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  1. In StaxRip there is a setting to convert ac3 5.1 demuxed from dvd, to aac 2.0, and it's called "Stereo downmix". It has 3 options:

    1. Simple
    2. Surround
    3. Surround 2

    I have no idea wich one to select, but by default, option 2 called "Surround" is selected. What is the difference between surround and surround 2 ? Should I select surround 2 instead ?

    When I decode ac3 5.1 to wav using headac3he, by default "Surround 2" option is selected, under "Downmix type". But if I change it to "Surround" like I saw in StaxRip's default settings, the volume is considerably lower that the wav decoded with "Surround 2" option. I'm confused...
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  2. on wikipedia it doesn't tell the difference between "surround" and "surround 2". It just says that "dolby surround" is a encoding method, and that "dolby pro logic" is a decoding technology.

    I just want to know what to choose when downmixing ac3 5.1 to aac 2.0. But for this, I have to know the difference between "surround" and "surround 2". Does surround 2 do something extra that I don't need ? Or "surround 2" method is made for Dolby Pro Logic II decoder ?
    Last edited by codemaster; 19th Mar 2011 at 20:59.
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  3. Member netmask56's Avatar
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    2.1 Channel Home Theater System is like a stereo system for home theater sound. A 2.1 Channel system uses two stereo speakers and a subwoofer to play TV sound, movies and music compared to a 5.1 channel surround sound system that uses left and right stereo speakers but adds two rear surround channel speakers and a center channel speaker for a total of 5 main speakers plus a subwoofer. A 2.1 channel home theater system is a great way to enjoy movies and music without the need for surround and center channel speakers and the clutter of additional wires. 2.1 channel sound is also a giant step up from the sound produced by the small speakers built into most televisions.

    http://stereos.about.com/od/buyingastereo/a/2point1Channel.htm

    The point 1 merely refers to using a subwoofer and the signal from the left and right channels are summed together and everything above around 120 Hz is attenuated leaving just the low bass energy that is fed to a sub woofer/amplifier combo
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  4. Originally Posted by codemaster View Post
    on wikipedia it doesn't tell the difference between "surround" and "surround 2".
    It shows the difference between Dolby Prologic and Prologic II, I assume that corresponds to Surround and Surround 2 in Staxrip. Basically, Dolby Prologic encodes only four channels, front left, front right, center, and rear. Prologic II encodes five channels front left, front right, center, rear left and rear right.
    Last edited by jagabo; 19th Mar 2011 at 22:33.
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  5. what does "1. Simple" stands for?

    i want to keep audio channels as original [Surround to Surround /Stereo to Stereo / Mono to Mono]
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  6. I don't use Staxrip but since the option is in the downmix section , "simple" means plain stereo. If you want to retain the original audio don't downmix.
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  7. Member budwzr's Avatar
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    Use audacity with the AC-3 plugin, free.
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