When I inspect some *.mp4 video (with AVC H.264 and AAC codecs) with well known MediaInfo tool then there are two similar values (see attached snapshot):
One bitrate for MPEG-4 (Base Media): In sample 19,7 MiB
One bitrate for (first) video stream): In sample 5907 kbps
Whats the difference?
Sometimes I saw MPEG-4 (Base Media) bitrates with more that 200 MiB (!) which is blowing up a 3 minutes video up to 250 MB file size.
When I re-encode such a video in Avidemux (with H.264 and AAC): How can I reduce the MPEG-4 (Base Media) value?
Lowering the video bitrate does not help (much).
The original file (before first encoding is a *.m4v video file (=old Flash Video) if this helps
Waves MediaInfo.png
The 19.7 MiB is the size of the file (equals to 20.6 MB)
The 5907 kbps is the bitrate of the video stream