Close all other apps before launching your video player to give the CPU maximum resources. If you want to get this running today, I can help you:
If you are determined to use an app rather than a browser, here are the most common paths: youtube android 4.4 2 apk
The stock "Internet" browser on KitKat is obsolete. Download a lighter, more modern browser like Opera Mini or a legacy version of Firefox . Close all other apps before launching your video