diff --git a/services/audioflinger/MmapTracks.h b/services/audioflinger/MmapTracks.h
index 85ce142..8758bd0 100644
--- a/services/audioflinger/MmapTracks.h
+++ b/services/audioflinger/MmapTracks.h
@@ -35,7 +35,8 @@
                             bool isOut,
                             const android::content::AttributionSourceState& attributionSource,
                             pid_t creatorPid,
-                            audio_port_handle_t portId = AUDIO_PORT_HANDLE_NONE);
+                            audio_port_handle_t portId = AUDIO_PORT_HANDLE_NONE,
+                            float volume = 0.0f);
     ~MmapTrack() override;
 
     status_t initCheck() const final;
@@ -65,6 +66,13 @@
     void processMuteEvent_l(const sp<IAudioManager>& audioManager,
                             mute_state_t muteState)
                             /* REQUIRES(MmapPlaybackThread::mLock) */ final;
+
+    // VolumePortInterface implementation
+    void setPortVolume(float volume) override {
+        mVolume = volume;
+    }
+    float getPortVolume() const override { return mVolume; }
+
 private:
     DISALLOW_COPY_AND_ASSIGN(MmapTrack);
 
@@ -87,6 +95,8 @@
             /* GUARDED_BY(MmapPlaybackThread::mLock) */;
     mute_state_t mMuteState
             /* GUARDED_BY(MmapPlaybackThread::mLock) */;
+
+    float mVolume = 0.0f;
 };  // end of Track
 
 } // namespace android
\ No newline at end of file