Let AGC raise the noise floor further to bring up a distant voice

AGC2 won't amplify the background noise above -50 dBFS, which also caps
the gain for a voice barely above that noise: a distant talker ended up
5 dB quieter than a near one with noise suppression on, 12 dB with it
off. A "Boost quiet speech" setting (0-20 dB, default 0) raises the cap,
live, on desktop and Android.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/java/com/ts3client/android/ui/SettingsScreen.kt

@@ -167,6 +167,12 @@ fun SettingsScreen(vm: SessionController, onBack: () -> Unit) {
                 agc = it
                 change { this.agc = it }
             }
+            if (agc) {
+                Level("Boost quiet speech", settings.agcBoostDb.toFloat(), 0f..Settings.MAX_AGC_BOOST_DB.toFloat(),
+                    { "+${it.roundToInt()} dB" }, steps = Settings.MAX_AGC_BOOST_DB - 1) {
+                    change { agcBoostDb = it.roundToInt() }
+                }
+            }
 
             Section("Playback")
             Level("Volume", settings.outputVolume.toFloat(), 0f..2f, { "${(it * 100).roundToInt()} %" }) {

ts3-client/README.md

@@ -38,6 +38,8 @@ Android app in [`../android`](../android) does.
   four levels) → **typing attenuation** (the transient suppressor, told about key presses)
   → **automatic gain control** (AGC2, WebRTC's successor to the AGC1 TS3 uses). Checked
   against WebRTC built from source.
+  - **Boost quiet speech** (0–20 dB) raises AGC2's cap on the amplified noise floor, which
+    otherwise holds back a distant voice that is barely above the background noise.
   - Echo cancellation (WebRTC AEC3) is intentionally omitted — it needs the loudspeaker
     reference signal and matters mainly for open speakers, not the typical headset.
 - **Push-to-Talk** — bind any key or mouse button as a global hotkey; transmits only while held.

ts3-client/core/src/main/java/com/ts3client/audio/CaptureVoiceInput.java

@@ -113,6 +113,7 @@ public final class CaptureVoiceInput implements VoiceInput {
         processor.setSuppressionLevel(SuppressionLevel.fromDenoiserLevel(settings.denoiserLevel));
         processor.setTransientSuppression(settings.typingAttenuation);
         processor.setGainControl(settings.agc);
+        processor.setGainBoost(settings.agcBoostDb);
     }
 
     // ---- live configuration (safe to call from the UI thread) ----
@@ -169,6 +170,10 @@ public final class CaptureVoiceInput implements VoiceInput {
         processor.setGainControl(enabled);
     }
 
+    public void setAgcBoost(int db) {
+        processor.setGainBoost(db);
+    }
+
     @Override
     public void keyPressed() {
         processor.keyPressed();

ts3-client/core/src/main/java/com/ts3client/audio/VoiceInput.java

@@ -60,6 +60,9 @@ public interface VoiceInput extends Microphone {
     /** Enables automatic gain control (normalise microphone loudness). */
     void setAgc(boolean enabled);
 
+    /** Lets AGC raise the background noise this many dB more to bring up a quiet voice. */
+    void setAgcBoost(int db);
+
     /** Applies Opus encoder parameters, taking effect immediately if capturing. */
     void setOpusParameters(OpusParameters parameters);
 
@@ -94,6 +97,7 @@ public interface VoiceInput extends Microphone {
         setDenoiserLevel(settings.denoiserLevel);
         setTypingAttenuation(settings.typingAttenuation);
         setAgc(settings.agc);
+        setAgcBoost(settings.agcBoostDb);
         setOpusParameters(OpusParameters.from(settings));
     }
 }

