mpTrim and WavTrim

mpTrim FAQ

Q: How does mpTrim clean MP3s? A: Most MP3s contain some 'junk'. So mpTrim parses the files looking for MPEG-audio frames and discards the rest... you end up with an absolutely clean MP3 containing only MPEG-audio frames (and eventually an ID3 tag). mpTrim has a little indicator on how much space you'll recover when saving an MP3. Check below the 'from the end' sentence in mpTrim main window.

Q: Does mpTrim support VBR files? A: Absolutely. Note that VBR MP3s usually have extra 'seek information' embedded in them. mpTrim displays 'VBR+' when seek information is present, and 'VBR' (no plus) when it's missing. Seek information is used when you 'seek' (move) directly to some point of an MP3. Seek information isn't part of the MPEG standard, doesn't affect the music quality and is not useful for a continuous playback. But some players time display may be confused if it's not present.

Q: What is 'digital silence'? A: Digital silence is a bunch of samples set artificially to 0 (silence!) to separate music tracks on CDs. It can easily make its way in MP3s at the beginning or at the end as a little bit of 'dead-zone'. One nice feature of mpTrim is that it is automatically able to recognize the silence in most MP3s. Who wants to store silence? Let's keep only the music.

Q: What's the biggest file size that mpTrim can handle? A: mpTrim file size support is not expressed in raw byte size but in number of MPEG frames. That makes the assertion of the limit a little more difficult. But for MPEG 1 layer III at 44.1kHz (MP3s made from Audio-CDs and usually in this format), mpTrim reads up to 7 minutes of music, so should be able to process most music tracks.
The 'Advanced info' dialog box in mpTrim shows the MPEG frame usage. For additional file size support, please consider registering mpTrim PE or mpTrim PRO.

Q: What is aggressive trimming? A: mpTrim was originally created to trim only the 'digital' silence that is sometimes found in MP3s made from Audio-CDs (because of the silence that exists to separate the tracks in Audio-CDs). Unfortunately, some MP3s also contain faint noise, or 'analog' silence. 'Aggressive trimming' is a feature that allows the removal of these near silent parts automatically. Please use it with care, since it might also erase a little bit of music on MP3s with soft beginning or end. Always preview (using mpTrim's preview buttons) the trimmed part, to make sure that nothing but silence is discarded.

Q: What happens if I over-amplify an MP3 so that it sounds distorted? A: You can get back to your original file if you decrease the volume by the same amount. Over-amplifying a WAV file is usually irreversible, but not for an MP3. The reason lies in the nature of the MP3 format. Simply put, the MP3 format describes a music waveform by a succession of coefficients. Increasing the coefficients too much would force an MP3 decoder (i.e. MP3 player) to clip its output and create distortion. But only the decoded output is distorted, so decreasing the MP3 coefficients by the same amount would restore the original non-distorded MP3 file! In the case of a PCM WAV file, since the waveform is stored 'decoded', increasing the volume too much would force some samples to be clipped, and a decrease in volume would not allow to restore them.

Here's more feedback and questions we got from users over the years.

From: "Joe"
Subject: mpTrim 1.85a

Hi This sounds like a great tool. How do I find out how to use it correctly? I downloaded it and I open it and open an MP3 file into it. A progress bar goes across the top and then there are some settings you can change but at this point I don't know what to do or how to correctly diagnose the MP3 file and perform all the tests it can perform. Can you help? .Thanks. JOE

to diagnose an mp3
1. if a warning message comes up with "missing frame headers", that means the mp3 is corrupted
2. you can go into the "advanced info" window to see what's going on. In particular the last tab shows where are the missing frame headers, if any.
From: "Roy"
Subject: Re: mpTrim Personal Edition 1.85a

Thank you for your kind renewal offer which I will gladly accept since "mptrim" is absolutely indispensable!
I use it all the time, and on my earlier purchase, was greatly impressed with your update service.
One suggestion - unless the new version has improved the feature - I find the "fade in" and "fade out" control difficult, if not impossible, to adjust for a "very gradual fade" which is very desirable for those mp3's one wants to keep but that have a drastic unplanned cut-off.
I try to find a suitable end of a music "bridge" and fade out at that point but your "fade out" parameter on version 1.77a is too steep - unless I have overlooked something in your program.
Kind regards


there is now 2 sliding bars to control the length of the fade. The depth of the fade is also controlable through a drop-down box in Options/Volume.
From: "margarita"
Subject: Re: purchase of mp3 Trim Pro

I had purchased mp3 Trim Personal Edition sometime earlier this year (the BEST investment in music software for me, as it works in an excellent fashion...kudos to you). I am interested in purchasing mp3 Trim Pro. My question is, if I purchase the Pro edition, having already purchased the Personal Edition, is there a discount price of some sort (as is the case with upgrades for certain software)? Or, is this not considered an upgrade and is instead, a completely separate purchase? Additionally, the address I provided at the time of purchase (registration) is now different. How do I change that information in my software, and is it necessary to change it? Please let me know at your convenience. Thanks.

