diff --git a/media/libaudioclient/AudioSystem.cpp b/media/libaudioclient/AudioSystem.cpp
index ff2608c..74fa343 100644
--- a/media/libaudioclient/AudioSystem.cpp
+++ b/media/libaudioclient/AudioSystem.cpp
@@ -18,6 +18,8 @@
 //#define LOG_NDEBUG 0
 
 #include <utils/Log.h>
+
+#include <android/media/BnCaptureStateListener.h>
 #include <binder/IServiceManager.h>
 #include <binder/ProcessState.h>
 #include <binder/IPCThreadState.h>
@@ -44,6 +46,10 @@
 dynamic_policy_callback AudioSystem::gDynPolicyCallback = NULL;
 record_config_callback AudioSystem::gRecordConfigCallback = NULL;
 
+// Required to be held while calling into gSoundTriggerCaptureStateListener.
+Mutex gSoundTriggerCaptureStateListenerLock;
+sp<AudioSystem::CaptureStateListener> gSoundTriggerCaptureStateListener = nullptr;
+
 // establish binder interface to AudioFlinger service
 const sp<IAudioFlinger> AudioSystem::get_audio_flinger()
 {
@@ -1623,6 +1629,48 @@
     return aps->getPreferredDeviceForStrategy(strategy, device);
 }
 
+class CaptureStateListenerImpl : public media::BnCaptureStateListener,
+                                 public IBinder::DeathRecipient {
+public:
+    binder::Status setCaptureState(bool active) override {
+        Mutex::Autolock _l(gSoundTriggerCaptureStateListenerLock);
+        gSoundTriggerCaptureStateListener->onStateChanged(active);
+        return binder::Status::ok();
+    }
+
+    void binderDied(const wp<IBinder>&) override {
+        Mutex::Autolock _l(gSoundTriggerCaptureStateListenerLock);
+        gSoundTriggerCaptureStateListener->onServiceDied();
+        gSoundTriggerCaptureStateListener = nullptr;
+    }
+};
+
+status_t AudioSystem::registerSoundTriggerCaptureStateListener(
+    const sp<CaptureStateListener>& listener) {
+    const sp<IAudioPolicyService>& aps =
+            AudioSystem::get_audio_policy_service();
+    if (aps == 0) {
+        return PERMISSION_DENIED;
+    }
+
+    sp<CaptureStateListenerImpl> wrapper = new CaptureStateListenerImpl();
+
+    Mutex::Autolock _l(gSoundTriggerCaptureStateListenerLock);
+
+    bool active;
+    status_t status =
+        aps->registerSoundTriggerCaptureStateListener(wrapper, &active);
+    if (status != NO_ERROR) {
+        listener->onServiceDied();
+        return NO_ERROR;
+    }
+    gSoundTriggerCaptureStateListener = listener;
+    listener->onStateChanged(active);
+    sp<IBinder> binder = IInterface::asBinder(aps);
+    binder->linkToDeath(wrapper);
+    return NO_ERROR;
+}
+
 // ---------------------------------------------------------------------------
 
 int AudioSystem::AudioPolicyServiceClient::addAudioPortCallback(
diff --git a/media/libaudioclient/include/media/AudioSystem.h b/media/libaudioclient/include/media/AudioSystem.h
index 575c910..19c2cbd 100644
--- a/media/libaudioclient/include/media/AudioSystem.h
+++ b/media/libaudioclient/include/media/AudioSystem.h
@@ -436,6 +436,30 @@
     static status_t getDeviceForStrategy(product_strategy_t strategy,
             AudioDeviceTypeAddr &device);
 
+    // A listener for capture state changes.
+    class CaptureStateListener : public RefBase {
+    public:
+        // Called whenever capture state changes.
+        virtual void onStateChanged(bool active) = 0;
+        // Called whenever the service dies (and hence our listener is no longer
+        // registered).
+        virtual void onServiceDied() = 0;
+
+        virtual ~CaptureStateListener() = default;
+    };
+
+    // Regiseters a listener for sound trigger capture state changes.
+    // There may only be one such listener registered at any point.
+    // The listener onStateChanged() method will be invoked sychronously from
+    // this call with the initial value.
+    // The listener onServiceDied() method will be invoked sychronously from
+    // this call if initial attempt to register failed.
+    // If the audio policy service cannot be reached, this method will return
+    // PERMISSION_DENIED and will not invoke the callback, otherwise, it will
+    // return NO_ERROR.
+    static status_t registerSoundTriggerCaptureStateListener(
+            const sp<CaptureStateListener>& listener);
+
     // ----------------------------------------------------------------------------
 
     class AudioVolumeGroupCallback : public RefBase