User:PeterSampson/Sand-Box

All MP3 exports are lossy

Every MP3 export reduces the quality of the original file because Audacity does not edit the file directly. Instead, Audacity decompresses the MP3 upon import to lossless PCM. This does not undo the audio losses caused by the original MP3 compression, but it enables more complex edits such as equalisation and other signal filtering to be made.

Having been decompressed, the MP3 therefore has to be re-encoded as a new compressed MP3 when exporting. The lower the bit rate exported at, the more quality will be lost with that re-encoding.

If you only want to do simple cut, copy, paste, fade and volume edits to your MP3 files, you can do so without audio losses in other tools that can edit MP3 directly without decompressing and re-encoding. Examples are:

• MP3DirectCut for Windows (this can also be run on Linux under WINE)
  • MP3 DirectCut can also direct edit raw AAC files (except for volume adjustment). M4A files must be extracted to raw AAC.
• Audion for Mac OS 8, OS 9 and OS X 10.0 to 10.5 (PPC only)
• Macsome for OS X (Intel Mac only). It can perform lossless split, trim, cut and volume adjustments on M4A files as well as MP3.
• mp3splt - Cross-Platform tool for splitting MP3, OGG and FLAC files. It can split files by silence detection or by time point (it can accept an Audacity Label Track.txt file as input). It does not perform volume adjustments. Direct Windows and Mac download links:
  • Windows: interface version or command-line version
  • Mac packages: MacPorts interface or command-line, Fink interface or command-line

• mp3wrap - Cross-Platform command-line only tool for joining MP3 files.

MP3 files of the same bit rate, sample rate, number of channels and stereo encoding mode can be typically be joined non-destructively with any of the above tools without the need for lossy re-encoding.