Re: Speaker setup + possible typo in CoreAudioTypes.h label value?
Re: Speaker setup + possible typo in CoreAudioTypes.h label value?
- Subject: Re: Speaker setup + possible typo in CoreAudioTypes.h label value?
- From: Derk-Jan Hartman <email@hidden>
- Date: Wed, 23 Mar 2005 22:00:25 +0100
On 23 mrt 2005, at 21:19, James McCartney wrote:
On Mar 23, 2005, at 11:40 AM, William Stewart wrote:
On 23/03/2005, at 8:51 AM, Derk-Jan Hartman wrote:
But to me it's sheer impossible to find out what channels should be
downmixed to. I mean how am i supposed to know what channel is LFE,
what channel is the Center speaker.
Well, that's all clearly specified either:
(1) In the bitmap
(2) In the channel descriptions
(3) Implied in the layout tag
That's how we implement the above property
There is also a property to get all of the channel descriptions
spelled out for a layout tag: kAudioFormatProperty_ChannelLayoutForTag
Aaaaah, this looks like it's more what I was looking for. Thank you for
this. I knew there had to be a way under 350 lines of switch case
statements.
DJ
If I'm VERY out of luck the things can even be specified by
coordinates.
It seems this system is more designed to account for channel layout
and positioning and not so much for keeping score of speaker
presence and speaker nature.
coordinates are optional. I would not recommend that a left channel be
defined only by its coordinates. I would expect coordinates to be used
without a specific channel label only if it is a non traditional
layout where the geometry is important to a faithful reproduction.
My sonica theater seems to use ACD with AClabels, but other devices
can simply have the ACLT set and nothing else?
Am I missing something here? Is there an easier way to figure out
which speakers are available for output?
as above, kAudioFormatProperty_ChannelLayoutForTag
Is it REQUIRED for instance that drivers set a proper ACBmap? If so
than this is not clear from the headers (let alone the documentation
:D ) and should be clarified, if it is not then maybe it would be a
good idea to have that as a requirement?
I would not use the bitmap unless you are dealing with WAVE files or
USB in a way that needs to preserve compatibility.
---
Universiteit Twente
Derk-Jan Hartman (d.hartman at student.utwente dot nl)
http://home.student.utwente.nl/d.hartman
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