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.