Don't know what your encoder is, but in general 192kbps MP3 sounds transparent to me for day-to-day purposes. Others will tell you differently. I suppose there is a CODEC bad enough to be problematic with normal music at 192 kbps or to someone with absolutely superior hearing (much more rare than you might expect, BTW), but that's not me.
Generally you might well lose sound quality by transcoding from 192 kbps MP3 to 128 WMA. Transcoding is generally risky in terms of sound quality.
You could re-rip if you have the original CDs. Unless you are short of space I wouldn't see much point in it. Since 192 kbps MP3 is generally transparent to me, for example, I have nothing to gain in terms of sound quality by re-ripping in any other CODEC at a lower bitrate. MP3 is very universal, so that's what I use, at a bitrate that generally sounds transparent to me.
For some hard-nosed objective data go to hydrogen audio. You may need to work your way up the learning curve before you can use the information there. That's up to you. It takes some work.
wxrkny said:
Most of my music collection is in mp3 format 192kbps. I've read that WMA produces much better sound than mp3 at the same bitrate. Would I lose a lot of quality by re-encoding the mp3's at 128 WMA? The reason I am doing this is to put more songs on my mp3 player which is compatible with both mp3 and WMA. Is re-encoding just a bad idea in general or is it ok if done properly? Thanks in advance for any help.