diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index cd855da..ca9aaf7 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -94,6 +94,8 @@
     static float linearToLog(int volume);
     static int logToLinear(float volume);
 
+    // Returned samplingRate and frameCount output values are guaranteed
+    // to be non-zero if status == NO_ERROR
     static status_t getOutputSamplingRate(uint32_t* samplingRate,
             audio_stream_type_t stream);
     static status_t getOutputFrameCount(size_t* frameCount,