I managed to change my code from using the dual thread codec to the AAC decoder directly. This gives me acces to the AudioData class which in turn gives me the number of channels and the sample rate for the AAC content. However, I am still not clear how frames and channels are associated. Are there multiple channels in a single frame? Is there a single channel in a single frame? If the former, how does one isolate the channels? If the latter, how does one determine which channel a given frame is associated with?
Frames and channels aren't associated in any way. A single frame can contain multiple channels. Inoutput file channels are mixed and are one after another. If you want to create aoutput file in a linear PCM monomay be better to take anarithmetic mean value on all channels and to write down in a file for example.