diff --git a/services/audioflinger/FastMixerState.h b/services/audioflinger/FastMixerState.h
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+++ b/services/audioflinger/FastMixerState.h
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+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_AUDIO_FAST_MIXER_STATE_H
+#define ANDROID_AUDIO_FAST_MIXER_STATE_H
+
+#include "AudioBufferProvider.h"
+#include "NBAIO.h"
+
+namespace android {
+
+struct FastMixerDumpState;
+
+class VolumeProvider {
+public:
+    // Return the track volume in U4_12 format: left in lower half, right in upper half. The
+    // provider implementation is responsible for validating that the return value is in range.
+    virtual uint32_t getVolumeLR() = 0;
+protected:
+    VolumeProvider() { }
+    virtual ~VolumeProvider() { }
+};
+
+// Represents the state of a fast track
+struct FastTrack {
+    FastTrack();
+    /*virtual*/ ~FastTrack();
+
+    AudioBufferProvider*    mBufferProvider; // must not be NULL
+    VolumeProvider*         mVolumeProvider; // optional; if NULL then full-scale
+    int                     mGeneration;     // increment when any field is assigned
+};
+
+// Represents a single state of the fast mixer
+struct FastMixerState {
+                FastMixerState();
+    /*virtual*/ ~FastMixerState();
+
+    static const unsigned kMaxFastTracks = 8;   // must be between 2 and 32 inclusive
+
+    // all pointer fields use raw pointers; objects are owned and ref-counted by the normal mixer
+    FastTrack   mFastTracks[kMaxFastTracks];
+    int         mFastTracksGen; // increment when any mFastTracks[i].mGeneration is incremented
+    unsigned    mTrackMask;     // bit i is set if and only if mFastTracks[i] != NULL
+    NBAIO_Sink* mOutputSink;    // HAL output device, must already be negotiated
+    int         mOutputSinkGen; // increment when mOutputSink is assigned
+    size_t      mFrameCount;    // number of frames per fast mix buffer
+    enum Command {
+        INITIAL = 0,            // used only for the initial state
+        HOT_IDLE = 1,           // do nothing
+        COLD_IDLE = 2,          // wait for the futex
+        IDLE = 3,               // either HOT_IDLE or COLD_IDLE
+        EXIT = 4,               // exit from thread
+        // The following commands also process configuration changes, and can be "or"ed:
+        MIX = 0x8,              // mix tracks
+        WRITE = 0x10,           // write to output sink
+        MIX_WRITE = 0x18,       // mix tracks and write to output sink
+    } mCommand;
+    int32_t*    mColdFutexAddr; // for COLD_IDLE only, pointer to the associated futex
+    unsigned    mColdGen;       // increment when COLD_IDLE is requested so it's only performed once
+    // This might be a one-time configuration rather than per-state
+    FastMixerDumpState* mDumpState; // if non-NULL, then update dump state periodically
+};  // struct FastMixerState
+
+}   // namespace android
+
+#endif  // ANDROID_AUDIO_FAST_MIXER_STATE_H