Merge branch 'main' into test/bots-voice

# Conflicts:
#	port/android/app/src/main/java/com/halo/decomp/LauncherActivity.java
#	tools/android_build.py

port/android/app/src/main/AndroidManifest.xml

@@ -19,6 +19,9 @@
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
+    <!-- the voice chat in multiplayer (host_voice.c) -->
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
     <!-- installing a new version of the game (Updater) -->
     <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
 

port/android/app/src/main/java/com/halo/decomp/LauncherActivity.java

@@ -1,7 +1,10 @@
 package com.halo.decomp;
 
+import android.Manifest;
 import android.app.Activity;
 import android.content.Intent;
+import android.content.SharedPreferences;
+import android.content.pm.PackageManager;
 import android.graphics.Color;
 import android.net.Uri;
 import android.os.Bundle;
@@ -35,6 +38,7 @@ import java.nio.channels.FileChannel;
  */
 public class LauncherActivity extends Activity {
     private static final int PICK_IMAGE = 1;
+    private static final int ASK_MICROPHONE = 2;
     private static final String SHARED_DATA_ROOT = "/home/steamos/Documents/HaloCE";
 
     private File dataRoot;
@@ -60,12 +64,37 @@ public class LauncherActivity extends Activity {
         passOnHardwareId();
         passOnInvite(getIntent());
         if (haveData()) {
-            startGame();
+            if (!askForMicrophone())
+                startGame();
             return;
         }
         buildInterface();
     }
 
+    /**
+     * The voice chat's microphone (port/android/host/host_voice.c), asked
+     * for here, once, on this flat panel, before the game starts: in the
+     * game, the question would stop it. Returns true if it asked (the game
+     * starts on the answer).
+     */
+    private boolean askForMicrophone() {
+        SharedPreferences preferences = getSharedPreferences("launcher", MODE_PRIVATE);
+
+        if (checkSelfPermission(Manifest.permission.RECORD_AUDIO) == PackageManager.PERMISSION_GRANTED
+            || preferences.getBoolean("asked_microphone", false))
+            return false;
+        preferences.edit().putBoolean("asked_microphone", true).apply();
+        requestPermissions(new String[] { Manifest.permission.RECORD_AUDIO }, ASK_MICROPHONE);
+        return true;
+    }
+
+    @Override
+    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] results) {
+        super.onRequestPermissionsResult(requestCode, permissions, results);
+        if (requestCode == ASK_MICROPHONE)
+            startGame();
+    }
+
     /**
      * An internet play invite link the app was opened with: the game
      * (port/linux/src/p2p.c) picks it up from join_link.txt, whether it is
@@ -118,6 +147,23 @@ public class LauncherActivity extends Activity {
             partial.delete();
     }
 
+    /**
+     * Whether the microphone may be used, for the game (port/linux/src/
+     * voice.c), which opens it only then: opening it otherwise would have
+     * Android ask in the middle of the game.
+     */
+    private void passOnMicrophonePermission() {
+        if (dataRoot == null)
+            return;
+        boolean granted =
+            checkSelfPermission(Manifest.permission.RECORD_AUDIO) == PackageManager.PERMISSION_GRANTED;
+        try (OutputStream out = new FileOutputStream(new File(dataRoot, "microphone_permission.txt"))) {
+            out.write((granted ? "1" : "0").getBytes("UTF-8"));
+        } catch (java.io.IOException e) {
+            // the game then does without the microphone
+        }
+    }
+
     /** The game data, or the marker file of the VR self-test (host_xr.c). */
     private boolean haveData() {
         return dataRoot != null && (new File(dataRoot, "maps/ui.map").isFile() ||
@@ -125,6 +171,7 @@ public class LauncherActivity extends Activity {
     }
 
     private void startGame() {
+        passOnMicrophonePermission();
         startActivity(new Intent(this, HaloActivity.class));
         finish();
     }

port/android/guest/runtime/guest_host.h

@@ -134,6 +134,21 @@ int host_xr_copy_layer_array(int layer, unsigned int texture, int array_layer);
 /* darkens the eye images from their edges, strength 0..1 (0: off) */
 void host_xr_set_vignette(float strength);
 
+/* ---------- the voice chat (host_voice.c) */
+
+/* opens the voices' playback, and the microphone if asked (else closes
+it): their volume, and the level (0..1 of full scale) the microphone's
+sound must reach to be sent */
+int host_voice_start(int microphone, float volume, float threshold);
+void host_voice_stop(void);
+/* the microphone's speech since asked: Opus packets, each after a byte of
+its length; returns the bytes */
+int host_voice_take_packets(void *buffer, int size);
+/* the microphone's level (0..1000) */
+int host_voice_level(void);
+/* a speaker's packet (sequence numbered), played at these gains */
+void host_voice_play(int id, int sequence, const void *data, int length, float gain_left, float gain_right);
+
 /* ---------- Android */
 
