diff --git a/services/camera/libcameraservice/Android.bp b/services/camera/libcameraservice/Android.bp
index 26562e0..a24b35d 100644
--- a/services/camera/libcameraservice/Android.bp
+++ b/services/camera/libcameraservice/Android.bp
@@ -84,6 +84,7 @@
         "device3/Camera3OutputUtils.cpp",
         "device3/Camera3DeviceInjectionMethods.cpp",
         "device3/UHRCropAndMeteringRegionMapper.cpp",
+        "device3/PreviewFrameScheduler.cpp",
         "gui/RingBufferConsumer.cpp",
         "hidl/AidlCameraDeviceCallbacks.cpp",
         "hidl/AidlCameraServiceListener.cpp",
@@ -107,6 +108,7 @@
     ],
 
     shared_libs: [
+        "libandroid",
         "libbase",
         "libdl",
         "libexif",
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
index 3738d01..d8bcc8a 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
@@ -22,6 +22,7 @@
 #include <fstream>
 
 #include <android-base/unique_fd.h>
+#include <cutils/properties.h>
 #include <ui/GraphicBuffer.h>
 #include <utils/Log.h>
 #include <utils/Trace.h>
@@ -347,20 +348,6 @@
             mTraceFirstBuffer = false;
         }
 
-        if (transform != -1) {
-            setTransformLocked(transform);
-        }
-
-        /* Certain consumers (such as AudioSource or HardwareComposer) use
-         * MONOTONIC time, causing time misalignment if camera timestamp is
-         * in BOOTTIME. Do the conversion if necessary. */
-        res = native_window_set_buffers_timestamp(mConsumer.get(),
-                mUseMonoTimestamp ? timestamp - mTimestampOffset : timestamp);
-        if (res != OK) {
-            ALOGE("%s: Stream %d: Error setting timestamp: %s (%d)",
-                  __FUNCTION__, mId, strerror(-res), res);
-            return res;
-        }
         // If this is a JPEG output, and image dump mask is set, save image to
         // disk.
         if (getFormat() == HAL_PIXEL_FORMAT_BLOB && getDataSpace() == HAL_DATASPACE_V0_JFIF &&
@@ -368,10 +355,31 @@
             dumpImageToDisk(timestamp, anwBuffer, anwReleaseFence);
         }
 
-        res = queueBufferToConsumer(currentConsumer, anwBuffer, anwReleaseFence, surface_ids);
-        if (shouldLogError(res, state)) {
-            ALOGE("%s: Stream %d: Error queueing buffer to native window:"
-                  " %s (%d)", __FUNCTION__, mId, strerror(-res), res);
+        /* Certain consumers (such as AudioSource or HardwareComposer) use
+         * MONOTONIC time, causing time misalignment if camera timestamp is
+         * in BOOTTIME. Do the conversion if necessary. */
+        nsecs_t adjustedTs = mUseMonoTimestamp ? timestamp - mTimestampOffset : timestamp;
+        if (mPreviewFrameScheduler != nullptr) {
+            res = mPreviewFrameScheduler->queuePreviewBuffer(adjustedTs, transform,
+                    anwBuffer, anwReleaseFence);
+            if (res != OK) {
+                ALOGE("%s: Stream %d: Error queuing buffer to preview buffer scheduler: %s (%d)",
+                        __FUNCTION__, mId, strerror(-res), res);
+                return res;
+            }
+        } else {
+            setTransform(transform);
+            res = native_window_set_buffers_timestamp(mConsumer.get(), adjustedTs);
+            if (res != OK) {
+                ALOGE("%s: Stream %d: Error setting timestamp: %s (%d)",
+                      __FUNCTION__, mId, strerror(-res), res);
+                return res;
+            }
+            res = queueBufferToConsumer(currentConsumer, anwBuffer, anwReleaseFence, surface_ids);
+            if (shouldLogError(res, state)) {
+                ALOGE("%s: Stream %d: Error queueing buffer to native window:"
+                      " %s (%d)", __FUNCTION__, mId, strerror(-res), res);
+            }
         }
     }
     mLock.lock();
@@ -412,6 +420,9 @@
 
 status_t Camera3OutputStream::setTransformLocked(int transform) {
     status_t res = OK;
+
+    if (transform == -1) return res;
+
     if (mState == STATE_ERROR) {
         ALOGE("%s: Stream in error state", __FUNCTION__);
         return INVALID_OPERATION;
@@ -437,7 +448,7 @@
         return res;
     }
 
