diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 8b420c0..51aeb7e 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -21,10 +21,11 @@
 
 public: // TODO(b/288339104) extract out of AudioFlinger class
 class ThreadBase : public Thread {
+    // TODO(b/288339104) remove friends
+    friend class RecordTrack;
+    friend class Track;
+    friend class TrackBase;
 public:
-
-#include "TrackBase.h"
-
     enum type_t {
         MIXER,              // Thread class is MixerThread
         DIRECT,             // Thread class is DirectOutputThread
@@ -488,7 +489,7 @@
                         result = EFFECT_SESSION;
                     }
                     for (size_t i = 0; i < tracks.size(); ++i) {
-                        const sp<TrackBase>& track = tracks[i];
+                        const sp<IAfTrackBase>& track = tracks[i];
                         if (sessionId == track->sessionId()
                                 && !track->isInvalid()       // not yet removed from tracks.
                                 && !track->isTerminated()) {
@@ -568,7 +569,7 @@
                 void invalidateTracksForAudioSession_l(audio_session_t sessionId,
                                                        const T& tracks) const {
                     for (size_t i = 0; i < tracks.size(); ++i) {
-                        const sp<TrackBase>& track = tracks[i];
+                        const sp<IAfTrackBase>& track = tracks[i];
                         if (sessionId == track->sessionId()) {
                             track->invalidate();
                         }
@@ -861,10 +862,11 @@
 // --- PlaybackThread ---
 class PlaybackThread : public ThreadBase, public StreamOutHalInterfaceCallback,
                        public VolumeInterface, public StreamOutHalInterfaceEventCallback {
+    // TODO(b/288339104) remove friends
+    friend class OutputTrack;
+    friend class Track;
 public:
 
-#include "PlaybackTracks.h"
-
     enum mixer_state {
         MIXER_IDLE,             // no active tracks
         MIXER_TRACKS_ENABLED,   // at least one active track, but no track has any data ready
@@ -913,14 +915,14 @@
     virtual     void        threadLoop_drain();
     virtual     void        threadLoop_standby();
     virtual     void        threadLoop_exit();
-    virtual     void        threadLoop_removeTracks(const Vector< sp<Track> >& tracksToRemove);
+    virtual     void        threadLoop_removeTracks(const Vector<sp<IAfTrack>>& tracksToRemove);
 
                 // prepareTracks_l reads and writes mActiveTracks, and returns
                 // the pending set of tracks to remove via Vector 'tracksToRemove'.  The caller
                 // is responsible for clearing or destroying this Vector later on, when it
                 // is safe to do so. That will drop the final ref count and destroy the tracks.
-    virtual     mixer_state prepareTracks_l(Vector< sp<Track> > *tracksToRemove) = 0;
-                void        removeTracks_l(const Vector< sp<Track> >& tracksToRemove);
+    virtual     mixer_state prepareTracks_l(Vector<sp<IAfTrack>>* tracksToRemove) = 0;
+                void        removeTracks_l(const Vector<sp<IAfTrack>>& tracksToRemove);
                 status_t    handleVoipVolume_l(float *volume);
 
     // StreamOutHalInterfaceCallback implementation
@@ -976,7 +978,7 @@
 
                 void        setVolumeForOutput_l(float left, float right) const override;
 
-                sp<Track>   createTrack_l(
+                sp<IAfTrack>   createTrack_l(
                                 const sp<Client>& client,
                                 audio_stream_type_t streamType,
                                 const audio_attributes_t& attr,
@@ -1021,14 +1023,14 @@
                                             audio_port_handle_t portId = AUDIO_PORT_HANDLE_NONE);
                 status_t    getRenderPosition(uint32_t *halFrames, uint32_t *dspFrames);
                 // Consider also removing and passing an explicit mMainBuffer initialization
-                // parameter to AF::PlaybackThread::Track::Track().
+                // parameter to AF::IAfTrack::Track().
                 float *sinkBuffer() const {
                     return reinterpret_cast<float *>(mSinkBuffer); };
 
     virtual     void detachAuxEffect_l(int effectId);
-                status_t attachAuxEffect(const sp<AudioFlinger::PlaybackThread::Track>& track,
+                status_t attachAuxEffect(const sp<IAfTrack>& track,
                         int EffectId);
-                status_t attachAuxEffect_l(const sp<AudioFlinger::PlaybackThread::Track>& track,
+                status_t attachAuxEffect_l(const sp<IAfTrack>& track,
                         int EffectId);
 
                 virtual status_t addEffectChain_l(const sp<IAfEffectChain>& chain);
@@ -1058,8 +1060,8 @@
 
                 status_t    getTimestamp_l(AudioTimestamp& timestamp);
 
