O.k. I have a question. I want to convert 320 Kbps CBR mp3s into 128-320 Kbps VBR mp3s. How do I do that ???? Please help me ......

Try this for a lossless approach.

you can't

Edit: .. read the other posts first [/note to self]

Rip the CDs again, then encode to VBR.
DON'T transcode your MP3s.

Thats the problem, I lost my orignal cd; but I had encoded all the songs of that cd to 320 Kbps CBR mp3s. Now I want to make an mp3 cd and the 320 Kbps CBR mp3s take way too much space so i wanted to convert them into 128-320 Kbps VBR mp3s.

Isn't it o.k. if i simply decode the 320 Kbps CBR mp3s into waves and then encode them again into 128-320 Kbps VBR mp3s ???

And do all this using RazorLame...............

if that is the only option, there is nothing to discuss about. You should do some tests with LAME, to see what -V setting gets acceptable results for you.

If you decode to WAV and then encode back to MP3 you will lose all your tags (if you have any).

As always, I will suggest foobar for the job. Another alternative is dbPowerAmp.

LAME.EXE will accept MP3 as the source, but that too will lose the tags. If tags aren't an issue and you don't want to bother with foobar or dbPowerAmp it may be worth seeing if RazorLame is clever enough to realise that it can pass MP3s to LAME as well as WAVs.

I don't care about the tags, the song quality is what i care about......................

Well, you can use dBpowerAMP as suggested by Synthetic Soul. It uses LAME for MP3 encoding, so you should not have any problem with the quality (other than the issue of converting from a lossy source). It also passes the tags during transcoding from one format to another or in your case, from MP3 to MP3.

Foobar2000 also uses the LAME encoder and passes the tags when you are transcoding.
Use the following parameters to get MP3s ~130 kbps VBR when converting in Foobar2000:
-V 5 --vbr-new - %d

IMPORTANT: In both the cases above, choose a different directory or folder to save the transcoded files in!

If that's the case then you should just stick with your 320kbps mp3s . Trans/re-coding to VBR will result in a loss in quality, see here. It's possible that you won't notice this loss, though whether the loss is noticeable/acceptable is soley up to you and your own ears. You want to reduce file size without reducing quality, but unfortunately you can't have it both ways (unless perhaps you want to follow abasher's mp3 repacker suggestion).

Maybe ALL2LAME or Multi Frontend, with TAG.EXE set to "copy tags"... ?

Should be easy enough to set up — and then actually performing the job would be as easy as drag + drop + click "Go".

Why does this thread keep dragging on? abasher stated the only quality-wise acceptable approach (MP3packer) in post #2, the other ten posts are a waste of space.

It depends what the OP means by "128-320 VBR".

Using MP3packer is surely going to end up with MP3s well over 200kbps. I get the impression that he's really after -V5, not -V0.

Yeah Synthetic Soul's right..............

Razorlame will convert mp3 to mp3, but unless it has been updated recently, doesn't support the new -V presets except via custom commnand line options. Even so, Razorlame is easier to set up than Foobar or DBPoweramp, and I'm guessing simplicity is important here.

As to the wisdom of transcoding, I get acceptable results going from 320CBR to -V4 but the original source is FM broadcast, so there is no audio above 16khz to start with.

Maybe a program could be written, that would analyze the source hi-bitrate MP3 and would convert it to lower bitrate, but where the original high bitrate is needed to preserve transparency, it would not transcode the frame, but copy it straitghly to the new file.

This would be especially useful at files containing silence. The program would copy all the frames with music and replace the silent parts with 32 kbps frames. So the transcoded file would be perceptually lossless (compared to the source MP3, of course)

Is it possible?