Looking for an Android app to replace audio at a video

The problem - I (legally) download movies that were shown on TV. These videos have stereo sound. In addition I can download an AC-3 audio file with the surround sound. Now I have to replace the stereo sound by the surround sound. In Windows I use for this the software Avidemux. But I download all these files with the Android tablet and so I want to do this directly on the tablet and not copy them to the PC for further processing. 

For Android I found this app 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjQ4sSet4fyAhX7gP0HHXNdBV8QFnoECBAQAw&url=https%3A%2F%2Fplay.google.com%2Fstore%2Fapps%2Fdetails%3Fid%3Dcom.placoder.videoreplacemixremoveaudio%26hl%3Den%26gl%3DUS&usg=AOvVaw2ybtjX30GB39oWs6k_cxT1

At first it seemed to work great until I discovered that it skips some frames. If a car drives for instance in the video then you can see the jumps. You can see this problem whenever something moves faster. So I cannot use this app but I didn't find any other app. Does anybody know an app that works? Again - I want to replace the existing sound with AC-3 and not for instance with mp3. For this I found apps.