What held quality down, empty when nothing did. Values are "rtt", "packetLoss", "jitter", "freeze", "framesDropped", "audioConcealment", and on the uplink the encoder's own reason such as "bandwidth" or "cpu".
This direction overall, on the shared 0-5 scale: 0 unknown, 1 bad, 2 poor, 3 fair, 4 good, 5 excellent. It is the worse of audio and video, so one bad kind drags the whole direction down — read factors to find out which.