwater_palette_line3: ds.w palette_line_size Underwater_palette_line4: ds.w palette_line_size

               ds.b    $500    ; $FFFFF100-$FFFFF5FF ; unused, leftover from the Sonic 1 sound driver (and used by it when you port it to 

Sonic 2) </asm> The last four lines before the ds.b $500 are used by the sound driver now, in addition to the 500 that is labeled as such.

Replace all of the above lines with this:

<asm> ds.b $100  ; Sonic 1 Sound Driver

                   ds.b    $500    ; Sonic 1 Sound Driver</asm>

After doing that, you will need to find at least $80 free bytes in RAM (besides the space we just put in) Fortunately, there is an area of RAM that has $C0 free bytes, and that is where the four lines we lost will go. Search for this:

<asm>CNZ_saucer_data:</asm>

And you will see this:

<asm>CNZ_saucer_data: ds.b $40  ; the number of saucer bumpers in a group which have been destroyed. Used to decide when to give 500 points instead of 10

               ds.b    $C0    ; $FFFFE740-$FFFFE7FF ; unused as far as I can tell

Ring_Positions: ds.b $600</asm>

Replace it with this:

<asm>CNZ_saucer_data: ds.b $40  ; the number of saucer bumpers in a group which have been destroyed. Used to decide when to give 500 points instead of 10 Underwater_palette: ds.w palette_line_size  ; main palette for underwater parts of the screen Underwater_palette_line2: ds.w palette_line_size Underwater_palette_line3: ds.w palette_line_size Underwater_palette_line4: ds.w palette_line_size

               ds.b    $40    ; $FFFFE740-$FFFFE7FF ; unused as far as I can tell

Ring_Positions: ds.b $600</asm>

Build it, and test!

The sega sound will be glitched up, and you can fix it by following this link. Everything that needs to be fixed will be in "Sonic 2 Clone Driver.asm".

Credits

   Varion Icaria - Puto's sound driver port.
   Esrael - Tweakers driver port, plus fixes for things broken in Puto's port, such as hanging on the title card. Extra thanks for fixing the Sega sound.
   Puto - Fixes for underwater palette stuff, as well as special stage ring stuff, and various other fixes to the original guide.
   Tweaker - Wrote the orignal guide to port Sonic 1's sound driver into Sonic 2.
   ValleyBell - lots of miscallanious help to get this to work, as well as worked on the Sonic 2 Clone Driver.
   ShadowsofYesterday - Telling me the fix for the SEGA sound.
   Caverns4 - I wrote this guide!