diff --git a/camera/CameraMetadata.cpp b/camera/CameraMetadata.cpp
index fad57ba..c78fc5d 100644
--- a/camera/CameraMetadata.cpp
+++ b/camera/CameraMetadata.cpp
@@ -79,7 +79,7 @@
     return mBuffer;
 }
 
-status_t CameraMetadata::unlock(const camera_metadata_t *buffer) {
+status_t CameraMetadata::unlock(const camera_metadata_t *buffer) const {
     if (!mLocked) {
         ALOGE("%s: Can't unlock a non-locked CameraMetadata!", __FUNCTION__);
         return INVALID_OPERATION;
diff --git a/camera/ndk/Android.mk b/camera/ndk/Android.mk
index ebd473d..40dbeef 100644
--- a/camera/ndk/Android.mk
+++ b/camera/ndk/Android.mk
@@ -49,6 +49,7 @@
     libcamera_client \
     libstagefright_foundation \
     libcutils \
+    libcamera_metadata
 
 LOCAL_CLANG := true
 
diff --git a/camera/ndk/NdkCameraMetadata.cpp b/camera/ndk/NdkCameraMetadata.cpp
index 18718d3..85fe75b 100644
--- a/camera/ndk/NdkCameraMetadata.cpp
+++ b/camera/ndk/NdkCameraMetadata.cpp
@@ -39,6 +39,18 @@
 }
 
 EXPORT
+camera_status_t ACameraMetadata_getAllTags(
+        const ACameraMetadata* acm, /*out*/int32_t* numTags, /*out*/const uint32_t** tags) {
+    ATRACE_CALL();
+    if (acm == nullptr || numTags == nullptr || tags == nullptr) {
+        ALOGE("%s: invalid argument! metadata %p, numTags %p, tags %p",
+               __FUNCTION__, acm, numTags, tags);
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+    return acm->getTags(numTags, tags);
+}
+
+EXPORT
 ACameraMetadata* ACameraMetadata_copy(const ACameraMetadata* src) {
     ATRACE_CALL();
     if (src == nullptr) {
diff --git a/camera/ndk/NdkCaptureRequest.cpp b/camera/ndk/NdkCaptureRequest.cpp
index 4fee09c..77b9a33 100644
--- a/camera/ndk/NdkCaptureRequest.cpp
+++ b/camera/ndk/NdkCaptureRequest.cpp
@@ -87,6 +87,18 @@
     return req->settings->getConstEntry(tag, entry);
 }
 
+EXPORT
+camera_status_t ACaptureRequest_getAllTags(
+        const ACaptureRequest* req, /*out*/int32_t* numTags, /*out*/const uint32_t** tags) {
+    ATRACE_CALL();
+    if (req == nullptr || numTags == nullptr || tags == nullptr) {
+        ALOGE("%s: invalid argument! request %p, numTags %p, tags %p",
+               __FUNCTION__, req, numTags, tags);
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+    return req->settings->getTags(numTags, tags);
+}
+
 #define SET_ENTRY(NAME,NDK_TYPE)                                                        \
 EXPORT                                                                                  \
 camera_status_t ACaptureRequest_setEntry_##NAME(                                        \
diff --git a/camera/ndk/impl/ACameraDevice.cpp b/camera/ndk/impl/ACameraDevice.cpp
index 880befe..6bca692 100644
--- a/camera/ndk/impl/ACameraDevice.cpp
+++ b/camera/ndk/impl/ACameraDevice.cpp
@@ -76,8 +76,8 @@
     mHandler = new CallbackHandler();
     mCbLooper->registerHandler(mHandler);
 
-    CameraMetadata metadata = mChars->mData;
-    camera_metadata_entry entry = metadata.find(ANDROID_REQUEST_PARTIAL_RESULT_COUNT);
+    const CameraMetadata& metadata = mChars->getInternalData();
+    camera_metadata_ro_entry entry = metadata.find(ANDROID_REQUEST_PARTIAL_RESULT_COUNT);
     if (entry.count != 1) {
         ALOGW("%s: bad count %zu for partial result count", __FUNCTION__, entry.count);
         mPartialResultCount = 1;
@@ -279,7 +279,7 @@
         const ACaptureRequest* request, /*out*/sp<CaptureRequest>& outReq) {
     camera_status_t ret;
     sp<CaptureRequest> req(new CaptureRequest());
-    req->mMetadata = request->settings->mData;
+    req->mMetadata = request->settings->getInternalData();
     req->mIsReprocess = false; // NDK does not support reprocessing yet
 
