diff --git a/media/module/foundation/ALooper.cpp b/media/module/foundation/ALooper.cpp
index a276722..61bac02 100644
--- a/media/module/foundation/ALooper.cpp
+++ b/media/module/foundation/ALooper.cpp
@@ -69,6 +69,10 @@
     return systemTime(SYSTEM_TIME_MONOTONIC) / 1000LL;
 }
 
+int64_t ALooper::getNowUs() {
+    return GetNowUs();
+}
+
 ALooper::ALooper()
     : mRunningLocally(false) {
     // clean up stale AHandlers. Doing it here instead of in the destructor avoids
@@ -170,11 +174,11 @@
 
     int64_t whenUs;
     if (delayUs > 0) {
-        int64_t nowUs = GetNowUs();
+        int64_t nowUs = getNowUs();
         whenUs = (delayUs > INT64_MAX - nowUs ? INT64_MAX : nowUs + delayUs);
 
     } else {
-        whenUs = GetNowUs();
+        whenUs = getNowUs();
     }
 
     List<Event>::iterator it = mEventQueue.begin();
@@ -185,6 +189,7 @@
     Event event;
     event.mWhenUs = whenUs;
     event.mMessage = msg;
+    event.mToken = nullptr;
 
     if (it == mEventQueue.begin()) {
         mQueueChangedCondition.signal();
@@ -193,7 +198,57 @@
     mEventQueue.insert(it, event);
 }
 
+status_t ALooper::postUnique(const sp<AMessage> &msg, const sp<RefBase> &token, int64_t delayUs) {
+    if (token == nullptr) {
+        return -EINVAL;
+    }
+    Mutex::Autolock autoLock(mLock);
+
+    int64_t whenUs;
+    if (delayUs > 0) {
+        int64_t nowUs = getNowUs();
+        whenUs = (delayUs > INT64_MAX - nowUs ? INT64_MAX : nowUs + delayUs);
+    } else {
+        whenUs = getNowUs();
+    }
+
+    // We only need to wake the loop up if we're rescheduling to the earliest event in the queue.
+    // This needs to be checked now, before we reschedule the message, in case this message is
+    // already at the beginning of the queue.
+    bool shouldAwakeLoop = mEventQueue.empty() || whenUs < mEventQueue.begin()->mWhenUs;
+
+    // Erase any previously-posted event with this token.
+    for (auto i = mEventQueue.begin(); i != mEventQueue.end();) {
+        if (i->mToken == token) {
+            i = mEventQueue.erase(i);
+        } else {
+            ++i;
+        }
+    }
+
+    // Find the insertion point for the rescheduled message.
+    List<Event>::iterator i = mEventQueue.begin();
+    while (i != mEventQueue.end() && i->mWhenUs <= whenUs) {
+        ++i;
+    }
+
+    Event event;
+    event.mWhenUs = whenUs;
+    event.mMessage = msg;
+    event.mToken = token;
+    mEventQueue.insert(i, event);
+
+    // If we rescheduled the event to be earlier than the first event, then we need to wake up the
+    // looper earlier than it was previously scheduled to be woken up. Otherwise, it can sleep until
+    // the previous wake-up time and then go to sleep again if needed.
+    if (shouldAwakeLoop){
+        mQueueChangedCondition.signal();
+    }
+    return OK;
+}
+
 bool ALooper::loop() {
+
     Event event;
 
     {
@@ -206,7 +261,7 @@
             return true;
         }
         int64_t whenUs = (*mEventQueue.begin()).mWhenUs;
-        int64_t nowUs = GetNowUs();
+        int64_t nowUs = getNowUs();
 
         if (whenUs > nowUs) {
             int64_t delayUs = whenUs - nowUs;
diff --git a/media/module/foundation/AMessage.cpp b/media/module/foundation/AMessage.cpp
index 5c99cc9..b61dc47 100644
--- a/media/module/foundation/AMessage.cpp
+++ b/media/module/foundation/AMessage.cpp
@@ -430,6 +430,17 @@
     return OK;
 }
 
