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Re: Lost audio on headphones (F9)





On Fri, Dec 19, 2008 at 2:57 PM, Tim <ignored_mailbox yahoo com au> wrote:
On Wed, 2008-12-17 at 05:45 -0200, Paulo Cavalcanti wrote:
> Unfortunately, some boards only detect the presence of jacks connected
> to the back of the computer. Plugging, say a headphone, to the front
> does not change anything.

In some computers, there's no "detecting" at all.  It's a mechanical
switch in the headphone socket, and the front and rear panel sockets are
often different (e.g. a simple one on the front).

Detecting a connection made to *any* socket, without requiring special
sockets, would require electronics designed for that (detecting a DC
change, impedance loading change, etc.).


Hi, Tim

You are right.

In fact, the problem was my computer case connectors, for the front panel.
I found out later that there are two types of Header connectors:
AC97 and HDA. The new standard, HDA, allows jack detection.
But the majority of computer cases still come with the old AC97 Header,
which does not allow jack detection:

Please, see figures on page 20 and 25 of the link below.

http://www.formfactors.org/developer/specs/A2928604-005.pdf

The good part is that Takashi Iwai (alsa developer) introduced new "models" for some codecs, which allow the use of the front panel, even without jack detection.

The alsa snapshot I am using right now, fixed all my problems. I can hear
both, the speakers on the back and headphones on the front, simoutaneously,
each one with a different mixer control.

I think these new drivers will be available for the public in the next alsa release.

--
Paulo Roma Cavalcanti
LCG - UFRJ

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