     for (auto outputTarget : request->targets->mOutputs) {
diff --git a/camera/ndk/impl/ACameraMetadata.cpp b/camera/ndk/impl/ACameraMetadata.cpp
index fbc8d19..8366ade 100644
--- a/camera/ndk/impl/ACameraMetadata.cpp
+++ b/camera/ndk/impl/ACameraMetadata.cpp
@@ -162,6 +162,8 @@
         return ACAMERA_ERROR_INVALID_PARAMETER;
     }
 
+    Mutex::Autolock _l(mLock);
+
     camera_metadata_ro_entry rawEntry = mData.find(tag);
     if (rawEntry.count == 0) {
         ALOGE("%s: cannot find metadata tag %d", __FUNCTION__, tag);
@@ -204,6 +206,38 @@
     return updateImpl<camera_metadata_rational_t>(tag, count, data);
 }
 
+camera_status_t
+ACameraMetadata::getTags(/*out*/int32_t* numTags,
+                         /*out*/const uint32_t** tags) const {
+    Mutex::Autolock _l(mLock);
+    if (mTags.size() == 0) {
+        size_t entry_count = mData.entryCount();
+        mTags.setCapacity(entry_count);
+        const camera_metadata_t* rawMetadata = mData.getAndLock();
+        for (size_t i = 0; i < entry_count; i++) {
+            camera_metadata_ro_entry_t entry;
+            int ret = get_camera_metadata_ro_entry(rawMetadata, i, &entry);
+            if (ret != 0) {
+                ALOGE("%s: error reading metadata index %zu", __FUNCTION__, i);
+                return ACAMERA_ERROR_UNKNOWN;
+            }
+            // Hide system key from users
+            if (sSystemTags.count(entry.tag) == 0) {
+                mTags.push_back(entry.tag);
+            }
+        }
+        mData.unlock(rawMetadata);
+    }
+
+    *numTags = mTags.size();
+    *tags = mTags.array();
+    return ACAMERA_OK;
+}
+
+const CameraMetadata&
+ACameraMetadata::getInternalData() {
+    return mData;
+}
 
 // TODO: some of key below should be hidden from user
 // ex: ACAMERA_REQUEST_ID and ACAMERA_REPROCESS_EFFECTIVE_EXPOSURE_FACTOR
@@ -286,6 +320,49 @@
     }
 }
 
+// System tags that should be hidden from users
+std::unordered_set<uint32_t> ACameraMetadata::sSystemTags ({
+    ANDROID_CONTROL_SCENE_MODE_OVERRIDES,
+    ANDROID_CONTROL_AE_PRECAPTURE_ID,
+    ANDROID_CONTROL_AF_TRIGGER_ID,
+    ANDROID_DEMOSAIC_MODE,
+    ANDROID_EDGE_STRENGTH,
+    ANDROID_FLASH_FIRING_POWER,
+    ANDROID_FLASH_FIRING_TIME,
+    ANDROID_FLASH_COLOR_TEMPERATURE,
+    ANDROID_FLASH_MAX_ENERGY,
+    ANDROID_FLASH_INFO_CHARGE_DURATION,
+    ANDROID_JPEG_MAX_SIZE,
+    ANDROID_JPEG_SIZE,
+    ANDROID_NOISE_REDUCTION_STRENGTH,
+    ANDROID_QUIRKS_METERING_CROP_REGION,
+    ANDROID_QUIRKS_TRIGGER_AF_WITH_AUTO,
+    ANDROID_QUIRKS_USE_ZSL_FORMAT,
+    ANDROID_REQUEST_INPUT_STREAMS,
+    ANDROID_REQUEST_METADATA_MODE,
+    ANDROID_REQUEST_OUTPUT_STREAMS,
+    ANDROID_REQUEST_TYPE,
+    ANDROID_REQUEST_MAX_NUM_REPROCESS_STREAMS,
+    ANDROID_SCALER_AVAILABLE_RAW_MIN_DURATIONS,
+    ANDROID_SCALER_AVAILABLE_RAW_SIZES,
+    ANDROID_SENSOR_BASE_GAIN_FACTOR,
+    ANDROID_SENSOR_PROFILE_HUE_SAT_MAP_DIMENSIONS,
+    ANDROID_SENSOR_TEMPERATURE,
+    ANDROID_SENSOR_PROFILE_HUE_SAT_MAP,
+    ANDROID_SENSOR_PROFILE_TONE_CURVE,
+    ANDROID_SENSOR_OPAQUE_RAW_SIZE,
+    ANDROID_SHADING_STRENGTH,
+    ANDROID_STATISTICS_HISTOGRAM_MODE,
+    ANDROID_STATISTICS_SHARPNESS_MAP_MODE,
+    ANDROID_STATISTICS_HISTOGRAM,
+    ANDROID_STATISTICS_SHARPNESS_MAP,
+    ANDROID_STATISTICS_INFO_HISTOGRAM_BUCKET_COUNT,
+    ANDROID_STATISTICS_INFO_MAX_HISTOGRAM_COUNT,
+    ANDROID_STATISTICS_INFO_MAX_SHARPNESS_MAP_VALUE,
+    ANDROID_STATISTICS_INFO_SHARPNESS_MAP_SIZE,
+    ANDROID_DEPTH_MAX_DEPTH_SAMPLES,
+});
+
 /*~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~
  * End generated code
  *~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~@~O@*/
diff --git a/camera/ndk/impl/ACameraMetadata.h b/camera/ndk/impl/ACameraMetadata.h
index 442e1dd..ab651a1 100644
--- a/camera/ndk/impl/ACameraMetadata.h
+++ b/camera/ndk/impl/ACameraMetadata.h
@@ -16,8 +16,12 @@
 #ifndef _ACAMERA_METADATA_H
 #define _ACAMERA_METADATA_H
 