 /* the storage directories the port uses, copied into buffer */

port/android/host/host_voice.c

@@ -0,0 +1,494 @@
+/*
+HOST_VOICE.C
+
+The voice chat's sound (the VR port's; port/linux/game/network_voice.c
+sends and receives it): the microphone, Opus, and the voices played. It
+runs here, natively, where SDL's audio threads may call it.
+
+- The microphone: SDL's default recording device, mono at 16 kHz, with
+  Android's voice communication preset (its echo cancelling and noise
+  suppression: SDL_HINT_ANDROID_AAUDIO_INPUT_PRESET). Every 20 ms of it
+  that is loud enough to be speech (or follows speech closely, VAD_HANGOVER)
+  is encoded (Opus, VOIP, 16 kbit/s) for the guest to send.
+- The voices: each speaker's packets, decoded as they come (a gap in their
+  numbers concealed by Opus's packet loss concealment), wait in the
+  speaker's buffer until JITTER_START of them is there, and are mixed, each
+  at the gains its latest packet was given (left and right: where the
+  speaker is), into a stream of their own.
+
+The devices are opened and closed on a thread of their own (voice_worker):
+opening a microphone can take a long while (an emulator's took a minute),
+which the game, whose clock the other machines follow, must not wait for.
+*/
+
+#include "host.h"
+
+#include <SDL3/SDL.h>
+#include <opus.h>
+#include <pthread.h>
+#include <string.h>
+
+enum
+{
+	VOICE_RATE = 16000,
+	FRAME_SAMPLES = VOICE_RATE / 50,
+	MAXIMUM_PACKET = 200,
+	MAXIMUM_SPEAKERS = 32,
+	/* a speaker's buffer: two seconds */
+	SPEAKER_BUFFER = VOICE_RATE * 2,
+	/* played from once this much is there, after silence */
+	JITTER_START = FRAME_SAMPLES * 3,
+	/* more than this behind: the oldest dropped */
+	JITTER_MAXIMUM = FRAME_SAMPLES * 15,
+	/* frames sent on after the voice drops below the threshold */
+	VAD_HANGOVER = 15,
+	BITRATE = 16000,
+};
+
+struct speaker
+{
+	int used;
+	int id;
+	OpusDecoder *decoder;
+	int has_sequence;
+	unsigned short sequence;
+	short buffer[SPEAKER_BUFFER];
+	int read;
+	int count;
+	int playing;
+	float gain_left;
+	float gain_right;
+	unsigned long long heard_ticks;
+};
+
+static struct
+{
+	SDL_Mutex *lock;
+	/* the devices wanted, which the worker opens and closes to match
+	(under worker_lock); the recording stream is read under it too */
+	pthread_mutex_t worker_lock;
+	pthread_cond_t worker_wake;
+	int worker_started;
+	int want_playback;
+	int want_recording;
+	/* the microphone */
+	SDL_AudioStream *recording;
+	OpusEncoder *encoder;
+	short frame[FRAME_SAMPLES];
+	int frame_count;
+	int hangover;
+	float threshold;
+	int level;
+	/* the voices */
+	SDL_AudioStream *playback;
+	struct speaker speakers[MAXIMUM_SPEAKERS];
+	float volume;
+} voice;
+
+static void voice_lock(void)
+{
+	if (!voice.lock)
+		voice.lock = SDL_CreateMutex();
+	SDL_LockMutex(voice.lock);
+}
+
+static void voice_unlock(void)
+{
+	SDL_UnlockMutex(voice.lock);
+}
+
+/* the voices mixed, as SDL asks for them (on its audio thread) */
+static void SDLCALL voice_playback_callback(void *userdata, SDL_AudioStream *stream, int additional, int total)
+{
+	short mixed[2 * 512];
+	(void)userdata;
+	(void)total;
+
+	while (additional > 0)
+	{
+		int frames = additional / 4;
+		int frame;
+		int index;
+
+		if (frames > 512)
+			frames = 512;
+		if (frames <= 0)
+			frames = 1;
+		memset(mixed, 0, sizeof(mixed));
+		voice_lock();
+		for (index = 0; index < MAXIMUM_SPEAKERS; index++)
+		{
+			struct speaker *speaker = &voice.speakers[index];
+
+			if (!speaker->used)
+				continue;
+			if (!speaker->playing && speaker->count >= JITTER_START)
+				speaker->playing = 1;
+			if (!speaker->playing)
+				continue;
+			for (frame = 0; frame < frames && speaker->count > 0; frame++)
+			{
+				float sample = (float)speaker->buffer[speaker->read] * voice.volume;
+				int left = mixed[2 * frame] + (int)(sample * speaker->gain_left);
+				int right = mixed[2 * frame + 1] + (int)(sample * speaker->gain_right);
+
+				mixed[2 * frame] = (short)(left > 32767 ? 32767 : left < -32768 ? -32768 : left);
+				mixed[2 * frame + 1] = (short)(right > 32767 ? 32767 : right < -32768 ? -32768 : right);
+				speaker->read = (speaker->read + 1) % SPEAKER_BUFFER;
+				speaker->count--;
+			}
+			/* (run dry: wait for enough again) */
+			if (!speaker->count)
+				speaker->playing = 0;
+		}
+		voice_unlock();
+		SDL_PutAudioStreamData(stream, mixed, frames * 4);
+		additional -= frames * 4;
+	}
+}
+
+static int voice_open_playback(void)
+{
+	SDL_AudioSpec spec;
+
+	if (voice.playback)
+		return 1;
+	spec.format = SDL_AUDIO_S16;
+	spec.channels = 2;
+	spec.freq = VOICE_RATE;
+	voice.playback = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &spec, voice_playback_callback,
+		NULL);
+	if (!voice.playback)
+	{
+		host_logf(HOST_LOG_WARN, "voice: cannot open the playback stream: %s", SDL_GetError());
+		return 0;
+	}
+	SDL_ResumeAudioStreamDevice(voice.playback);
+	return 1;
+}
+
+static SDL_AudioStream *voice_open_recording(void)
+{
+	SDL_AudioSpec spec;
+	SDL_AudioStream *recording;
+	int error;
+
+	if (!voice.encoder)
+	{
+		voice.encoder = opus_encoder_create(VOICE_RATE, 1, OPUS_APPLICATION_VOIP, &error);
+		if (!voice.encoder)
+		{
+			host_logf(HOST_LOG_WARN, "voice: cannot make the encoder (%d)", error);
+			return NULL;
+		}
+		opus_encoder_ctl(voice.encoder, OPUS_SET_BITRATE(BITRATE));
+		opus_encoder_ctl(voice.encoder, OPUS_SET_SIGNAL(OPUS_SIGNAL_VOICE));
+		opus_encoder_ctl(voice.encoder, OPUS_SET_INBAND_FEC(1));
+		opus_encoder_ctl(voice.encoder, OPUS_SET_PACKET_LOSS_PERC(10));
+	}
+	/* Android's voice communication preset: echo cancelling, noise
+	suppression (AAUDIO_INPUT_PRESET_VOICE_COMMUNICATION) */
+	SDL_SetHint(SDL_HINT_ANDROID_AAUDIO_INPUT_PRESET, "7");
+	spec.format = SDL_AUDIO_S16;
+	spec.channels = 1;
+	spec.freq = VOICE_RATE;
+	recording = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_RECORDING, &spec, NULL, NULL);
+	if (!recording)
+	{
+		host_logf(HOST_LOG_WARN, "voice: cannot open the microphone: %s", SDL_GetError());
+		return NULL;
+	}
+	SDL_ResumeAudioStreamDevice(recording);
+	host_logf(HOST_LOG_INFO, "voice: the microphone is open");
+	return recording;
+}
+
+static void voice_close_recording(void)
+{
+	SDL_AudioStream *recording;
+
+	pthread_mutex_lock(&voice.worker_lock);
+	recording = voice.recording;
+	voice.recording = NULL;
+	voice.level = 0;
+	pthread_mutex_unlock(&voice.worker_lock);
+	if (!recording)
+		return;
+	SDL_DestroyAudioStream(recording);
+	host_logf(HOST_LOG_INFO, "voice: the microphone is closed");
+}
+
+static void voice_close_playback(void)
+{
+	SDL_AudioStream *playback = voice.playback;
+
+	voice.playback = NULL;
+	if (playback)
+		SDL_DestroyAudioStream(playback);
+}
+
+/* opens and closes the devices as wanted, for as long as the app runs */
+static void *voice_worker(void *unused)
