ffmpeg prints traces despite `quiet` log level

[alxmrs]

Related to #2, I can't find a configuration of xarray2video that suppresses ffmpeg console log output. I've set verbose=True and loglevel='quiet', but I still notice a decent amount of logging output. Am I holding this wrong?

[alxmrs]

Ok, I do think I was holding it wrong! I turned off capturing metrics and the log traces went away.

[OscarPellicer]

As I mentioned in #2, some codecs like x265 like to output to stderr even with loglevel set to quiet. I'm not sure I can do much about that.