I have a project for cctv over wireless, it will be mix between ptp and pmp and all going to be 450i models.
There are a lot of cascaded points which will be connected via ptp.
Does there any recommendation for the max number of cascaded links in order to avoid delay in video streaming.
I don't think there's any recommendations for max number of hops.
Depending on how your network and cameras are setup, you'll probably want to avoid just bridging everything and having every camera directly on your network. Try to reduce the number of MAC's floating around in the PtP's bridge tables... you can reduce this by using the client radios in router mode, or a dedicated router that provides PoE support at each site/camera location (assuming you're using multiple cameras at each location).
On the RF side you'll probably want to make sure your links are well engineered, use 2.5ms frame duration to reduce latency... maybe even use GPS sync on all your gear to make sure you don't run into issues with each PtP and the PtMP radios interfering with each other.
Adding to Eric comments.
Few more things to consider:
How much capacity of video streaming are you planning on your network ?
What link availability are you targeting ?
What is acceptable level of delay for CCTV streaming?