Hello,

I wonder if it is any bad to cut mp3 files, in terms of quality etc. ...there are 2 main reasons why I sometimes do it (using mp3Trim).

1.) There is a 3 second pause after the track has finished (Mp3Trim finds it automatically and also how much can be cut)
2.) There is a song which ending I don't like...so I fade it out earlier or cut it (also using mp3Trim)

So what do you guys think, shouldn't I do this 'trimming' or is it fine?

As long as this is for your own use, do whatever you want with MP3Trim. The only "quality" issues will be the loss of information in the bit reservoir for the relevant few frames of audio, but in a compliant player this shouldn't cause any problems. Other than that, the unmodified portions of your MP3 will be bit-identical with the original. (The MAD plugin for Winamp will probably show something like "Errors" > "Other" > "x" under the "Statistics" tab, but all this seems to imply is that the last frame - or first, if that's where the edit took place - is incomplete. If this still sounds good to you, have fun.)

- M.

I don't think that there will be a bad last frame...Mp3Trim shows when there is a bad last frame or when the last frame is missing at all...but in either case Mp3Trim is able to fix that bad frame (some files I downloaded of the Internet have such issues as well)...so after trimming a file there shouldn't be any problem like that...not even EncSpot says that there is a 'bad frame'...


I don't really understand what you mean by that, so could you please give some further information? Thanks

Sorry... not the same as a "bad last frame"; the "error" some players might identify is strictly related to the bit reservoir problem I mentioned (and this is not something MP3Trim can fix!).

Briefly: The bit reservoir is a way for MP3 frames to contain more information than would be possible if the data were restricted to the actual frame length. That is, a 128 kbps MP3 using the bit reservoir might have frames which are effectively much longer... because the bit reservoir tells the player "this extra data belongs with that last frame/series of frames." So if you truncate an MP3 - even though you have cut the file on a frame boundary - that little bit of extra data which belongs with the preceding frame will be lost.

Most of the time this won't matter, if you are cutting in a silent section, of fading the ends of the file. What is lost is generally inaudible, or at least not as important (given that you probably aren't paying that much attention to the quality of a short section, if it is silent/near silent). But technically, it means some of the data that the player expected is missing, and therefore it is perceived as an error.

Again, most players will ignore this and play the files without any difficulty. (MAD will simply report that an error was present, but will play the file anyway; Winamp ignores it and plays the file; foobar 2000 ignores it and plays the file; iRiver style players ignore it and play the file...)

- M.

Ok, I asked the author of mp3Trim about that...this is what he answered:



So according to that there won't be any quality issue or something

I use mp3trim a lot and never had any problem. Especially the "VBR header repair" feature is great when you obtain VBR mp3s from ppl that screwed it up at encoding. It also kicks off any weird tags (id3v2) and junk that can cause problems on some players.
Cutting is also safe, it creates a valid last frame for the saved file and adjusts the header if it is a VBR file.

I've used mp3Trim and, taking the next step, have decoded to wav for burning to audio CDs. The CD turns out fine, no issues related to the fade or trimming. This is a great tool for annoying problems, particularly with hard-to-find tracks.

If you download files then trim them, it screws up programmes like Winmx a little.

For instance, a file being traded by four people would not increase to 5 if it is trimmed.

If you are not sharing these files, obviously there is no problem.