Aspect ratio of videos
"However, the standard Android media player won’t stretch the film to fit the screen, which can lead to some unpleasant letterbox bars at top and bottom."
That's cos your film will probably be 2.35:1 and not 16:9. In fact, films generally aren't 16:9 at all.
So thank God for the media player showing it properly. I'd much rather the media player showed the film exactly as it was intended to be shown instead of either 1. stretching it vertically (making things look out of proportion) or 2. zooming into it, cutting off the sides in the process.
Make no mistake, watching stuff in the ORIGINAL ASPECT RATIO is better than zoom-to-fit or stretch-to-fit. Borders are hardly an issue and is far better than distorting the image.