-    if ((res = configureConsumerQueueLocked()) != OK) {
+    if ((res = configureConsumerQueueLocked(true /*allowPreviewScheduler*/)) != OK) {
         return res;
     }
 
@@ -461,7 +472,7 @@
     return OK;
 }
 
-status_t Camera3OutputStream::configureConsumerQueueLocked() {
+status_t Camera3OutputStream::configureConsumerQueueLocked(bool allowPreviewScheduler) {
     status_t res;
 
     mTraceFirstBuffer = true;
@@ -547,6 +558,15 @@
     }
 
     mTotalBufferCount = maxConsumerBuffers + camera_stream::max_buffers;
+    if (allowPreviewScheduler && isConsumedByHWComposer()) {
+        // We cannot distinguish between a SurfaceView and an ImageReader of
+        // preview buffer format. The PreviewFrameScheduler needs to handle both.
+        if (!property_get_bool("camera.disable_preview_scheduler", false)) {
+            mPreviewFrameScheduler = std::make_unique<PreviewFrameScheduler>(*this, mConsumer);
+            mTotalBufferCount += PreviewFrameScheduler::kQueueDepthWatermark;
+        }
+    }
+
     mHandoutTotalBufferCount = 0;
     mFrameCount = 0;
     mLastTimestamp = 0;
@@ -1185,6 +1205,11 @@
     }
 }
 
+bool Camera3OutputStream::shouldLogError(status_t res) {
+    Mutex::Autolock l(mLock);
+    return shouldLogError(res, mState);
+}
+
 }; // namespace camera3
 
 }; // namespace android
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.h b/services/camera/libcameraservice/device3/Camera3OutputStream.h
index 0872687..b2b574a 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.h
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.h
@@ -27,6 +27,7 @@
 #include "Camera3IOStreamBase.h"
 #include "Camera3OutputStreamInterface.h"
 #include "Camera3BufferManager.h"
+#include "PreviewFrameScheduler.h"
 
 namespace android {
 
@@ -229,6 +230,7 @@
     static void applyZSLUsageQuirk(int format, uint64_t *consumerUsage /*inout*/);
 
     void setImageDumpMask(int mask) { mImageDumpMask = mask; }
+    bool shouldLogError(status_t res);
 
   protected:
     Camera3OutputStream(int id, camera_stream_type_t type,
@@ -255,7 +257,7 @@
 
     status_t getEndpointUsageForSurface(uint64_t *usage,
             const sp<Surface>& surface) const;
-    status_t configureConsumerQueueLocked();
+    status_t configureConsumerQueueLocked(bool allowPreviewScheduler);
 
     // Consumer as the output of camera HAL
     sp<Surface> mConsumer;
@@ -370,6 +372,8 @@
 
     int mImageDumpMask = 0;
 
+    // The preview stream scheduler for re-timing frames
+    std::unique_ptr<PreviewFrameScheduler> mPreviewFrameScheduler;
 }; // class Camera3OutputStream
 
 } // namespace camera3
diff --git a/services/camera/libcameraservice/device3/Camera3SharedOutputStream.cpp b/services/camera/libcameraservice/device3/Camera3SharedOutputStream.cpp
index 15cf7f4..9e0c8f3 100644
--- a/services/camera/libcameraservice/device3/Camera3SharedOutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3SharedOutputStream.cpp
@@ -247,7 +247,7 @@
         return res;
     }
 
