hey,
If you are in the Video content delivery business using mcast then these folks are one of the leaders. You can put multiple probes and make sure your mcast coming off source is solid, through the core router solid, and at the edge... http://www.ineoquest.com/ they are not cheap but worth every dollar
I can recommend http://www.agama.tv/ We use it for general purpose monitoring but not so much for interactive debugging. Shameless plug: for debugging I wrote https://github.com/tarko/CCmon some years ago and it works great. Wanted to have alternative to all windows based software out there that will just report number of CC errors but will not support multiple streams (or copies of the software running), will not produce useful logs for correlation etc. -- tarko