+{
+	(void)unused;
+	pthread_mutex_lock(&voice.worker_lock);
+	for (;;)
+	{
+		int want_playback = voice.want_playback;
+		int want_recording = voice.want_recording;
+		int have_playback = voice.playback != NULL;
+		int have_recording = voice.recording != NULL;
+
+		if (want_playback == have_playback && want_recording == have_recording)
+		{
+			pthread_cond_wait(&voice.worker_wake, &voice.worker_lock);
+			continue;
+		}
+		pthread_mutex_unlock(&voice.worker_lock);
+		if (want_recording && !have_recording)
+		{
+			/* (opened outside the lock, which the game reads it under) */
+			SDL_AudioStream *recording = voice_open_recording();
+
+			pthread_mutex_lock(&voice.worker_lock);
+			voice.recording = recording;
+			pthread_mutex_unlock(&voice.worker_lock);
+			/* (a microphone that will not open is not tried again until
+			wanted anew) */
+			if (!recording)
+			{
+				pthread_mutex_lock(&voice.worker_lock);
+				voice.want_recording = 0;
+				pthread_mutex_unlock(&voice.worker_lock);
+			}
+		}
+		else if (!want_recording && have_recording)
+		{
+			voice_close_recording();
+		}
+		if (want_playback && !have_playback)
+		{
+			if (!voice_open_playback())
+			{
+				pthread_mutex_lock(&voice.worker_lock);
+				voice.want_playback = 0;
+				pthread_mutex_unlock(&voice.worker_lock);
+			}
+		}
+		else if (!want_playback && have_playback)
+		{
+			voice_close_playback();
+		}
+		pthread_mutex_lock(&voice.worker_lock);
+	}
+	return NULL;
+}
+
+static void voice_want(int playback, int recording)
+{
+	if (!voice.worker_started)
+	{
+		voice.worker_started = 1;
+		pthread_mutex_init(&voice.worker_lock, NULL);
+		pthread_cond_init(&voice.worker_wake, NULL);
+		if (host_native_thread_create(voice_worker, NULL, 256 * 1024) != 0)
+		{
+			host_logf(HOST_LOG_WARN, "voice: cannot start the device thread");
+			return;
+		}
+	}
+	pthread_mutex_lock(&voice.worker_lock);
+	voice.want_playback = playback;
+	voice.want_recording = recording;
+	pthread_cond_signal(&voice.worker_wake);
+	pthread_mutex_unlock(&voice.worker_lock);
+}
+
+/* ---------- the guest's side */
+
+int host_voice_start(int microphone, float volume, float threshold)
+{
+	voice_lock();
+	voice.volume = volume < 0.0f ? 0.0f : volume > 4.0f ? 4.0f : volume;
+	voice.threshold = threshold;
+	voice_unlock();
+	voice_want(1, microphone);
+	return 1;
+}
+
+void host_voice_stop(void)
+{
+	int index;
+
+	voice_want(0, 0);
+	voice_lock();
+	for (index = 0; index < MAXIMUM_SPEAKERS; index++)
+	{
+		if (voice.speakers[index].decoder)
+			opus_decoder_destroy(voice.speakers[index].decoder);
+	}
+	memset(voice.speakers, 0, sizeof(voice.speakers));
+	voice_unlock();
+}
+
+int host_voice_take_packets(void *buffer, int size)
+{
+	unsigned char *out = buffer;
+	int used = 0;
+
+	if (!voice.worker_started)
+		return 0;
+	pthread_mutex_lock(&voice.worker_lock);
+	if (!voice.recording)
+	{
+		voice.frame_count = 0;
+		voice.hangover = 0;
+		pthread_mutex_unlock(&voice.worker_lock);
+		return 0;
+	}
+	for (;;)
+	{
+		int wanted = (FRAME_SAMPLES - voice.frame_count) * (int)sizeof(short);
+		int got = SDL_GetAudioStreamData(voice.recording, voice.frame + voice.frame_count, wanted);
+		double energy = 0.0;
+		int index;
+
+		if (got <= 0)
+			break;
+		voice.frame_count += got / (int)sizeof(short);
+		if (voice.frame_count < FRAME_SAMPLES)
+			break;
+		voice.frame_count = 0;
+		for (index = 0; index < FRAME_SAMPLES; index++)
+			energy += (double)voice.frame[index] * voice.frame[index];
+		energy = SDL_sqrt(energy / FRAME_SAMPLES) / 32768.0;
+		voice.level = (int)(energy * 1000.0);
+		if (energy >= voice.threshold)
+			voice.hangover = VAD_HANGOVER;
+		else if (voice.hangover > 0)
+			voice.hangover--;
+		else
+			continue;
+		if (used + 1 + MAXIMUM_PACKET > size)
+			continue;
+		{
+			int length = opus_encode(voice.encoder, voice.frame, FRAME_SAMPLES, out + used + 1, MAXIMUM_PACKET);
+
+			if (length > 0 && length < 256)
+			{
+				out[used] = (unsigned char)length;
+				used += 1 + length;
+			}
+		}
+	}
+	pthread_mutex_unlock(&voice.worker_lock);
+	return used;
+}
+
+int host_voice_level(void)
+{
+	return voice.level;
+}
+
+void host_voice_play(int id, int sequence, const void *data, int length, float gain_left, float gain_right)
+{
+	struct speaker *speaker = NULL;
+	struct speaker *oldest = NULL;
+	short decoded[FRAME_SAMPLES * 6];
+	int frames[4];
+	int frame_count = 0;
+	int index;
+
+	if (length <= 0 || length > MAXIMUM_PACKET)
+		return;
+	voice_lock();
+	for (index = 0; index < MAXIMUM_SPEAKERS && !speaker; index++)
+	{
+		if (voice.speakers[index].used && voice.speakers[index].id == id)
+			speaker = &voice.speakers[index];
+	}
+	if (!speaker)
+	{
+		for (index = 0; index < MAXIMUM_SPEAKERS && !speaker; index++)
+		{
+			if (!voice.speakers[index].used)
+				speaker = &voice.speakers[index];
+			else if (!oldest || voice.speakers[index].heard_ticks < oldest->heard_ticks)
+				oldest = &voice.speakers[index];
+		}
+		if (!speaker)
+			speaker = oldest;
+		if (!speaker->decoder)
+		{
+			int error;
+
+			speaker->decoder = opus_decoder_create(VOICE_RATE, 1, &error);
+			if (!speaker->decoder)
+			{
+				voice_unlock();
+				return;
+			}
+		}
+		else
+		{
+			opus_decoder_ctl(speaker->decoder, OPUS_RESET_STATE);
+		}
+		speaker->used = 1;
+		speaker->id = id;
+		speaker->has_sequence = 0;
+		speaker->read = speaker->count = 0;
+		speaker->playing = 0;
+	}
+	speaker->heard_ticks = SDL_GetTicks();
+	speaker->gain_left = gain_left;
+	speaker->gain_right = gain_right;
+	{
+		unsigned short number = (unsigned short)sequence;
+
+		if (speaker->has_sequence)
+		{
+			short gap = (short)(number - speaker->sequence);
+
+			/* (late, or again: dropped) */
+			if (gap <= 0)
+			{
+				voice_unlock();
+				return;
+			}
+			/* (lost ones: concealed, a few) */
+			if (gap > 1 && gap <= 4 && speaker->count > 0)
+			{
+				int missing;
+
+				for (missing = 1; missing < gap && frame_count < 3; missing++)
+				{
+					frames[frame_count] = opus_decode(speaker->decoder, NULL, 0, decoded + frame_count * FRAME_SAMPLES,
+						FRAME_SAMPLES, 0);
+					frame_count++;
+				}
+			}
+		}
+		speaker->has_sequence = 1;
+		speaker->sequence = number;
+	}
+	frames[frame_count] = opus_decode(speaker->decoder, data, length, decoded + frame_count * FRAME_SAMPLES,
+		FRAME_SAMPLES * 2, 0);
+	frame_count++;
+	for (index = 0; index < frame_count; index++)
+	{
+		int sample;
+
+		for (sample = 0; sample < frames[index] && sample < FRAME_SAMPLES * 2; sample++)
+		{
+			if (speaker->count >= JITTER_MAXIMUM)
+			{
+				speaker->read = (speaker->read + 1) % SPEAKER_BUFFER;
+				speaker->count--;
+			}
+			speaker->buffer[(speaker->read + speaker->count) % SPEAKER_BUFFER] =
+				decoded[index * FRAME_SAMPLES + sample];
+			speaker->count++;
+		}
+	}
+	voice_unlock();
+}

