good night as configuration when converting a mkv file that I left with audio aac fdk as I get it :-\
AAC (FDK), AAC (Faac) and AAC (lav) are different encoders for one and the same thing: for the AAC codec. Just it happens that the aac-fdk encoder can potentially output AAC with some extensions other AAC encoders don't use (these features are not enabled in the AAC (FDK) configuration in Avidemux).
Please post the output of MediaInfo for the MKV file you are speaking about.
sale to configure it but the output file is not audio AAC FDK
The output audio track is AAC LC, which can be produced by AAC FDK or any other AAC encoder. Do you want HE-AAC? In this case you would need ffmpeg as Avidemux doesn't request HE-AAC from AAC (FDK) encoder.
Again, "AAC FDK" is an encoder, not a variety of AAC compression format.