Regarding the MP3 RTMP this is a known issue. There are several bugs logged for this:
You can vote for them and we will try to fix them for the next release.
Regarding the Progressive issues please log a new bug,
Thanks for the quick Reply Gelu - voted for the one issue you noted, the other one was marked as closed, so I voted on the original issue it referred to.
I will log a bug for the same issues with http progressive sources.
Given I am the only person to upvote that issue so far, what is the likeliehood that this wil get any attention at all?
It is a bit dissapointing that OSMF and SMP still have issues loading audio only content.
Thanks for your help.
FYI: After seeing this get deferred to the next release, I spent a couple hours last night and was able to work around the bugs noted and get rtmp based mp3 streams working properly in Strobe/SMP 1.6. When I get a chance I will post some more details. Just wanted to note that it is possible, if you are willing to make a few small patches and maintain them yourself over the next few iterations of OSMF/SMP until things are fixed properly and the approach to audio in SMP/Strobe is revamped.