You can upgrade for the price difference.
About the email address change, just let me know through email.
From: "Ken"
Subject: Re: mpTrim Personal Edition1.81

I have read the FAQetc and looked for as much information as I could find.
Is there an instruction manual so you could get "more" out of your program.
I am one of the few that actually rtfm! :)
I have the PE1.81.
One question woudl be
How to properly use the volume control....what does auto on volume control do.
I read the FAQ page etc.

Thanks again for great program.
It is working perfectly.


there is no manual yet... or I'm it! I guess I should write one though.

The 'auto' calculates the normalized volume value. It helps getting the track that were encoded with a low value in line with others.
To use it:
1. open an mp3
2. push on the 'auto' button in the volume panel
3. after a few seconds, the volume bar moves to a new position, to indicate the value mpTrim thinks is best for normalization.
4. click 'save'
From: "Mike"
Subject: Re: New release 1.80 of MptrimPro.

If I remove the missing header frames, what happens to the file quality?



If you remove the missing frame headers... it's usually better, but not always. It depends of your mp3 player and the type of corruption that was in the mp3. Missing frame headers means that the file is somehow corrupted (usually a bad transfer over the net), so there is no way to fix it at 100%. If you encounter such file, the easiest is to throw it away. If you want to keep it, mpTrim tells you where in the mp3 the missing frame headers occur, so you can check with a player that there is no loud 'pops' at these positions. You can also check both fixed and non-fixed files, depending on how much effort you want to put into recovering the file...
From: "Mike"
Subject: Re: MPtrimPE 1.77

What are the buttons to the right of the beginning and ending playback buttons for? It says to 'Update Winamp playback position." Yet, I have not found what they do.



the 'W' buttons work in conjunction with WinAmp.
1. load an mp3 into mpTrim
2. play the same mp3 with WinAmp (needs to be version 2+, doesn't seem to work with the latest WinAmp 3.00+)
3. the 'W's become active. You can click them to update the trimming points.
Play with them, that should become more obvious.
From: "Stevo"
Subject: About your program

Hi, just wanted to praise you. The program is great!!
I have a question, though.
How does the program fix corrupted mp3's? Do I have to set something up, or it just does it automatically, so, I just have to save an mp3 as trimmed, right?

Kind regards

mpTrim doesn't really 'fix' MP3s, but cleans them up from the non-MPEG data. Just opening and saving an MP3 will do the job, as long as the 'cleanup the MP3' option is checked. But if an MP3 was originaly corrupted, no mystery there, cleaning will probably help but you should double-check the result!
From: "George"
Subject: Re: mpTrim PRO 1.75


Thanks for your help.

Things are working fine. I have now processed more than 1000 files with excellent results.

Perhaps in the future you could add some way to do batch processing using just the keyboard. I can see, but I don't know how a blind person could ever use this program in batch mode as it is now designed. If you are blind, using a mouse to drag and drop is an impossible task.

The blind are very heavy users of computers and mp3 technology, so this is not an abstract issue.

Also, a page or two of written instructions might reduce the amount of "hand holding" you have to do with new users like myself.

Again, thanks for your prompt replies and help. And thanks for making a good product. Getting all this functionality in a 200k binary is an impressive achievement.

Best regards,

Done starting from mpTrim PRO 1.77a: allows to open multiple files using the file-open dialog. Also I now include a file dedicated to mpTrim PRO special operation within its distribution.
From: "Chris F."
Subject: MPtrim

Had it for a few weeks - it's brilliant! My MP3 collection is so much more tidier now. 1 thing though - could there be a speed thing to change the speed of the MP3? I find I prefer certain songs to be faster or slower (Nancy Boy by Placebo seems to be too slow in my opinion, so it would be great if it could be sped up about 5%)


I'd love to add this functionality, but so far it eluded me (i.e. it's hard to do without re-encoding the files).
From: "Paolo B."
Subject: mpTrim 1.55

Dear sirs,
I find your software (MPTrim) is the most convenient, easy to use and useful utility for its purposes. I regularly use it on my mp3 files before burning them into a CD. Now the question: is there any chance you'll release a version that allows to handle files whose size exceeds 10 MB? This would be extremely useful, since many songs encoded with a very good quality bitrate (192) are definitely bigger. Leaving a gap during a long "suite" made up from two consecutive songs.
I'll appreciate an answer from you.

Thanks anyway

Please take a look to mpTrim PE and mpTrim PRO!