I have intermittent problem with receiving audio for RPG 300. Call was establish between HDX8000 (ver 3.1.13) and RPG300 ( ver 4.02). HDX8000 can get good video and audio from RPG300 but RPG 300 get intermittent audio (video is OK) from HDX8000, example when count 1 to 10, 5 or 6 is missing. (breaking audio). We have conducted test from HDX8000 to others two more remote site and it is working fine.
RPG is at off shore office with satellite link, the round trip ping latency is approx 500ms without much package lost ( less than 0.5% base on HDX Tx and RX call statistic) call was connected at 128K and 256K. Also test from HDX8000 to other off shore site with similar latency which is OK but they are using HDX and Cisco.
Try to do the test again with the local site (GS300) audio muted.
What is the output of the audio on the GS300? If it is directly through the display try changing the mode on the display to game mode (or something with a similar tag). Also try using an external audio system to see if that helps.
Some displays actually 'process' video to enhance it and in doing so they delay audio to keep lip sync, by doing so with interactive technologies like video they actually delay it beyond the echo cancellers and that could be causing the issue.