I have some videos that the audio volume is too low to hear from a tablet even with the volume maxed. It's not a problem with the tablet itself. It can play other music and videos loud enough.

I have the videos on my computer running Linux. Is there anything I can do to them to make the volume louder?

If the volume on these files is low on other PCs as well, then you'll need to amplify the audio (using a program like audacity), remove the amplified noise, and use e.g. ffmpeg to create an avi file without volume, then bond it with the new, amplified wav file you made in audacity.
Ffmpeg is beautiful; http://linux.die.net/man/1/ffmpeg

Not ideal, but it can raise the volume.

If this only happens on youtube(?) for all youtube videos, it could be a hardware decoding error given that the graphics card is nvidia. Disable hardware decoding of youtube videos by right-clicking a youtube vid and de-select hardware encoding.

Other than that, need more info

Even if it's maxed on the system, it probably isn't maxed in alsamixer. I run 'sudo alsamixer' and just up the master & pcm until you can hear properly. You can leave alsamixer open. To undo, close aslamixer and run 'alsactl restore'

That usually produces playable volume.

What player are you using?
Or re-encode example
Double the volume of an audio file, output to .mp3