: While it supports common formats like WAV (16/24-bit) , MP2 , MP3 , AC3 , and DTS , it may struggle with certain AAC encodings unless they are in an ADTS or LATM envelope.
If you are trying to use a FLAC or Opus file as an external track, you must change your output format to MKV . MP4 does not support FLAC natively. avidemux+cannot+use+that+file+as+audio+track