Since typical video files are a combination of a video and an audio component, as far as movie files on your tablet an audio editor app won't work out for you. Instead you might want to look into an equalizer app to tweak your tablet's audio output. I don't have any experience with any of them so hopefully others who have will make suggestions.
But if you're willing to sacrifice some time in a more labor intensive way, you can manually separate the audio component, edit/correct it, and then remerge it back into a single movie file again. This requires a computer (Linux, Mac, or Windows) and a couple of applications. Both are free, Open Source, and available for multiple platforms. One is Avidemux, a video editor, and the other is Audacity, an audio editor. (You'll be using Avidemux to extract the audio, Audacity to correct the audio, and then Avidemux again to combine the original video and newly edited audio in a single file again.)
http://fixounet.free.fr/avidemux/
http://www.audacityteam.org/
Using Avidemux, open the video file and in the left side panel there's an 'Audio' section. Click on 'Copy' to open up the drop-down menu and select 'MP3 (lame)'. Now click on the 'Configure' button and in the 'Bitrate' pull down menu select one of the upper numbers (maybe 128 or even up to 320). Now, in Avidemux's upper menubar, click on the 'Audio' tab and then select 'Save...', choose a directory to store the file, give it name (such as Movie.mp3), and then click on the 'Save' button. Wait for Avidemux to extract and save your audio file.
Next, using Audacity open your newly created audio file. In Avidemux's upper menubar in the 'Effect' tab, there will be several functions listed its pull-down menu. Select 'Compressor' to apply dynamic range compression. The default settings will probably be fine but you can adjust them to suit your needs.
http://manual.audacityteam.org/man/compressor.html
You might also then want to use either 'Leveler' or 'Normalize' to further smooth out the higher and lower sound levels.
http://manual.audacityteam.org/man/leveler.html
http://manual.audacityteam.org/man/normalize.html
A nice aspect to Audacity is you can make alterations using its graphical representation that you can zoom in for a granular view or out for an overall view, along being able to listen to the before and after changes as you apply them. Once you've made your alterations/corrections, go to the 'File' menu, select 'Export...', choose 'MP3 files' as the file format, in 'Options...' select 128 (or whichever you prefer) for the bitrate. (Be sure to give it a unique name so you don't confuse it with the orginal.) Wait for Audacity to process and save your edited MP3 file.
Switch back to Avidemux and now in the 'Audio' tab in the menubar select 'Main Track...' To the direct right of 'Audio Source:' in its pull down menu select 'External MP3' and then under that in the 'External file' box you'll need to navigate and select that edited MP3 file you recently created.
Now in the regular Avidemux window in the 'Audio' section be sure to change the 'MP3' selection back to 'Copy' (as you've changed audio sources in the previous step). In the 'Video' section you can just leave it as is, the default is 'Copy' or you can select a different codec. I tend to prefer h.264 for video and mp3 for audio as those two codecs are the two most common ones that are integral with hardware decoding. (Generally hardware decoding is more efficient than software decoding.) Anyway, select 'Save', give your new movie file a new name, and let it process the results.
Note if the audio doesn't need a lot of correcting, Avidmux does have some basic functions in the 'Filters' section that include a 'Dynamic range compression' check box and a 'Gain' selection but it's nothing as extensive as what you can do using Audacity. Also, all these options are just what I found to work for me, adjust specifics to your needs accordingly, and I'm only suggesting Avidemux and Audacity as they're both freely available and capable. There are numerous alternatives for both out there.
Finally, if you want to hear a discussion about sound editing in the movie industry and why audio wasn't such an annoying problem as it is in today's films, this 'Home Theater Geeks' podcast is worth listening to:
https://twit.tv/shows/home-theater-geeks/episodes/195