port/android/host_imports.list

@@ -60,6 +60,11 @@ host_xr_copy_layer_region
 host_xr_end_frame
 host_xr_haptic
 host_xr_set_vignette
+host_voice_start
+host_voice_stop
+host_voice_take_packets
+host_voice_level
+host_voice_play
 host_xr_copy_layer_array
 host_android_path
 

port/linux/game/network_distributed.c

@@ -3136,6 +3136,7 @@ void network_distributed_new_game(
 	network_damage_new_game();
 	network_vr_new_game();
 	bots_new_game();
+	network_voice_new_game();
 }
 
 /* after each tick (game_time.c) */
@@ -3181,6 +3182,7 @@ void network_distributed_tick(
 		distributed_host_send_players();
 		network_vr_tick();
 		bots_tick();
+		network_voice_tick();
 		distributed_send_pickups();
 		if (game_time_get() % GAME_STATE_INTERVAL_TICKS == 0)
 			distributed_send_game_state(NONE);
@@ -3190,6 +3192,7 @@ void network_distributed_tick(
 		distributed_note_own_positions();
 		distributed_client_send_inputs();
 		network_vr_tick();
+		network_voice_tick();
 		distributed_client_send_predictions();
 		network_objects_client_tick();
 		network_damage_client_tick();
@@ -3667,6 +3670,7 @@ void network_distributed_handle_message(
 	case _distributed_message_client_ready: entry_size = 0; break;
 	case _distributed_message_client_identity: entry_size = sizeof(struct distributed_client_identity); break;
 	case _distributed_message_vr_poses: entry_size = network_vr_entry_size(); break;
+	case _distributed_message_voice: entry_size = network_voice_entry_size(); break;
 	case _distributed_message_damage_events:
 	case _distributed_message_hit_reports: entry_size = network_damage_entry_size(header.type); break;
 	default: entry_size = network_objects_entry_size(header.type); break;
@@ -3680,6 +3684,16 @@ void network_distributed_handle_message(
 
 	/* (each kind from the host, or from a client; a VR player's hands
 	both ways) */
+	if (header.type == _distributed_message_voice)
+	{
+		if (machine_index == NONE ? game_connection() != _game_connection_network_client :
+				game_connection() != _game_connection_network_server)
+		{
+			return;
+		}
+		network_voice_handle(machine_index, message, size);
+		return;
+	}
 	if (header.type == _distributed_message_vr_poses)
 	{
 		if (machine_index == NONE ? game_connection() != _game_connection_network_client :

port/linux/game/network_distributed.h

@@ -72,6 +72,10 @@ enum
 	/* a VR player's hands, every tick: a client's own to the host, the
 	host's of the others to each client (unreliable; network_vr.c) */
 	_distributed_message_vr_poses = 240,
+	/* a player's speech, every tick while they speak: a client's own to
+	the host, the host's and the other clients' to each client (unreliable;
+	network_voice.c) */
+	_distributed_message_voice,
 
 	NUMBER_OF_DISTRIBUTED_MESSAGES
 };
@@ -252,4 +256,10 @@ void network_vr_handle_poses(long machine_index, void const *entries, short coun
 void bots_new_game(void);
 void bots_tick(void);
 
+/* the voice chat (network_voice.c) */
+void network_voice_new_game(void);
+void network_voice_tick(void);
+word network_voice_entry_size(void);
+void network_voice_handle(long machine_index, void const *message, word size);
+
 #endif // __NETWORK_DISTRIBUTED_H

