[Sugar-devel] GSoC Proposal: Multimedia Broadcasting

[Geza Kovacs]

Since you apparently have more experience with multicasting over
wireless I'll assume it's not a realistic option in this context
(though it might nevertheless be an interesting experiment to try if
have spare time over the course of GSoC after finishing a
unicast-based implementation).

Returning to unicasting and simply limiting net bandwidth usage, as I
understand the "slowest client sets the speed" issue with the access
node switching to Mode1 for broadcast applies only to multicasting. If
I have the XO send the video in a single UDP stream to the central XS
server (which as I understand has a wired connection to the AP), then
have those streams be individually relayed by the XS over the AP to
each designated viewer in over unicast UDP, then as I understand the
AP will be able to operate near its 56 Mbps net throughput limit,
which, factoring in the fact that the effective throughput will be
decreased due to noise and that my application of course can't hog all
the bandwidth and airtime, means that I will have around 20 Mbps
available for unicasting to all clients.

Rather than limiting the number of viewers as I originally proposed, I
believe that automatically limiting the framerate of the broadcast
based on the number of viewers will be a better way to scale for
larger numbers of viewers - that is, once the broadcaster gets to the
"broadcast" stage and selects the intended viewers, then based on the
available bandwidth and network congestion, then an ideal framerate is
calculated out and the stream is encoded and broadcast to all of the
viewers at that framerate. Given that the most interest has been
expressed over the remote desktop broadcasting feature, and given that
there's rather little motion overall on a desktop broadcast, the
desktop activity should still be easily viewed at very low framerates.