diff --git a/audio/4.0/IStreamOut.hal b/audio/4.0/IStreamOut.hal
index 3aa93fc..65eba60 100644
--- a/audio/4.0/IStreamOut.hal
+++ b/audio/4.0/IStreamOut.hal
@@ -264,4 +264,16 @@
      */
     getPresentationPosition()
             generates (Result retval, uint64_t frames, TimeSpec timeStamp);
+
+    /**
+     * Selects a presentation for decoding from a next generation media stream
+     * (as defined per ETSI TS 103 190-2) and a program within the presentation.
+     * Optional method
+     *
+     * @param presentationId selected audio presentation.
+     * @param programId refinement for the presentation.
+     * @return retval operation completion status.
+     */
+    selectPresentation(int32_t presentationId, int32_t programId)
+            generates (Result retval);
 };
diff --git a/audio/4.0/types.hal b/audio/4.0/types.hal
index 7853f3c..7b2035b 100644
--- a/audio/4.0/types.hal
+++ b/audio/4.0/types.hal
@@ -23,6 +23,10 @@
     NOT_INITIALIZED,
     INVALID_ARGUMENTS,
     INVALID_STATE,
+    /**
+     * Methods marked as "Optional method" must return this result value
+     * if the operation is not supported by HAL.
+     */
     NOT_SUPPORTED
 };