I have about 80GB of MP3 files that I ripped from my CD collection with --alt-preset extreme. They are all properly tagged with ID3v1 and v2 (since v1 artist/album/song name tags are too short -- no lyrics, jpgs or anything like that) tags. I need to resample the entire collection down to a lower bitrate for use with portable players (namely a 20GB iPod) and normalize them.

What's the best way to go about doing this? I've read the info/FAQ on mp3gain, but it's not clear to me if I need to normalize before resampling or not (will be using lame 3.96.1 to resample). From my reading, it appears that I can add additional tracks/albums and normalize them separately from the rest of the album and they'll still have the same "volume", correct?

Any suggestions on lame options to use? I've done some testing with --preset standard -Y and it appears to average at 180-190 kbps, which is a good bit higher than the 160 kbps I was expecting (and is in the FAQ).

I would vastly prefer Linux tools, since all the MP3s are on a Linux server (FC2 if it matters), but I can shuffle the data across the network if needed.

And yes, I know that lame won't copy the ID3 tags. I've already written a program that does that for both ID3v1 and v2... I can extend it to do APEv2 as well, since the tag is pretty simple. If anyone wants the source, I can post it/email it. It's pretty trivial.

If you're going to copy all tags including *APE* tags, you have 2 solutions.

1. If you're interested in keeping the replaygain info on your original (rather than only process the low bitrate copies) :
- launch mp3gain on your originals
like :
mp3gain *.mp3
inside each album's directory. (make sure the files you run it on in one call really are an album, since it will compute the REPLAYGAIN_ALBUM_GAIN value. if it is not one album, call mp3gain separately on each file so it will only make the REPLAYGAIN_TRACK_GAIN tag and no incorrect album gain)
-make your low bitrate copies and clone all tags to them from the originals, including APE tags (that's where mp3gain stored the result of the processing)
-on all the low bitrate copies, do :
for f in *.mp3; do mp3gain -r "$f"; done
(don't pass several files in one call, mp3gain would assume it needs to recompute the album gain)

This final step applies the track gain directly to the mp3 data, so it will effectively make all your files play at the same level on your iPod.
(it uses the stored gain tag, so it's pretty fast)

2. you only care about replaygain on the copies
-make your low bitrate copies, and just do the final step of the previous case


Note that if you computed album gains, you might wish to apply those rather than track gains.
if so the last step would be :
for f in *.mp3; do mp3gain -a "$f"; done
But for mobile playback, I think track gain is more useful.
(anyway you can switch from one to the other by re-applying mp3gain with the corresponding option)

btw, you can't "resample" mp3's. I think what you're looking for is called transcoding.

--preset medium

--preset fast medium

--preset 160