I got the sound o/p on my headphones jack. This time, I included all the available options such as (surround, front speaker, PC speaker) in the alsa mixer. The surround one is muted by default, so I tried unmuting it and it worked!!
strangely my headphones jack is being called as surround speaker jack by alsa mixer.
I guess alsa has detected my sound card as a 5.1 sound card and it mapped my headphones out jack to the surround speaker jack. To support this, even when I plug my headphones, the normal PC speaker which is mapped as 'front speaker' is still playing. I have to mute it manually to cut the audio from it.
I tried the command alsaunmute command and it says that it 'guessed the card "HDA Intel" "ALC888" .... '
From the above line its evident that it didnt determine my sound card exactly and that's why the mapping errors.
Is there a way in which we can specify the type or operational mode of my sound card to set it to work as a stereo one, not as 5.1??