After reinstalling the operating system (OS X EL Capitan) I can't open video files in .mov format. I can open them using VLC but I can't open them in QuickTime and Adobe Premiere - what could be wrong? Maybe I need some codecs?
Here's what Google says:
According to the info in Apple official site, QuickTime does support MOV files. However, MOV is a multimedia container file that contains one or more tracks, each of which stores a particular type of data: audio, video, effects, or text (e.g. for subtitles).
So it could be possible that a part of the .mov file may not be supported by the QuickTime player. In this case, I would suggest you to convert the file to a .mp4 or a QuickTime compatible .mov format using a third party application.
Are you using the latest version of QT? If not, install the latest version. MOV is a file container format. Your mov file can be encoded with different types of codecs that may be incompatible with QT. You can check the video detailed info with Mediainfo.