Axis's ARTPEC-3 chip is a key element in the positioning and performance of Axis network cameras. Axis has released a technical paper with metrics on the ARTPEC-3's performance. ARTPEC-3 was announced in 2008. Their next generation chipset, ARTPEC-4 is scheduled for release this year. Also not that ARTPEC-3's performance is important not only for video streaming but for Axis video analytic's platform (where resource limitations can restrict analytic performance).
In the ARTPEC-3 whitepaper, Axis concludes that D1 and VGA "can actually deliver 5 simultaneous individually configured H.264 streams in D1 at 30/25 fps, and 3 simultaneous individually configured H.264 streams in SVGA at 30 fps. For higher resolution products, we get a lower number of streams in maximum resolution and full frame rate." The paper includes a series of tables that map the reduction in maximum frame rate and simultaneous channels of video streaming.