First, you need an understanding of C6000 program cache and how it can affect performance. For that, please read the first part of this wiki article. You can stop when it starts discussing the cache layout tool clt6x. Whether you decide to use that tool has nothing to do with understanding this link command file.
This link command file is carefully tailored to place functions in this implementation of H264 so that they minimize conflicts in the program cache. If you somehow change the relative location of these functions, performance of the code could get much worse because of cycles lost to cache conflicts.
Thanks and regards,
-George