Here is the result.
I bought a cheap 5.1 home theater amplifier, hook it up to my satellite receiver with an optical cable. For those channels on which my TV has sound, the amplifier detected "FCM Stereo". For those without sound (suppose to have audio format
AC3), the amplifier didn't show anything. That means, no AC3, or Dolby digitial, data input to the amplifier. Do all of you agree?
Then I found an easier way to determine whether the receiver pass thru AC3 data. I removed the amplifier, but left the
optical cable attached to the receiver. When there was audio data output from the receiver, the other end of the cable lit up (red light); when no audio data (including AC3), the cable did not light up. Correct me if I am wrong.
FYI, my staellite receiver is "TRANXIS DBS-3500" from "DMS International". But the maker is not shown on either the original box, the receiver, or the manual. I bought it from eBay.
I have another problem with the receiver. Although it claims "Stores up to 100 satellites/4000 channels", I have fewer than 10 satellites/200 channels, but I got "No Space" error when I tried to search other satellites. Even after I deleted a lot channels which I did not need and left about 40 channels, this error still exists. Any reasons/tips? Thanks.