Introduction of slow motion in video playback

Hi,
I needed a specific feature that allowed the end-user to slow down the video playback and, as much as I researched around, I couldn't find anywhere someone working on it. I am new to Git so I hope I'm doing this the right way.

I have tried to minimize the impact on overall code so used a trick to multiply the playback speed by a factor (OMX_SLOMO_MULTIPLIER). I am currently using a factor of 16 which provides an extra 15 possible values (from 1 to 15) between normal speed and full pause.

I only needed 4 slowed down speeds (i.e. 1/2, 1/4, 1/8 and 1/16 of normal speed) so I used a logarithm calculation to do the trick on changing the  playback speed.

I admit I just did basic testing and it worked as expected (I even didn't need audio to work fine but the synchronization still worked ok). I didn't have a sample video with subtitles so I'm not sure I have messed up any synchronization needed. 

Cheers,
Mike