-    res = configureConsumerQueueLocked();
+    res = configureConsumerQueueLocked(false/*allowPreviewScheduler*/);
     if (res != OK) {
         ALOGE("Failed to configureConsumerQueueLocked: %s(%d)", strerror(-res), res);
         return res;
diff --git a/services/camera/libcameraservice/device3/PreviewFrameScheduler.cpp b/services/camera/libcameraservice/device3/PreviewFrameScheduler.cpp
new file mode 100644
index 0000000..1fbdb18
--- /dev/null
+++ b/services/camera/libcameraservice/device3/PreviewFrameScheduler.cpp
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#define LOG_TAG "Camera3-PreviewFrameScheduler"
+#define ATRACE_TAG ATRACE_TAG_CAMERA
+//#define LOG_NDEBUG 0
+
+#include <utils/Log.h>
+#include <utils/Trace.h>
+
+#include <android/looper.h>
+#include "PreviewFrameScheduler.h"
+#include "Camera3OutputStream.h"
+
+namespace android {
+
+namespace camera3 {
+
+/**
+ * Internal Choreographer thread implementation for polling and handling callbacks
+ */
+
+// Callback function for Choreographer
+static void frameCallback(const AChoreographerFrameCallbackData* callbackData, void* data) {
+    PreviewFrameScheduler* parent = static_cast<PreviewFrameScheduler*>(data);
+    if (parent == nullptr) {
+        ALOGE("%s: Invalid data for Choreographer callback!", __FUNCTION__);
+        return;
+    }
+
+    size_t length = AChoreographerFrameCallbackData_getFrameTimelinesLength(callbackData);
+    std::vector<nsecs_t> timeline(length);
+    for (size_t i = 0; i < length; i++) {
+        nsecs_t timestamp = AChoreographerFrameCallbackData_getFrameTimelineExpectedPresentTime(
+                callbackData, i);
+        timeline[i] = timestamp;
+    }
+
+    parent->onNewPresentationTime(timeline);
+
+    AChoreographer_postExtendedFrameCallback(AChoreographer_getInstance(), frameCallback, data);
+}
+
+struct ChoreographerThread : public Thread {
+    ChoreographerThread();
+    status_t start(PreviewFrameScheduler* parent);
+    virtual status_t readyToRun() override;
+    virtual bool threadLoop() override;
+
+protected:
+    virtual ~ChoreographerThread() {}
+
+private:
+    ChoreographerThread &operator=(const ChoreographerThread &);
+
+    // This only impacts the shutdown time. It won't impact the choreographer
+    // callback frequency.
+    static constexpr nsecs_t kPollingTimeoutMs = 5;
+    PreviewFrameScheduler* mParent = nullptr;
+};
+
+ChoreographerThread::ChoreographerThread() : Thread(false /*canCallJava*/) {
+}
+
+status_t ChoreographerThread::start(PreviewFrameScheduler* parent) {
+    mParent = parent;
+    return run("PreviewChoreographer");
+}
+
+status_t ChoreographerThread::readyToRun() {
+    ALooper_prepare(ALOOPER_PREPARE_ALLOW_NON_CALLBACKS);
+    if (AChoreographer_getInstance() == NULL) {
+        return NO_INIT;
+    }
+
+    AChoreographer_postExtendedFrameCallback(
+            AChoreographer_getInstance(), frameCallback, mParent);
+    return OK;
+}
+
+bool ChoreographerThread::threadLoop() {
+    if (exitPending()) {
+        return false;
+    }
+    ALooper_pollOnce(kPollingTimeoutMs, nullptr, nullptr, nullptr);
+    return true;
+}
+
+/**
+ * PreviewFrameScheduler implementation
+ */
+
+PreviewFrameScheduler::PreviewFrameScheduler(Camera3OutputStream& parent, sp<Surface> consumer) :
+        mParent(parent),
+        mConsumer(consumer),
+        mChoreographerThread(new ChoreographerThread()) {
+}
+
+PreviewFrameScheduler::~PreviewFrameScheduler() {
+    {
+        Mutex::Autolock l(mLock);
+        mChoreographerThread->requestExit();
+    }
+    mChoreographerThread->join();
+}
+
