Suppress the recording sound in the recorded video

bug - 3309194

Change-Id: Ib8fb248943bc22f963d67537bfdbc6056c5a159b

Author: James Dong

include/media/stagefright/AudioSource.h

@@ -54,11 +54,11 @@ struct AudioSource : public MediaSource {
 
         // After the initial mute, we raise the volume linearly
         // over kAutoRampDurationUs.
-        kAutoRampDurationUs = 300000,
+        kAutoRampDurationUs = 700000,
 
         // This is the initial mute duration to suppress
         // the video recording signal tone
-        kAutoRampStartUs = 700000,
+        kAutoRampStartUs = 1000000,
       };
 
     AudioRecord *mRecord;