Re: [...] multichannel questions
Re: [...] multichannel questions
- Subject: Re: [...] multichannel questions
- From: William Stewart <email@hidden>
- Date: Fri, 9 Jan 2004 18:27:06 -0800
I think there's some confusion here. The poster was originally talking
about changes in QT, not CoreAudio. Nor are there any changes needed in
CA to enable this functionality. For instance, AAC encode and decode
as shipped with Panther already will do several different surround
formats (see <CoreAudio/CoreAudioTypes.h>, which can also be stored
into ADTS files and thus read and written using the AudioFile API -
(ADTS is a bit stream described in MPEG2)
The original post is really more appropriate for the QT API list (where
it was cross-posted too) rather than this one I think.
Bill
On 09/01/2004, at 5:41 PM, Austin Shoemaker wrote:
I am just curious- what will the new multichannel support enable that
we cannot do now? Is there a technote or is it just discussion now?
If there will be a new API that will make multichannel audio (output)
better, I am interested because I am just starting on a new project
that heavily utilizes multiple channels, and I am researching the best
way to do this.
Thanks a lot,
Austin
On Jan 9, 2004, at 4:39 PM, Dave Addey wrote:
Hello there CoreAudio list (this was posted to AT API list too),
I remember hearing in the WWDC QuickTime presentation that a new
version of
QT would be featuring the "Sound Manager 2", one feature of which
would be
sample-accurate synchronisation of tracks in a QuickTime movie. Is
this
coming in the next version (perhaps alongside the upcoming
multichannel
audio)? Will this mean that (for example) MP3 audio tracks will be
synced
exactly, rather than just being synced to the nearest MP3 sample size
(about
0.03 sec for a 44100Hz track, I think)? I currently sync two
identical MP3
tracks in one movie, but output each track to a different audio
device for
live and cue DJ purposes, and they're never quite in sync, resulting
in
bogus 'latency' :-(
Second question - in the upcoming multichannel audio code, will it be
possible to:
A) output both channels of a stereo audio track to one channel on a
CoreAudio output device such as the Emagic 2:6? (i.e. stereo track
mapped
to mono output without the need to resample)
B) output one stereo audio track to more than one stereo output
device (e.g.
output the same track to both the built-in Mac audio and also an
iMic), with
different volumes for each device? I'm thinking of this especially
to avoid
the need to duplicate the track as described above.
It'd be great if these things were possible! Any comments much
appreciated
(and best of luck in getting the multichannel code finished :-) )
Dave.
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