MKV to AAC Converter
The MKV to AAC Converter is currently the best MKV to AAC Converting Program which could help you convert MKV files to AAC format at a high speed and in great quality!
A wide range of video and audio formats are supported, such as, MPG, MPEG, MPEG2, SWF, FLV, VOB, MOD, MP4, H.264, M4V, AVI, WMV, 3GP, 3GPP, MOV, DivX, XviD, Quciktime Video, DV, MPV, M4A, MP3, AC3, WMA, WAV, OGG, AU, Nut, AIFF, ect.
More functions are supported too, like trimming segments of the files, preview before converted, shut down the computer after conversion done... Try to find more about it!
Screenshot:

Several steps to convert MKV files to AAC.
Step 1: Download the MKV to AAC Converter, run it.
Step 2: Click the button "Add File" to import MKV videos.
Step 3: Select AAC as its output format, then choose a place to store the export file.

Step 4: Press the the button
to start trim window, in which you can extract segments by setting the values of Start Time, End Time and Select Length.

Step 5: Click the button
to start converting.

Note: If you want to shut down computer when conversion done, or if you want to open the output folder automatically when the conversion finished, check the items marked in red in the above picture.
After the conversion work done, it's time for you to enjoy the converted files now!