Merge changes I921c81db,If2a22882,Ide7e7642,I5593cd1a,I923e6043, ...

* changes:
  aaudio_loopback: rectify and low pass filter
  aaudio examples: make tests portable to O
  aaudio test: fix looping multiple times using -l
  aaudio_loopback: improve tolerance to noise
  aaudio: add callback size options to examples
  aaudio_loopback: do not set buffer capacity by default