I have some M4A audio files (with an AAC codec) that I need to perform basic trimming operations on. The problem is that, to my understanding, the few programs that support M4A/AAC files trim the files lossily. Some research came up with a few programs that do so without loss, without re-encoding the file, namely Fission and Boilersoft Video Splitter; the former is OSX-only, and the latter is paid. Does anyone know of any freeware programs that will do what I want?


  • Needs to be free

  • Needs to work through a GUI

  • Needs to run on Windows 7

  • Needs to be able to trim M4A/AAC files without re-encoding them

Would really appreciate some help, thanks.

1 Answer 1


I would suggest using FFMPEG + a GUI such as Avanti. FFMPEG allows all sorts of operations on the majority of video & audio files including trimming without recoding from the command line and Avanti provides a GUI that boasts access to all of the FFMPEG features.

To trim an Audio file from the command line without re-encoding and skipping the first minute then limiting the time to 10 minutes you would use:

ffmpeg -i Infile.ext -acodec copy -ss 00:01:00.000 -t 00:00:10.000 Outfile.ext

N.B. the .ext must be the same for both the input and output file if you wish to avoid re-encoding the file.

Any decent FFMPEG GUI should let you do the same

Screenshot from the Avanti web site: enter image description here

  • 2
    The only thing I would add to your answer is that the outfile.ext is very important - if you add outfile.mp4 it'll try to create a "standards compliant" MP4 file - if your input and conversion options don't match that you'll probably get an error.
    – Adam
    Commented Feb 23, 2016 at 22:16
  • Thanks for this, Steve. I'm no stranger to the command line, but for ease of use, I decided to give Avanti a try. One thing I'm confused about is where it specifies the bitrate - isn't it the case that there's no point in recoding an audio file to a higher bitrate because there's no sound quality to be gained? I just wanted to confirm that. Commented Feb 24, 2016 at 23:19
  • 1
    @Hashim Once something has been encoded at a given bit rate re-encoding at a higher bit rate will not improve the sound quality as the data just isn't there. You might still do it if the destination device struggles with the lower rate. Leaving the destination Audio settings un-ticked should be the same as -acodec copy to not re-encode the audio or not changing the settings that it is populated with once the input file is selected will. Commented Feb 25, 2016 at 6:33

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