Kamal said:
It used to work in the past. It only started happening a few days ago.
This won't help you, but it provides a partial explanation of how it
is supposed to work.
(PDF Page 172)
ftp://download.intel.com/standards/hdaudio/pdf/HDAudio_03.pdf
Typically, there are two chains of four jacks. As plugs are inserted into
the jacks, a separate contact pair inside the jack changes state. One of
16 possible DC voltage values (all possible combinations of four jack
states), is presented to the "CODEC Jack Sense Pin". The audio chip has
an ADC, that converts the voltage into a four bit pattern. It is a really
high tech way, of detecting four jack insertion states, via only one
input pin on the audio chip.
That method should be pretty foolproof. But a DC upset, or a failure of
the input pin, could mess it up. My guess would be, that the registry
probably contains a fair amount of stuff related to HDaudio. But I don't
have HDaudio here, so cannot advise on just what could be responsible in
there. You could always try an uninstall and a reinstall, but you never
know whether the uninstaller is smart enough to remove the registry
changes it made or not.
HDaudio also has an optional method, of actual impedance sensing at
each jack. That may be used for front panel audio, since computer cases
typically lack an HDaudio jack sense setup (the computer case has the wrong
kind of jack). But how that works, is unclear to me, and is not documented
anywhere. Since the method is optional, it may show up in an HDaudio chip
datasheet, but usually there are no details as to when it is invoked.
Presumably the Hdaudio driver would have to poll the jacks, and measure
the impedance, at regular intervals. This would be a backup procedure,
in case the "jack sense chain" shown on PDF page 172, was not implemented
on the motherboard.
Best guess,
Paul
