Hansang - I'm more than willing to admit I'm wrong (but at least to this point I'm not certain I am, or I'm actually saying the same thing you are in a more confusing way)
I'll wait for others to come along and confirm one way or the other.
My understanding though is that each of the speaker connections from DVD player with analog outs to a receiver like the Denon with an "Ext In" section requires a single RCA cable.
Even though FL and FR are typically grouped using Red and White (see the picture below for reference), I didn't think there was a difference between using two separate single RCA cables and using a joined pair of RCA cables that includes a left + right termination in white and red. What I was saying above is that you could use 4 pairs of Red/white cables as long as you matched the ends to the associated inputs/outputs, or you could run 8 single RCA cables. The key in the end is that the opposite ends of the cable are connected to the corresponding inputs/outputs.
To further clarify, I am not talking about anything having to do with connections from receiver to speakers, I am talking about connections from a device with 7.1 analog outputs to the receiver.
Jason