ffplay: set time_base of audio filter buffer src

Fixes ticket #2408.

Signed-off-by: Marton Balint <cus@passwd.hu>
ffplay: handle audio buffersink output properly with buffering filters

Fixes cases when the audio filter generates less or more frames than the input.

Signed-off-by: Marton Balint <cus@passwd.hu>
ffplay: fix indentation

Signed-off-by: Marton Balint <cus@passwd.hu>
ffplay: simplify video pts calculation

Also use frame->pts instead of a standalone variable

Signed-off-by: Marton Balint <cus@passwd.hu>
Merge remote-tracking branch 'cus/stable'

* cus/stable:
  ffplay: simplify video pts calculation
  ffplay: fix indentation
  ffplay: handle audio buffersink output properly with buffering filters
  ffplay: set time_base of audio filter buffer src

Merged-by: Michael Niedermayer <michaelni@gmx.at>