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Old 31st July 2011, 15:41   #7  |  Link
sneaker_ger
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Join Date: Dec 2002
Posts: 5,565
Very interesting topic you brought up. I'm by no means an expert on audio topics, but I made a very small test:

I created three aac files of a 90 seconds stereo music file using neroaacenc 1.5.4.
1.) just stereo, i.e. two channels
2.) a 5.1 file, with the stereo on front left and front right channels, all other channels (center, LFE, surround) digital silence
3.) a 5.1 file, with the stereo on front and surround left and front and surround right, other channels (center, LFE) digital silence

File sizes:
1.) 1.46 MB
2.) 1.54 MB
3.) 2.94 MB

Sample 3 has almost exactly double the size of sample 1. It seems that neroaacenc doesn't do any "coupling" between front and surround channels, so that would confirm your assumption. I have no idea why sample 2 has more "overhead" from the silent channels, than sample 3.
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