From a couple of days a problem has arised which has the following symptoms
When somebody calls me or I call anybody through skype video call, Tango video call, or google hangouts video call, the other party receives no sound. Only video is received. I hear and see just fine.
When I skype without video, the voice is heard at the other end but as soon as I enable video, the sound goes out.
Viber and normal GSM calls work fine. The videos recorded through the SGS2 camera has sound too. The inbuilt sound recorder works fine.
When I call on the echo service on Skype, I can hear my recorded sound all right if I don't do anything else. However if I turn on the speaker(by using the on skype-screen button) and then record my voice, I don't hear anything in the recorded voice. It looks like that the mic is muted while on speaker phone.
Info: My mobile's warranty has expired. I am still using the stock rom. Current Android version is JB 4.1.2. There hasn't been any recent upgrade which means this problem hasn't resulted after any software upgrade.
I would request you all for your valuable suggestions. I want to first try to solve the issue without factory reset or putting a new custom rom.