A/V synchronization at the beginning of a recording session

o do not use edts/elst boxes since these optional boxes are ignored
o manipulate the first video/audio frame duration to make sure that the rest
  of the audio/video is in sync (ideally, we should only manipulate
  the vidoe frame duration, not the audio)
o reduce the initial audio mute/suppression period, which is used to
  eliminate the "recording" sound.

bug - 3405882 and 3362703

Change-Id: Ib0acfb4f3843b365157288951dc122b006299c18