port/linux/game/network_voice.c

@@ -0,0 +1,326 @@
+/*
+NETWORK_VOICE.C
+
+The voice chat (the VR port's): an extension of the distributed netcode
+(port/linux/NETCODE.md, network_distributed.c), as the VR players' hands
+are (network_vr.c).
+
+- Every tick, a machine sends what its microphone heard of its player's
+  speech (halo_voice.h: Opus packets of 20 ms, only while they speak) in
+  _distributed_message_voice (unreliable): a client to the host, which
+  plays it and passes it on to its other clients; the host its own to
+  every client.
+- A machine plays each speaker's voice from where they are: a teammate
+  (in a game of teams) over the radio, as loud anywhere and only a little
+  to the side they are on; anyone else as near as they are (no further off
+  than VOICE_RANGE), from their side. A speaker with no unit (dead) is
+  heard over the radio by their team, and not by the rest.
+
+A machine that does not know the message (a build without this, of the same
+network version) drops it, as it drops any type past its own.
+*/
+
+#include "cseries.h"
+#include "game/game.h"
+#include "game/game_engine.h"
+#include "game/players.h"
+#include "units/units.h"
+#include "network_distributed.h"
+#include "halo_voice.h"
+#include "halo_vr.h"
+
+#include <math.h>
+
+void platform_log(char const *format, ...);
+
+/* ---------- constants */
+
+enum
+{
+	/* an entry: the speaker, its sequence number and the packet's length,
+	and the packet */
+	VOICE_ENTRY_HEADER = 4,
+	VOICE_MAXIMUM_PACKET = 200,
+	VOICE_MAXIMUM_TAKEN = 1024,
+};
+
+/* how far off someone not on the radio is heard (world units: 60 metres) */
+#define VOICE_RANGE 20.0f
+/* how far to the side a voice is put: on the radio, and near */
+#define VOICE_RADIO_PAN 0.3f
+#define VOICE_NEAR_PAN 0.8f
+
+/* ---------- globals */
+
+static struct
+{
+	boolean active;
+	word sequence;
+	long sent;
+	long played;
+	long log_time;
+} network_voice;
+
+/* ---------- private code */
+
+static boolean network_voice_in_network_game(
+	void)
+{
+	short connection = game_connection();
+
+	return (connection == _game_connection_network_server || connection == _game_connection_network_client) &&
+		game_in_progress();
+}
+
+/* where a player's head is, and whether they have a unit */
+static boolean network_voice_player_head(
+	struct player_datum const *player,
+	real_point3d *head)
+{
+	long unit_index = distributed_living_unit(player);
+
+	if (unit_index == NONE)
+		return FALSE;
+	unit_get_camera_position(unit_index, head);
+	return TRUE;
+}
+
+/* the gains a speaker is heard at here (FALSE: not heard) */
+static boolean network_voice_gains(
+	struct player_datum const *speaker,
+	real *left,
+	real *right)
+{
+	long listener_index = local_player_get_player_index(0);
+	struct player_datum *listener = listener_index != NONE ? player_try_and_get(listener_index) : NULL;
+	boolean teammate = listener && game_engine_has_teams() && listener->team_index == speaker->team_index;
+	real_point3d speaker_head;
+	real_point3d listener_head;
+	real gain = 1.0f;
+	real pan = 0.0f;
+
+	if (!listener)
+		return FALSE;
+	if (!network_voice_player_head(speaker, &speaker_head))
+	{
+		/* (dead: on the radio, to the team) */
+		if (!teammate)
+			return FALSE;
+		*left = *right = 1.0f;
+		return TRUE;
+	}
+	if (network_voice_player_head(listener, &listener_head))
+	{
+		real dx = speaker_head.x - listener_head.x;
+		real dy = speaker_head.y - listener_head.y;
+		real dz = speaker_head.z - listener_head.z;
+		real distance = (real)sqrt(dx * dx + dy * dy + dz * dz);
+		real flat = (real)sqrt(dx * dx + dy * dy);
+		float look[3];
+		real forward_x;
+		real forward_y;
+		real length;
+		struct unit_datum *unit = unit_try_and_get(distributed_living_unit(listener));
+
+		/* (where the listener looks: the head, in VR) */
+		if (halo_vr_look_vector(0, look))
+		{
+			forward_x = look[0];
+			forward_y = look[1];
+		}
+		else
+		{
+			forward_x = unit ? unit->unit.looking_vector.i : 1.0f;
+			forward_y = unit ? unit->unit.looking_vector.j : 0.0f;
+		}
+		length = (real)sqrt(forward_x * forward_x + forward_y * forward_y);
+		if (length > 0.0001f && flat > 0.0001f)
+		{
+			/* (the right: forward turned clockwise) */
+			pan = (dx * forward_y - dy * forward_x) / (flat * length);
+		}
+		if (!teammate)
+		{
+			gain = 1.0f - distance / VOICE_RANGE;
+			if (gain <= 0.0f)
+				return FALSE;
+			gain *= gain;
+		}
+		pan *= teammate ? VOICE_RADIO_PAN : VOICE_NEAR_PAN;
+	}
+	else if (!teammate)
+	{
+		/* (the listener dead: the others as from where the body is not:
+		not at all) */
+		return FALSE;
+	}
+	*left = gain * (pan > 0.0f ? 1.0f - pan : 1.0f);
+	*right = gain * (pan < 0.0f ? 1.0f + pan : 1.0f);
+	return TRUE;
+}
+
+static void network_voice_play_entries(
+	byte const *entries,
+	byte const *end,
+	short count,
+	long machine_index)
+{
+	short index;
+
+	for (index = 0; index < count && entries + VOICE_ENTRY_HEADER <= end; index++)
+	{
+		byte player_byte = entries[0];
+		word sequence = (word)(entries[1] | entries[2] << 8);
+		short length = entries[3];
+		long player_index;
+		struct player_datum *player;
+		real left;
+		real right;
+
+		if (length <= 0 || entries + VOICE_ENTRY_HEADER + length > end)
+			break;
+		player_index = distributed_player_from_byte(player_byte);
+		player = player_index != NONE ? player_try_and_get(player_index) : NULL;
+		/* (the host: only a client's own players') */
+		if (player && (machine_index == NONE || distributed_machine_has_player(machine_index, player_byte)) &&
+			player->local_player_index == NONE && network_voice_gains(player, &left, &right))
+		{
+			halo_voice_play(player_byte, sequence, entries + VOICE_ENTRY_HEADER, length, left, right);
+			network_voice.played++;
+		}
+		entries += VOICE_ENTRY_HEADER + length;
+	}
+}
+
+/* ---------- public code */
+
+void network_voice_new_game(
+	void)
+{
+	network_voice.sequence = 0;
+}
+
+word network_voice_entry_size(
+	void)
+{
+	return VOICE_ENTRY_HEADER;
+}
+
+/* after each tick (network_distributed_tick): this machine's speech sent */
+void network_voice_tick(
+	void)
+{
+	struct
+	{
+		struct distributed_message_header header;
+		byte entries[VOICE_MAXIMUM_TAKEN + 64];
+	} message;
+	byte taken[VOICE_MAXIMUM_TAKEN];
+	long player_index = local_player_get_player_index(0);
+	long size;
+	long offset = 0;
+	long used = 0;
+	short count = 0;
+
+	if (!network_voice_in_network_game() || !halo_voice_enabled())
+	{
+		if (network_voice.active)
+		{
+			network_voice.active = FALSE;
+			halo_voice_end();
+		}
+		return;
+	}
+	if (!network_voice.active)
+	{
+		network_voice.active = TRUE;
+		halo_voice_begin();
+	}
+	if (game_time_get() - network_voice.log_time >= 150 && (network_voice.sent || network_voice.played))
+	{
+		platform_log("voice: sent %ld, played %ld packets (in 150 ticks)", network_voice.sent, network_voice.played);
+		network_voice.sent = network_voice.played = 0;
+		network_voice.log_time = game_time_get();
+	}
+	size = halo_voice_take(taken, sizeof(taken));
+	if (player_index == NONE)
+		return;
+	while (offset < size)
+	{
+		short length = taken[offset];
+
+		if (length <= 0 || offset + 1 + length > size || length > VOICE_MAXIMUM_PACKET)
+			break;
+		if (used + VOICE_ENTRY_HEADER + length > (long)sizeof(message.entries))
+			break;
+		message.entries[used] = distributed_player_to_byte(player_index);
+		message.entries[used + 1] = (byte)(network_voice.sequence & 0xFF);
+		message.entries[used + 2] = (byte)(network_voice.sequence >> 8);
+		message.entries[used + 3] = (byte)length;
+		csmemcpy(message.entries + used + VOICE_ENTRY_HEADER, taken + offset + 1, length);
+		used += VOICE_ENTRY_HEADER + length;
+		offset += 1 + length;
+		network_voice.sequence++;
+		count++;
+	}
+	if (!count)
+		return;
+	network_voice.sent += count;
+	distributed_send(&message, _distributed_message_voice, count, (word)(sizeof(message.header) + used),
+		game_connection() == _game_connection_network_server ? _distributed_to_clients : _distributed_to_host);
+}
+
+/* a machine's speech: on the host a client's, played and passed on to the
+other clients; on a client the host's of any other */
+void network_voice_handle(
+	long machine_index,
+	void const *message,
+	word size)
+{
+	struct distributed_message_header header;
+	byte const *entries = (byte const *)message + sizeof(header);
+	byte const *end = (byte const *)message + size;
+
+	if (!halo_voice_enabled() || !network_voice.active)
+		return;
+	csmemcpy(&header, message, sizeof(header));
+	network_voice_play_entries(entries, end, header.count, machine_index);
+	if (machine_index != NONE)
+	{
+		long machine_indices[HALO_PORT_MAXIMUM_NETWORK_MACHINES];
+		short machine_count = distributed_client_machines(machine_indices, HALO_PORT_MAXIMUM_NETWORK_MACHINES);
+		short number;
+		struct
+		{
+			struct distributed_message_header header;
+			byte entries[VOICE_MAXIMUM_TAKEN + 64];
+		} relayed;
+		word entries_size = (word)(end - entries);
+
+		byte const *entry = entries;
+		short index;
+
+		/* (only the sender's own players' speech is passed on, whole) */
+		if (entries_size < VOICE_ENTRY_HEADER || entries_size > sizeof(relayed.entries))
+			return;
+		for (index = 0; index < header.count; index++)
+		{
+			if (entry + VOICE_ENTRY_HEADER > end || entry[3] == 0 || entry + VOICE_ENTRY_HEADER + entry[3] > end ||
+				!distributed_machine_has_player(machine_index, entry[0]))
+			{
+				return;
+			}
+			entry += VOICE_ENTRY_HEADER + entry[3];
+		}
+		if (entry != end)
+			return;
+		for (number = 0; number < machine_count; number++)
+		{
+			if (machine_indices[number] == machine_index)
+				continue;
+			csmemcpy(relayed.entries, entries, entries_size);
+			distributed_send_to_machine(machine_indices[number], &relayed, _distributed_message_voice, header.count,
+				(word)(sizeof(relayed.header) + entries_size));
+		}
+	}
+}

