We have found one software suitable in our database for this conversion.
Dedicated voice transcription software such as VoiceBase can "extract" the text from a voice in a multimedia file, let's say MPEG-4 format (.m4a files for audio only), and save the output in a text form (.txt files). which is more or less what m4a to txt conversion represents.
The end result is usually not perfect and must be corrected manually by the user. However, the only viable alternative to this would be a human making a manual transcript of the speech.
M4A
Files with m4a extension are audio files stored in MPEG-4 (MP4) container and use AAC (Advanced Audio Coding), or Apple Lossless (ALAC) audio compression. M4A is very popular on Mac computers, because it is default audio format used by iTunes. M4A is also default audio format for Apple portable devices (iPod, iPhone, iPad).
TXT
Files with txt extension are simple plain text files viewable in any text editor.