I've been testing SimplePlus and Ekiga on a C2C connection to a Polycom h/w device over the LAN.
I've run into the following 2 issues with both of the applications:
1. the device only shows a broken static video frame every once in a while
2. the device closes the signalling channel right after receiving the first message
Both issues seem to be have the same underlying cause: the messages and samples are not packetized according to the ITU H.225.0 standard.
More specifically, my understanding of H.225.0:2006 section 6.1 and appendix IV seem to require all messages to fit in a non-fragmented datagram.
However, when I add 1 video codec (H.261) and 6 audio codecs (G.722, G.722.2, GSM06.10, GSM-AMR, Speex), the first message (which contains the codec list) grows beyond 2 KiB and ends up fragmented and rejected by the h/w device.
Also, the video keyframes produce media samples larger than the network's MTU and end up fragmented and the fragments are no longer macroblock-aligned and are dropped by the receiving h/w device (as showed by the device's real-time log). Every once in a while, the beginning of a keyframe is fragmented on a macroblock boundary and the device accepts that part of a frame, which is displayed partly broken (the picture is incomplete) and stays there until the next accidental valid paclet (if ever).
I am in no way an expert on H.323, so my understanding of what is going on may be incorrect. If so, what can I do to correct this observed behavior?