+#include <unordered_set>
+
 #include <sys/types.h>
+#include <utils/Mutex.h>
 #include <utils/RefBase.h>
+#include <utils/Vector.h>
 #include <camera/CameraMetadata.h>
 
 #include "NdkCameraMetadata.h"
@@ -51,12 +55,17 @@
     camera_status_t update(uint32_t tag, uint32_t count, const int64_t* data);
     camera_status_t update(uint32_t tag, uint32_t count, const ACameraMetadata_rational* data);
 
+    camera_status_t getTags(/*out*/int32_t* numTags,
+                            /*out*/const uint32_t** tags) const;
+
     bool isNdkSupportedCapability(const int32_t capability);
-    inline bool isVendorTag(const uint32_t tag);
-    bool isCaptureRequestTag(const uint32_t tag);
+    static inline bool isVendorTag(const uint32_t tag);
+    static bool isCaptureRequestTag(const uint32_t tag);
     void filterUnsupportedFeatures(); // Hide features not yet supported by NDK
     void filterStreamConfigurations(); // Hide input streams, translate hal format to NDK formats
 
+    const CameraMetadata& getInternalData();
+
     template<typename INTERNAL_T, typename NDK_T>
     camera_status_t updateImpl(uint32_t tag, uint32_t count, const NDK_T* data) {
         if (mType != ACM_REQUEST) {
@@ -68,18 +77,27 @@
             return ACAMERA_ERROR_INVALID_PARAMETER;
         }
 
+        Mutex::Autolock _l(mLock);
+
         // Here we have to use reinterpret_cast because the NDK data type is
         // exact copy of internal data type but they do not inherit from each other
         status_t ret = mData.update(tag, reinterpret_cast<const INTERNAL_T*>(data), count);
         if (ret == OK) {
+            mTags.clear();
             return ACAMERA_OK;
         } else {
             return ACAMERA_ERROR_INVALID_PARAMETER;
         }
     }
 
-    CameraMetadata mData;
+  private:
+    // guard access of public APIs: get/update/getTags
+    mutable Mutex    mLock;
+    CameraMetadata   mData;
+    mutable Vector<uint32_t> mTags; // updated in getTags, cleared by update
     const ACAMERA_METADATA_TYPE mType;
+
+    static std::unordered_set<uint32_t> sSystemTags;
 };
 