ts3-client/core/src/main/java/com/ts3client/audio/processing/AudioProcessor.java

@@ -18,7 +18,9 @@ import java.util.concurrent.atomic.AtomicBoolean;
  *       whenever noise suppression runs, so a 100&nbsp;Hz high-pass comes with it;</li>
  *   <li>transient suppression ("Typing attenuation"), told about key presses;</li>
  *   <li>automatic gain control. TS3 runs WebRTC's legacy AGC1 (adaptive digital, target
- *       -9&nbsp;dBFS, 20&nbsp;dB compression); this runs its successor, AGC2 adaptive digital.</li>
+ *       -9&nbsp;dBFS, 20&nbsp;dB compression); this runs its successor, AGC2 adaptive digital. AGC2 won't
+ *       amplify the noise floor above -50&nbsp;dBFS, which also holds back a distant voice
+ *       barely above the noise; {@link #setGainBoost} trades more noise for more of it.</li>
  * </ol>
  *
  * <p>One deliberate difference: APM only splits into bands for band-wise stages, so with noise
@@ -39,6 +41,7 @@ public final class AudioProcessor {
     private volatile SuppressionLevel suppressionLevel = SuppressionLevel.DB_12;
     private volatile boolean transientSuppression;
     private volatile boolean gainControl;
+    private volatile float gainBoostDb;
     private final AtomicBoolean keyPressed = new AtomicBoolean();
 
     private final ThreeBandFilterBank filterBank = new ThreeBandFilterBank();
@@ -66,6 +69,11 @@ public final class AudioProcessor {
         this.gainControl = enabled;
     }
 
+    /** Lets the gain control raise the noise floor this many dB higher to reach quiet speech. */
+    public void setGainBoost(float db) {
+        this.gainBoostDb = db;
+    }
+
     /** Reports a key press anywhere on the system; the transient suppressor only acts while typing. */
     public void keyPressed() {
         keyPressed.set(true);
@@ -146,5 +154,8 @@ public final class AudioProcessor {
         } else if (gainController == null) {
             gainController = new GainController2(AdaptiveDigitalConfig.DEFAULT);
         }
+        if (gainController != null) {
+            gainController.setMaxOutputNoiseLevelDbfs(AdaptiveDigitalConfig.DEFAULT.maxOutputNoiseLevelDbfs() + gainBoostDb);
+        }
     }
 }

ts3-client/core/src/main/java/com/ts3client/audio/processing/agc2/AdaptiveDigitalGainController.java

@@ -21,6 +21,7 @@ final class AdaptiveDigitalGainController {
     private final AdaptiveDigitalConfig config;
     private final int adjacentSpeechFramesThreshold;
     private final float maxGainChangeDbPer10ms;
+    private float maxOutputNoiseLevelDbfs;
     private int framesToGainIncreaseAllowed;
     private float lastGainDb;
 
@@ -31,6 +32,11 @@ final class AdaptiveDigitalGainController {
         this.maxGainChangeDbPer10ms = config.maxGainChangeDbPerSecond() * FRAME_DURATION_MS / 1000.0f;
         this.framesToGainIncreaseAllowed = adjacentSpeechFramesThreshold;
         this.lastGainDb = config.initialGainDb();
+        this.maxOutputNoiseLevelDbfs = config.maxOutputNoiseLevelDbfs();
+    }
+
+    void setMaxOutputNoiseLevelDbfs(float dbfs) {
+        maxOutputNoiseLevelDbfs = dbfs;
     }
 
     void process(FrameInfo info, float[] frame, int samples) {
@@ -80,7 +86,7 @@ final class AdaptiveDigitalGainController {
     }
 
     private float limitGainByNoise(float targetGainDb, float inputNoiseLevelDbfs) {
-        final float maxAllowedGainDb = config.maxOutputNoiseLevelDbfs() - inputNoiseLevelDbfs;
+        final float maxAllowedGainDb = maxOutputNoiseLevelDbfs - inputNoiseLevelDbfs;
         return Math.min(targetGainDb, Math.max(maxAllowedGainDb, 0.0f));
     }
 

ts3-client/core/src/main/java/com/ts3client/audio/processing/agc2/GainController2.java

