How to Convert AAC to AC3 in .MKV File

While I was looking for a better way to convert mkv file with soft subtitles to be played on my Playstation 3, I found there are some tools that allow me to to the conversion. Most of the conversion tools assume the mkv file uses H.264 as the video codec and AC3 as the audio codec. Even though most mkv files stick to H.264 for video, a lot of them use AAC as the audio codec.

Without re-inventing the wheel, I came up a way to convert the AAC sound track in mkv file to AC3 without re-encode the video.  Here are the tools needed. Download and install them. Note that MKVToolnix doesn’t require installation, just extract it to a folder.


MKVE Wizard

VLC Player

  1. Run MKVE Wizard to extract the audio. Specify the file location and click on Next.
  2. Select the AAC audio track and click on Next to continue. Note that if the Wizard cannot find where you install MKVToolnix, you have to click on Settings to specify it manually. After a few moments, the AAC audio track is saved. It’s save as test_Track2.aac in this example.
  3. Run VLC player to convert the AAC sound track to AC3. Click on Media and select Convert/ Save.
    Change the Filter in the dialog window to All Files (*.*) , so you can select the AAC file extracted by step 2.
  4. In the Stream Output Windows, check File box and enter the file name. I named it test_Track2.ac3. In the Encapsulation tab, select RAW.
  5. Click on the Audio codec tab, select Audio check box and change the Codec to A52/AC-3. Specify the Bitrate and Channels if needed. Click on Save to convert the audio.
  6. Run mkvmerge GUI(mmg.exe) from the MKVToolnix folder.
  7. Drag and drop the original mkv file (test.mkv) and the converted audio track (test_Track2.ac3) to the Input files box. Uncheck the A_AAC track and move the AC3 track up before the subtitles tracks. Enter an output file name. Click on Start muxing to create the new mkv file.

There are quite a few steps, but the whole process doesn’t take long because the video is not re-encoded.

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