OnSIP supports the following audio codecs:

G.722 for High Definition Calls (approx 100 Kbps IP bandwidth in each direction)
G.711 (ulaw/alaw) for PSTN Quality Calls (approx 100 Kbps IP bandwidth in each direction)
GSM for Cellular Quality Calls (approx 30 Kbps IP bandwidth in each direction)

OnSIP supports the following video codecs:

H264 for HD quality (~1.2 Mbps IP bandwidth for each video endpoint)
VP8 for flexible quality (100 Kbps - 1.2 Mbps IP bandwidth for each video endpoint depending on resolution)