foo.py

import os
import sys
import subprocess
import json
import pprint
import glob

def getlen(filename):
	avdata = json.loads(
		subprocess.check_output(
			['ffprobe', '-hide_banner', '-show_format', '-print_format', 'json', filename],
			stderr=open(os.devnull, 'w')
		).decode('UTF-8')
	)
	return float(avdata['format']['duration'])

if __name__ == "__main__":
	total = {
		root: sum(
			getlen(os.path.join(path, file))
			for (path, dirs, files) in os.walk(root) # path contains root
			for file in files
			if file.endswith((".m2ts", ".MTS"))
		)
		# or just for root in sys.argv[1:]
		for globbable in sys.argv[1:]
		for root in glob.glob(globbable)
		if os.path.isdir(root)
	}
	json.dump(total, sys.stdout, indent=1, sort_keys=True)
	# pprint.pprint works too