We don't currently have a way to standardize audio volume across your video assets, but we are looking into this for a future software update. In the meantime, you can control the volume of your videos in three ways:
Volume Control Options
a) Adjust the volume on your TV itself.
b) Use your video editing application
If you have access to the video source files in your editing application (i.e. Final Cut Pro, Adobe Premier or similar) then you can simply turn down the volume in your video and re-render it.
c) Use Handbrake (Free Application)
If you only have a finished video file to work with, you can download a free application called Handbrake and use it to raise or lower the volume in your video. Just install the app on your computer and then click on Open Source, navigate to your video, and click Open. Then click the audio tab and adjust the gain somewhere between +15 and -5. (It's better to tone down a louder video than to increase volume on a quieter one.) When you're done just select a new "Save As" file name and click Start; within a minute or so your new video will be ready! Double click to play it and if you're happy with the new volume, you can delete your old one in XOGO and upload the new one.