@@ -16,6 +16,12 @@ import com.ts3client.audio.vad.RnnSpeechDetector;
  * WebRTC: it measures the speech level only on frames its RNN VAD calls speech, and caps
  * the gain so the measured noise floor stays below -50 dBFS.
  *
+ * <p>It is also slower to adapt: the gain rises at most 6&nbsp;dB/s, and only after 12
+ * frames in a row that its VAD rates at 0.95 or more, holding still through pauses. A
+ * distant voice in a reverberant room (half its frames that confident) took about 9&nbsp;s
+ * of talking to go from the initial 15&nbsp;dB to the 26&nbsp;dB it settled at. How fast
+ * AGC1 follows the same voice hasn't been measured.
+ *
  * <p>Takes 10&nbsp;ms mono frames at 48&nbsp;kHz on the 16-bit scale, in place.
  */
 public final class GainController2 {
@@ -39,6 +45,14 @@ public final class GainController2 {
         this.adaptiveDigitalController = new AdaptiveDigitalGainController(config, ADJACENT_SPEECH_FRAMES_THRESHOLD);
     }
 
+    /**
+     * Moves the cap on the amplified noise floor away from the configured
+     * {@code maxOutputNoiseLevelDbfs}, keeping the rest of the controller's state.
+     */
+    public void setMaxOutputNoiseLevelDbfs(float dbfs) {
+        adaptiveDigitalController.setMaxOutputNoiseLevelDbfs(dbfs);
+    }
+
     public void process(float[] frame) {
         final float speechProbability = analyzeVad(frame);
 

ts3-client/core/src/main/java/com/ts3client/config/Settings.java

@@ -138,6 +138,9 @@ public final class Settings {
     public boolean typingAttenuation = true;
     /** Automatic gain control: normalise microphone loudness to a target level. */
     public boolean agc = true;
+    public static final int MAX_AGC_BOOST_DB = 20;
+    /** How many dB louder AGC may make the background noise to bring up a quiet or distant voice. */
+    public int agcBoostDb = 0;
     /** Beep when speech is picked up while the microphone is muted. */
     public boolean mutedTalkWarning = true;
 
@@ -257,6 +260,7 @@ public final class Settings {
         typingAttenuation = parseB(props.getProperty("typingAttenuation"), typingAttenuation);
         mutedTalkWarning = parseB(props.getProperty("mutedTalkWarning"), mutedTalkWarning);
         agc = parseB(props.getProperty("agc"), agc);
+        agcBoostDb = Math.max(0, Math.min(MAX_AGC_BOOST_DB, parseI(props.getProperty("agcBoostDb"), agcBoostDb)));
         soundPack = props.getProperty("soundPack", soundPack);
         soundVolume = parseD(props.getProperty("soundVolume"), soundVolume);
         soundPackDir = props.getProperty("soundPackDir", soundPackDir);
@@ -309,6 +313,7 @@ public final class Settings {
         props.setProperty("typingAttenuation", Boolean.toString(typingAttenuation));
         props.setProperty("mutedTalkWarning", Boolean.toString(mutedTalkWarning));
         props.setProperty("agc", Boolean.toString(agc));
+        props.setProperty("agcBoostDb", Integer.toString(agcBoostDb));
         props.setProperty("soundPack", soundPack);
         props.setProperty("soundVolume", Double.toString(soundVolume));
         props.setProperty("soundPackDir", soundPackDir);

ts3-client/core/src/test/java/com/ts3client/audio/processing/AudioProcessorTest.java

@@ -166,6 +166,26 @@ class AudioProcessorTest {
                 "quiet speech should be raised by more than 12 dB");
     }
 
