Some operations can modify Mp3 audio files if the free FFmpeg package has been installed on your computer.
ffmpeg.exe is an open source free GNU commandline tool to convert and modify media files (video, audio, images).
Disclaimer
FFmpeg is no part and no property of GNMIDI product. GNMIDI only calls ffmpeg.exe if a user has installed the package self.
FFmpeg is a trademark of Fabrice Bellard the initiator of the FFmpeg project ( https://www.ffmpeg.org )
Download and Installation
Windows 32 bit (also works in Windows 64 bit systems)
Hint: On a Windows computer you can find out if your processor is 64 bit or 32 bit by pressing the key combination WINDOWSLOGO+Pause.
Unzip the zip file using file explorer (or your favorite unzip tool) into a new folder. Make sure that the folders contained in the zip archive are created (ffmpeg\bin).
Start GNMIDI and open a mp3 file and choose one of the available operations (e.g. check file, copy part, fade in, volume) that are enabled in the menus. GNMIDI will tell about required FFmpeg package installation and ask you to select the ffmpeg.exe file with a open file dialog. It should be in the folder where you have unzipped the package inside the ffmpeg\bin sub folder.
After checking if this is a usable FFmpeg version the operation starts.
Flickering
Every time when ffmpeg.exe is started a new (black) commandline window will be visible. Momentarily this cannot be suppressed by GNMIDI.
Speed
Analysing and modifying *.mp3 files costs more time than modifying MIDI files.
mp3 does not store the exact song duration in a header so sometimes it requires to read a file twice (first analyse the file and then modify the file).
Hint: GNMIDI mp3 operations do not overwrite your file. Single conversion creates a temporary result file and batch operation creates results in a result folder.
Hint: do not overwrite your original files without keeping a backup of the original file.
Lyrics in mp3 files
FFmpeg for unknown reasons does not keep the important lyrics contained in an mp3 song (ID3 USLT, SYLT, Lyrics3). GNMIDI tries to copy the original lyrics from input file after using ffmpeg.exe
Problems during conversions
GNMIDI can only use the results of ffmpeg.exe when modifying a mp3 file. If FFmpeg fails for any reason or produces something that is not optimal then GNMIDI cannot create something better.
gnmediahelper
See our product gnmediahelper that helps (batch-) converting or modifying video, audio, images using FFmpeg.