OK understood now I think.

1) An inbound signal to an HD621 can be thought of as having separate VIDEO and SOUND channels. The HD621 extracts the SOUND channels from the feed. It is capable of extracting up to 8 UNCOMPRESSED channels from the signal. It extracts the VIDEO channels also from the feed and sends them out to a monitor attached to the "HDMI OUT" socket.

2) Scenario 1: Connection of a 861v4 to HD621 using the three RCA plugs. Since each each plug can take two uncompressed channels the maximum number of channels extracted and fed to the 861 would be SIX. This would be fine for uncompressed 5.1.

3) Scenario 2: Connection to a 861v6 using RJ45. When thus connected, the HD621 can deliver up to 8 uncompressed audio channels to the 861. This means it could handle uncompressed 7.1 for example.

4) The audio channels are there as conduits for the audio and do not define the type of multi channel encoding used. The same audio channels here discussed can be used for a variety of different encoding systems, however, the decoding algorithm must be supported by the 861 for the audio to be delivered correctly to the speakers.

Did I get this right?

Thanks guys
/Marcus

Lounge: 861v4+ID40 (hardwired Cat 6), HD621, 2xDSP6000.2VC (l/r), DSP5500.2HC, 2*Jamo ARTina (rears), D2500, 556, 596P, PS3, Humax HDR-1000S
Bed 2: MD600 (hardwired Cat 6) , QNAP 453 Pro