I am a newbie for audio editing, so this is probably a very stupid question. I read the guide to command line options of Lame, but to my surpise, there are only some downmix options, so is there any ways to upmix two mono MP3 files(with same length, format and bit rate) into one stereo file?

Thanks for any suggestions.

hmm, i doubt there's a way to do this losslessly

sure there is...

if you are on linux there is a cli program called "combine-wave" that ONLY does this (join mono files to stereo).

i'm sure there are a bunch of others, and i imagine any decent audio editing software will do this (audacity, etc.)


later

I don't think thats going to work on an MP3. It'd take a lot of effort to get the two streams together, and if any frames were large enough, it'd probably be impossible due to bitrate limitations.

If it makes any sense for the two files to be together to produce a stereo image, it will be easy to work with them, once decoded, in any audio editor.

... but reprise was talking about combining 2 mono MP3 files into one stereo MP3. Without re-encoding if I understood him correctly

but while it is an easy, everyday operation, in any audio editor, none of which, of course, work with mp3, has anyone else even contemplated such an overall waste of time as trying to make something like that function with mp3s?

It's been a long time since I dealt with the internals of audio codecs and I am not sure if I ever looked at this aspect, but how exactly is stereo information saved inside an MP3 file? I know that depending on the mode, you have simple stereo, dual channel and joint stereo with its various modes, but AFAIK, Wave saves the data as RLRLRL... How is this done in MP3?

I am not sure how easy it would be to write such a program because you would probably have to change the bitreservoir and the pointers to it in every frame.

I guess, the -join function of beSplit beta could be the answer here. It is known to merge mono files into a stereo or multichannel file. It will also work with MP3 files. But whether or not it makes sense with mono MP3's and that you get some sound instead of noise out of the joining process? You need to try....

You need to provide an <input.lst> file with the two mono files added as input to that file...