Movies in QuickTime: extra tracks and software ?

Since a couple of weeks movies recorded with my iPhone 5s are not played properly in QuickTime.

- First of all I noticed that each movie has two extra tracks: Windows > Show Movie Properties: each movie has a video track, audio track, basic track 1, basic track 2. In the past I only had video and audio. What are the two extra tracks about?

- Each time I open a movie QuickTime says it needs extra software to play the movie and directs me to this page:

http://www.apple.com/quicktime/resources/components.html?os=Windows&ctype=6d686c 72&csubtype=6d657461

But even when I do not install any additional codec the movie is played.

- Most movies, but not all are "half-empty" meaning that when I record something for 30 seconds the .mov is 1 min long with 30s of movie and 30s of white

I believe the problem started when I upgraded my iPhone to iOS9, but I may be wrong.

I'm not sure how to solve this. For the moment I haven't installed any additional software since I never had to do this before.

Using QuickTime Pro 7.7.8

Thanks for your help

http://www.apple.com/quicktime/resources/components.html?os=Windows&ctype=6d686c 72&csubtype=6d657461