You can use PotPlayer to play an external audio file for a video that has no embedded audio stream.
The external audio can also be loaded in a video with an existing audio stream however you’ll have to override it by selecting the external audio. e.g. a commentary audio
Option 1: Load External Audio Manually
1. Open your video with PotPlayer.
2. Right-click inside its window and select Open > Load external audio.
|Select external audio|
3. Browse and open the external audio file in a playable format (e.g. aac/m4a, ac3, mp3, ogg/opus etc). You can also select a video to use its audio stream as the external audio.
To do that, in the Browse window beside the filename box click the dropdown box and select All files. You can then select a video file.
4. If the opened video had no audio track, PotPlayer will now automatically play the selected external audio file.
|Switch between audio internal and external treams|
If the video had audio, you’ll have to switch to the external audio track by right-clicking and selecting Audio > Select Audio Stream > External Audio File ID.
Option 2: Load External Audio Automatically
You can have PotPlayer load an external audio automatically on opening a video. To do this, first go to the Preferences > Playback and enable the option Auto load external audio files.
After doing this, put both the external audio file in the same folder as the video then rename them so that they have the same filename e.g Video.mkv and Video.mp3
Now on opening the video, PotPlayer will automatically load and play the external audio provided the video has no embedded audio stream. If it has one, you’ll have to override it by right-clicking and selecting Audio > Select Audio Stream > External Audio File ID.