Do not mind, I have found an "old" m2ts sample with 2 audio tracks and FFMpegSource does not seem to like this kind of container.
A workaround is needed. I will think about it. Thanks for the input and any suggestion (from anybody) is welcomed.
BTW you can extract the video/audio stream you wish processing your m2ts file with TsRemux and then feed AVStoDVD with the elementary streams.
Bye