How to shrink MP3 files when transferring to Rockbox ?

[pacman]

I have a bunch of MP3 files that are large because they were ripped or recorded at the maximum quality setting (320 bits per something). I want to transfer some of them to my Sansa Zip Clip for use in a noisy gym or street jogging where the ambient noise level makes the sound quality less important. I want to keep the original files at their original quality. Is there a batch processing utility which will transfer the files to my Zip Clip in a lower quality (i.e. more compressed or re-sampled to a smaller file size) ?

[saratoga]

foobar2000, dbpoweramp, etc

Check google, theres a lot of programs that can do this. 

[pacman]

Thanks for this. I had already checked Google etc. but was probably using the wrong search arguments. I tried "convert" and "converters" but that gets me utilities which, as far as I can see, convert from MP3 to WAV or FLAC or some other format. I want to stay with MP3 but simply reduce the quality. I'll look at the ones you mention.

[silvertree]

I would suspect any so called converter also recodes to the same format as the source.

It all depends on your work flow and the frequency of the conversion requirements.

Foobar2000 works great for me but it is quite a few steps to set it up.  The LAME MP3 encoder is required and not included.

Winamp has an helpful interface but will only transcode to MP3 in the registered version.

Winamp is the most elegant solution but I don't use it.

Nero Burning ROM used to have a transcoder built into.  I remember it being quite helpful.

The internet talks very fondly of DBPoweramp.  Never used it myself but I bet it works.

[toehser]

I think usually it is called transcoding or re-encoding.  I think I  used ffmpeg.  Never used it on Windows, but it exists there.

[pacman]

Thanks, everybody, for these replies.

I think I have found the solution. Media Monkey has a Convert function which is under Tools (but is not mentioned in the Help function) and which, as far as I can see, can "convert" a file to the same format but lower quality (i.e. it shrinks or compresses the file further). I write "I think...." because I'll need to test it a bit to make sure it is doing what I think it is.