I’m using Audacity to edit audio from MP4’s.
I can open the AAC audio directly from the MP4, or after extracting the audio from the MP4 file. Which ever method I use, when exported there is a small additional amount of silent audio at the start of the file. This happens if I export directly, even without editing. I 'm using the FFmpeg plugin for AAC & AC3 import and export which works well apart from this minor issue.
There is less than a second silence added (and less at the end which is of no concern). The same happens with AC3 export but less so. I can work around it but does anyone know why this might be happening.