+status_t AMessage::postUnique(const sp<RefBase> &token, int64_t delayUs) {
+    sp<ALooper> looper = mLooper.promote();
+    if (looper == NULL) {
+        ALOGW("failed to post message as target looper for handler %d is gone.",
+              mTarget);
+        return -ENOENT;
+    }
+
+    return looper->postUnique(this, token, delayUs);
+}
+
 status_t AMessage::postAndAwaitResponse(sp<AMessage> *response) {
     sp<ALooper> looper = mLooper.promote();
     if (looper == NULL) {
diff --git a/media/module/foundation/include/media/stagefright/foundation/ALooper.h b/media/module/foundation/include/media/stagefright/foundation/ALooper.h
index 09c469b..60bda1f 100644
--- a/media/module/foundation/include/media/stagefright/foundation/ALooper.h
+++ b/media/module/foundation/include/media/stagefright/foundation/ALooper.h
@@ -59,6 +59,9 @@
     }
 
 protected:
+    // overridable by test harness
+    virtual int64_t getNowUs();
+
     virtual ~ALooper();
 
 private:
@@ -67,6 +70,7 @@
     struct Event {
         int64_t mWhenUs;
         sp<AMessage> mMessage;
+        sp<RefBase> mToken;
     };
 
     Mutex mLock;
@@ -87,9 +91,14 @@
 
     // START --- methods used only by AMessage
 
-    // posts a message on this looper with the given timeout
+    // Posts a message on this looper with the given timeout.
     void post(const sp<AMessage> &msg, int64_t delayUs);
 
+    // Post a message uniquely on this looper with the given timeout.
+    // This method ensures that there is exactly one message with the same token pending posted on
+    // this looper after the call returns. A null token will result in an EINVAL error status.
+    status_t postUnique(const sp<AMessage> &msg, const sp<RefBase> &token, int64_t delayUs);
+
     // creates a reply token to be used with this looper
     sp<AReplyToken> createReplyToken();
     // waits for a response for the reply token.  If status is OK, the response
diff --git a/media/module/foundation/include/media/stagefright/foundation/AMessage.h b/media/module/foundation/include/media/stagefright/foundation/AMessage.h
index 960212a..6f73597 100644
--- a/media/module/foundation/include/media/stagefright/foundation/AMessage.h
+++ b/media/module/foundation/include/media/stagefright/foundation/AMessage.h
@@ -141,6 +141,11 @@
 
     status_t post(int64_t delayUs = 0);
 
+    // Post a message uniquely to its target with the given timeout.
+    // This method ensures that there is exactly one message with the same token posted to its
+    // target after the call returns. A null token will result in an EINVAL error status.
+    status_t postUnique(const sp<RefBase> &token, int64_t delayUs = 0);
+
     // Posts the message to its target and waits for a response (or error)
     // before returning.
     status_t postAndAwaitResponse(sp<AMessage> *response);
diff --git a/media/module/foundation/tests/AMessage_test.cpp b/media/module/foundation/tests/AMessage_test.cpp
index 2b11326..e08ed77 100644
--- a/media/module/foundation/tests/AMessage_test.cpp
+++ b/media/module/foundation/tests/AMessage_test.cpp
@@ -17,18 +17,43 @@
 //#define LOG_NDEBUG 0
 #define LOG_TAG "AData_test"
 
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include <utils/RefBase.h>
 
 #include <media/stagefright/foundation/AMessage.h>
+#include <media/stagefright/foundation/AHandler.h>
+#include <media/stagefright/foundation/ALooper.h>
 
 using namespace android;
 
-class AMessageTest : public ::testing::Test {
+using ::testing::InSequence;
+using ::testing::NiceMock;
+
+class LooperWithSettableClock : public ALooper {
+public:
+  LooperWithSettableClock() : mClockUs(0) {}
+
+  void setClockUs(int64_t nowUs) {
+    mClockUs = nowUs;
+  }
+
+  int64_t getNowUs() override {
+    return mClockUs;
+  }
+
+private:
+  int64_t mClockUs;
 };
 
+timespec millis100 = {0, 100L*1000*1000};
 
-TEST(AMessage_tests, item_manipulation) {
+class MockHandler : public AHandler {
+public:
+    MOCK_METHOD(void, onMessageReceived, (const sp<AMessage>&), (override));
+};
+
+TEST(AMessage_tests, settersAndGetters) {
   sp<AMessage> m1 = new AMessage();
 
   m1->setInt32("value", 2);
@@ -120,6 +145,171 @@
   EXPECT_TRUE(m1->findInt32("alittlelonger", &i32));
 