port/linux/include/halo_voice.h

@@ -0,0 +1,31 @@
+/*
+HALO_VOICE.H
+
+The voice chat's sound for the game (port/linux/src/voice.c: on Android the
+host's microphone, Opus and mixer, port/android/host/host_voice.c; elsewhere
+nothing). port/linux/game/network_voice.c sends and receives it.
+*/
+
+#ifndef __HALO_VOICE_H
+#define __HALO_VOICE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* whether the voice chat is on (voice.enabled) */
+int halo_voice_enabled(void);
+/* starts playing voices, and the microphone if voice.microphone; stops */
+int halo_voice_begin(void);
+void halo_voice_end(void);
+/* the microphone's speech since asked: Opus packets, each after a byte of
+its length; returns the bytes */
+int halo_voice_take(void *buffer, int size);
+/* a speaker's packet, played at these gains (left, right) */
+void halo_voice_play(int speaker, int sequence, const void *data, int length, float left, float right);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

port/linux/src/port_config.c

@@ -413,6 +413,17 @@ static const struct config_setting config_settings[] =
 		"The Discord application internet play invites go through while the\n"
 		"Discord desktop client runs; empty for none." },
 
+	{ "voice.enabled", _config_boolean, "true", "HALO_VOICE_ENABLED", _environment_value, _platform_android,
+		"Voice chat in multiplayer: hear the other players (teammates over the\n"
+		"radio, the rest when near, from where they are)." },
+	{ "voice.microphone", _config_boolean, "true", "HALO_VOICE_MICROPHONE", _environment_value, _platform_android,
+		"Send your voice in multiplayer, whenever you speak (the headset's\n"
+		"microphone; Android asks for it once). False only listens." },
+	{ "voice.volume", _config_real, "1.0", "HALO_VOICE_VOLUME", _environment_value, _platform_android,
+		"The other players' voices' volume (1 as they come)." },
+	{ "voice.threshold", _config_real, "0.02", "HALO_VOICE_THRESHOLD", _environment_value, _platform_android,
+		"How loud the microphone must be to send (0..1 of full scale): higher\n"
+		"if it sends noise, lower if it cuts words off." },
 	{ "bots.count", _config_integer, "0", "HALO_BOTS_COUNT", _environment_value, _platform_android,
 		"Bots in the multiplayer games this machine hosts (0 to 15; 0: none):\n"
 		"players it drives itself, which every machine sees as players. Set in\n"

