AACX or AAC eXaminer is an AAC frame analysis tool inspired by LAME's mp3x. The program is still in its very early stages and is not yet complete. It requires a PCM decoded copy of the stream and a custom format log file. A patch to modify FFmpeg into generating the log file is included with the program.
AACX does not yet support stereo or surround streams. The interface is still very ugly. The coding style is also pretty ugly. Still the program has passed the threshold where it may be useful to others so I'm making the source public under the GPLv2 (or at your option any later version).