   EXPECT_NE(OK, m1->removeEntryByName("notpresent"));
-
 }
 
+TEST(AMessage_tests, deliversMultipleMessagesInOrderImmediately) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msgNow1 = new AMessage(0, mockHandler);
+  msgNow1->post();
+  sp<AMessage> msgNow2 = new AMessage(0, mockHandler);
+  msgNow2->post();
+
+  {
+    InSequence inSequence;
+    EXPECT_CALL(*mockHandler, onMessageReceived(msgNow1)).Times(1);
+    EXPECT_CALL(*mockHandler, onMessageReceived(msgNow2)).Times(1);
+  }
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, doesNotDeliverDelayedMessageImmediately) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msgNow = new AMessage(0, mockHandler);
+  msgNow->post();
+  sp<AMessage> msgDelayed = new AMessage(0, mockHandler);
+  msgDelayed->post(100);
+
+  EXPECT_CALL(*mockHandler, onMessageReceived(msgNow)).Times(1);
+  // note: never called
+  EXPECT_CALL(*mockHandler, onMessageReceived(msgDelayed)).Times(0);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, deliversDelayedMessagesInSequence) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msgIn500 = new AMessage(0, mockHandler);
+  msgIn500->post(500);
+  sp<AMessage> msgNow = new AMessage(0, mockHandler);
+  msgNow->post();
+  sp<AMessage> msgIn100 = new AMessage(0, mockHandler);
+  msgIn100->post(100);
+  // not expected to be received
+  sp<AMessage> msgIn1000 = new AMessage(0, mockHandler);
+  msgIn1000->post(1000);
+
+  looper->setClockUs(500);
+  {
+    InSequence inSequence;
+
+    EXPECT_CALL(*mockHandler, onMessageReceived(msgNow)).Times(1);
+    EXPECT_CALL(*mockHandler, onMessageReceived(msgIn100)).Times(1);
+    EXPECT_CALL(*mockHandler, onMessageReceived(msgIn500)).Times(1);
+  }
+  // note: never called
+  EXPECT_CALL(*mockHandler, onMessageReceived(msgIn1000)).Times(0);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, deliversDelayedUniqueMessage) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  msg->postUnique(msg, 50);
+
+  looper->setClockUs(50);
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg)).Times(1);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, deliversImmediateUniqueMessage) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  // note: we don't need to set the clock, but we do want a stable clock that doesn't advance
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  msg->postUnique(msg, 0);
+
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg)).Times(1);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, doesNotDeliverUniqueMessageAfterRescheduleLater) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  msg->postUnique(msg, 50);
+  msg->postUnique(msg, 100); // reschedule for later
+
+  looper->setClockUs(50); // if the message is correctly rescheduled, it should not be delivered
+  // Never called because the message was rescheduled to a later point in time
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg)).Times(0);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, deliversUniqueMessageAfterRescheduleEarlier) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  msg->postUnique(msg, 100);
+  msg->postUnique(msg, 50); // reschedule to fire earlier
+
+  looper->setClockUs(50); // if the message is rescheduled correctly, it should be delivered
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg)).Times(1);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, deliversSameMessageTwice) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  msg->post(50);
+  msg->post(100);
+
+  looper->setClockUs(100);
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg)).Times(2);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+// When messages are posted twice with the same token, it will only be delivered once after being
+// rescheduled.
+TEST(AMessage_tests, deliversUniqueMessageOnce) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<LooperWithSettableClock> looper = new LooperWithSettableClock();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg1 = new AMessage(0, mockHandler);
+  msg1->postUnique(msg1, 50);
+  sp<AMessage> msg2 = new AMessage(0, mockHandler);
+  msg2->postUnique(msg1, 75); // note, using the same token as msg1
+
+  looper->setClockUs(100);
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg1)).Times(0);
+  EXPECT_CALL(*mockHandler, onMessageReceived(msg2)).Times(1);
+  looper->start();
+  nanosleep(&millis100, nullptr); // just enough time for the looper thread to run
+}
+
+TEST(AMessage_tests, postUnique_withNullToken_returnsInvalidArgument) {
+  sp<NiceMock<MockHandler>> mockHandler = new NiceMock<MockHandler>;
+  sp<ALooper> looper = new ALooper();
+  looper->registerHandler(mockHandler);
+
+  sp<AMessage> msg = new AMessage(0, mockHandler);
+  EXPECT_EQ(msg->postUnique(nullptr, 0), -EINVAL);
+}
diff --git a/media/module/foundation/tests/Android.bp b/media/module/foundation/tests/Android.bp
index e72ce43..c409dd2 100644
--- a/media/module/foundation/tests/Android.bp
+++ b/media/module/foundation/tests/Android.bp
@@ -20,10 +20,14 @@
 
     shared_libs: [
         "liblog",
-        "libstagefright_foundation",
         "libutils",
     ],
 
+    static_libs: [
+        "libstagefright_foundation",
+        "libgmock",
+    ],
+
     srcs: [
         "AData_test.cpp",
         "AMessage_test.cpp",