-                void        addPatchTrack(const sp<PatchTrack>& track);
-                void        deletePatchTrack(const sp<PatchTrack>& track);
+                void        addPatchTrack(const sp<IAfPatchTrack>& track);
+                void        deletePatchTrack(const sp<IAfPatchTrack>& track);
 
     virtual     void        toAudioPortConfig(struct audio_port_config *config);
 
@@ -1096,7 +1098,7 @@
                     mDownStreamPatch = *patch;
                 }
 
-                PlaybackThread::Track* getTrackById_l(audio_port_handle_t trackId);
+                IAfTrack* getTrackById_l(audio_port_handle_t trackId);
 
                 bool hasMixer() const {
                     return mType == MIXER || mType == DUPLICATING || mType == SPATIALIZER;
@@ -1259,7 +1261,7 @@
                 }
 
 protected:
-    ActiveTracks<Track>     mActiveTracks;
+    ActiveTracks<IAfTrack> mActiveTracks;
 
     // Time to sleep between cycles when:
     virtual uint32_t        activeSleepTimeUs() const;      // mixer state MIXER_TRACKS_ENABLED
@@ -1304,9 +1306,9 @@
 
     DISALLOW_COPY_AND_ASSIGN(PlaybackThread);
 
-    status_t    addTrack_l(const sp<Track>& track);
-    bool        destroyTrack_l(const sp<Track>& track);
-    void        removeTrack_l(const sp<Track>& track);
+    status_t    addTrack_l(const sp<IAfTrack>& track);
+    bool        destroyTrack_l(const sp<IAfTrack>& track);
+    void        removeTrack_l(const sp<IAfTrack>& track);
 
     void        readOutputParameters_l();
     MetadataUpdate          updateMetadata_l() final;
@@ -1364,7 +1366,7 @@
         SortedVector<sp<T>> mTracks; // wrapped SortedVector.
     };
 
-    Tracks<Track>                   mTracks;
+    Tracks<IAfTrack>                   mTracks;
 
     stream_type_t                   mStreamTypes[AUDIO_STREAM_CNT];
     AudioStreamOut                  *mOutput;
@@ -1425,7 +1427,7 @@
 
     Mutex                                    mAudioTrackCbLock;
     // Record of IAudioTrackCallback
-    std::map<sp<Track>, sp<media::IAudioTrackCallback>> mAudioTrackCallbacks;
+    std::map<sp<IAfTrack>, sp<media::IAudioTrackCallback>> mAudioTrackCallbacks;
 
 private:
     // The HAL output sink is treated as non-blocking, but current implementation is blocking
@@ -1533,7 +1535,7 @@
                                     audio_channel_mask_t channelMask, audio_format_t format,
                                     audio_session_t sessionId, uid_t uid) const override;
 protected:
-    virtual     mixer_state prepareTracks_l(Vector< sp<Track> > *tracksToRemove);
+    virtual     mixer_state prepareTracks_l(Vector<sp<IAfTrack>>* tracksToRemove);
     virtual     uint32_t    idleSleepTimeUs() const;
     virtual     uint32_t    suspendSleepTimeUs() const;
     virtual     void        cacheParameters_l();
@@ -1663,7 +1665,7 @@
                 void        dumpInternals_l(int fd, const Vector<String16>& args) override;
 
