Using FFmpeg's (libavformat) RTP data structures via dynamic linking

Question

I want to use the RTP data structures (e.g. RTPMuxContext in libavformat/rtpenc.h) provided by FFmpeg's libavformat however they don't seem to be available with the following install:

ffmpeg version 0.8.2.git, Copyright (c) 2000-2011 the FFmpeg developers
  built on Sep 14 2011 16:04:33 with gcc 4.2.1 (Apple Inc. build 5666) (dot 3)
  configuration: --enable-shared --disable-mmx --arch=x86_64
  libavutil    51. 16. 0 / 51. 16. 0
  libavcodec   53. 14. 0 / 53. 14. 0
  libavformat  53. 12. 0 / 53. 12. 0
  libavdevice  53.  3. 0 / 53.  3. 0
  libavfilter   2. 40. 0 /  2. 40. 0
  libswscale    2.  1. 0 /  2.  1. 0

When I look in /usr/local/include, I see the libavformat directory however only a few files are there: avformat.h, avio.h, and version.h. Of course, when I try to include libavformat/rtpenc.h I get "error: libavformat/rtpenc.h: No such file or directory"

I'd like to achieve this by dynamic linking to the FFmpeg libraries (for LGPL compliance, among other reasons), but it doesn't seem to be possible.

Is there a parameter for the configure script that I'm missing, or a post-installation step that I've neglected?