v2.2.1

Added

• Added support for seek preroll in AAC and other audio codecs (#452). This also
  addressed 'Unexpected seek preroll for codecs ...' warnings.
• Computes and sets VP9 Level in the codec config if it is not already set
  (#469). This fixed VP9 in ISO-BMFF files generated by FFmpeg v4.0.2 or earlier
  which does not have level set in the codec config.

Fixed

• Added a workaround for TS contents with dts moving backwards (#451). So
  instead of generating a sample with negative duration, which ExoPlayer does
  not handle, use an arbitrarily short duration instead.
• Fixed pattern signaling in seig for key rotation with cbcs (#460).
• Fixed incorrect segment name with $Time$ in segment_template (#472). This
  resulted in the first segment being overwritten and led to playback problems.
• Fixed TTML text input passthrough in DASH (#478). This is a regression
  introduced in v2.2.0.