I think the problem is with the Videocon HD set top box. When Dolby digital sound mode is enabled in my Videocon HD set top box, the audio level is very low. I am not feeling like I am getting 5.1 surround sound in all the speakers and in the sub woofer too.
I am sure the decoder is working fine. Because, when I connected my DVD player through optical cable input, it is giving 5.1 surround sound in all speakers and with a good bass in the sub woofer.
Are the Videocon HD channels really giving 5.1 surround sound?