I have four Rpi devices, three RPi2 and one RPi3. When I first switched to LibreElec, I tested the MPEG codec to see if I would need to add my key's or not, and the results on the first couple were enabled, so I never added the key's.
After a bit of use, I started to realized that the voice and video would start to get out of sync on the main media RPi (an RPi3 device). I decided to test it for the codec and it came back disabled, so I added the keys for that particular devices.
Even after adding in the key's, the voice and video get out of sync. I test, and the codec comes back as disabled. Other than putting the codes in the config.txt file, I'm not sure what else I need to do to get the voice/video back in sync. Any suggestions?