Can PS3 show rtsp streams?
I don't recall for sure but I think it might be doable with movian.
It might also be doable using a Flash 9 based movie player in the ps3 browser.. I said "might" because Flash 9 was the first major revision that introduced AS3 to Flash development, many additional features of the AS3 scripting language were added in the following major revisions 10 to 13 so I am not 100% sure about the capability of Flash 9 internal classes to stream rtsp. But that's easily confirmed, you can check this page, there is actionscript 3 source code available so you can try compiling a minimal proof of concept (just a few lines of script) for Flash 9 & see if it outputs a swf build which can be tested on PC first if you install the local swf player or a swf player plugin in a browser.
https://flashphoner.com/7-ways-to-stream-rtsp-on-the-page/
Alternatively you can use the AS3 language reference manual on Adobe's website & check that the necessary classes used in the sample scripts are available on Flash 9.
I would recommend using the open source FlashDevelop app for PC to compile actionscript, it's an easy to use IDE & it's free.
FYI
Generally speaking to test web stuff targeting the ps3, it's useful to have the closest browser environment to the ps3 you can get on PC.
For that purpose, the best choice imho is to install an old Safari 4.0.4 or close (still available out there, a quick search on oldversion.com or whatever should get you some working links, choose the safari 4.0 build which is closest to ps3 webkit build 531.22.8, for instance Safari 4.0.4 using webkit 531.21.8), with the appropriate Flash Player 9 web plugin installed (still available in Adobe Flash archives last I checked, no idea for how long though).
The safari webkit is more featureful than the equivalent ps3 webkit however the rendering is extremely similar & the general level of js/css/Flash support (with FP9 plugin installed) is adequately similar to test most things targeting the ps3.
A Flash 9 player for the XMB is also available with the faust_widget.sprx, it is used to display some XMB swf thumbnails without requiring the browser.
We might be able to hack that sprx file to display windowed or fullscreen flash movies directly from the XMB without browser. If so, one could make nice looking Flash apps for the XMB, including an audio/video streamer...
I plan to investigate this plugin at some point for exploitation purposes, I will try to get us answers about potential usage for XMB apps at the same time.