AC3 5.1 and iTunes

[Draco_myst]

I have researched this to death on the web, and have found no answer. PLEASE PLEASE help if you have figured this out.

As a reference, I have a "digital copy" of Star Trek 2009 that was downloaded from the iTunes store. It is 720p not 1080p, so I wanted to make my own 1080p from my Blue-Ray. The iTunes copy has two audio tracks, a default stereo, and an AC3 5.1 48.000kHZ configured L C R Ls Rs LFE. I can choose either track during playback in iTunes, and they work fine. With track 2 selected, my AVR shows Dolby Digital 5.1 playback.

Now for my copy. I extracted the main movie using the latest MakeMKV keeping the AC3 5.1 track and the subtitles. If I open this extracted uncompressed mkv in VLC it works fine, and my AVR shows Dolby Digital 5.1 playback. If I open it in Quicktime (I have Perian installed), the audio will not work. I the opened the raw mkv in Handbrake, selected the AppleTV3 preset, and then changed the container to mkv. I also set the first audio track as a stereo downmix to Dolby Prologic II, and retained the AC3 5.1 as passthrough. When completed, the now much smaller mkv again worked flawlessly in VLC using either audio track, but would only work in Quicktime with the stereo track. When I inspected the audio, I noticed that the AC3 from the mkv rip had a different channel order L R C LFE Ls Rs but was otherwise the same as the iTunes copy. I used the latest Subler to repackage the mkv as m4v, again keeping the default stereo track, and the ac3 5.1 track. I tried it a second time with Subler converting the AC3 to AAC 5.1 surround. Neither method would play the surround track in iTunes, in fact the AAC converted file was worse!

So, what is wrong? Why does the iTunes copy work, and the handbrake copy doesn't when both have AC3 5.1 48.000 mHZ audio? Is it the channel order? Is there a way to reorder the channels? This is driving me nuts!

[mike admin]

My guess is that Subler repackages AC3 track incorrectly. BTW, starting with 1.8.8 you can make a stereo AAC downmix right in MakeMKV.