     // threadLoop snippets
-    virtual     mixer_state prepareTracks_l(Vector< sp<Track> > *tracksToRemove);
+    virtual     mixer_state prepareTracks_l(Vector<sp<IAfTrack>>* tracksToRemove);
     virtual     void        threadLoop_mix();
     virtual     void        threadLoop_sleepTime();
     virtual     void        threadLoop_exit();
@@ -1679,13 +1681,13 @@
     DirectOutputThread(const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output,
                        audio_io_handle_t id, ThreadBase::type_t type, bool systemReady,
                        const audio_offload_info_t& offloadInfo);
-    void processVolume_l(Track *track, bool lastTrack);
+    void processVolume_l(IAfTrack *track, bool lastTrack);
     bool isTunerStream() const { return (mOffloadInfo.content_id > 0); }
 
     // prepareTracks_l() tells threadLoop_mix() the name of the single active track
-    sp<Track>               mActiveTrack;
+    sp<IAfTrack>               mActiveTrack;
 
-    wp<Track>               mPreviousTrack;         // used to detect track switch
+    wp<IAfTrack>               mPreviousTrack;         // used to detect track switch
 
     // This must be initialized for initial condition of mMasterBalance = 0 (disabled).
     float                   mMasterBalanceLeft = 1.f;
@@ -1725,7 +1727,7 @@
 
 protected:
     // threadLoop snippets
-    virtual     mixer_state prepareTracks_l(Vector< sp<Track> > *tracksToRemove);
+    virtual     mixer_state prepareTracks_l(Vector<sp<IAfTrack>>* tracksToRemove);
     virtual     void        threadLoop_exit();
 
     virtual     bool        waitingAsyncCallback();
@@ -1812,8 +1814,8 @@
 private:
 
                 uint32_t    mWaitTimeMs;
-    SortedVector < sp<OutputTrack> >  outputTracks;
-    SortedVector < sp<OutputTrack> >  mOutputTracks;
+    SortedVector <sp<IAfOutputTrack>>  outputTracks;
+    SortedVector <sp<IAfOutputTrack>>  mOutputTracks;
 public:
     virtual     bool        hasFastMixer() const { return false; }
                 status_t    threadloop_getHalTimestamp_l(
@@ -1864,55 +1866,12 @@
 // record thread
 class RecordThread : public ThreadBase
 {
+    // TODO(b/288339104) remove friends
+    friend class PassthruPatchRecord;
+    friend class RecordTrack;
+    friend class ResamplerBufferProvider;
 public:
 
-    class RecordTrack;
-
-    /* The ResamplerBufferProvider is used to retrieve recorded input data from the
-     * RecordThread.  It maintains local state on the relative position of the read
-     * position of the RecordTrack compared with the RecordThread.
-     */
-    class ResamplerBufferProvider : public AudioBufferProvider
-    {
-    public:
-        explicit ResamplerBufferProvider(RecordTrack* recordTrack) :
-            mRecordTrack(recordTrack),
-            mRsmpInUnrel(0), mRsmpInFront(0) { }
-        virtual ~ResamplerBufferProvider() { }
-
-        // called to set the ResamplerBufferProvider to head of the RecordThread data buffer,
-        // skipping any previous data read from the hal.
-        virtual void reset();
-
-        /* Synchronizes RecordTrack position with the RecordThread.
-         * Calculates available frames and handle overruns if the RecordThread
-         * has advanced faster than the ResamplerBufferProvider has retrieved data.
-         * TODO: why not do this for every getNextBuffer?
-         *
-         * Parameters
-         * framesAvailable:  pointer to optional output size_t to store record track
-         *                   frames available.
-         *      hasOverrun:  pointer to optional boolean, returns true if track has overrun.
-         */
-
-        virtual void sync(size_t *framesAvailable = NULL, bool *hasOverrun = NULL);
-
-        // AudioBufferProvider interface
-        virtual status_t    getNextBuffer(AudioBufferProvider::Buffer* buffer);
-        virtual void        releaseBuffer(AudioBufferProvider::Buffer* buffer);
-
-                int32_t     getFront() const { return mRsmpInFront; }
-                void        setFront(int32_t front) { mRsmpInFront = front; }
-    private:
-        RecordTrack * const mRecordTrack;
-        size_t              mRsmpInUnrel;   // unreleased frames remaining from
-                                            // most recent getNextBuffer
-                                            // for debug only
-        int32_t             mRsmpInFront;   // next available frame
-                                            // rolling counter that is never cleared
-    };
-
-#include "RecordTracks.h"
 
