diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index fa6ab57..59fb9a3 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -112,6 +112,7 @@
 /* Bluetooth SCO wideband */
 #define AUDIO_PARAMETER_KEY_BT_SCO_WB "bt_wbs"
 
+
 /**
  *  audio stream parameters
  */
@@ -133,6 +134,11 @@
  * "sup_sampling_rates=44100|48000" */
 #define AUDIO_PARAMETER_STREAM_SUP_SAMPLING_RATES "sup_sampling_rates"
 
+/* Get the HW synchronization source used for an output stream.
+ * Return a valid source (positive integer) or AUDIO_HW_SYNC_INVALID if an error occurs
+ * or no HW sync source is used. */
+#define AUDIO_PARAMETER_STREAM_HW_AV_SYNC "hw_av_sync"
+
 /**
  * audio codec parameters
  */