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Old 10th June 2010, 23:18   #9  |  Link
Nick
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Join Date: Mar 2002
Location: Heart of the Broad Acres
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OK. Well, with Aften, sox and ffmpeg installed from my distro's repositories, the following seem to work:
If your audio is already demuxed to an ac3 file, just use this as ffmpeg's input

Code:
ffmpeg -i /path/to/capture.avi -f sox - | sox -p -t wav -r 48000 - tempo 0.96 | aften -b 224 -readtoeof 1 - output.ac3 ####(slow down retaining pitch) or
 
ffmpeg -i /path/to/capture.avi -f sox - | sox -p -t wav -r 48000 - speed 0.96 | aften -b 224 -readtoeof 1 - output.ac3 ####(slow down with lowering of pitch)
From the sox manual, it says for most uses, tempo seems to be better than stretch, so I've used that.

<edit>only tested with stereo source - may or may not need minor modification for 5.1</edit>

Last edited by Nick; 10th June 2010 at 23:25.
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