You are entirely right except for the second point.
A GPL code cannot be integrated (even by linkage) to a non-GPL application.
An LGPL code can be linked to any other code but the changes to the actual
LGPL code must be under this same LGPL license. This make sense when making a
library that already exists in the proprietary/permissive world: it cannot be
turned proprietary (copyleft) although its adoption is maximized (including
by proprietary software that would have otherwise used the equivalent
proprietary/permissive library).
If the library includes novel features, then the GNU GPL makes more sense
(people who want to use those features will either have to release their
applications under the GPL or they will have to redo all developments).
Now, you are talking about codecs. Assuming competing proprietary formats
exist, it is a particular area where the promotion of a free format matters
more than the code. In this particular case, permissive licensing makes sense
(you actually want proprietary software to adopt the free format).
