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i got 2 mp3 files, one for left and one for right audio channel and would like to merge them to one single stereo mp3, preferably without the need to re-encode them . From what i read joint-stereo mode is a way to go, but i cant find a tool to do so.

How can i achieve this?

(I could just trow them into Audacity but the files are already 96kbps, don't want hurt the quality even more)

EDIT: i have Windows 7 on my PC, Ubuntu and Xp in a virtual machine and access to a MAC OSX Tiger, so any tool for any platform is fine (except Lion-and-up-only application)

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Please always include your OS. Solutions very often are dependent on the Operating System being used. Are you using Windows, Linux, Unix, OSX, BSD? Which version? – terdon Feb 6 '13 at 19:09
If anything, joint stereo is NOT what you want - joint stereo shares audio data between channels so by definition implies a re-encoding. Standard stereo channels are independent, thus more likely to be joinable without re-encoding. – mtone Feb 7 '13 at 2:30
Can't find a way to do this with ffmpeg. You can join channels from 2 different streams (using -filter_complex "amerge"), but you can't do it without re-encoding. I tried with -acodec copy and got the error "Filtering and streamcopy cannot be used together." – Luke Feb 7 '13 at 4:07

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