Current state of ac3 passthrough
David
Graham Booker's blog it can be tricky. Let's say my receiver can play
it ok (it's an HK AVR-340). Once you install Perian, edit the plist,
and change the audio-out of the Mac to 48000/16-bit, is it true that
all audio coming out the Mac will be ac3 bitstream? Or when you close
a video using ac3 passthrough (say, a .mkv with x264 and ac3), does
the audio output from the mac go back to PCM so you can play iTunes in
regular stereo?
Much thanks in advance! I got an iMac at work and am really impressed
with Mac OS X.
elan
David
Graham Booker
On Jun 6, 2009, at 10:34 PM, David wrote:
>
> I'm pondering buying a Mac Mini for htpc use; from what I've read on
> Graham Booker's blog it can be tricky. Let's say my receiver can play
> it ok (it's an HK AVR-340). Once you install Perian, edit the plist,
> and change the audio-out of the Mac to 48000/16-bit, is it true that
> all audio coming out the Mac will be ac3 bitstream? Or when you close
> a video using ac3 passthrough (say, a .mkv with x264 and ac3), does
> the audio output from the mac go back to PCM so you can play iTunes in
> regular stereo?
Only when you are playing something that's AC3 does it play a
bitstream. All other audio sources (such as mp3 or aac) will be PCM.
The AC3 bitstream is actually encoded in PCM, so any sounds played at
the same time as the AC3 will actually screw up the AC3 for the
sound's duration. QuickTime doesn't have any idea it's sending an AC3
bitstream to the receiver. This is due to the fact that QuickTime has
no non-PCM output, a feature I've requested a long time ago and Apple
still has not given us.
If you want playback of AC3/DTS passthrough while still retaining the
Front Row interface, I recommend Sapphire (http://
appletv.nanopi.net/), one of my projects, or ATVFiles (http://code.google.com/p/atvfiles/
) which are both AppleTV/Front Row plugins that set the sample rate
and plist for you when you are playing an AC3 file.
>
> Much thanks in advance! I got an iMac at work and am really impressed
> with Mac OS X.
- Graham
David Bennett
Only when you are playing something that's AC3 does it play a bitstream. All other audio sources (such as mp3 or aac) will be PCM. The AC3 bitstream is actually encoded in PCM, so any sounds played at the same time as the AC3 will actually screw up the AC3 for the sound's duration. QuickTime doesn't have any idea it's sending an AC3 bitstream to the receiver. This is due to the fact that QuickTime has no non-PCM output, a feature I've requested a long time ago and Apple still has not given us.
On Jun 6, 2009, at 10:34 PM, David wrote:
I'm pondering buying a Mac Mini for htpc use; from what I've read on
Graham Booker's blog it can be tricky. Let's say my receiver can play
it ok (it's an HK AVR-340). Once you install Perian, edit the plist,
and change the audio-out of the Mac to 48000/16-bit, is it true that
all audio coming out the Mac will be ac3 bitstream? Or when you close
a video using ac3 passthrough (say, a .mkv with x264 and ac3), does
the audio output from the mac go back to PCM so you can play iTunes in
regular stereo?
If you want playback of AC3/DTS passthrough while still retaining the Front Row interface, I recommend Sapphire (http://appletv.nanopi.net/), one of my projects, or ATVFiles (http://code.google.com/p/atvfiles/) which are both AppleTV/Front Row plugins that set the sample rate and plist for you when you are playing an AC3 file.