+status_t PreviewFrameScheduler::queuePreviewBuffer(nsecs_t timestamp, int32_t transform,
+        ANativeWindowBuffer* anwBuffer, int releaseFence) {
+    // Start choreographer thread if it's not already running.
+    if (!mChoreographerThread->isRunning()) {
+        status_t res = mChoreographerThread->start(this);
+        if (res != OK) {
+            ALOGE("%s: Failed to init choreographer thread!", __FUNCTION__);
+            return res;
+        }
+    }
+
+    {
+        Mutex::Autolock l(mLock);
+        mPendingBuffers.emplace(timestamp, transform, anwBuffer, releaseFence);
+
+        // Queue buffer to client right away if pending buffers are more than
+        // the queue depth watermark.
+        if (mPendingBuffers.size() > kQueueDepthWatermark) {
+            auto oldBuffer = mPendingBuffers.front();
+            mPendingBuffers.pop();
+
+            status_t res = queueBufferToClientLocked(oldBuffer, oldBuffer.timestamp);
+            if (res != OK) {
+                return res;
+            }
+
+            // Reset the last capture and presentation time
+            mLastCameraCaptureTime = 0;
+            mLastCameraPresentTime = 0;
+        } else {
+            ATRACE_INT(kPendingBufferTraceName, mPendingBuffers.size());
+        }
+    }
+    return OK;
+}
+
+void PreviewFrameScheduler::onNewPresentationTime(const std::vector<nsecs_t>& timeline) {
+    ATRACE_CALL();
+    Mutex::Autolock l(mLock);
+    if (mPendingBuffers.size() > 0) {
+        auto nextBuffer = mPendingBuffers.front();
+        mPendingBuffers.pop();
+
+        // Find the best presentation time by finding the element in the
+        // choreographer timeline that's closest to the ideal presentation time.
+        // The ideal presentation time is the last presentation time + frame
+        // interval.
+        nsecs_t cameraInterval = nextBuffer.timestamp - mLastCameraCaptureTime;
+        nsecs_t idealPresentTime = (cameraInterval < kSpacingResetIntervalNs) ?
+                (mLastCameraPresentTime + cameraInterval) : nextBuffer.timestamp;
+        nsecs_t presentTime = *std::min_element(timeline.begin(), timeline.end(),
+                [idealPresentTime](nsecs_t p1, nsecs_t p2) {
+                        return std::abs(p1 - idealPresentTime) < std::abs(p2 - idealPresentTime);
+                });
+
+        status_t res = queueBufferToClientLocked(nextBuffer, presentTime);
+        ATRACE_INT(kPendingBufferTraceName, mPendingBuffers.size());
+
+        if (mParent.shouldLogError(res)) {
+            ALOGE("%s: Preview Stream: Error queueing buffer to native window:"
+                    " %s (%d)", __FUNCTION__, strerror(-res), res);
+        }
+
+        mLastCameraCaptureTime = nextBuffer.timestamp;
+        mLastCameraPresentTime = presentTime;
+    }
+}
+
+status_t PreviewFrameScheduler::queueBufferToClientLocked(
+        const BufferHolder& bufferHolder, nsecs_t timestamp) {
+    mParent.setTransform(bufferHolder.transform);
+
+    status_t res = native_window_set_buffers_timestamp(mConsumer.get(), timestamp);
+    if (res != OK) {
+        ALOGE("%s: Preview Stream: Error setting timestamp: %s (%d)",
+                __FUNCTION__, strerror(-res), res);
+        return res;
+    }
+
+    res = mConsumer->queueBuffer(mConsumer.get(), bufferHolder.anwBuffer.get(),
+            bufferHolder.releaseFence);
+    if (res != OK) {
+        close(bufferHolder.releaseFence);
+    }
+
+    return res;
+}
+
+}; // namespace camera3
+
+}; // namespace android
diff --git a/services/camera/libcameraservice/device3/PreviewFrameScheduler.h b/services/camera/libcameraservice/device3/PreviewFrameScheduler.h
