diff --git a/core/java/android/hardware/Camera.java b/core/java/android/hardware/Camera.java
index 4dddfd80ad377..abebdeb91489c 100644
--- a/core/java/android/hardware/Camera.java
+++ b/core/java/android/hardware/Camera.java
@@ -532,11 +532,15 @@ public class Camera {
      * called with value 3. Three ZoomCallback will be generated with zoom value
      * 1, 2, and 3. The applications can call {@link #stopSmoothZoom} to stop
      * the zoom earlier. The applications should not call startSmoothZoom again
-     * or change the zoom value before zoom stops. This method is supported if
-     * {@link android.hardware.Camera.Parameters#isSmoothZoomSupported} is true.
+     * or change the zoom value before zoom stops. If the passing zoom value
+     * equals to the current zoom value, no zoom callback will be generated.
+     * This method is supported if {@link
+     * android.hardware.Camera.Parameters#isSmoothZoomSupported} is true.
      *
      * @param value zoom value. The valid range is 0 to {@link
      *              android.hardware.Camera.Parameters#getMaxZoom}.
+     * @throws IllegalArgumentException if the zoom value is invalid.
+     * @throws RuntimeException if the method fails.
      */
     public native final void startSmoothZoom(int value);
 
@@ -545,6 +549,8 @@ public class Camera {
      * ZoomCallback} to know when the zoom is actually stopped. This method is
      * supported if {@link
      * android.hardware.Camera.Parameters#isSmoothZoomSupported} is true.
+     *
+     * @throws RuntimeException if the method fails.
      */
     public native final void stopSmoothZoom();
 
diff --git a/core/jni/android_hardware_Camera.cpp b/core/jni/android_hardware_Camera.cpp
index 9c0e2825574c9..b85466b5925d6 100644
--- a/core/jni/android_hardware_Camera.cpp
+++ b/core/jni/android_hardware_Camera.cpp
@@ -530,7 +530,12 @@ static void android_hardware_Camera_startSmoothZoom(JNIEnv *env, jobject thiz, j
     sp<Camera> camera = get_native_camera(env, thiz, NULL);
     if (camera == 0) return;
 
-    if (camera->sendCommand(CAMERA_CMD_START_SMOOTH_ZOOM, value, 0) != NO_ERROR) {
+    status_t rc = camera->sendCommand(CAMERA_CMD_START_SMOOTH_ZOOM, value, 0);
+    if (rc == BAD_VALUE) {
+        char msg[64];
+        sprintf(msg, "invalid zoom value=%d", value);
+        jniThrowException(env, "java/lang/IllegalArgumentException", msg);
+    } else if (rc != NO_ERROR) {
         jniThrowException(env, "java/lang/RuntimeException", "start smooth zoom failed");
     }
 }
diff --git a/libs/camera/ICamera.cpp b/libs/camera/ICamera.cpp
index 724bd20821ac7..13673b53ea4cd 100644
--- a/libs/camera/ICamera.cpp
+++ b/libs/camera/ICamera.cpp
@@ -208,7 +208,7 @@ public:
     }
     virtual status_t sendCommand(int32_t cmd, int32_t arg1, int32_t arg2)
     {
-        LOGD("sendCommand");
+        LOGV("sendCommand");
         Parcel data, reply;
         data.writeInterfaceToken(ICamera::getInterfaceDescriptor());
         data.writeInt32(cmd);