[Ground-station] Test Plan - Update!

[Michelle Thompson]

We're back from Visalia International DX Convention. Plenty happened!

Here's a test plan update.

Test plan is located at
https://github.com/phase4ground/documents/blob/master/Papers_Articles_Presentations/Papers/P4G%20Testbed%20Proposal.md

H.264 video streamed from a Raspberry Pi is working over multicast IP, with
ffmpeg sending and VLC on multiple computers receiving. We tried muilticast
IP opus audio, from a microphone and from a looped opus file and from a
looped wav file. The output on the other end using VLC was hopelessly
garbled or entirely absent in all cases. If you have a working command line
setup for this, let us know.

Back to the video, since that worked better than the audio.

ffmpeg streams multicast IP video with SAP, the session announcement
protocol in Multicast IP. SAP uses SDP formatted messages (session
description protocol) to explain what it's doing. The SAP packets are sent
out periodically. It's fast enough for the application to receive and
present the stream to the operator without much obvious delay at all.

The multicast H.264 from ffmpeg is successfully recognized as RTP in
Wireshark. Streams show up under VLC. You can click them, the video then
plays in a window. There's a heck of a delay, but it works. Multicast video
works with the command line VLC as well.

Wireshark flags multicast IP streams from Phil's code (ka9q-sdr) as
malformed. They come up as RDP, not the RTP which was expected. This
appears to be because there's no SAP emitted from the multicast IP streams
in Phil's code. Before the SAP is received using ffmpeg, the same behavior
is seen.

We haven't figured out how to get Phil's code to work for the test plan.
Edson Pereira is working on getting the latest version into the repository
at https://github.com/phase4ground/ka9q-sdr

Next step here is over the air transmission using GSE, the generic stream
encapsulation from DVB-S2/X. We'll use the SR-1 Pro for this at first.

I advocated for moving to phase 3 with the video stream, instead of Opus,
until we learn what we are doing wrong with the streaming.

This means that for phase 3 we would send multicast video over the air with
the SR-1 Pro in DVB-S2 GSE format. Audio as soon as it works.

Got any advice or pointers? Let us know!

-Michelle W5NYV
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