M4A file being recorded as WAV pcm_s16le file

[meghead]

When trying to extract a section of audio using FFMPEG, I discovered that the .M4A file was actually being recorded as a WAV file. Here's what FFMPEG reports;

  Guessed Channel Layout for Input Stream #0.0 : mono
  Input #0, wav, from 'myaudio.m4a':
  Duration: 00:00:04.02, bitrate: 705 kb/s
  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s 

I'm guessing it's because I've boosted the sample rate up to 44K in order to achieve higher quality.

_recorder = FlutterAudioRecorder(customPath, audioFormat: AudioFormat.AAC, sampleRate: 44100);

Here's a discussion I've started at Stackoverflow with some useful comments;

https://stackoverflow.com/questions/68542728/flutter-audio-recorder-plugin-records-m4a-as-wav-file