A friend is asking if he can connect a blu-ray player using L and R RCA cables to the AUX input of his 5.1 HTIB and will the HTIB be able to decode the 5.1 channels ?
The answer is maybe (and very likely yes). If your components support Dolby Surround/Pro Logic, you can get true (but not discrete) surround sound.
Set the player to output in Dolby Surround. That would matrix encode multichannel information (4.0 channels) into two channels. Selecting Dolby Surround or Pro Logic in the receiver will then instruct the receiver to decode the matrixed channels as intended (upto 3.0 and 4.0 channels respectively), thereby giving you surround sound. Pro Logic II (PLII) can create 5.1 channels from the encoded 4.0 based on assumptions. PLIIx can do 7.1, while PLIIz can do 9.1 from the encoded 4.0.
This was how we enjoyed surround sound during the Beta, VHS and early LD days.
Even TV programs are often encoded in Dolby Surround (remember McGuyver's "in Surround Sound where available" text?).
Here's an image of a VHS cover indicating Dolby Surround: