This is a simple command-line program that modifies the box (atom) structure of
an .m4a (MPEG-4) file while ensuring that it's still a valid file. The tool
removes all "meta" boxes from the file, and updates the size of any enclosing
boxes, as well as any offsets that are based on the absolute file size.

To use the file, specify the name of an input file, and the name of the desired
output file. There are no other options.

The tool will show you the original tree structure, but only shows the portions
of the tree that are relavant to the changes. Container boxes which have a
substructure that will not contain "meta" boxes or boxes tracking offsets will
not be shown in detail.

Then, the tool will modify the box tree, removing all "meta" boxes, and updating
any relevant offsets. The modified tree is displayed for visual verification,
and then it is written out to the provided output file name using MPEG-4 layout.

This simple tool does not support large containers that might contain boxes
larger than 2^32 bytes, or chunk offsets large than 2^32. However, it could be
trivially modified to support such files.

For a quick example, just run 

make test