port/linux/src/voice.c

@@ -0,0 +1,87 @@
+/*
+VOICE.C
+
+The voice chat's sound (halo_voice.h): on Android, the host's
+(port/android/host/host_voice.c); elsewhere none.
+*/
+
+#include "halo_voice.h"
+#include "platform.h"
+#include "port_config.h"
+
+#ifdef HALO_ANDROID
+#include "guest_host.h"
+
+#include <stdio.h>
+
+static int voice_started;
+
+/* whether the app may use the microphone, as the launcher found
+(LauncherActivity.java): opened without it, Android would ask in the middle
+of the game */
+static int voice_microphone_allowed(void)
+{
+	char path[512];
+	FILE *file;
+	int allowed = 0;
+
+	snprintf(path, sizeof(path), "%s/microphone_permission.txt", platform_data_root());
+	file = fopen(path, "rb");
+	if (file)
+	{
+		allowed = fgetc(file) == '1';
+		fclose(file);
+	}
+	return allowed;
+}
+
+int halo_voice_enabled(void)
+{
+	return config_boolean("voice.enabled");
+}
+
+int halo_voice_begin(void)
+{
+	int microphone;
+
+	if (voice_started)
+		return 1;
+	voice_started = 1;
+	microphone = config_boolean("voice.microphone") && voice_microphone_allowed();
+	platform_log("voice: on, %s", microphone ? "with the microphone" :
+		config_boolean("voice.microphone") ? "without the microphone (not allowed)" : "listening only");
+	return host_voice_start(microphone, (float)config_real("voice.volume"), (float)config_real("voice.threshold"));
+}
+
+void halo_voice_end(void)
+{
+	if (!voice_started)
+		return;
+	voice_started = 0;
+	host_voice_stop();
+	platform_log("voice: off");
+}
+
+int halo_voice_take(void *buffer, int size)
+{
+	return voice_started ? host_voice_take_packets(buffer, size) : 0;
+}
+
+void halo_voice_play(int speaker, int sequence, const void *data, int length, float left, float right)
+{
+	if (voice_started)
+		host_voice_play(speaker, sequence, data, length, left, right);
+}
+
+#else
+
+int halo_voice_enabled(void) { return 0; }
+int halo_voice_begin(void) { return 0; }
+void halo_voice_end(void) {}
+int halo_voice_take(void *buffer, int size) { (void)buffer; (void)size; return 0; }
+void halo_voice_play(int speaker, int sequence, const void *data, int length, float left, float right)
+{
+	(void)speaker; (void)sequence; (void)data; (void)length; (void)left; (void)right;
+}
+
+#endif

source/interface/ui_widget.c

@@ -5990,16 +5990,18 @@ void p2p_set_public_game(int public_game);
 int p2p_join_invite(char const *text);
 int p2p_public_game(void);
 int p2p_public_games(struct ui_public_game *games, int maximum);
+int config_boolean(char const *name);
+int config_write_boolean(char const *name, int value);
 long config_integer(char const *name);
 int config_write_integer(char const *name, long value);
 
 enum
 {
 	MAXIMUM_SHOWN_PUBLIC_GAMES = 32,
-	/* the online games panel's rows: "enter a code" and the games */
+	/* the online games panel's rows: "enter a code", the voice chat's
+	switches, and the games */
 	ONLINE_PANEL_ROWS = 11,
-	/* (the rows before the games: "enter a code") */
-	ONLINE_PANEL_FIXED_ROWS = 1,
+	ONLINE_PANEL_FIXED_ROWS = 3,
 };
 
 static struct
@@ -6073,7 +6075,7 @@ it, B closes it */
 static void ui_join_code_panel_event(
 	struct event_record const *event)
 {
-	short rows = (short)(ui_join_code_globals.game_count + 1);
+	short rows = (short)(ui_join_code_globals.game_count + ONLINE_PANEL_FIXED_ROWS);
 	short move = 0;
 
 	if (event->type == _event_type_left_stick)
@@ -6099,9 +6101,20 @@ static void ui_join_code_panel_event(
 			break;
 		case _gamepad_analog_button_a:
 		case _gamepad_binary_button_start:
+			/* (the voice chat's switches, kept in config.toml) */
+			if (ui_join_code_globals.selection == 1)
+			{
+				config_write_boolean("voice.enabled", !config_boolean("voice.enabled"));
+				break;
+			}
+			if (ui_join_code_globals.selection == 2)
+			{
+				config_write_boolean("voice.microphone", !config_boolean("voice.microphone"));
+				break;
+			}
 			ui_join_code_globals.panel_open = FALSE;
 			if (ui_join_code_globals.selection == 0 ||
-				ui_join_code_globals.selection > ui_join_code_globals.game_count)
+				ui_join_code_globals.selection >= ui_join_code_globals.game_count + ONLINE_PANEL_FIXED_ROWS)
 			{
 				ui_join_code_launch_keyboard();
 			}
@@ -6403,7 +6416,7 @@ static void ui_join_code_render_panel(
 	ui_join_code_globals.game_count =
 		(short)p2p_public_games(ui_join_code_globals.games, MAXIMUM_SHOWN_PUBLIC_GAMES);
 	ui_join_code_globals.selection =
-		(short)PIN(ui_join_code_globals.selection, 0, ui_join_code_globals.game_count);
+		(short)PIN(ui_join_code_globals.selection, 0, ui_join_code_globals.game_count + ONLINE_PANEL_FIXED_ROWS - 1);
 	ui_join_code_draw_quad(40, 72, 600, 410, 0xF0050A18);
 	ui_join_code_draw_quad(40, 72, 600, 74, 0xFF3A6EA5);
 	ui_join_code_draw_quad(40, 408, 600, 410, 0xFF3A6EA5);
@@ -6418,7 +6431,7 @@ static void ui_join_code_render_panel(
 		short index = (short)(ui_join_code_globals.scroll + row);
 		short y = (short)(128 + row * 22);
 
