* Inject silence opus frames on mute.
If not, under certain circumstances, residual noise
seems to trigger comfort noise generation at the decoder
which is not all that comfortable.
* inject silence only when muting
* Add comment
* augment comment
* Delete blank line
* Adjust TS offset on blank frames
* Remove debug
* Do not modify `lastTS` as it affects timestamp on next switch.
* use duration to calculate number of blank frames
* log errors in blank frames write path
d828e0fbd8