Okay, after reading the code, it seems to me that the generator, which is fed with audio data, has some smarts to accept various audio content according to the frame type. Thus, I suspect that it's acceptable for the generator in some cases, e.g. audio of type `1+'a`, to have audio layout change on the fly, in which case we don't need to check for the number of channels reported by the decoder and just let the generator handle the situation. 

@dbaelde should be able to confirm if I'm on crack or what.. ^^