 #endif // _ACAMERA_METADATA_H
diff --git a/include/camera/CameraMetadata.h b/include/camera/CameraMetadata.h
index db400de..28f47a1 100644
--- a/include/camera/CameraMetadata.h
+++ b/include/camera/CameraMetadata.h
@@ -64,7 +64,7 @@
      * from getAndLock must be provided to guarantee that the right object is
      * being unlocked.
      */
-    status_t unlock(const camera_metadata_t *buffer);
+    status_t unlock(const camera_metadata_t *buffer) const;
 
     /**
      * Release a raw metadata buffer to the caller. After this call,
diff --git a/include/camera/ndk/NdkCameraMetadata.h b/include/camera/ndk/NdkCameraMetadata.h
index 56412ad..9b56a9d 100644
--- a/include/camera/ndk/NdkCameraMetadata.h
+++ b/include/camera/ndk/NdkCameraMetadata.h
@@ -93,7 +93,13 @@
 camera_status_t ACameraMetadata_getConstEntry(
         const ACameraMetadata*, uint32_t tag, ACameraMetadata_const_entry* entry);
 
-// TODO: need an API to list all tags in the metadata. Same for ACaptureRequest
+/*
+ * List all the entry tags in this metadata.
+ * The memory of tags is managed by ACameraMetadata itself and must NOT be free/delete
+ * by application. Do NOT access tags after calling ACameraMetadata_free
+ */
+camera_status_t ACameraMetadata_getAllTags(
+        const ACameraMetadata*, /*out*/int32_t* numTags, /*out*/const uint32_t** tags);
 
 /**
  * Copy a metadata. Duplicates a metadata structure.
diff --git a/include/camera/ndk/NdkCaptureRequest.h b/include/camera/ndk/NdkCaptureRequest.h
index 566d78f..d9fb164 100644
--- a/include/camera/ndk/NdkCaptureRequest.h
+++ b/include/camera/ndk/NdkCaptureRequest.h
@@ -54,6 +54,19 @@
  */
 camera_status_t ACaptureRequest_getConstEntry(
         const ACaptureRequest*, uint32_t tag, ACameraMetadata_const_entry* entry);
+
+/*
+ * List all the entry tags in this capture request.
+ * The memory of tags is managed by ACaptureRequest itself and must NOT be free/delete
+ * by application. Calling ACaptureRequest_setEntry_* API will invalidate previous
+ * output of ACaptureRequest_getAllTags. Do not access tags after calling
+ * ACaptureRequest_setEntry_*. To get new list of tags after updating capture request,
+ * application must call ACaptureRequest_getAllTags again.
+ * Do NOT access tags after calling ACaptureRequest_free.
+ */
+camera_status_t ACaptureRequest_getAllTags(
+        const ACaptureRequest*, /*out*/int32_t* numTags, /*out*/const uint32_t** tags);
+
 /*
  * Set an entry of corresponding type.
  * The entry tag's type must match corresponding set API or an
diff --git a/include/media/stagefright/foundation/ADebug.h b/include/media/stagefright/foundation/ADebug.h
index 65f415a..564b3f7 100644
--- a/include/media/stagefright/foundation/ADebug.h
+++ b/include/media/stagefright/foundation/ADebug.h
@@ -24,8 +24,9 @@
 #include <media/stagefright/foundation/AString.h>
 #include <utils/Log.h>
 
-inline static const char *asString(android::status_t i, const char *def = "??") {
-    using namespace android;
+namespace android {
+
+inline static const char *asString(status_t i, const char *def = "??") {
     switch (i) {
         case NO_ERROR:              return "NO_ERROR";
         case UNKNOWN_ERROR:         return "UNKNOWN_ERROR";
@@ -49,8 +50,6 @@
     }
 }
 
-namespace android {
-
 #define LITERAL_TO_STRING_INTERNAL(x)    #x
 #define LITERAL_TO_STRING(x) LITERAL_TO_STRING_INTERNAL(x)
 
diff --git a/media/libstagefright/MediaCodecSource.cpp b/media/libstagefright/MediaCodecSource.cpp
index bdfddc7..5f9a1c0 100644
--- a/media/libstagefright/MediaCodecSource.cpp
+++ b/media/libstagefright/MediaCodecSource.cpp
@@ -286,6 +286,7 @@
                 }
                 if (queue->mPulling && err == OK) {
                     msg->post(); // if simply paused, keep pulling source
+                    break;
                 } else if (err == ERROR_END_OF_STREAM) {
                     ALOGV("stream ended, mbuf %p", mbuf);
                 } else if (err != OK) {