Re: M4P through AUHAL to multichannel device (last call)
Re: M4P through AUHAL to multichannel device (last call)
- Subject: Re: M4P through AUHAL to multichannel device (last call)
- From: Greg Chapman <email@hidden>
- Date: Fri, 23 Jan 2004 10:05:35 -0800
Definitely choose CoreAudio over SoundMgr as your long term solution!
QuickTime is in the process of making that switch (finally), and when
that happens (I wouldn't start holding your breath just yet) you'll be
able to use QuickTime to play m4p's to your multichannel hardware.
However, CoreAudio can't play these files. For two reasons: one is
that CoreAudio doesn't play MPEG4 files. m4a (unprotected iTunes AAC)
and m4p (protected iTunes AAC) files really are MPEG-4 files under the
hood (MPEG-4 files are almost exactly like QuickTime movie files, and
CoreAudio has never been in the business of parsing such things). The
second reason is that CoreAudio doesn't do the "protected content"
thing. That's QuickTime's job.
So, until QuickTime switches to CoreAudio-based playback, you're stuck
with convoluted solutions, trying to get QuickTime to generate PCM
samples, and then using CoreAudio to play them to your multichannel
device.
Greg Chapman
QuickTime Engineering
email@hidden
On Jan 22, 2004, at 6:25 PM, Austin Shoemaker wrote:
All I want to do is play my music to any stereo pair on my
multichannel output hardware. The only problem is protected AAC,
which is not friends with CoreAudio.
The only workarounds I have found to be effective are convoluted and
inefficient, and hence not acceptable.
I guess the dust has not settled around the technology line between QT
and CA, and that this niche of functionality (M4P on multichannel
hardware) has been caught in the fringe.
Before I rewrite everything to use QT through sdev components, I would
really appreciate any official comment on this. Especially if the
answer is "I don't know" or "That's right, CoreAudio will not work",
because I really need to know, and I would prefer to choose CoreAudio
as my long-term solution.
Thanks to everyone who has contributed to this inquiry so far.
Sincerely,
Austin
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