Be generous: give us a clue as to which of the million or so RTMP streams on the internet you're trying to download!
And which Operating System you're using!
In general terms, taking (as a random example) the BBC in London, television companies quite often offer a half dozen (or more!) different streams for each tv show on their website. Each of these is streamed at a different bitrate, so that a computer user can choose a stream which is slow enough for his internet connection.
This answers both of your questions at once!
1. It sounds as if you might be downloading different streams, instead of always getting the one that you want. Check that the
-y option in RTMPDUMP (also known as the
--playlist option), which allows you to specify one single stream, has been set. If it hasn't, just copy-and-paste the stream url you want, from the several contained in the
--app string.
2. If you download a live stream, on a slow connection, you will (obviously) experience dropped frames, because the server is streaming faster than your connection can handle. Well, the same sort of thing can happen with an on-demand stream.
You might think you've got a 15 Mbps ADSL connection, but there are many bottlenecks on the internet that can slow the true connection speed way, way down. If you, in Australia (well, I don't know where you are, because you didn't say
) try to connect to the BBC in the UK (again, you didn't say
), international routing will kill the connection speed stone dead.
On the other hand, if you in the Bronx (!) connect to NBC in Manhattan, you might get a genuine 15 Mbps connection. But I'm guessing you're way out in the outback.
Amazingly, you might actually get a better result by downloading at the busiest time of the day!! The heavier load will slow the server down, so that it streams high bitrate on-demand files much slower than in the dead of night.
On the technical front, a live server (i.e. one serving a live stream) has a fixed output per second for each given bitrate stream, so the system is designed to drop frames if your connection can't keep up. An 800 Kbps stream will drop 50% of the frames if the connection is 400 Kbps, for example.
No, there's nothing you can do (except move house, closer to the server!). I don't think too many tv stations are streaming at above 15 Mbps, so the trouble is internet botlenecks, most likely.