             RecordThread(const sp<AudioFlinger>& audioFlinger,
                     AudioStreamIn *input,
@@ -1922,8 +1881,8 @@
             virtual     ~RecordThread();
 
     // no addTrack_l ?
-    void        destroyTrack_l(const sp<RecordTrack>& track);
-    void        removeTrack_l(const sp<RecordTrack>& track);
+    void        destroyTrack_l(const sp<IAfRecordTrack>& track);
+    void        removeTrack_l(const sp<IAfRecordTrack>& track);
 
     // Thread virtuals
     virtual bool        threadLoop();
@@ -1938,7 +1897,7 @@
 
     virtual sp<IMemory> pipeMemory() const { return mPipeMemory; }
 
-            sp<AudioFlinger::RecordThread::RecordTrack>  createRecordTrack_l(
+            sp<IAfRecordTrack> createRecordTrack_l(
                     const sp<Client>& client,
                     const audio_attributes_t& attr,
                     uint32_t *pSampleRate,
@@ -1955,13 +1914,13 @@
                     audio_port_handle_t portId,
                     int32_t maxSharedAudioHistoryMs);
 
-            status_t    start(RecordTrack* recordTrack,
+            status_t start(IAfRecordTrack* recordTrack,
                               AudioSystem::sync_event_t event,
                               audio_session_t triggerSession);
 
             // ask the thread to stop the specified track, and
             // return true if the caller should then do it's part of the stopping process
-            bool        stop(RecordTrack* recordTrack);
+            bool stop(IAfRecordTrack* recordTrack);
 
             AudioStreamIn* clearInput();
             virtual sp<StreamHalInterface> stream() const;
@@ -1979,8 +1938,8 @@
             void        updateOutDevices(const DeviceDescriptorBaseVector& outDevices) override;
             void        resizeInputBuffer_l(int32_t maxSharedAudioHistoryMs) override;
 
-            void        addPatchTrack(const sp<PatchRecord>& record);
-            void        deletePatchTrack(const sp<PatchRecord>& record);
+            void        addPatchTrack(const sp<IAfPatchRecord>& record);
+            void        deletePatchTrack(const sp<IAfPatchRecord>& record);
 
             void        readInputParameters_l();
     virtual uint32_t    getInputFramesLost();
@@ -2066,10 +2025,10 @@
 
             AudioStreamIn                       *mInput;
             Source                              *mSource;
-            SortedVector < sp<RecordTrack> >    mTracks;
+            SortedVector <sp<IAfRecordTrack>>    mTracks;
             // mActiveTracks has dual roles:  it indicates the current active track(s), and
             // is used together with mStartStopCond to indicate start()/stop() progress
-            ActiveTracks<RecordTrack>           mActiveTracks;
+            ActiveTracks<IAfRecordTrack>           mActiveTracks;
 
             Condition                           mStartStopCond;
 
@@ -2139,9 +2098,6 @@
 class MmapThread : public ThreadBase
 {
  public:
-
-#include "MmapTracks.h"
-
     MmapThread(const sp<AudioFlinger>& audioFlinger, audio_io_handle_t id,
                AudioHwDevice *hwDev, const sp<StreamHalInterface>& stream, bool systemReady,
                bool isOut);
@@ -2258,7 +2214,7 @@
                 sp<StreamHalInterface>  mHalStream;
                 sp<DeviceHalInterface>  mHalDevice;
                 AudioHwDevice* const    mAudioHwDev;
-                ActiveTracks<MmapTrack> mActiveTracks;
+                ActiveTracks<IAfMmapTrack> mActiveTracks;
                 float                   mHalVolFloat;
                 std::map<audio_port_handle_t, bool> mClientSilencedStates;
 
@@ -2363,7 +2319,7 @@
                      audio_io_handle_t id, bool systemReady);
 
 protected:
-    mixer_state prepareTracks_l(Vector<sp<Track>> *tracksToRemove) override;
+    mixer_state prepareTracks_l(Vector<sp<IAfTrack>>* tracksToRemove) override;
     void threadLoop_mix() override;
 
 private:
@@ -2372,4 +2328,4 @@
     float mVolumeRight = 0.f;
 };
 
-private:
+private:
\ No newline at end of file