Re: Speaker Audio when Headphone connected?
Re: Speaker Audio when Headphone connected?
- Subject: Re: Speaker Audio when Headphone connected?
- From: Jeff Moore <email@hidden>
- Date: Mon, 25 Feb 2008 12:41:06 -0800
One thing to keep in mind is that when hardware is getting
bootstrapped is that it often will work a lot differently than it does
once the OS is all up and running. This is one such case. During boot,
the audio chip is brought up just enough to squeeze out the chime and
nothing more. The point of booting is to get through the sequence as
quickly as possible. Thus, having a more complex driver for the sound
chip that can run all the jack detect circuitry and do the right
switching would get in the way of booting quickly.
So, I would not be drawing any conclusions from the fact that the boot
chime comes out the speaker, even when headphones are plugged in with
regard to what you can and can't do with the hardware. They are
completely different operating environments doing completely different
jobs. Any conclusions you would draw would be completely erroneous.
On Feb 22, 2008, at 7:46 PM, Brian Willoughby wrote:
It must be a matter of language, because what you seem to be trying
to communicate, and the words you're actually writing, are not
entirely in accord.
Observation alone is enough to confirm that Apple's boot code is
able to direct the single audio signal to the built-in speakers,
even when headphones are plugged in. Apparently, users and
developers want to do the same thing at other times after startup.
If Apple has no plans to publicly support any access to this
internal feature, then you're saying something quite different, and
nobody could argue with that theoretical position.
"Mutually exclusive" means nothing more than that you cannot have
both audio outputs operating at the same time. This is a well-
understood fact that is written in stone (or etched in silicon, as
it were). The method for choosing between these two mutually
exclusive options is completely independent of the fact that only
one can operate at a time. There is no semantic, logical, or
hardware design correlation between the two statements.
Brian Willoughby
Sound Consulting
On Feb 22, 2008, at 19:15, Jeff Moore wrote:
The speakers and the headphones are mutually exclusive. Whether
this is because of hard wiring or flipping bits in a register
somewhere really doesn't matter. This is just another one of the
facts about the hardware you have to deal with. There's no secret
back door to make it work different.
If you don't want the sound coming out of the headphones, just
unplug them.
--
Jeff Moore
Core Audio
Apple
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