+    @Test
+    void gainBoostLetsTheNoiseFloorRiseFurther() {
+        // -60 dBFS of noise alone: AGC2 starts at 15 dB of gain and, with no speech to
+        // raise it, can only lower it, down to what keeps the noise under its cap.
+        Random random = new Random(3);
+        float[] noise = new float[RATE * 3];
+        for (int i = 0; i < noise.length; i++) noise[i] = (float) (random.nextGaussian() * 0.001);
+
+        AudioProcessor plain = new AudioProcessor();
+        plain.setGainControl(true);
+        AudioProcessor boosted = new AudioProcessor();
+        boosted.setGainControl(true);
+        boosted.setGainBoost(20);
+
+        double plainDb = 20 * Math.log10(rms(run(plain, noise, Set.of()), RATE * 2, RATE * 3));
+        double boostedDb = 20 * Math.log10(rms(run(boosted, noise, Set.of()), RATE * 2, RATE * 3));
+        assertEquals(-50, plainDb, 1.5, "the noise is held at AGC2's -50 dBFS cap");
+        assertEquals(-45, boostedDb, 1.5, "with the cap 20 dB higher, the initial 15 dB of gain stays");
+    }
+
     private static double rms(float[] x, int from, int to) {
         double sum = 0;
         for (int i = from; i < to; i++) sum += x[i] * x[i];

ts3-client/swing/src/main/java/com/ts3client/ui/DevicesPanel.java

@@ -33,6 +33,7 @@ final class DevicesPanel extends FormPanel {
     private final JSlider denoiseLevel;
     private final JCheckBox typingCheck;
     private final JCheckBox agcCheck;
+    private final JSlider agcBoost;
     private final JCheckBox mutedWarningCheck;
 
     DevicesPanel(Settings settings, AudioIo io, VoiceOutput livePlayback,
@@ -99,6 +100,12 @@ final class DevicesPanel extends FormPanel {
         agcCheck.setToolTipText("<html><b>Automatic gain control</b> normalises your "
                 + "microphone loudness to a target level, boosting quiet mics and taming "
                 + "loud ones.</html>");
+        agcBoost = new JSlider(0, Settings.MAX_AGC_BOOST_DB, settings.agcBoostDb);
+        agcBoost.setMajorTickSpacing(5);
+        agcBoost.setPaintTicks(true);
+        limitWidth(agcBoost, SLIDER_WIDTH);
+        agcBoost.setToolTipText("<html>Lets AGC bring up a quiet or distant voice further, "
+                + "at the cost of up to this many dB more background noise (0&ndash;20 dB).</html>");
 
         c.gridx = 0;
         c.gridy = row++;
@@ -113,9 +120,11 @@ final class DevicesPanel extends FormPanel {
         c.gridy = row++;
         add(agcCheck, c);
         c.gridwidth = 1;
+        addRow(this, c, row++, new JLabel("Boost quiet speech:"), agcBoost);
 
         Runnable syncNoise = () -> {
             denoiseLevel.setEnabled(denoiseCheck.isSelected());
+            agcBoost.setEnabled(agcCheck.isSelected());
             applyLive.accept(m -> {
                 m.setNoiseSuppression(denoiseCheck.isSelected());
                 m.setDenoiserLevel(denoiseLevel.getValue());
@@ -128,6 +137,8 @@ final class DevicesPanel extends FormPanel {
         agcCheck.addActionListener(e -> syncNoise.run());
         denoiseLevel.addChangeListener(e ->
                 applyLive.accept(m -> m.setDenoiserLevel(denoiseLevel.getValue())));
+        agcBoost.addChangeListener(e ->
+                applyLive.accept(m -> m.setAgcBoost(agcBoost.getValue())));
         syncNoise.run();
 
         mutedWarningCheck = new JCheckBox("Beep when talking while muted", settings.mutedTalkWarning);
@@ -156,6 +167,7 @@ final class DevicesPanel extends FormPanel {
         target.denoiserLevel = denoiseLevel.getValue();
         target.typingAttenuation = typingCheck.isSelected();
         target.agc = agcCheck.isSelected();
+        target.agcBoostDb = agcBoost.getValue();
         target.mutedTalkWarning = mutedWarningCheck.isSelected();
     }