new file mode 100644
index 0000000..c0574fd
--- /dev/null
+++ b/services/camera/libcameraservice/device3/PreviewFrameScheduler.h
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2021 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_SERVERS_CAMERA_CAMERA3_PREVIEWFRAMESCHEDULER_H
+#define ANDROID_SERVERS_CAMERA_CAMERA3_PREVIEWFRAMESCHEDULER_H
+
+#include <queue>
+
+#include <android/choreographer.h>
+#include <gui/Surface.h>
+#include <gui/ISurfaceComposer.h>
+#include <utils/Condition.h>
+#include <utils/Mutex.h>
+#include <utils/Looper.h>
+#include <utils/Thread.h>
+#include <utils/Timers.h>
+
+namespace android {
+
+namespace camera3 {
+
+class Camera3OutputStream;
+struct ChoreographerThread;
+
+/***
+ * Preview stream scheduler for better preview display synchronization
+ *
+ * The ideal viewfinder user experience is that frames are presented to the
+ * user in the same cadence as outputed by the camera sensor. However, the
+ * processing latency between frames could vary, due to factors such
+ * as CPU load, differences in request settings, etc. This frame processing
+ * latency results in variation in presentation of frames to the user.
+ *
+ * The PreviewFrameScheduler improves the viewfinder user experience by:
+ * 1. Cache preview buffers in the scheduler
+ * 2. For each choreographer callback, queue the oldest cached buffer with
+ *    the best matching presentation timestamp. Frame N's presentation timestamp
+ *    is the choreographer timeline timestamp closest to (Frame N-1's
+ *    presentation time + camera capture interval between frame N-1 and frame N).
+ * 3. Maintain at most 2 queue-able buffers. If the 3rd preview buffer becomes
+ *    available, queue the oldest cached buffer to the buffer queue.
+ */
+class PreviewFrameScheduler {
+  public:
+    explicit PreviewFrameScheduler(Camera3OutputStream& parent, sp<Surface> consumer);
+    virtual ~PreviewFrameScheduler();
+
+    // Queue preview buffer locally
+    status_t queuePreviewBuffer(nsecs_t timestamp, int32_t transform,
+            ANativeWindowBuffer* anwBuffer, int releaseFence);
+
+    // Callback function with a new presentation timeline from choreographer. This
+    // will trigger a locally queued buffer be sent to the buffer queue.
+    void onNewPresentationTime(const std::vector<nsecs_t>& presentationTimeline);
+
+    // Maintain at most 2 queue-able buffers
+    static constexpr int32_t kQueueDepthWatermark = 2;
+
+  private:
+    // structure holding cached preview buffer info
+    struct BufferHolder {
+        nsecs_t timestamp;
+        int32_t transform;
+        sp<ANativeWindowBuffer> anwBuffer;
+        int releaseFence;
+
+        BufferHolder(nsecs_t t, int32_t tr, ANativeWindowBuffer* anwb, int rf) :
+                timestamp(t), transform(tr), anwBuffer(anwb), releaseFence(rf) {}
+    };
+
+    status_t queueBufferToClientLocked(const BufferHolder& bufferHolder,
+            nsecs_t presentTime);
+
+    static constexpr char kPendingBufferTraceName[] = "pending_preview_buffers";
+
+    // Camera capture interval for resetting frame spacing between preview sessions
+    static constexpr nsecs_t kSpacingResetIntervalNs = 1000000000L; // 1 second
+
+    Camera3OutputStream& mParent;
+    sp<ANativeWindow> mConsumer;
+    mutable Mutex mLock;
+
+    std::queue<BufferHolder> mPendingBuffers;
+    nsecs_t mLastCameraCaptureTime = 0;
+    nsecs_t mLastCameraPresentTime = 0;
+
+    // Choreographer related
+    sp<Looper> mLooper;
+    sp<ChoreographerThread> mChoreographerThread;
+};
+
+}; //namespace camera3
+}; //namespace android
+
+#endif