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Apple devices: Best audio settings for my setup?

Posted: Sat May 19, 2012 7:57 pm
by i69
I want to encode movies and tv shows for use in iTunes, Apple TV (which is hooked up via HDMI to a surround sound A/V receiver), and other iOS devices. Besides surround sound for my 3rd gen Apple TV, I only use stereo on my Mac Pro/iPad 3/iPhone 4s, but I want to keep the surround sound track for those as well - you never know what kind of speaker tech they might come up with a few years from now. I use a Mac to encode.

I want the audio settings to be the closest to the original quality as possible while only using Handbrake for encoding. I also want to avoid having a lot of custom settings depending on the movie/tv show... I want to keep the settings as generic as possible, even if it means a little larger resulting file (but I don't want to be "stupid" about it either).

DVD: Typically when I open a DVD rip with AC3, and choose a preset such as the "AppleTV 2" one, it defaults the audio tracks to:

Track #1:
Codec: AAC (CoreAudio)
Mixdown: Dolby Pro Logic II
Samplerate: Auto
Bitrate: 160

Track#2:
Codec: AC3 Passthru
Mixdown: None (greyed out)
Samplerate: Auto (greyed out)
Bitrate: 448 (greyed out)

Track #1: The bitrate only affects the audio when Track #2 is not being automatically passed through to my receiver via the Apple TV, correct? That bitrate of 160 is for all the channels combined? e.g. 160/5 channels = 32kb/s per channel... so if I want the "best" sound for iTunes/iOS devices, I want to crank up that default setting all the way (e.g. 384), correct?

Track #2: The AC3 track is a bit for bit reproduction of the original rip, and is unaffected by the bitrate settings listed in Track #1, correct? Since it's passed through to my receiver for decoding via the Apple TV (just like if it was the actual DVD in my DVD player), this audio track doesn't suffer the problem of Track #1 (Dolby Pro Logic II) not being able to have a separate subwoofer channel, correct?

Blu-ray: Typically when I open a BR rip (MKV container) with DTS, and choose the same preset, it defaults the audio tracks to:

Track #1:
Codec: AAC (CoreAudio)
Mixdown: Dolby Pro Logic II
Samplerate: Auto
Bitrate: 160

Track#2:
Codec: AC3 (ffmpeg)
Mixdown: 6-channel discrete
Samplerate: Auto
Bitrate: 640

Track #1: (same as when ripping from DVD).

Track #2: Since the Apple TV doesn't support DTS passthrough, I understand that the DTS track needs to be encoded into something else and "mixed down". So with the settings indicated, is an AC3 passthrough track being created from the original DTS track? This is not related to the problem of 6-channel discrete AAC not being able to be sent over HDMI cables, correct? (since it's not AAC, but rather AC3 being passed through?)

If someone who understands this stuff better than I do can just let me know that I seem to have gotten it all right, that would be appreciated. Or please let me know if I'm misunderstanding something (please be specific :wink: ). Thanks for any help/explanations/clarifications!