Packet loss is one of three key video conferencing performance metrics. The other two are latency and jitter.
Typical numbers for acceptable packet loss during a conference range from 0.1% to 2% and anything less than 1% should be the highest tolerable threshold you would expect.
Packet loss for telepresence systems typically needs to be under 0.1% to remain unnoticed, with some vendors recommending even tighter specifications for their telepresence systems. The effect of packet loss on the video application is "blockiness" or pixelation and/or jerkiness of the video, as well as audio drop-outs. A commonly-used term is "artifacting" or a "video artifact".