I tried to play a video file using MX Player on my Android device. It played the video, but there was no audio. This error message is shown:
This audio format (AC3) is not supported
Download codec: The required codec files are available here. You will find the codec files for the different versions of MX Player and for each you see the codec compiled for different chip architectures. I recommend downloading the AIO pack that matches your MX Player. If you download the wrong version MX Player will complain later when you try to use the codec.
Load codec: Open MX Player and go to Settings → Decoder → Custom Codec. Navigate to the directory containing the codec zip file and choose it. MX Player will restart after loading the codec. You can now play the video and should be able to hear the audio stream.