change aspect ratio in mp4box saves a few megs?

[silverwolf0]

Sometimes I forget to change the aspect ratio when encoding an x264 mp4 file in avidemux and use mp4box to set the aspect ratio, which creates a new file. For some reason, the output file always ends up 2-3 megs smaller. Is it removing anything important? Maybe mp4box is more efficient and cutting excess fat? I would think the filesize is already as small as it can get...

[Baldrick]

2-3 megs smaller on a 1GB file or 10mb file or?

It's probably just some different mp4 overhead data.