-		if (index > ui_join_code_globals.game_count)
+		if (index >= ui_join_code_globals.game_count + ONLINE_PANEL_FIXED_ROWS)
 			break;
 		if (index == ui_join_code_globals.selection)
 			ui_join_code_draw_quad(48, y, 592, (short)(y + 21), 0x803A6EA5);
@@ -6426,9 +6439,20 @@ static void ui_join_code_render_panel(
 		{
 			ui_join_code_draw_text(56, 584, (short)(y + 1), "Enter a join code...", FALSE, 0, &text_color);
 		}
+		else if (index == 1)
+		{
+			ui_join_code_draw_text(56, 584, (short)(y + 1),
+				config_boolean("voice.enabled") ? "Voice chat: On" : "Voice chat: Off", FALSE, 0, &text_color);
+		}
+		else if (index == 2)
+		{
+			ui_join_code_draw_text(56, 584, (short)(y + 1),
+				config_boolean("voice.microphone") ? "Microphone: On (sent while you speak)" :
+					"Microphone: Off (listening only)", FALSE, 0, &text_color);
+		}
 		else
 		{
-			struct ui_public_game const *game = &ui_join_code_globals.games[index - 1];
+			struct ui_public_game const *game = &ui_join_code_globals.games[index - ONLINE_PANEL_FIXED_ROWS];
 
 			ui_join_code_draw_text(56, 212, (short)(y + 1), game->name, FALSE, 0, &text_color);
 			ui_join_code_draw_text(216, 372, (short)(y + 1), ui_join_code_map_name(game->map), FALSE, 0,
@@ -6439,9 +6463,9 @@ static void ui_join_code_render_panel(
 		}
 	}
 	if (!ui_join_code_globals.game_count)
-		ui_join_code_draw_text(56, 584, 152, "No public games right now", FALSE, 0, &dim_color);
-	ui_join_code_draw_text(56, 584, 384, "%a-button Join   %x-button Enter a code   %b-button Back", TRUE, 0,
-		&text_color);
+		ui_join_code_draw_text(56, 584, 196, "No public games right now", FALSE, 0, &dim_color);
+	ui_join_code_draw_text(56, 584, 384, "%a-button Join or switch   %x-button Enter a code   %b-button Back", TRUE,
+		0, &text_color);
 }
 
 /* over the screens, as they are drawn */

tools/android_build.py

@@ -48,6 +48,10 @@ MUSL_URL = f"https://musl.libc.org/releases/musl-{MUSL_VERSION}.tar.gz"
 SDL_TAG = "release-3.4.16"
 SDL_DIR = THIRD_PARTY / "SDL3"
 SDL_URL = "https://github.com/libsdl-org/SDL.git"
+# Opus, the voice chat's codec (host_voice.c), built into the host library
+OPUS_TAG = "v1.5.2"
+OPUS_DIR = THIRD_PARTY / "opus"
+OPUS_URL = "https://github.com/xiph/opus.git"
 # the Khronos OpenXR loader for Android (the VR build, host_xr.c): its
 # headers and library are linked from here; the app packages the same AAR
 # through Gradle (port/android/app/build.gradle), which also merges the
@@ -221,6 +225,10 @@ def fetch_third_party() -> None:
         print(f"Cloning SDL3 {SDL_TAG}")
         subprocess.run(["git", "clone", "-q", "--depth", "1", "--branch", SDL_TAG, SDL_URL, str(SDL_DIR)],
                        check=True)
+    if not OPUS_DIR.is_dir():
+        print(f"Cloning Opus {OPUS_TAG}")
+        subprocess.run(["git", "clone", "-q", "--depth", "1", "--branch", OPUS_TAG, OPUS_URL, str(OPUS_DIR)],
+                       check=True)
     patch_sdl_java()
     if not OPENXR_DIR.is_dir():
         print(f"Downloading {OPENXR_URL}")
@@ -564,6 +572,23 @@ def generate_android_build(n: Writer, sln: Any) -> None:
     )
     n.build(outputs=libsdl, rule="android_sdl3", implicit=[SDL_DIR / "CMakeLists.txt"])
 
+    # ---------- Opus (the voice chat's codec, host_voice.c)
+
+    opus_build = BUILD / "opus-build"
+    libopus = opus_build / "libopus.a"
+    n.rule(
+        name="android_opus",
+        command=(f"cmake -S {OPUS_DIR} -B {opus_build} -G Ninja "
+                 f"-DCMAKE_TOOLCHAIN_FILE={ndk}/build/cmake/android.toolchain.cmake "
+                 f"-DANDROID_ABI=arm64-v8a -DANDROID_PLATFORM=android-{ANDROID_API} -DCMAKE_BUILD_TYPE=Release "
+                 f"-DCMAKE_POSITION_INDEPENDENT_CODE=ON -DOPUS_BUILD_SHARED_LIBRARY=OFF -DOPUS_BUILD_TESTING=OFF "
+                 f"-DOPUS_BUILD_PROGRAMS=OFF -DOPUS_INSTALL_PKG_CONFIG_MODULE=OFF -DOPUS_INSTALL_CMAKE_CONFIG_MODULE=OFF "
+                 f"> {BUILD}/opus-configure.log && ninja -C {opus_build} > {BUILD}/opus-build.log"),
+        description="ANDROID OPUS",
+        pool="console",
+    )
+    n.build(outputs=libopus, rule="android_opus", implicit=[OPUS_DIR / "CMakeLists.txt"])
+
     # ---------- the host library
 
     host_objects: List[Path] = []
@@ -578,7 +603,7 @@ def generate_android_build(n: Writer, sln: Any) -> None:
     host_cflags = " ".join([
         "-O2", "-g", "-fPIC", "-Wall", "-Wno-unused-function", "-D_GNU_SOURCE",
         f"-I{PORT_DIR}/include", f"-I{PORT_DIR}/host", f"-I{SDL_DIR}/include", f"-I{LINUX_DIR}/src",
-        f"-I{TOML_DIR}", f"-I{OPENXR_DIR}/include",
+        f"-I{TOML_DIR}", f"-I{OPENXR_DIR}/include", f"-I{OPUS_DIR}/include",
     ])
     host_sources = sorted((PORT_DIR / "host").glob("*.c")) + [
         LINUX_DIR / "src" / "posix_files.c", LINUX_DIR / "src" / "posix_net.c",
@@ -604,12 +629,12 @@ def generate_android_build(n: Writer, sln: Any) -> None:
     host_objects.append(table_obj)
     n.rule(
         name="android_host_link",
-        command=(f"$android_host_cc -shared -o $out $in -L{sdl_build} -L{OPENXR_DIR}/lib -lopenxr_loader "
+        command=(f"$android_host_cc -shared -o $out $in {libopus} -L{sdl_build} -L{OPENXR_DIR}/lib -lopenxr_loader "
                  + " ".join(f"-l{lib}" for lib in HOST_LIBRARIES)
                  + " -Wl,-z,max-page-size=16384 -Wl,--no-undefined"),
         description="ANDROID HOST LINK $out",
     )
-    n.build(outputs=libmain, rule="android_host_link", inputs=host_objects, implicit=[libsdl])
+    n.build(outputs=libmain, rule="android_host_link", inputs=host_objects, implicit=[libsdl, libopus])
 
     # a do-nothing OpenXR layer under the Steam Frame's implicit layer's
     # library name (port/android/xr_layer/fdm_injection_stub.c)