See Supported YouTube file formats at YouTube help page https://support.google.com/youtube/troubleshooter/2888402?hl=en.
The DMC Canon video cameras record videos in two formats: MP4 or MTS.
  1. MP4 files can be uploaded to YouTube directly. 
  2. MTS files
    1. on a Mac, import the footage in MTS files into Final Cut Pro X, then locate the imported .Mov files on the Mac. Then upload the .Mov files to YouTube. 
      Note, in FCP X, https://support.apple.com/en-us/HT201237, when importing MTS files, the wrapper gets changed, but the codec gets preserved. So the importing process is pretty fast. The file size doesn't change either, only the file extension gets changed from .MTS to .Mov. 
    2. on a Mac, import the footage in MTS files into iMovie, then located the imported .Mov files on the Mac. Then upload the .Mov files to YouTube. 
       Note, with iMovie, when importing MTS files, the wrapper gets changed, but the codec gets preserved. So the importing process is pretty fast. The file size doesn't change either(this needs to verify, 2/22/2016),  the file extension gets changed from .MTS to .Mov.