Guide 02

Graphics and sound fixes

How the Xbox-era renderer and audio got onto SDL2, OpenGL and a 5-channel float mixer, and how the music and voice streams of the PC release were made to play.

GoalSame picture and sound as the PC release, from the original data files, on a Mac.

The renderer and the base audio landed in the first commit (962139d), so there's no "before" to diff; those steps show the key code as excerpts. Music and streams came later, with real diffs.

1Render into a backbuffer, present it scaled

The game draws into an off-screen framebuffer at the render resolution; presenting draws that texture as one quad into the window. Everything else (resolution, letterboxing, motion blur) hangs off this.

excerptWn32/Code/Plat/Gfx/p_nx.cpp

// Bind screen FBO (cleared to black for the bars when the window's aspect ratio differs from the backbuffer's)
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Bind backbuffer texture
glActiveTexture(GL_TEXTURE0);
NxWn32::EngineGlobals.backbuffer->BindColorTexture();

// Draw backbuffer quad, scaled to fit the window
NxWn32::SetPresentViewport();
NxWn32::EngineGlobals.fullscreen_quad->Bind();
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, nullptr);

SDL_GL_SwapWindow(NxWn32::EngineGlobals.window);

The present pass: backbuffer drawn as one quad, scaled into the window.

Motion blur, too: it reuses the previous frame from the same backbuffer.

2Decode console-flavoured textures

Xbox textures are swizzled (Morton order) and fonts are 8-bit palettized. They're unswizzled and expanded to RGBA before glTexImage2D.

excerptWn32/Code/Plat/Gfx/nx/chars.cpp

// Decode palettized texture
for( i = 0; i < NumBytes; ++i )
{
	uint8 *p = p_clut[*p_texel_data_p++];
	*p_texture_p++ = p[0];
	*p_texture_p++ = p[1];
	*p_texture_p++ = p[2];
	*p_texture_p++ = (p[3] >= 0x80) ? 0xFF : (p[3] * 2); // Alpha is halved, PS2 remnant?
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Width, Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, p_texture);

PS2 alpha goes 0–128, because 128 means "fully opaque" on the GS. Twenty years later we're still multiplying by two.

3One mixer for everything

A single SDL audio callback at 48 kHz, 5 float channels: music and voice streams first, sound effects on top. Locks around it keep the game thread from swapping streams mid-buffer.

excerptWn32/Code/Plat/Audio/Mixer.cpp

void AudioCallback(void *userdata, Uint8 *stream, int len)
{
	std::fill((float*)stream, (float*)(stream + len), 0.0f);
	Pcm::PCMAudio_Mix((char*)stream, len);     // music + streams
	Sfx::MixSoundFX((char*)stream, len);        // sound effects
}

SDL_AudioSpec s_wanted_spec = {};
s_wanted_spec.format = AUDIO_F32SYS;
s_wanted_spec.freq = 48000;
s_wanted_spec.channels = 5;
s_wanted_spec.samples = 1024;
s_wanted_spec.callback = AudioCallback;

excerptWn32/Code/Plat/Gel/SoundFX/p_sfx.cpp

static constexpr float SOUND_VOLUME = 0.5f; // PC sounds are much too loud

The pause menu's now-playing box: proof the soundtrack is running (Flamethrower, "I Want It All").

4Turn the soundtrack on

The retail scripts only queue the soundtrack when running from CD or with TestMusicFromHost. CD mode drags debug behaviour along, so a one-line script patch flips the other switch.

new fileScripts/patches/scripts/game/skater/skater_sfx.q · 28ef9a3

+// Patch for scripts\game\skater\skater_sfx.qb (from qb.pre), see Script::LoadQBPatch.
+
+// The retail scripts only add the soundtrack (LoadPermSongs) and level music tracks (load_level)
+// when running from CD or with TestMusicFromHost set. CD is off on this port (it also switches
+// debug/dev behaviour), so set TestMusicFromHost instead. The tracks are played from
+// Data/streams/music.
+TestMusicFromHost = 1

5Find the tracks: hex names and a .wad

The PC release names music files after the checksum of the track name, in hex (a9a6af00.bik), and packs the voice streams into pcm.wad, indexed by pcm.dat.

diffWn32/Code/Plat/Gel/Music/p_music.cpp · 28ef9a3

@@ -205,14 +350,51 @@ namespace Pcm
+				// The PC version's files are named after the checksum of the track name in hex (e.g. a9a6af00.bik)
 				std::string name = i.path().stem().string();
-				uint32 checksum = Crc::GenerateCRCFromString(name.c_str());
+				uint32 checksum;
+				if (name.size() == 8 && name.find_first_not_of("0123456789abcdefABCDEF") == std::string::npos)
+					checksum = (uint32)std::stoul(name, nullptr, 16);
+				else
+					checksum = Crc::GenerateCRCFromString(name.c_str());
@@
+	static void IndexWad(const std::filesystem::path &dat, const std::filesystem::path &wad)
+	{
+		// pcm.dat: the number of streams, then the checksum of the name, offset and size of each one's .bik
+		std::ifstream file(dat, std::ios::binary);
+		uint32 count = 0;
+		if (!file.read((char*)&count, sizeof(count)))
+			return;
+
+		for (uint32 i = 0; i < count; i++)
+		{
+			uint32 entry[3];
+			if (!file.read((char*)entry, sizeof(entry)))
+				break;
+			wad_streams[entry[0]] = { entry[1], entry[2] };
+		}
+		wad_path = wad;
+	}

6Decode Bink audio, resample, spread over 5 channels

A built-in Bink audio decoder (binkaudio.cpp) feeds a streamer that resamples to 48 kHz (with pitch, because the game bends voice pitch) and places stereo on the 5 mixer channels the way sound effects do.

diffWn32/Code/Plat/Gel/Music/p_music.cpp · 28ef9a3

@@ -171,6 +173,140 @@ namespace Pcm
+	// Decoder for the PC version's music and streams: the audio of the .bik files in Data/streams/music,
+	// and of the ones packed in Data/streams/pcm/pcm.wad
+	class BinkDecoder : public Streamer
+	{
+			// Pitch in percent
+			void SetPitch(float pitch) override
+			{
+				if (valid && pitch > 0.0f)
+					step = pitch / 100.0 * bink.GetSampleRate() / 48000.0;
+			}
+
+				float l = frame_a[0] + (frame_b[0] - frame_a[0]) * (float)position;
+				float r = frame_a[1] + (frame_b[1] - frame_a[1]) * (float)position;
+				position += step;
+
+				// Spread over the 5 mixer channels the same way sound effects place their left and
+				// right volumes (Sfx::SetVoiceParameters)
+				*out++ = l;
+				*out++ = r;
+				*out++ = (l + r) * 0.5f;
+				*out++ = l * 0.5f;
+				*out++ = r * 0.5f;
+	};
@@ -639,8 +824,12 @@ namespace Pcm
 	bool PCMAudio_SetStreamPitch( float fPitch, int whichStream )
 	{
-		(void)fPitch;
-		(void)whichStream;
+		Audio::Lock();
+
+		if (stream_stream[whichStream] != nullptr)
+			stream_stream[whichStream]->SetPitch(fPitch);
+
+		Audio::Unlock();
 		return true;
 	}

(void)fPitch; is a stub's way of saying "I heard you, I just don't care". Now it cares.

FOR EDUCATION PURPOSES ONLY. Screenshots are captured from the port running the reader's own copy of the game. The diffs are trimmed to the interesting lines (unchanged context is cut, marked ⋯); the repository has the full changes. Paths are relative to the THUG/ folder.