10.6.2 and AC3 Passthru

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zorro2b
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10.6.2 and AC3 Passthru

Postby zorro2b » Tue Dec 08, 2009 9:40 am

I previously had AC3 passthru working with 10.5. I am now on 10.6.2 and trying to use my mini as a media centre again. m4v files encoded with handbrake and including an ac3 passthru channel work fine with VLC. When I try with quicktime I just get the PLII mixdown. I also tried encoding a short video with only AC3 passthru audio and quicktime rewarded me with a machine gun like sound.

I have confirmed with a friend who has QT7 Pro that the channels are NOT in the correct order specified here:
http://www.cod3r.com/2008/02/the-correc ... quicktime/

Would this be causing these problems or just make the sound play out the wrong speakers? If this is the problem, what is the best way to get the channels encoded in the right order in the first place? Handbrake does not seem to have any options for this.

thanks,
Andrew

gbooker
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Re: 10.6.2 and AC3 Passthru

Postby gbooker » Tue Dec 08, 2009 3:09 pm

The wrong channel layout will cause problems. Best way for it to be correct in the first place is to tell Handbrake to fix the issue of which I informed them around two years ago. I told them exactly how to set the channel layout, and they didn't do it. Alternatively, we could work around these issues if Apple would fix either rdar 5799879 or 6921431.

zorro2b
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Re: 10.6.2 and AC3 Passthru

Postby zorro2b » Tue Dec 08, 2009 7:23 pm

Are there any alternatives to Handbrake people are using?

Trevize
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Re: 10.6.2 and AC3 Passthru

Postby Trevize » Wed Dec 09, 2009 12:03 pm

HandBrake produces mp4 files, not mov. You can't assign a custom channel layout to an ac3 track inside mp4. So there is nothing to fix in HandBrake, if there was, it would have already been fixed.

gbooker
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Re: 10.6.2 and AC3 Passthru

Postby gbooker » Wed Dec 09, 2009 2:23 pm

Trevize wrote:HandBrake produces mp4 files, not mov.

Producing Mov files is one trivial way to fix it. Mov files sync with the AppleTV (Passthrough works), and will sync with the iPod. I don't see a reason to use MP4 in this case. At the least, it could be a good option.

Trevize wrote:You can't assign a custom channel layout to an ac3 track inside mp4

According to the standards, yes, but Apple didn't entirely follow the standards with the insertion of AC3. They more closely followed the format for mov. I'm betting Apple's code will read the chan atom. I was going to try and modify handbrake's source to test this, but it doesn't build without first installing yasm (which I may try at a later time).


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